Here’s a common challenge when tuning a race car from trackside – you want a particular improvement, but you are limited to a specific choice of possible changes or adjustments. It’s not unusual for one change have several possible effects.
For example, let’s say the car is unstable on corner entry, due to some oversteer on initial turn-in. Let’s say you’ve decided to try to cure this by adding some anti-dive to the front suspension geometry.
In an ideal world, your car will have finely adjustable heights at both the fore and aft inboard pickup points of the upper and lower A-frames. You will whip out the laptop, make a quick run of your kinematics software, and away you go.
But, it’s the real world. Let’s say the only trackside adjustment available is the height of the inboard pickup at the rear of the upper A-frame.
See where this leads – adjusting that inner pickup point will not only change the anti-dive, it will also change the roll center height, the camber gain, and the caster gain. Will those changes work for you or against you?
In a fit of indecision, you decide to abandon the notion of adding anti-dive, and just make a shock adjustment to prop up the front end with a little low speed bump damping. Uh oh, trouble again. More low speed damping could indeed prop up the front, but then again, it could possibly make the entry oversteer even worse by sharpening the turn-in.
Things can get uglier. A stiffer front anti-roll bar, raising the front roll center, stiffer front springs, less front downforce are all changes with more than one possible outcome.
So, here’s the question: Who wins?
First, you’ve got to identify all the possible effects of the change you’re considering. Then, you’ve got to identify the magnitude of difference you are making on each of those effects. After that, you’ve got to decide how powerful each effect is on handling. Finally, and perhaps most importantly, you’ve got to assess whether the effects all work in the direction you want to go, or if some effects work against your desired result, or even in some wholly new direction.
If all the possible effects work in the same tuning direction, you have a winner! The probability of getting the desired result is pretty good, unless you commit the error of making too big a change and “going over center”.
The fun starts when some effects work against others. Using the anti-dive example, let’s say the only adjustment available to us is the height of the forward inner pickup point of the upper A-frame. If you raise it to increase anti-dive, you also lower the front roll center, possibly increasing front grip and working against your desired result. Who wins?
The danger…
As you stand there on pit lane, with a vacant look on your face, considering the possibilities, the driver and mechanics are growing increasingly impatient.
There are two ways to avoid this happening. One way is analysis. Work through the changes possible on your car ahead of time and consider your options. Hand calculations, vehicle dynamics analysis, and simulation runs can all be helpful. The other way is to scan various changes on your car and learn how it reacts, preferably doing this on an open test day. Both will help with a quick “gut call” on pit lane in the middle of a busy practice session on a race weekend.
Tuesday, August 30, 2011
Monday, May 16, 2011
Race Strategy - Indy 500 compared to Rolex GT
The May 2011 issue of Racecar Engineering recently arrived in the mail. The cover promised that Andy Brown, Target Ganassi engineer, would reveal the secrets of Indy 500 race-winning strategy calls. I opened it right up and read the article with interest, having made race strategy calls in ALMS and Grand Am for the past 11 seasons.
Now, I’m not normally one for comparisons – my dog is meaner than yours, my car is faster than yours, and so on. And I don’t know if Andy told it all, or just the parts that he thought would be obvious enough that his competitors would have already figured them out. Also, I don’t have recent experience with the Indycar rules and race control procedures, so I’m assuming everything relevant from them is factored into Andy’s strategy calls.
But, I gotta tell you, it sure looks equally, if not more, challenging to call a GT class car in a Grand Am Rolex race than it does to call the Indy 500. Here’s why:
Number of sets of tires
Indy 500 – Limited number of tire sets
Rolex GT – Limited number of tire sets
Comparison – Neither series seriously cramps your style on race day, unless things get weird. Same for both.
Tire performance
Indy 500 – Tires wear out in slightly more than one stint. No performance falloff over the stint.
Rolex GT – Tires don’t wear out. Performance falls off considerably over the stint.
Comparison – The end result is similar.
There is a “drop dead” point in a fuel stint for either series, beyond which you must change tires. Rule of thumb applies for a relatively easy call during the race.
Race length
Indy 500 – 200 laps, and that’s that.
You know exactly how many laps remain, but the timing, number, and duration of caution periods will affect your strategy.
Rolex GT – All races by time, not by number of laps
You can calculate how many laps remain, IF the remainder of the race stays green. If there are yellows, the number of laps remaining reduces, since a pace car laps takes more time than a green race lap.
Comparison – Rolex is tougher
Yellow flag laps save fuel AND reduce the number of laps remaining. So, you have a moving target. If you wait until you are clearly in the window to the end of the race before pitting, you will likely give up track position to those who gambled and pitted prior to the window, counting on being saved by a yellow or two before the finish. But, how early is too early? And what if there isn’t a yellow to save you, and now you have to stop for a splash to make it to the end, giving up track position? No easy answers…
Green flag pit stops
Indy 500 – You lose a lap
So, it’s fairly straightforward. You try to avoid intentionally forcing yourself to pit under green.
Rolex GT – You may lose a lap. Then again, you may not.
It depends on how long a green flag lap takes, which in turn is depends on both track length and average speed. It also depends on how long the pit lane is and how fast the past car goes. And, it depends on whether you need a full fuel fill or partial, and whether you must change tires or not. So, it may be a sin to stop under green, or it may be an advantage, depending on the situation.
Comparison – Rolex is tougher
Any time you can set a “rule of thumb”, that’s one less thing to worry about during the race. And, even at little bullrings like Barber, there’s no sure rule of thumb for Rolex green flag stops.
Pace car waveby
Indy 500 – Leader restarts first. Cars between leader and pace car waved by. Pits closed.
You can forego a pit stop if circumstances lead you to expect a waveby. Useful to get back on the lead lap, if you don't lose it again with a green flag stop shortly afterward.
Rolex GT – DP leader restarts first. Cars between pace car and leader waved by. Pits open.
Here’s a critical distinction. The “GT” leader can indeed take the waveby, if in front of the DP leader, thereby gaining nearly a full lap on any GT cars that do not take the waveby. ALMS used to do this too, but they changed their rules a couple of seasons ago to avoid creating this situation. And, the pits are open, so you can also make a pit stop, if you think you can beat the pace car around, then pit and get out before the pack arrives. The waveby is on the final lap of caution, though, and there won’t be time to pit AND catch the field. Not to mention the increased risk if something goes wrong during the pit stop. High stakes, high rewards, quick decisions
Comparison – Rolex GT is tougher
Tougher than Indy, and tougher than DP, too. Whenever the race leader can get a waveby, the stakes are high.
Rain
Indy 500 - Park it
Rolex GT - Keep going
Comparison - You've got to decide when to switch to wet tires and when to switch to back to dry tires, and whether to do this under green or wait for the nearly inevitable caution. Then, there's the question of how thoroughly do you convert the setup to wet specs, and whether to make any of these changes during a pit stop. And finally, there's a lot of dependence on driver comments.
Reading what I've written, I'm afraid you'd conclude that I'm saying the lot of the Rolex GT race strategist is tougher than that of the Indy 500 strategist. I seriously doubt that is true, and that's not my intent, as I said at the start. They are competing against teams with deep specialized experience in a unique event. There is little margin for error, or even for good, but not optimum, strategy calls. Meanwhile, endurance road racing has a certain amount of fuzziness that can compensate for these same good, but not optimum calls. Apples and oranges...
Still, I think it's pretty clear that calling strategy for a GT car in a garden-variety Rolex race is at least as challenging a calling the 500. And that was a bit of a surprise to me when I read Andy's article.
Special thanks to Andy Brown for opening up on this subject, one that most race engineers, team managers, and other race strategists would rather not discuss.
Now, I’m not normally one for comparisons – my dog is meaner than yours, my car is faster than yours, and so on. And I don’t know if Andy told it all, or just the parts that he thought would be obvious enough that his competitors would have already figured them out. Also, I don’t have recent experience with the Indycar rules and race control procedures, so I’m assuming everything relevant from them is factored into Andy’s strategy calls.
But, I gotta tell you, it sure looks equally, if not more, challenging to call a GT class car in a Grand Am Rolex race than it does to call the Indy 500. Here’s why:
Number of sets of tires
Indy 500 – Limited number of tire sets
Rolex GT – Limited number of tire sets
Comparison – Neither series seriously cramps your style on race day, unless things get weird. Same for both.
Tire performance
Indy 500 – Tires wear out in slightly more than one stint. No performance falloff over the stint.
Rolex GT – Tires don’t wear out. Performance falls off considerably over the stint.
Comparison – The end result is similar.
There is a “drop dead” point in a fuel stint for either series, beyond which you must change tires. Rule of thumb applies for a relatively easy call during the race.
Race length
Indy 500 – 200 laps, and that’s that.
You know exactly how many laps remain, but the timing, number, and duration of caution periods will affect your strategy.
Rolex GT – All races by time, not by number of laps
You can calculate how many laps remain, IF the remainder of the race stays green. If there are yellows, the number of laps remaining reduces, since a pace car laps takes more time than a green race lap.
Comparison – Rolex is tougher
Yellow flag laps save fuel AND reduce the number of laps remaining. So, you have a moving target. If you wait until you are clearly in the window to the end of the race before pitting, you will likely give up track position to those who gambled and pitted prior to the window, counting on being saved by a yellow or two before the finish. But, how early is too early? And what if there isn’t a yellow to save you, and now you have to stop for a splash to make it to the end, giving up track position? No easy answers…
Green flag pit stops
Indy 500 – You lose a lap
So, it’s fairly straightforward. You try to avoid intentionally forcing yourself to pit under green.
Rolex GT – You may lose a lap. Then again, you may not.
It depends on how long a green flag lap takes, which in turn is depends on both track length and average speed. It also depends on how long the pit lane is and how fast the past car goes. And, it depends on whether you need a full fuel fill or partial, and whether you must change tires or not. So, it may be a sin to stop under green, or it may be an advantage, depending on the situation.
Comparison – Rolex is tougher
Any time you can set a “rule of thumb”, that’s one less thing to worry about during the race. And, even at little bullrings like Barber, there’s no sure rule of thumb for Rolex green flag stops.
Pace car waveby
Indy 500 – Leader restarts first. Cars between leader and pace car waved by. Pits closed.
You can forego a pit stop if circumstances lead you to expect a waveby. Useful to get back on the lead lap, if you don't lose it again with a green flag stop shortly afterward.
Rolex GT – DP leader restarts first. Cars between pace car and leader waved by. Pits open.
Here’s a critical distinction. The “GT” leader can indeed take the waveby, if in front of the DP leader, thereby gaining nearly a full lap on any GT cars that do not take the waveby. ALMS used to do this too, but they changed their rules a couple of seasons ago to avoid creating this situation. And, the pits are open, so you can also make a pit stop, if you think you can beat the pace car around, then pit and get out before the pack arrives. The waveby is on the final lap of caution, though, and there won’t be time to pit AND catch the field. Not to mention the increased risk if something goes wrong during the pit stop. High stakes, high rewards, quick decisions
Comparison – Rolex GT is tougher
Tougher than Indy, and tougher than DP, too. Whenever the race leader can get a waveby, the stakes are high.
Rain
Indy 500 - Park it
Rolex GT - Keep going
Comparison - You've got to decide when to switch to wet tires and when to switch to back to dry tires, and whether to do this under green or wait for the nearly inevitable caution. Then, there's the question of how thoroughly do you convert the setup to wet specs, and whether to make any of these changes during a pit stop. And finally, there's a lot of dependence on driver comments.
Reading what I've written, I'm afraid you'd conclude that I'm saying the lot of the Rolex GT race strategist is tougher than that of the Indy 500 strategist. I seriously doubt that is true, and that's not my intent, as I said at the start. They are competing against teams with deep specialized experience in a unique event. There is little margin for error, or even for good, but not optimum, strategy calls. Meanwhile, endurance road racing has a certain amount of fuzziness that can compensate for these same good, but not optimum calls. Apples and oranges...
Still, I think it's pretty clear that calling strategy for a GT car in a garden-variety Rolex race is at least as challenging a calling the 500. And that was a bit of a surprise to me when I read Andy's article.
Special thanks to Andy Brown for opening up on this subject, one that most race engineers, team managers, and other race strategists would rather not discuss.
Wednesday, March 2, 2011
Setup Questions from Readers
In response to a recent reader request, this post will kick off a more interactive way to blog.
The reader asked, "Would you mind answering some setup questions on the blog?"
You bet. Here we go. Send your questions in the comments to this post.
Let's do it this way:
1-Keep the questions short, punchy, and focused. It's difficult, if not impossible, to reply to something as broad as "How do I get rid of mid-corner understeer?" in a short answer.
2-If there are a lot of questions, I may have to pick and choose which ones to answer. If your question doesn't show up in the blog comments, it's either been delayed or set aside.
3-In this initial thread, why don't we limit questions to setup? Maybe we'll start another thread or two later for other topics, like "life as a race engineer", race strategy, organization and planning, etc. In other words, other topics in the scope of the blog.
4-I'm going to reserve the option to wrap up the thread, for later resurrection, if needed. My upcoming schedule is pretty busy and I'd rather avoid leaving a bunch of folks hanging.
The reader asked, "Would you mind answering some setup questions on the blog?"
You bet. Here we go. Send your questions in the comments to this post.
Let's do it this way:
1-Keep the questions short, punchy, and focused. It's difficult, if not impossible, to reply to something as broad as "How do I get rid of mid-corner understeer?" in a short answer.
2-If there are a lot of questions, I may have to pick and choose which ones to answer. If your question doesn't show up in the blog comments, it's either been delayed or set aside.
3-In this initial thread, why don't we limit questions to setup? Maybe we'll start another thread or two later for other topics, like "life as a race engineer", race strategy, organization and planning, etc. In other words, other topics in the scope of the blog.
4-I'm going to reserve the option to wrap up the thread, for later resurrection, if needed. My upcoming schedule is pretty busy and I'd rather avoid leaving a bunch of folks hanging.
Sunday, February 6, 2011
The Daytona 24 Hour Race
The 24 Hour race at Daytona is, for crews, quite possibly the toughest road race in the world. Some thoughts:
Darkness
It’s dark for just about twelve hours, much longer than at Le Mans. Le Mans is dark for only about half as long, between its June date and its northern latitude. And the “new” start time for Daytona of 3:30 PM, instituted just a few years ago (for TV?) insures that it will get dark very soon after the start of the race. Of course, the darkness isn’t as big a challenge for the drivers as it might initially appear to be. The course is fairly well lit, not at all like blackness of Le Mans, Sebring, or the 25 hour race at Thunderhill. For the crews, the effect of the long darkness is this: You know you are going to have to miss a night’s sleep. So, you want the night to be over, so you can at least stand a better chance of staying alert in the light of the second day. But, the night drags on and on, and so do you.
The early visit to the garage
The worst thing for any team member is, sometime in the first half of the race, getting that radio call from the driver that the car has been involved in an incident or isn’t running right. If the solution takes 30 minutes in the garage, you are totally out of contention. And yet, there’s still the remainder of the night’s sleep to miss, 10 more pit stops to accomplish successfully, and the reward of loading a trailer when it’s all over.
It’s the first race
Preparing the car is a lot of work. Everything on it has to be touched, freshened, made ready for a long trouble-free run. As soon as the race is over, there is even more work ahead to restore the car to top condition for the next race.
It’s a 24 hour sprint
Yes, I know the TV commentators are fond of pointing this out every year. Yes, they are right. The significance of this isn’t really about the cars, though. The cars, both DP and GT, are fully capable of being run hard for 24 straight hours, without any babying. The real significance is on the crew. The engineers have to be on their game for race strategy and tactics. The over-the-wall guys have to execute 24 or more fast and flawless pit stops.
Smart phones and other connectivity
Having an Android, iPhone, iPad, or Blackberry on the timing stand has become essential. The number one reason is to monitor weather radar. That's such a biggie! A very close number two is NEVER losing touch with your drivers. It used to sometimes be fun to locate the driver who was due for the next stint. Beyond that - tweets, Facebook status updates, and texting help keep everyone in the loop. If done correctly (and not obsessively), they don't get in the way of running the race. This year, our PR guy was updating the website every hour or two, direct from the timing stand, via his PC's wireless card. If done wrong, it's just tech obsession. If done right, everything is lifted a notch.
Brakes
Grand-Am doesn’t allow carbon brakes, which can comfortably last 24 hours. With the “sprint” nature of the race, teams may choose to run aggressive pad compounds, in search of improved braking performance. For an engineer working on a unfamiliar car, or for a new team, or for a team running its first 24 hour on a new brake pad compound, there is always a bit of uncertainty. Did we get enough practice running to forecast pad and rotor life accurately? Have we correctly judged the tradeoff of braking performance against brake life? Will we get a conveniently timed caution flag to allow changing pads, or will we be stuck with changing them in a green flag pit stop?
Is it cold enough for you?
The overnight low is frequently in the mid 40s, and can be colder. That doesn’t sound so grueling, does it? Not so. Being outdoors, and yet largely immobile, for eight or ten hours straight in mid 40s, with no warmth from the sun, can be chilling and draining, both physically and mentally. There’s no secret, but having a tent with enclosed sides, staying hydrated and well fed, and wearing every stitch of warm clothing that you own can all help.
The payoff
Win or lose, there’s a fine sense of accomplishment that comes with seeing the checker. That’s what keeps us all coming back.
See you there next year!
Darkness
It’s dark for just about twelve hours, much longer than at Le Mans. Le Mans is dark for only about half as long, between its June date and its northern latitude. And the “new” start time for Daytona of 3:30 PM, instituted just a few years ago (for TV?) insures that it will get dark very soon after the start of the race. Of course, the darkness isn’t as big a challenge for the drivers as it might initially appear to be. The course is fairly well lit, not at all like blackness of Le Mans, Sebring, or the 25 hour race at Thunderhill. For the crews, the effect of the long darkness is this: You know you are going to have to miss a night’s sleep. So, you want the night to be over, so you can at least stand a better chance of staying alert in the light of the second day. But, the night drags on and on, and so do you.
The early visit to the garage
The worst thing for any team member is, sometime in the first half of the race, getting that radio call from the driver that the car has been involved in an incident or isn’t running right. If the solution takes 30 minutes in the garage, you are totally out of contention. And yet, there’s still the remainder of the night’s sleep to miss, 10 more pit stops to accomplish successfully, and the reward of loading a trailer when it’s all over.
It’s the first race
Preparing the car is a lot of work. Everything on it has to be touched, freshened, made ready for a long trouble-free run. As soon as the race is over, there is even more work ahead to restore the car to top condition for the next race.
It’s a 24 hour sprint
Yes, I know the TV commentators are fond of pointing this out every year. Yes, they are right. The significance of this isn’t really about the cars, though. The cars, both DP and GT, are fully capable of being run hard for 24 straight hours, without any babying. The real significance is on the crew. The engineers have to be on their game for race strategy and tactics. The over-the-wall guys have to execute 24 or more fast and flawless pit stops.
Smart phones and other connectivity
Having an Android, iPhone, iPad, or Blackberry on the timing stand has become essential. The number one reason is to monitor weather radar. That's such a biggie! A very close number two is NEVER losing touch with your drivers. It used to sometimes be fun to locate the driver who was due for the next stint. Beyond that - tweets, Facebook status updates, and texting help keep everyone in the loop. If done correctly (and not obsessively), they don't get in the way of running the race. This year, our PR guy was updating the website every hour or two, direct from the timing stand, via his PC's wireless card. If done wrong, it's just tech obsession. If done right, everything is lifted a notch.
Brakes
Grand-Am doesn’t allow carbon brakes, which can comfortably last 24 hours. With the “sprint” nature of the race, teams may choose to run aggressive pad compounds, in search of improved braking performance. For an engineer working on a unfamiliar car, or for a new team, or for a team running its first 24 hour on a new brake pad compound, there is always a bit of uncertainty. Did we get enough practice running to forecast pad and rotor life accurately? Have we correctly judged the tradeoff of braking performance against brake life? Will we get a conveniently timed caution flag to allow changing pads, or will we be stuck with changing them in a green flag pit stop?
Is it cold enough for you?
The overnight low is frequently in the mid 40s, and can be colder. That doesn’t sound so grueling, does it? Not so. Being outdoors, and yet largely immobile, for eight or ten hours straight in mid 40s, with no warmth from the sun, can be chilling and draining, both physically and mentally. There’s no secret, but having a tent with enclosed sides, staying hydrated and well fed, and wearing every stitch of warm clothing that you own can all help.
The payoff
Win or lose, there’s a fine sense of accomplishment that comes with seeing the checker. That’s what keeps us all coming back.
See you there next year!
Tuesday, September 7, 2010
Rain Setups
First, sincere apologies to faithful readers for the long, long dry spell in new blog posts. I’ve been busy with two racing programs. That’s the reason, but it’s no excuse. Oh, well.
If you followed the 2010 ALMS race weekend at Lime Rock, then the topic of this blog will come as no surprise at all. Let’s end the dry spell in blog posts by talking about rain.
I’ll be the first to tell you that I am never totally comfortable with rain setups, despite having run in the rain quite a bit and even having engineered a major series race win in the rain. Rain setups are always a conundrum. First, you don’t get a lot of opportunities to develop your rain setup. Then, there’s the really big question of how far do you take the rain setup. Then, there’s the other really big question of how skilled and comfortable your driver is on a wet track. Compared to those, the technical issues of the rain setup are almost “cut and dry”, to make a weak pun. Contrary to what the advice columns say, I’ll tackle the easy part first.
For starters, let’s assume we have a properly wet track (at least light rooster tails), with rain still falling at a steady enough rate to keep the track from drying. It’s been raining for a while, and there isn’t much heat left in the pavement. We don’t anticipate that it will quit raining during the session.
Let’s start with a small handful of basic principals. We need grip. The brake bias needs to be shifted to the rear. We absolutely cannot tolerate understeer. Let me say that one more time. We absolutely cannot tolerate understeer.
Chasing grip first…
First, we need all the downforce we can produce. Wing(s) to the maximum, more rake, add on all the gadgets, do it all. Drag be damned. That much, I know for sure. It’s essential that we remain respectful of the car’s fundamental aero characteristics. Pitch and ride height sensitivity will affect decisions to adjust rake, as well as spring or bump rubber rate decisions. I believe that as you add total downforce, you need to try to keep the aero balance as far forward as possible. All in the interest of avoiding understeer.
In pursuit of grip, it’s tempting to dramatically open the bump and rebound bleeds in the shocks. On the other hand, we need to remain respectful of the car’s needs for aero platform control, which may or may not change in the rain. We also have to remember that the bumps, curbs, and other surface irregularities in the track will not go away just because they get wet. So, how much bleed is enough? It depends.
In race series where the rules allow driver-adjustable anti-roll bars, it’s easy to soften the bars for some grip. Perhaps equally important, it’s easy to reverse the adjustment. In other series, it becomes more of a judgment call whether to soften the bars, and if so, how much.
So that’s it for the easy changes. Now, if it’s really clear that the rain will continue, and at a track-soaking pace, we can also consider softening springs and reducing negative camber. Again, we need to be cognizant of platform control, if we choose to soften springs. It’s much safer to soften dramatically on a low-dowforce car than on a high-downforce one. Meanwhile, the camber change can be quite helpful, presuming the weather has the courtesy to stay properly wet. If not, you’re in trouble, aren’t you?
Finally, let’s have a look at the rain tires themselves. How fresh are they? If they’ve been previously run on a drying track, they will have worn away the chiseled edges that are so essential to cutting through the water to the track. If it’s really wet, fresh rains always help.
Now, a brief word about brake bias…
Braking Gs in the rain won’t be as high as in the dry, so we won’t have as much forward weight transfer. Lacking that, we’ll need less front brake bias. It’s pretty easy to make a rough calculation of the needed change. The whole process is almost painless if you have driver-adjustable bias and brake pressure sensors wired into onboard math in the data logger and displayed on the dash. A word to the wise – brake bias adjusters can be cranky little pieces of crap, and the time to debug them is not when the rain starts falling.
OK, so let’s talk about understeer…
Understeer in the rain is more than just an inconvenience. It’s an opportunity to arrive at a corner and plow straight off into the muddy grass, gravel, wall, or whatever other dramatic and damaging fate awaits the car. Not good, and it won’t endear you to either the driver or the mechanics.
Let’s remember that our dry-track handling balance assumes a lot of weight transfer to the front in braking, helping corner entry. Then, on exit, the rear lateral grip is reduced with an aggressive application of power. Neither condition is there for us in the wet. It will be necessary to shift the handling balance in the oversteer direction. It’s not as simple as aggressively softening the front springs and bar, because that might lose aero or roll platform control in a way we won’t like. You should work within the tuning options you’ve proven for your car in the dry.
The oft-mentioned option to disconnect both the front and rear anti-roll bars can, in the right circumstances, be a good move for preventing understeer. The wheel rate of the front bar is almost always higher than the rear. Nuff said.
Here are two serious “gotchas” related to cooling…
First, be careful of your engine temperatures. Some ECU calibrations may default into “cold-start” mode if temperatures drop too much.
And, some brake materials don’t take kindly at all to getting wet or getting too cool.
Everyone wants to just lay a strip or two of duct tape over the radiator opening or the brake ducts. Step back for a minute and think about how well duct tape will stick to a wet, dirty, oily surface, and you will see why I strongly prefer sheet aluminum blanking plates held in place by Camlocs.
Now, let’s talk drivers for a minute…
Some are really good in the rain, some are OK, and some are, well, not OK. I hope yours is in the first group. If so, you’ll look pretty good, no matter how well the car works. I once had a special case of a driver who was good in the rain, but didn’t care for losing any of his cherished platform support to softer springs, bars, or shocks. We just turned up the wing, reset the brake bias, bolted on the rains, and went off to win the race. As always, tune to the driver’s comments.
So, here’s the ugly question…
How far do you go with “messing up” your nice dry setup for the rain?
Here are some of the questions we’ll need to consider:
Will the rain let up soon, or get worse?
Is it real rain, or just a shower?
How much of the track is wet?
What can we learn from radar and the sky?
When will the track be wet enough to need rains, or dry enough to take them off?
How much heat remains in the track surface?
If this is a practice session, do we expect to qualify or race in the rain?
Do we even go out on the track?
All questions are for another day. Hopefully soon. See you later.
If you followed the 2010 ALMS race weekend at Lime Rock, then the topic of this blog will come as no surprise at all. Let’s end the dry spell in blog posts by talking about rain.
I’ll be the first to tell you that I am never totally comfortable with rain setups, despite having run in the rain quite a bit and even having engineered a major series race win in the rain. Rain setups are always a conundrum. First, you don’t get a lot of opportunities to develop your rain setup. Then, there’s the really big question of how far do you take the rain setup. Then, there’s the other really big question of how skilled and comfortable your driver is on a wet track. Compared to those, the technical issues of the rain setup are almost “cut and dry”, to make a weak pun. Contrary to what the advice columns say, I’ll tackle the easy part first.
For starters, let’s assume we have a properly wet track (at least light rooster tails), with rain still falling at a steady enough rate to keep the track from drying. It’s been raining for a while, and there isn’t much heat left in the pavement. We don’t anticipate that it will quit raining during the session.
Let’s start with a small handful of basic principals. We need grip. The brake bias needs to be shifted to the rear. We absolutely cannot tolerate understeer. Let me say that one more time. We absolutely cannot tolerate understeer.
Chasing grip first…
First, we need all the downforce we can produce. Wing(s) to the maximum, more rake, add on all the gadgets, do it all. Drag be damned. That much, I know for sure. It’s essential that we remain respectful of the car’s fundamental aero characteristics. Pitch and ride height sensitivity will affect decisions to adjust rake, as well as spring or bump rubber rate decisions. I believe that as you add total downforce, you need to try to keep the aero balance as far forward as possible. All in the interest of avoiding understeer.
In pursuit of grip, it’s tempting to dramatically open the bump and rebound bleeds in the shocks. On the other hand, we need to remain respectful of the car’s needs for aero platform control, which may or may not change in the rain. We also have to remember that the bumps, curbs, and other surface irregularities in the track will not go away just because they get wet. So, how much bleed is enough? It depends.
In race series where the rules allow driver-adjustable anti-roll bars, it’s easy to soften the bars for some grip. Perhaps equally important, it’s easy to reverse the adjustment. In other series, it becomes more of a judgment call whether to soften the bars, and if so, how much.
So that’s it for the easy changes. Now, if it’s really clear that the rain will continue, and at a track-soaking pace, we can also consider softening springs and reducing negative camber. Again, we need to be cognizant of platform control, if we choose to soften springs. It’s much safer to soften dramatically on a low-dowforce car than on a high-downforce one. Meanwhile, the camber change can be quite helpful, presuming the weather has the courtesy to stay properly wet. If not, you’re in trouble, aren’t you?
Finally, let’s have a look at the rain tires themselves. How fresh are they? If they’ve been previously run on a drying track, they will have worn away the chiseled edges that are so essential to cutting through the water to the track. If it’s really wet, fresh rains always help.
Now, a brief word about brake bias…
Braking Gs in the rain won’t be as high as in the dry, so we won’t have as much forward weight transfer. Lacking that, we’ll need less front brake bias. It’s pretty easy to make a rough calculation of the needed change. The whole process is almost painless if you have driver-adjustable bias and brake pressure sensors wired into onboard math in the data logger and displayed on the dash. A word to the wise – brake bias adjusters can be cranky little pieces of crap, and the time to debug them is not when the rain starts falling.
OK, so let’s talk about understeer…
Understeer in the rain is more than just an inconvenience. It’s an opportunity to arrive at a corner and plow straight off into the muddy grass, gravel, wall, or whatever other dramatic and damaging fate awaits the car. Not good, and it won’t endear you to either the driver or the mechanics.
Let’s remember that our dry-track handling balance assumes a lot of weight transfer to the front in braking, helping corner entry. Then, on exit, the rear lateral grip is reduced with an aggressive application of power. Neither condition is there for us in the wet. It will be necessary to shift the handling balance in the oversteer direction. It’s not as simple as aggressively softening the front springs and bar, because that might lose aero or roll platform control in a way we won’t like. You should work within the tuning options you’ve proven for your car in the dry.
The oft-mentioned option to disconnect both the front and rear anti-roll bars can, in the right circumstances, be a good move for preventing understeer. The wheel rate of the front bar is almost always higher than the rear. Nuff said.
Here are two serious “gotchas” related to cooling…
First, be careful of your engine temperatures. Some ECU calibrations may default into “cold-start” mode if temperatures drop too much.
And, some brake materials don’t take kindly at all to getting wet or getting too cool.
Everyone wants to just lay a strip or two of duct tape over the radiator opening or the brake ducts. Step back for a minute and think about how well duct tape will stick to a wet, dirty, oily surface, and you will see why I strongly prefer sheet aluminum blanking plates held in place by Camlocs.
Now, let’s talk drivers for a minute…
Some are really good in the rain, some are OK, and some are, well, not OK. I hope yours is in the first group. If so, you’ll look pretty good, no matter how well the car works. I once had a special case of a driver who was good in the rain, but didn’t care for losing any of his cherished platform support to softer springs, bars, or shocks. We just turned up the wing, reset the brake bias, bolted on the rains, and went off to win the race. As always, tune to the driver’s comments.
So, here’s the ugly question…
How far do you go with “messing up” your nice dry setup for the rain?
Here are some of the questions we’ll need to consider:
Will the rain let up soon, or get worse?
Is it real rain, or just a shower?
How much of the track is wet?
What can we learn from radar and the sky?
When will the track be wet enough to need rains, or dry enough to take them off?
How much heat remains in the track surface?
If this is a practice session, do we expect to qualify or race in the rain?
Do we even go out on the track?
All questions are for another day. Hopefully soon. See you later.
Wednesday, February 17, 2010
Finding the Setup, Part 2
Have a look at this Wikipedia entry. While not written specifically about racing, it relates directly to Jeff's "secondary effects".
http://en.wikipedia.org/wiki/Law_of_Unintended_Consequences
In response to a request on the FSAE forum, Jeff has kindly taken the time to make a PDF of his setup change spreadsheet. Note that all the second page shows the selections for the pull-downs (not seen) that are used to fill in the individual setup changes on the sheet.
Jeff Braun Setup Change Database PDF
http://en.wikipedia.org/wiki/Law_of_Unintended_Consequences
In response to a request on the FSAE forum, Jeff has kindly taken the time to make a PDF of his setup change spreadsheet. Note that all the second page shows the selections for the pull-downs (not seen) that are used to fill in the individual setup changes on the sheet.
Jeff Braun Setup Change Database PDF
Saturday, February 13, 2010
Finding the Setup
Here's another guest post, this time from Jeff Braun. Jeff's a successful working race engineer, concentrating these days on endurance sports car racing, but with a broad background in many racing series.
He also has the dubious distinction of being the only race engineer who actually drove against me. It was a while ago... If I recall, I beat him then, but he's paid it back as an engineer, more than once.
Since we're friends, I'll indulge him for scooping me on material that was to have been included in the "Philosophy" series. But, there's much more than that in his post. I'm sure you'll find it thought-provoking.
The Setup – How to get it right
Apart from money, a good setup may be the most sought after thing in racing.
One thing before we talk about how to get the setup right. Who is ultimately responsible for the setup on the car? The driver! Not the engineers, not the team manager, not the chief mechanic, or anyone else except the driver. I hate it when people say “the engineer really has that car set up well.” It has little to do with the engineer. I have yet to see an engineer put a setup on a car, install a new driver, never change the setup, and win everything in sight. It never happens. The driver guides the setup process, he directs the engineers in the areas that need improvement, he is in charge of the car, and he has to get it to his liking to be fast. The engineer only interprets what the driver tells him and comes up with suggestions on what changes could help the problems the driver has identified as the main thing preventing him from going quicker. The engineer has the technical resources to come up with the best change to get the desired results, but he can’t identify and prioritize the areas that need improving without a technically good driver to point him in the right direction.
The magic setup – No numbers
Getting the setup right is not about cambers, toe, springs, and all the technical numbers. It is about the approach you take and the procedures you use to get there. So, I am not going to tell you the perfect springs to run at Laguna, or what wing setting works best at Montreal. Why? Because, it all depends on way too many things. I just plain don’t know the answer. What I am sure of is that, if you follow the things below, you will be ahead of the game in finding the springs or wing settings for your driver, your car, and the track on the weekend you are racing.
Best way to a great setup – Don’t change anything!
So, you spend hours with your driver and the data in the shop designing the starting setup for the weekend. You have experience with the car and kind of know the type of track you are going to, but have never been there before. You have it nailed, you think. You unload and head out for the first session. Four laps later, the driver is in the pits looking for a change. You jump in and start changing things; you want it to be better for him.
After the session you make more changes, maybe three or four, because he was 1 second off the pace. Next session the car is doing different things than before. Oh no, the changes were in the wrong direction. You remove the three changes and go the other way with four more. Now it’s better, but now a there is a different problem.
The data looks confusing, the driver is confused, but time is running out now, and you are still 0.8 seconds off. Something must be way different about this track than you thought. You decide you may have to rethink the entire setup, or that you may not really understand the car like you thought.
The next session you are better. The times are closer to fast guys and the driver just needs a few small changes. The changes help and the panic subsides some. But, you still need three tenths.
Now, it’s qualifying. The changes helped, and you’re now two tenths off the pole and on the second row. So, let’s look at the qualifying setup. It is exactly how we unloaded! We went in a big circle.
I see this all the time, at all levels of motorsport. I don’t know of any race engineers who get paid by the change. Slow down. Let the driver learn the track, and then figure out what he needs. The track will clean up and get some rubber down. Have confidence in your starting setup. Don’t be in a hurry to change it all around right away. Talk with your driver and write out a testing plan listing each session and what you hope to get done. This will only be a guide for the weekend, but it allows you to plan the sessions as you wish they would go.
A driver’s feed back is junk for the first session, anyway. He is getting a feel for the track, the grip level, and the car. Use that session to set the ride height (as the best engineer/driver I have ever known told me - lower is better always, always), log some baseline data, check the car, read the tires, and get some fuel consumption data. Robbie Groff used to tell me he needed the car to “talk to him” before he could tell me what we needed. Don’t screw up a good setup in the first session. Think where our driver could have qualified if he had kept the setup he ended up with and progressed forward in the sessions instead of going in a circle.
The spec car
If you have a restricted car or spec car, you have less things to try on the weekend. You should know the car well, if you have some experience with it. Otherwise, you can get a good starting set up from someone in the series. These cars are really relatively simple and require a methodical approach, rather than the shotgun approach of multiple wild guesses in search of the magic set up that gives you the 1 second you need. Now, there are some spec cars that are so bad that you do need the tricks that only the veterans know. My advice is to be prepared for a frustrating time, buy or steal the tricks, or run a real race car series.
Most series in North America have good cars that behave as expected. Try to stay within your setup window. You must define that window and keep refining it as you get to know the car better. But, resist the urge to go way out of what you know on a race weekend. Save that for testing. Keep a list of things you wanted to try at a race weekend, but did not because you did not know what it would do. Answer those questions at the next test.
On race weekends, it is always best to make changes that produce known results. If you don’t know what a change will do, go testing. If things are going well and you can afford to test for a session, then give some of the unknowns a poke. You can always go back to your baseline. Just remember, the other drivers will be moving forward in their setup when you are testing. You may find yourself behind by losing the session.
The track will tip your base setup some, but not much in a spec car. Try to come up with a base setup which will be refined each weekend. Run it at each track for the first session or two. You know how the car performs and feels with this setup, you know you liked it at the last race and there are no surprises to it. If the car feels different at this new track, you have just quantified the track. Using your base setup for the car, you can see what the track did to it. Make adjustments in the window of what you know works. Be sure the car is talking to you before you start. My driver/engineer friend likes to say “the laws of physics don’t change when you cross state lines.”
One last thing on this subject. Don’t fall into what I call the “Runoffs mistake”. A driver does a great job all year and qualifies for the prestigious SCCA Runoffs by hard work, good understanding of the car, and good procedures to get the set up right. He makes the trip to Road America and knows he has a shot to win this thing. But he knows there are some very good drivers from all over the U.S., and he thinks he needs something special to win. He finds a trick tire that he has never run but it is “worth 0.3 seconds”. The expert shock guy gave him the best Road America set up. The engine guy has the new development exhaust system. The result – the poor guy gets clobbered, not only by the out of division drivers, but also by the guys he beat all year, who now run away from him. Run what you know and tune it better than the next guy. Save the tricks for winter testing.
Changes – The secondary effects
In talking to engineers and drivers, I hear that they made a change and it did not help or did something completely different than they expected. Most of the time, the reason is what I call the secondary effect of a change.
Most racers have a good idea of what a change will do to the car, or at least they know what they want it to do. The problem is that seldom does a change only do one thing to the performance of the car. Each change has a primary effect and a secondary effect. There are third and fourth effects I am sure, but I am just barely smart enough to figure out the second effect.
If you are trying to decide between a few changes to improve something in the balance of the car, make a list of the three or four possible changes and what you expect each to do. For example, assume we have an understeer from the apex to the exit. We could change:
1 – More front wing
2 – More rake
3 – Stiffer rear springs
4 – More front rebound
There may be fifteen other things you could do, but list the top contenders. Now, list what you think the secondary effect of each might be:
1 – More front wing – oversteer in high speed turns
2 – More rake – nervous rear in high speed turns
3 – Stiffer rear springs – worse power down traction
4 – More front rebound – harsher in the bumps
Look at the list and try to find a change that has a primary effect and secondary effect that are in the same direction. Also, consider what other problems the driver may be having, which we’ll call the secondary complaint. In our example, if the high speed turns were good or bordering on oversteer, then we can eliminate the wing and rake. The stiffer rear springs will keep the dynamic rake in the car (primary effect) and free the car up on exit, while with less power down traction (secondary effect). Everything works in the direction we want.
What we want to avoid is a change with the primary effect opposite from the secondary effect. Often, this results in the driver comment of “can’t really tell much difference.” When a change has an unexpected result, you should look at the secondary effect. Sometimes, what you thought was the secondary effect was really the primary effect, and it was in the opposite direction.
Keeping track of all these effects and changes can get very confusing. The problem is that the effect of a change on a FF-1600 is very likely to be different from the same change on a Formula Atlantic car.
The change data base
There is a way to help sort the changes and what they did to your car. It helps you learn the car and can be a great tool to suggest changes that you know the result of like we talked about earlier.
One year at the test days for the Daytona 24 Hour, I was done with a session and walked past the factory Nissan NISMO team from Japan. In their pit were four racks of computers and more electronics than a modern day F1 team has. I watched for a while, as the Group C Nissan went around and around. There were only two guys manning the computer banks, so I walked up and asked what they were logging. The answer was that they were logging over 200 channels of data. I tried to think of 200 channels I would want to have logged. I got to about 30 and had to ask “what are you guys logging?” The Japanese engineer said “mostly engine parameters”. He said the engine block had twenty strain gauges cast into the block to measure stress in various sections of the block.
I thought that was very cool, but wanted to know what they were going to do with the data. The engineer said that, sometime in the future, a Nissan engineer was going to want to know what the stress was in an engine block. When that happened, the data would be there. He said that the cost of running a race car was so high, that collecting data while it was running reduced the cost of gaining that information later, when someone needed it. That impressed me with the long term thinking to collect data. Collect the data when you can, sort it out when you have time.
Any race team can do the same thing, on a smaller scale. Using a spread sheet, make a matrix with each column being a parameter in your setup. Include columns for driver comment, change, and result of the change. Each row will be a track outing. Start to log the result of each change you make to your car. In short order, you will have a history of each change made to your car.
Using the data sort function of the spread sheet, you can sort the data. For example, you can show every time you had exit understeer. Then, look at what you changed when you had that problem and what the result was. This will prevent you from making the same set up mistake twice. And, it will tell you what things have worked to correct an exit understeer in the past. It will keep you in the window of your knowledge. When testing, look at the data base and try some things that you have not tried before. This expands your understanding of the car and makes your data base more helpful at the track.
Using a data base program, like Access, takes it to the next level with tables, forms, and special queries to make the search results more meaningful and detailed. If you spend some time (it took me about 30 hours and I am NOT an Access expert), you can answer more questions. You can ask the database to show what we changed to reduce a mid corner oversteer in a third gear turn when we had tire pressures above 15 psi and a rear wing setting below 10 degrees.
Remember, the sooner you start collecting the data, the cheaper every mile you do becomes, because you are getting more value for your dollar. I can say that this has helped me a bunch over the years. My Daytona Prototype data base has over 900 changes logged in it. It just makes me a better guesser.
So, to recap…
1 – The driver is in charge of his setup. The engineer just makes the change he thinks will help him the most.
2 – Resist making changes until the driver really has a good feel for the car. It has to “talk to him” first.
3 – Physics does not change when you cross state lines. Go with what you know.
4 – The secondary effect of a change can be in the opposite of the primary effect. Never make a change without considering the secondary effect.
5 – Use a data base to increase your understanding of your car quicker and with more accuracy.
6 – If a change does not have the effect you thought it would, than you are missing some effect that you did not consider. There is not some weird phenomenon going on, you just don’t understand the circumstances of the particular situation.
7 – When in doubt, go back to your base setup and start over from there.
8 – Never copy another faster team’s setup. You need to know why yours does not work, so you can be better next time.
9 - If a change works the way you thought it would, you did not learn anything. You did become faster, which is always a good thing. But, when the change does not work as planned, you have a great chance to become smarter. Grab on to that and figure it out.
10 – When recording changes in your notes, write down why you made that change, your thinking on what you expect it to do, and why. Then, you can go back later and see what your thinking was for making that change and decide where your thinking was wrong. This may happen months later, as you get to know the car better, but it allows you to see where your mistake was, not just that it was a mistake.
OK, one more thing.
My friend, the driver/engineer mentor of mine, wrote these points down once about problem solving. Think about them. It may change your approach to finding the perfect set up.
1 – What’s right is right and everything else is wrong to some degree.
2 – What is REALLY happening here?
3 – Nothing happens for no reason.
4 – Everything is attributable.
5 – If X is true then Y must also be true. If I can’t prove that Y actually does as I predict, then I don’t know anything at all about X.
6 – What I am certain is correct can change instantly in the light of what is REALLY correct, whether I like it or not.
7 – Just because I don’t want to believe it, doesn’t make it wrong.
7a – Just because I want to believe it doesn’t make it right, either.
8 – Knowing what is wrong is every bit as important as knowing what is right.
9 – If it isn’t all the things you think it is, then it is something else. (Sherlock Holmes)
10 – You only know something if you can prove it. Everything else is “I suspect” or “I guess” or “I wonder if” or “it is my theory that...”
11 – The right answer is still the right answer even if you didn’t think of it.
12 – The right answer is still the right answer even if you don’t have any idea of why it works... but find out later for sure, because the underlying principles will always apply.
13 – Asking other people for answers is perfectly acceptable, as long as you never believe them.
He also has the dubious distinction of being the only race engineer who actually drove against me. It was a while ago... If I recall, I beat him then, but he's paid it back as an engineer, more than once.
Since we're friends, I'll indulge him for scooping me on material that was to have been included in the "Philosophy" series. But, there's much more than that in his post. I'm sure you'll find it thought-provoking.
The Setup – How to get it right
Apart from money, a good setup may be the most sought after thing in racing.
One thing before we talk about how to get the setup right. Who is ultimately responsible for the setup on the car? The driver! Not the engineers, not the team manager, not the chief mechanic, or anyone else except the driver. I hate it when people say “the engineer really has that car set up well.” It has little to do with the engineer. I have yet to see an engineer put a setup on a car, install a new driver, never change the setup, and win everything in sight. It never happens. The driver guides the setup process, he directs the engineers in the areas that need improvement, he is in charge of the car, and he has to get it to his liking to be fast. The engineer only interprets what the driver tells him and comes up with suggestions on what changes could help the problems the driver has identified as the main thing preventing him from going quicker. The engineer has the technical resources to come up with the best change to get the desired results, but he can’t identify and prioritize the areas that need improving without a technically good driver to point him in the right direction.
The magic setup – No numbers
Getting the setup right is not about cambers, toe, springs, and all the technical numbers. It is about the approach you take and the procedures you use to get there. So, I am not going to tell you the perfect springs to run at Laguna, or what wing setting works best at Montreal. Why? Because, it all depends on way too many things. I just plain don’t know the answer. What I am sure of is that, if you follow the things below, you will be ahead of the game in finding the springs or wing settings for your driver, your car, and the track on the weekend you are racing.
Best way to a great setup – Don’t change anything!
So, you spend hours with your driver and the data in the shop designing the starting setup for the weekend. You have experience with the car and kind of know the type of track you are going to, but have never been there before. You have it nailed, you think. You unload and head out for the first session. Four laps later, the driver is in the pits looking for a change. You jump in and start changing things; you want it to be better for him.
After the session you make more changes, maybe three or four, because he was 1 second off the pace. Next session the car is doing different things than before. Oh no, the changes were in the wrong direction. You remove the three changes and go the other way with four more. Now it’s better, but now a there is a different problem.
The data looks confusing, the driver is confused, but time is running out now, and you are still 0.8 seconds off. Something must be way different about this track than you thought. You decide you may have to rethink the entire setup, or that you may not really understand the car like you thought.
The next session you are better. The times are closer to fast guys and the driver just needs a few small changes. The changes help and the panic subsides some. But, you still need three tenths.
Now, it’s qualifying. The changes helped, and you’re now two tenths off the pole and on the second row. So, let’s look at the qualifying setup. It is exactly how we unloaded! We went in a big circle.
I see this all the time, at all levels of motorsport. I don’t know of any race engineers who get paid by the change. Slow down. Let the driver learn the track, and then figure out what he needs. The track will clean up and get some rubber down. Have confidence in your starting setup. Don’t be in a hurry to change it all around right away. Talk with your driver and write out a testing plan listing each session and what you hope to get done. This will only be a guide for the weekend, but it allows you to plan the sessions as you wish they would go.
A driver’s feed back is junk for the first session, anyway. He is getting a feel for the track, the grip level, and the car. Use that session to set the ride height (as the best engineer/driver I have ever known told me - lower is better always, always), log some baseline data, check the car, read the tires, and get some fuel consumption data. Robbie Groff used to tell me he needed the car to “talk to him” before he could tell me what we needed. Don’t screw up a good setup in the first session. Think where our driver could have qualified if he had kept the setup he ended up with and progressed forward in the sessions instead of going in a circle.
The spec car
If you have a restricted car or spec car, you have less things to try on the weekend. You should know the car well, if you have some experience with it. Otherwise, you can get a good starting set up from someone in the series. These cars are really relatively simple and require a methodical approach, rather than the shotgun approach of multiple wild guesses in search of the magic set up that gives you the 1 second you need. Now, there are some spec cars that are so bad that you do need the tricks that only the veterans know. My advice is to be prepared for a frustrating time, buy or steal the tricks, or run a real race car series.
Most series in North America have good cars that behave as expected. Try to stay within your setup window. You must define that window and keep refining it as you get to know the car better. But, resist the urge to go way out of what you know on a race weekend. Save that for testing. Keep a list of things you wanted to try at a race weekend, but did not because you did not know what it would do. Answer those questions at the next test.
On race weekends, it is always best to make changes that produce known results. If you don’t know what a change will do, go testing. If things are going well and you can afford to test for a session, then give some of the unknowns a poke. You can always go back to your baseline. Just remember, the other drivers will be moving forward in their setup when you are testing. You may find yourself behind by losing the session.
The track will tip your base setup some, but not much in a spec car. Try to come up with a base setup which will be refined each weekend. Run it at each track for the first session or two. You know how the car performs and feels with this setup, you know you liked it at the last race and there are no surprises to it. If the car feels different at this new track, you have just quantified the track. Using your base setup for the car, you can see what the track did to it. Make adjustments in the window of what you know works. Be sure the car is talking to you before you start. My driver/engineer friend likes to say “the laws of physics don’t change when you cross state lines.”
One last thing on this subject. Don’t fall into what I call the “Runoffs mistake”. A driver does a great job all year and qualifies for the prestigious SCCA Runoffs by hard work, good understanding of the car, and good procedures to get the set up right. He makes the trip to Road America and knows he has a shot to win this thing. But he knows there are some very good drivers from all over the U.S., and he thinks he needs something special to win. He finds a trick tire that he has never run but it is “worth 0.3 seconds”. The expert shock guy gave him the best Road America set up. The engine guy has the new development exhaust system. The result – the poor guy gets clobbered, not only by the out of division drivers, but also by the guys he beat all year, who now run away from him. Run what you know and tune it better than the next guy. Save the tricks for winter testing.
Changes – The secondary effects
In talking to engineers and drivers, I hear that they made a change and it did not help or did something completely different than they expected. Most of the time, the reason is what I call the secondary effect of a change.
Most racers have a good idea of what a change will do to the car, or at least they know what they want it to do. The problem is that seldom does a change only do one thing to the performance of the car. Each change has a primary effect and a secondary effect. There are third and fourth effects I am sure, but I am just barely smart enough to figure out the second effect.
If you are trying to decide between a few changes to improve something in the balance of the car, make a list of the three or four possible changes and what you expect each to do. For example, assume we have an understeer from the apex to the exit. We could change:
1 – More front wing
2 – More rake
3 – Stiffer rear springs
4 – More front rebound
There may be fifteen other things you could do, but list the top contenders. Now, list what you think the secondary effect of each might be:
1 – More front wing – oversteer in high speed turns
2 – More rake – nervous rear in high speed turns
3 – Stiffer rear springs – worse power down traction
4 – More front rebound – harsher in the bumps
Look at the list and try to find a change that has a primary effect and secondary effect that are in the same direction. Also, consider what other problems the driver may be having, which we’ll call the secondary complaint. In our example, if the high speed turns were good or bordering on oversteer, then we can eliminate the wing and rake. The stiffer rear springs will keep the dynamic rake in the car (primary effect) and free the car up on exit, while with less power down traction (secondary effect). Everything works in the direction we want.
What we want to avoid is a change with the primary effect opposite from the secondary effect. Often, this results in the driver comment of “can’t really tell much difference.” When a change has an unexpected result, you should look at the secondary effect. Sometimes, what you thought was the secondary effect was really the primary effect, and it was in the opposite direction.
Keeping track of all these effects and changes can get very confusing. The problem is that the effect of a change on a FF-1600 is very likely to be different from the same change on a Formula Atlantic car.
The change data base
There is a way to help sort the changes and what they did to your car. It helps you learn the car and can be a great tool to suggest changes that you know the result of like we talked about earlier.
One year at the test days for the Daytona 24 Hour, I was done with a session and walked past the factory Nissan NISMO team from Japan. In their pit were four racks of computers and more electronics than a modern day F1 team has. I watched for a while, as the Group C Nissan went around and around. There were only two guys manning the computer banks, so I walked up and asked what they were logging. The answer was that they were logging over 200 channels of data. I tried to think of 200 channels I would want to have logged. I got to about 30 and had to ask “what are you guys logging?” The Japanese engineer said “mostly engine parameters”. He said the engine block had twenty strain gauges cast into the block to measure stress in various sections of the block.
I thought that was very cool, but wanted to know what they were going to do with the data. The engineer said that, sometime in the future, a Nissan engineer was going to want to know what the stress was in an engine block. When that happened, the data would be there. He said that the cost of running a race car was so high, that collecting data while it was running reduced the cost of gaining that information later, when someone needed it. That impressed me with the long term thinking to collect data. Collect the data when you can, sort it out when you have time.
Any race team can do the same thing, on a smaller scale. Using a spread sheet, make a matrix with each column being a parameter in your setup. Include columns for driver comment, change, and result of the change. Each row will be a track outing. Start to log the result of each change you make to your car. In short order, you will have a history of each change made to your car.
Using the data sort function of the spread sheet, you can sort the data. For example, you can show every time you had exit understeer. Then, look at what you changed when you had that problem and what the result was. This will prevent you from making the same set up mistake twice. And, it will tell you what things have worked to correct an exit understeer in the past. It will keep you in the window of your knowledge. When testing, look at the data base and try some things that you have not tried before. This expands your understanding of the car and makes your data base more helpful at the track.
Using a data base program, like Access, takes it to the next level with tables, forms, and special queries to make the search results more meaningful and detailed. If you spend some time (it took me about 30 hours and I am NOT an Access expert), you can answer more questions. You can ask the database to show what we changed to reduce a mid corner oversteer in a third gear turn when we had tire pressures above 15 psi and a rear wing setting below 10 degrees.
Remember, the sooner you start collecting the data, the cheaper every mile you do becomes, because you are getting more value for your dollar. I can say that this has helped me a bunch over the years. My Daytona Prototype data base has over 900 changes logged in it. It just makes me a better guesser.
So, to recap…
1 – The driver is in charge of his setup. The engineer just makes the change he thinks will help him the most.
2 – Resist making changes until the driver really has a good feel for the car. It has to “talk to him” first.
3 – Physics does not change when you cross state lines. Go with what you know.
4 – The secondary effect of a change can be in the opposite of the primary effect. Never make a change without considering the secondary effect.
5 – Use a data base to increase your understanding of your car quicker and with more accuracy.
6 – If a change does not have the effect you thought it would, than you are missing some effect that you did not consider. There is not some weird phenomenon going on, you just don’t understand the circumstances of the particular situation.
7 – When in doubt, go back to your base setup and start over from there.
8 – Never copy another faster team’s setup. You need to know why yours does not work, so you can be better next time.
9 - If a change works the way you thought it would, you did not learn anything. You did become faster, which is always a good thing. But, when the change does not work as planned, you have a great chance to become smarter. Grab on to that and figure it out.
10 – When recording changes in your notes, write down why you made that change, your thinking on what you expect it to do, and why. Then, you can go back later and see what your thinking was for making that change and decide where your thinking was wrong. This may happen months later, as you get to know the car better, but it allows you to see where your mistake was, not just that it was a mistake.
OK, one more thing.
My friend, the driver/engineer mentor of mine, wrote these points down once about problem solving. Think about them. It may change your approach to finding the perfect set up.
1 – What’s right is right and everything else is wrong to some degree.
2 – What is REALLY happening here?
3 – Nothing happens for no reason.
4 – Everything is attributable.
5 – If X is true then Y must also be true. If I can’t prove that Y actually does as I predict, then I don’t know anything at all about X.
6 – What I am certain is correct can change instantly in the light of what is REALLY correct, whether I like it or not.
7 – Just because I don’t want to believe it, doesn’t make it wrong.
7a – Just because I want to believe it doesn’t make it right, either.
8 – Knowing what is wrong is every bit as important as knowing what is right.
9 – If it isn’t all the things you think it is, then it is something else. (Sherlock Holmes)
10 – You only know something if you can prove it. Everything else is “I suspect” or “I guess” or “I wonder if” or “it is my theory that...”
11 – The right answer is still the right answer even if you didn’t think of it.
12 – The right answer is still the right answer even if you don’t have any idea of why it works... but find out later for sure, because the underlying principles will always apply.
13 – Asking other people for answers is perfectly acceptable, as long as you never believe them.
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