FWD vs RWD: Adders, Subtractors, and Weight, Oh my...!

[jlucas]

7pg write up so everyone can understand the differences between the free version and pro version of LapSim
http://www.tuev-sued.de/uploads/imag...van_rutten.pdf

It's a very capable program but understanding limitations & assumptions are important.
Also correlating with your DL1 data can help improve your results.

[chuck baader]

First: Jake = voice of reason...carry on......from: the silent majority

Second...If you are going to factor wheel sizes, you need to do that across the board. Some A cars run 14" by choice, some 15, etc. R and S are larger still while B and C have other options. My point is, I really don't think the process is broken. We have quite a bit of parity within the classes (A down) between several makes and without actual data on R and S, we are shooting in the dark. I understand your desire for an all inclusive formula with which to classify new cars but experience is the best teacher.

My suggestion is to classify the new FWD cars according to the formula and see where the limbs fall. If they are too far from the tree, adjust. Chuck

[Eagle7]

So I think something we need to do is choose a "bogey" for each class that would help give us data point targets.

I think we should use the Integra's for the bogey's for ITR - ITA. since that give us the least amount of variables.

ITR - Type R - 195hp*1.20=234

ITS - GSR - 170hp*1.25=212.5

ITA - LS/RS- 142hp*1.27=180.34


ITR - 234*11.25=2633-175=2483
ITS - 212.5*12.9=2741-150=2591
ITA - 180.34*14.5=2615-50=2565

I can't for the life of me find one formula to make that work I am trying to think of a way to factor in wheel width since I think that might be the key.

What I meant my lots of data points was several from each class - ideally ones at both ends of the extremes, as well as some from the center. Once we understand what the formula is supposed to spit out for each class, then we can try to find what the appropriate formula is.

The formula I've used to date simply has a slope and an offset. Wheel width could be used to modify either or both of the slope and offset.

However I think we're getting the cart before the horse. We need the set of data points before we even try to fit a formula to it. The data points have to be determined through some engineering work (like you've been doing) or by "what we know". The formula can help to smooth the data and make it more consistent, but can't be used to create the original data.

[Knestis]

Exactly. A 200 HP ITS car needs a different amount of weight subtracted than a 200 HP ITR car because the wheel widths are different. If we used a single formula for all classes it would need a factor for the wheel width. Whether the single formula is feasible or desirable is another matter.

That's not actually what I meant but on further consideration, ultimately, we don't really need to CARE about comparisons between classes, do we? All that matters is that the factors applied within each class shake out to make for a reasonably equitable situation. A single FWD factor formula might have different effects on different classes but does it matter?

K

[ekim952522000]

That's not actually what I meant but on further consideration, ultimately, we don't really need to CARE about comparisons between classes, do we? All that matters is that the factors applied within each class shake out to make for a reasonably equitable situation. A single FWD factor formula might have different effects on different classes but does it matter?

K

I think in order to get it right we are going to have to use a different number within one formula for each class the same way you guys use 12.9 for ITS and 11.25 for ITR.

[Knestis]

...If you are going to factor wheel sizes, you need to do that across the board. Some A cars run 4" by choice, some 15, etc. R and S are larger still while B and C have other options. ...

No way.

Tire diameter is WAY too small a contributing factor to get included in specification math. And as you point out, drivers can decide what they want to do. That puts tire diameter in a category more like that including spring rates or shock manufacturer.

We have quite a bit of parity within the classes (A down) between several makes and without actual data on R and S, we are shooting in the dark. I understand your desire for an all inclusive formula with which to classify new cars but experience is the best teacher. ...

I'm VERY leery of suggestions that we need "data" like you describe. I daresay you're talking about race results - right? And while I'm generally happy with the current state of the category, it's completely possible that the "parity" you see is an accident created by the competitive trajectories of the current cars and drivers in the category. Some are getting more developed, others increasingly neglected. Fast drivers are running out of money so scaling back, while others are deciding that this is the season they'll make a push.

We just can't count on results as an indicator that we've got the formulas "right."

K

[Knestis]

I think in order to get it right we are going to have to use a different number within one formula for each class the same way you guys use 12.9 for ITS and 11.25 for ITR.

Help me understand what you mean by "right...?" The different class multiplier just accommodates the fact that all cars, regardless of power, tend to be about the same size "box," so weigh similar amounts. Are you just talking about making the adjustment amounts commensurate with that reality (e.g., preventing the adjustments from making too big an impact)...?

K

[Andy Bettencourt]

I think in order to get it right we are going to have to use a different number within one formula for each class the same way you guys use 12.9 for ITS and 11.25 for ITR.

I agree. That is why I am still in line with the 5%, 2%, 5.2% etc that I came up with earlier.

[ekim952522000]

Help me understand what you mean by "right...?" The different class multiplier just accommodates the fact that all cars, regardless of power, tend to be about the same size "box," so weigh similar amounts. Are you just talking about making the adjustment amounts commensurate with that reality (e.g., preventing the adjustments from making too big an impact)...?

K

What I was trying to say was I think using a single formula for all classes would most likely end up too much weight coming off of A cars and not enough coming off of R cars. (rereading what I wrote can see how it did not make much sense)

[ekim952522000]

I agree. That is why I am still in line with the 5%, 2%, 5.2% etc that I came up with earlier.

I am also in agreement with those numbers Andy but feel like the adjusted pw/wt ratios are a slightly cleaner way to apply those percents. But is does not really matter you end up with the same numbers either way.

[Knestis]

What I was trying to say was I think using a single formula for all classes would most likely end up too much weight coming off of A cars and not enough coming off of R cars. (rereading what I wrote can see how it did not make much sense)

Okay - thanks. That's making sense for me now. I retract my earlier queston.

K

[lateapex911]

Yea, if we were to go with a single "all knowing" formula, it needs to be rather non linear for the reasons Mike points out. Complicating that is the non linear wheel width allowances. (Same for a couple classes, different for a few).

That's why I see the exercise as wiser to do class by class. Choose a mid point, then do the math with percentages.

I think my ITR numbers made sense, but I don't have the data I need to do ITS.

I'd REALLY like to figure out how to get LapSim to have a representative factor of our different wheel/tire widths injected to get a handle on the class to class interactions. While Kirk makes a good point that class to class isn't as important as we might at first assume, we need to remember that the classes are set up relative to each other.

If we can get lapSim to output reasonable numbers that help show the effects of increased traction available in the higher classes, we'd be further along in the setting of reasonable "bogeys"

Keep in mind that so far while it has been generating variables for differences in power, it has assumed grip to be the same, and it isn't in reality.

[Knestis]

Deal with grip using a tire factor...

Hoosiers = 1.0, full-tread Toyo RA1s = 0.4. Everything else is something in between. We can use mean qualifying lap times from races all across the country to come up with the numbers.

K

[Knestis]

Not.

K

[Andy Bettencourt]

Deal with grip using a tire factor...

Hoosiers = 1.0, full-tread Toyo RA1s = 0.4. Everything else is something in between. We can use mean qualifying lap times from races all across the country to come up with the numbers.

K

This HAS to be your first official drunk-post of 2009.

[lateapex911]

Nice AB, now get down here and clean off my screen! Maybe Kirks been reading the wine thread on RRAX.

[ekim952522000]

Deal with grip using a tire factor...

Hoosiers = 1.0, full-tread Toyo RA1s = 0.4. Everything else is something in between. We can use mean qualifying lap times from races all across the country to come up with the numbers.

K

LOL.

The trouble I am having trying to come up with a grip variable for each class is for example. Even though a 2250lb CRX has less tire than a RSX the RSX weighs in at 2640lbs and has worse suspension it is very possible the CRX has more grip.

[ekim952522000]

Nevermind see chart below.

Jake what numbers do you need for ITS I can look them up?

[ekim952522000]

Kirk I am really starting to see the problems with using "what we know" this simulation had the exact oppsite result of what I thought would happen.

I figured as grip increased given the same weight and HP that FWD would need less weight taken off but it needs more.

[Eagle7]

LOL.

The trouble I am having trying to come up with a grip variable for each class is for example. Even though a 2250lb CRX has less tire than a RSX the RSX weighs in at 2640lbs and has worse suspension it is very possible the CRX has more grip.

I know nothing about LapSim, but would assume for the same tire compound, that its grip factor is proportional to contact patch, and contact patch is essentially proportional to wheel width.