Hey guys,

This post is directed at those that track their cars often and have made a couple of changes to the car, and noted the difference, if any.

As I posted in the "another physics question" thread, I am building a decision model to aid in picking the optimal modifcation set, given a certain budget. It uses Microsoft Solver. The objective function is to minimize lap time. In other words, modifications are decided upon based on their effect on laptime as a function of cost.

Three of my decision variables that effect laptime are:

1) Required lbs lost to drop 1 second of laptime.
2) Required HP gain to drop 1 second of laptime.
3) Required lbs of downforce to drop 1 second of laptime.

Clearly, what track you are minimizing laptime on, is important. That is why the three above are variables and not constants.

Here is a recommended format for your reply.

BWR S/C +53 hp, 1 second gain at Leguna Seca
CF Diffuser, -10lbs weight, +5lbs downforce, 8 tenths at Sebring

anything helps.

BTW, the numbers I am using now are 100 lbs/sec weight, 15hp/sec, 20lbs/sec downforce

Sounds like an interesting project; I've written software models for other fields, never for a car. Actually started in HS writing a mathematical model for the performance envelope of an F-14.

Which brings me to a question: are you adding in the effect of increased aero drag with the increased aero downforce? Also, are you taking into consideration that aero lift/drag has a square law relationship with speed?

 

While you are correct with those effects, I am not considering those directly, but accounting for them indirectly.

Specifically, I am asking for lbs of DF and how many seconds of gain. That would take into account the drag effect on top speed as speed is a function of time and distance. I get the distance from the track name, and the time from the poster. Hopefully,

 

Hey guys,

This post is directed at those that track their cars often and have made a couple of changes to the car, and noted the difference, if any.

As I posted in the "another physics question" thread, I am building a decision model to aid in picking the optimal modifcation set, given a certain budget. It uses Microsoft Solver. The objective function is to minimize lap time. In other words, modifications are decided upon based on their effect on laptime as a function of cost.

Three of my decision variables that effect laptime are:

1) Required lbs lost to drop 1 second of laptime.
2) Required HP gain to drop 1 second of laptime.
3) Required lbs of downforce to drop 1 second of laptime.

Clearly, what track you are minimizing laptime on, is important. That is why the three above are variables and not constants.

Here is a recommended format for your reply.

BWR S/C +53 hp, 1 second gain at Leguna Seca
CF Diffuser, -10lbs weight, +5lbs downforce, 8 tenths at Sebring

anything helps.

BTW, the numbers I am using now are 100 lbs/sec weight, 15hp/sec, 20lbs/sec downforce

One variable you've not listed is "driver experience" - perhaps intentionally, or not? If you consider youself an expert driver, and have little new to learn, great, this experiment makes sense, but if you are new to road course driving, your best bang for the buck in terms of reducing your laptime is driver training/experience.... just my $0.02...

R Warden

 

Unless any of the answers have the condition that the driver is a professional (as in good enough to get paid for his driving and opinion) then the answers are pretty meaningless in any scientific sense - the drivers own learning curve, conditions on the day and lack of consistency / clean data or even reliable data acquisition / laptiming would render the answer akin to butt-dyno stuff at best.

In any case, even with perfect driver etc. the answers to your questions would vary very widely from track to track and day to day e.g. a tight, twisty, slow track would have a very different answer to the lbs or hp per second answer than an oval with an infield. Ditto for a hot day, cold day, damp day etc.

With the greatest respect, this isn't a serious exercise!

All that said, with the goal of at least being a bit helpful, have you checked out the (free) Bosch Lapsim also discussed here RaceSim Central

 

Another factor is the condition of the track. How "green" is it. What's the ambient temperature? On a track day with optimum weather, you'll often see track records get broken by almost 2 seconds in many "stock" classes.

 

Bleu

My apologies - I didn't mean to be quite so negative. But I am serious that the biggest single difference one track event to the other, is likely to be the driver, so - I didn't miss the point - I do not believe you will get data that is meaningful for YOU.

I'd also be suspect of your model / assumptions: by way of example - in your OP you stated that 10lbs of downforce = 1 sec. Can I tell you what 10lbs of downforce equals. No .... but I can tell you that an Exige with 100lbs of downforce is not even close to being 5 seconds faster than an Elise, all else equal. I wish

If your goal is to decide an upgrade path .... that is relatively simple - and I would suggest should be based more around what is holding you back or frustrating you as a driver instead of laptimes, although there is some correlation between the two.

For my money, as you get more skilled, then you'll probably want to upgrade to Track Pads, then upgrade the Suspension, then run Hoosiers: in that order. Or maybe not - maybe you will be happy with stock suspension but the tracks you run or your technique are hard on brakes - YMMV. My point being YOUR Mileage May Vary. Someone else's experience may be very different. Summary - I think, once you have done a few track days, the upgrade will be pretty obvious to you and for only YOU. Advice is all good, but I think you will know what your "weakest link in the chain" is pretty quickly and without the advanced modelling. Of course ...... taking my own advice, YMMV

 

Bleu

My apologies - I didn't mean to be quite so negative. But I am serious that the biggest single difference one track event to the other, is likely to be the driver, so - I didn't miss the point - I do not believe you will get data that is meaningful for YOU.

I'd also be suspect of your model / assumptions: by way of example - in your OP you stated that 10lbs of downforce = 1 sec. Can I tell you what 10lbs of downforce equals. No .... but I can tell you that an Exige with 100lbs of downforce is not even close to being 5 seconds faster than an Elise, all else equal. I wish

If your goal is to decide an upgrade path .... that is relatively simple - and I would suggest should be based more around what is holding you back or frustrating you as a driver instead of laptimes, although there is some correlation between the two.

For my money, as you get more skilled, then you'll probably want to upgrade to Track Pads, then upgrade the Suspension, then run Hoosiers: in that order. Or maybe not - maybe you will be happy with stock suspension but the tracks you run or your technique are hard on brakes - YMMV. My point being YOUR Mileage May Vary. Someone else's experience may be very different. Summary - I think, once you have done a few track days, the upgrade will be pretty obvious to you and for only YOU. Advice is all good, but I think you will know what your "weakest link in the chain" is pretty quickly and without the advanced modelling. Of course ...... taking my own advice, YMMV

While I am certainly always learning, I am also well past "a few track days". I had 3 track days last week alone. My skill level is progressing on a pace that I like. The part you are missing is that I am asking for data points, not recommendations. There is no simulation involved here. Please don't confuse a decision model with a simulation model. Totally different animals and goals. My goal here is not to find the most laptime drop per dollar. That would be impossible and driver dependent IMO. Forgive me for being terse, I am only trying to be clear and I am not sure I can be more clear than the OP.

And to show that I am a nice guy, here is a dancing banana for you...:nanner2:

 

I think Loki "Alan" who has many track days on the same track
has gone from a stock Elise to shock upgrades to a wing and splitter and then a katana, he may be able to provide real data points.
He does not seem too active here so it may take a while for him to respond.

 

Badaraones, no weight change, no downforce change, 2 or 3 seconds at MSR-Cresson.

 

wait for it. Wait for it.

is there laughing yet?

Wait for it...

 

Not sure what the laughing is for, Christian finally gave you a serious answer instead of criticisizing the exercise. I'll kind of do both. I can't give you laptime improvement estimates because, as you know, that will vary heavily from track to track. I can tell you what I recommend for changes in priority order for going faster.

* Toe link brace
* Toyo RA1s or R888s
* Light 15/16 wheels with RA1s or R888s
* Brake pads
* 4 or 5 point harness
* Camera system
* Lap timer
* Ohlins or Nitron suspension
* Replace other stuff (like brake rotors) as they wear out

Things that we all have, and that don't make a bit of difference to lap times:
* Rorty exhaust
* Wings and splitters
* SS brake lines

 

Not sure what the laughing is for, Christian finally gave you a serious answer instead of criticisizing the exercise. I'll kind of do both.

While I have no idea who Christian is, I am sure that xtn's post above mine warrants some laughter.:shrug:

Thanks for your response though. You talk about safety gear which of course does not reduce lap times. I am after things that directly reduce lap times. The harness, HANS, suit, gloves, shoes, extinguisher, battery cut of, etc, are all beyond the scope. While I recognize safety gear is a necessary precondition to doing dangerous things, it is not the point of my solver to decide what safety gear provides the most safety for the dollar. That would be a different object function and one that would be based on user utility.

Thank you to everybody that has responded with data points. Most of them via PM, which is fine. Thank you!

For those interested in telling me this project is not a serious endeavor: If you don't have a data point to share, please go troll elsewhere. There are plenty of other threads you can pull off topic. Please let this one be.

 

I've been working on this for a while and should have some data soon.

I have so far got:

Driver rust removal (it's a while since I raced)
Instructor removal
Shim removal
AD07s to old R6s

All at the same track.

I should be running on Friday with Nitrons/corner weighting/alignment
Then next week with new R6s
Then - as soon as Charlie's mates pull their fingers out - I'll be SuperCharlied.

At some point I'll stick the roof on for a session.

I know the track pretty well and know that I'm a pretty consistent driver (typically running within half a second a lap each session).

So - watch this space.....

 

One comment. I would be willing to bet that going to a proper seat and a 6 point harness will be a significant improvement to your lap times.

Why? Because you will gain substantial finesse in all your pedal and hand inputs when you are no longer bracing yourself from being tossed around. Not to mention you'll "feel" what the car is doing MUCH better.

My belief is that 6 point and soft tires are the best bang for the buck by an order of magnitude that you can do for your car. Everything else will be very expensive and incremental. Horsepower is probably the biggest gain you can get and still drive the car on the streets (i.e., radical aero will make the car a trailer-only machine), but that just makes the straightaways shorter and the brakes work harder

Sorry for being slightly off kilter, but I really wanted to say that "safety" stuff has a lot of bonuses, especially when it comes to being planted in the car.

Steve

 

One comment. I would be willing to bet that going to a proper seat and a 6 point harness will be a significant improvement to your lap times.

Why? Because you will gain substantial finesse in all your pedal and hand inputs when you are no longer bracing yourself from being tossed around. Not to mention you'll "feel" what the car is doing MUCH better.

My belief is that 6 point and soft tires are the best bang for the buck by an order of magnitude that you can do for your car. Everything else will be very expensive and incremental. Horsepower is probably the biggest gain you can get and still drive the car on the streets (i.e., radical aero will make the car a trailer-only machine), but that just makes the straightaways shorter and the brakes work harder

Sorry for being slightly off kilter, but I really wanted to say that "safety" stuff has a lot of bonuses, especially when it comes to being planted in the car.

Steve

Steve, I agree. When I installed my first Harness, I found a significant gain. if you have any inclination as to what type of gain you found, then I'd like to hear/read it. I certainly have tires in the mix. For cost, I am assuming a 5 year life. Essentially, I figure many parts (Harness, Helmet, Tires, brakes, engine mods) all have costs associated with them that go beyond the original purchase price, given they wear out or become outdated.

The more data points (and info on those data points) the more accurate my regression and subsequent correction factors can be. So any thing helps.

Thanks

 

there is no set formula, this is why testing is done ON THE TRACK.

 

Bringing things back on track...

I'll make one last ditch request at this point. I am seeking data on the following.

1. Modification to your own car
2. Track you tested it on
3. Gain you found

I'll use this data to set a few base variables in a decision tool I am nearly finished building. If you think it made you (your car) faster then it probably applies. If it will not stay with the car when the driver switches out, it probably does not apply. One way of looking at this, is if you bought a special seat it probably applies. If you had a seat poured for your personal rear end, and that resulted in gains beyond a bolt in seat, then that probably does not count.

Thanks guys:wave:

 

I'll make one last ditch request at this point. I am seeking data on the following.

1. Modification to your own car
2. Track you tested it on
3. Gain you found

I'll make one last ditch effort to give you a valid data point, and see if you laugh at it again.

1. Badaraones. (nickname for Toyo RA-1 tires)
2. Motorsport Ranch, Cresson, TX
3. From 2:40/2:41 down to 2:37/2:38, expressed this way so you can figure percentage benefit if you like. Sorry it's a range, but I'm a medium level DEer, not consistant enough to narrow the tires alone down to a specific milisecond.

Other regulars at this track, who have switched from Yoko A048 to these Badaraones, will likely go along with this assessment.

xtn

 

1 - harnesses
2 - front shim removal for max camber resulted in a car that feels much more neutral
3 - R888s knocked a couple seconds off

Harnesses. I know fast guys who don't have 'em but I can't figure out how they do it or stand it.

Shims are obvious once you've had the car on track with factory camber.

The Toyos are a mixed blessing - the car doesn't feel quite as sharp as it did on the Yokohamas but at the same or quicker pace, I don't spend near as much time in "recovery mode."

 

1 - harnesses
2 - front shim removal for max camber resulted in a car that feels much more neutral
3 - R888s knocked a couple seconds off

Harnesses. I know fast guys who don't have 'em but I can't figure out how they do it or stand it.

Shims are obvious once you've had the car on track with factory camber.

The Toyos are a mixed blessing - the car doesn't feel quite as sharp as it did on the Yokohamas but at the same or quicker pace, I don't spend near as much time in "recovery mode."

Thanks Cody!! Tire data is especially valuable.

 

Also, if anyone has had the same tire with different wheel widths (I know it's a stretch) that would be cool to. Also, different wheel diameters are nice.

 

I went from RA-1 to Hoosier R6 slicks.
Ran the same lap time at Homestead. I was too chicken to increase my corner
entry speed.

Not what your looking for, but all I got.

 

Bleu,
Great project--keep us informed of your learnings.
I don't think my improvements are valid because my driving isn't consistent enough. I know what I like, though.
Good luck!
Thanks,
Joe

 

I will keep you updated. I might post a working copy. It's functional but does not have all the data I want in it yet.

Then maybe a few people can join in. Assuming they understand how a solver model works, they would then be able to data info (like other mods) to the file. Right now, it has functionality to choose the mods in such a way to ensure you don't buy 2 brake kits for example. It also allows the user to choose whether or not the mods must be reversible. e.g. no drilling to install an aftermarket wing, etc.

 

fyi, I just posted my track day checklist in this thread: http://www.lotustalk.com/forums/f100/elise-exige-track-day-tech-checklist-46332/#post1002156

Those of you who are collecting data may find that it helps you create your own tuning checklists.

Thanks,

Joe