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

[ekim952522000]

So Lapsim seems to indicate the higher the weight, horsepower, and grip get, the larger the percent of weight that needs to come off in order to balance FWD and RWD.

<----Why do I have a FWD car again......

[jjjanos]

...but it seems to me it's boiling down to somewhere between 50lbs and 100lbs difference in the FWD subtractor.

Which, may I remind everyone means that the weights should not be adjusted as their current weights are within where "the process (next generation)" would place them.

Is it not at least defacto, if not dejure, ITAC policy to deny requests to adjust weight when the current weight is within that margin of error?

Now, I'm in the use the process weight camp, not the use the process weight +/- error factor camp, but it seems to me a but odd to muck about with the model when delta is within the margin of error.

[esuvee]

I have to respectfully disagree Alex while I do not expect a guarantee of competitiveness. I do appreciate that the ITAC is willing to try to get as close as possible. I accept at some point "it is, what it is" I just don't think we are quite there yet, close but not quite.

By "gaming the system" do you mean making it so FWD cars can race with RWD cars? Isn't that the whole point of the process to "try" to get things close? Otherwise you could say we are "gaming the system" by making it so a 180HP car can race with a 160HP car.

By gaming the system I am talking about making 200+ pound weight adjustments for one factor. If a car needs that much taken off maybe it's not in the right class in the first place?

Alex

[esuvee]

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.

I can see how it's counterintuitive but it makes sense to me, kind of like being able to increase rear brake bias in the rain. Less grip = less weight transfer = more weight on drive wheels for FWD.

As for LapSim, my CRX model is within 0.5s of ITA pole times at the few tracks available that we run. It's a pretty impressive program for exactly what is being done here, one big, fundamental variable change. I think the key is validating each normal model with track times before 'converting' to other-wheel drive. Again, if you want a new modifier

Alex

[dickita15]

.

<----Why do I have a FWD car again......

Why do you hate the handicapped, Dick? We're not a different race, Dick, we're "special".

GA

[Knestis]

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

That result actually doesn't surprise me. If our theoretical starting point - that RWD platforms are inherently more efficient at turning other factors into velocity - then RWD will realize greater advantages as those factors increase in magnitude.

Picture an FWD F1 car. Hard, huh?

K

[Ron Earp]

So what is the conclusion? Since ITS/ITR figures in this discussion prominently, what will be the weight of an ITS Integra GSR now?

[Jeremy Billiel]

So what is the conclusion? Since ITS/ITR figures in this discussion prominently, what will be the weight of an ITS Integra GSR now?

#2250 lbs

[Andy Bettencourt]

So what is the conclusion? Since ITS/ITR figures in this discussion prominently, what will be the weight of an ITS Integra GSR now?

If we go to -150, the weight won't change as I demonstrated earlier. Other ITS FWDers may lose 50lbs depending on the caluculations.

[Ron Earp]

If we go to -150, the weight won't change as I demonstrated earlier. Other ITS FWDers may lose 50lbs depending on the caluculations.

Whoa, I looked more than two pages back and didn't see it but I'm assuming from memory that:

*The car already got the 100# drop for FWD
*It didn't get the 50# adder for double A arm

Thus the adder and the additional 50lbs for FWD (100# already, change to 150#) net to nothing for the car.

If 200lbs were used I'd assume the ITS Integra would lose 50#?

Just wondering. Cars are fast as is here in the SE and interested to see how much they might improve.

R

[Jeremy Billiel]

Whoa, I looked more than two pages back and didn't see it but I'm assuming from memory that:

*The car already got the 100# drop for FWD
*It didn't get the 50# adder for double A arm

Thus the adder and the additional 50lbs for FWD (100# already, change to 150#) net to nothing for the car.

If 200lbs were used I'd assume the ITS Integra would lose 50#?

Just wondering. Cars are fast as is here in the SE and interested to see how much they might improve.

R

Ron you are correct. *IF* all of a sudden there was a ground swell of approval for such a measure and the break was 200 lbs instead of 150 the car will be 50 lbs lighter, which you really should not worry about.

[lateapex911]

Sez the guy who's not driving the old rusty drum braked Z car, LOL.

(Just pushing yer buttons there Jeremy, Joe's been quiet lately, so somebody's got to keep you in line!)

[Ron Earp]

Ron you are correct. *IF* all of a sudden there was a ground swell of approval for such a measure and the break was 200 lbs instead of 150 the car will be 50 lbs lighter, which you really should not worry about.

I agree with you, 50 lbs won't make a class killer. I was worried that 150lbs to 200lbs would be lobbed off the car as is and that would be a problem.

Standing offer to all you "spoiled" new car drivers - any test day I'm at the track you are welcome to have a few laps in the Z. Then you'll get to learn what a braking disadvantage is all about after 4-5 hot laps...

[Andy Bettencourt]

The grass is always greener Ron! Might not be a great idea to complain about the warts on your (the collective your) car until you see how ugly some of the others are!

[Jeremy Billiel]

The grass is always greener Ron! Might not be a great idea to complain about the warts on your (the collective your) car until you see how ugly some of the others are!

LOL.... Back at you Ron.

Standing offer to all you rear-wheel-drivers: any test we're at you are welcome to have a few laps in the Integra. Then you'll get to learn what trying to put all your power, steering, AND braking into only half of your tire patches - coupled to really, really bad weight balance - is all about after 4-5 hot laps...

[Jeremy Billiel]

Remember the order of importance.

1. Engine output (HP/Tq)
2. FWD/RWD configuration

All other crap goes significantly below the line if you will.

[Ron Earp]

Remember the order of importance.

1. Engine output (HP/Tq)
2. FWD/RWD configuration

All other crap goes significantly below the line if you will.

Some might disagree and I will for my particular situation as it stands. I'd take 15 less horsepower (putting my wheel hp less than an Integra or any other ITS car for that matter) to have some modern brakes like an Integra or other non-dinosaur ITS cars. While I don't think races are won in the braking zone, they can be lost. Toward the mid-part of the race when you've had to come off your braking zones 200, 300, 400 ft you tend to give up corners from time to time. Sometimes you have an agroculturial excursion. But it is part of "run what you brung", no need to bitch about it.

Let's swap up some cars. Educate your FWD/RWD buddy, just keep the shiny side up. I'd like to learn about these FWD cars.

[Knestis]

Back to the top!

You won't see this in Fastrack because it's not a rule change as such, but you'll probably be interested to hear that the ITAC has adopted a new approach to the FWD "subtractor" question. Instead of subtracting big chunks (defined for each class), we will now deduct a percentage of each FWD car's "base weight." Percentages to be applied are...

C - 0%
B - 2%
A - 2%
S - 5.5%
R - 6%

These percentages were established using an average "IT preparation" HP figure and weight multiplier for each class, to define imaginary "average cars." We then used LapSim to model the differences between front- and rear-wheel drive versions of each of these mythical beasts, and to derive weights required to account for those differences - 175, 150, 50, 50, 0; from R to C. That weight, as a percentage of the "average car's" weight, established the percentages you see above.

Again - this subtractor will be applied to the base weight, defined by the stock power, IT power factor, and class multiplier.

There are a few big assumptions buried in here, of course (e.g., that the effect of mass on performance is linear), any of which may be debatable, but we had to make them in order to move forward. This solution isn't "angels dancing on the head of a pin," nor is it "we can't be perfect so let's not do anything." It's better than what we've had in the past even if it's not perfect, and the ITAC thinks it strikes a good balance.

This does away with the trap we were in, where cars were treated inequitably by the subtractor, depending on their weight (and power). Depending on the luck of the draw, some cars will net out heavier under the new regime, and some lighter. (So the degree to which you individually think this change is a good idea might also be influenced by that same luck!) Regardless, it is repeatable and has a greater degree of granularity, and it takes subjectivity out of the process for yet another step - in this case, the subjectivity of the amount subtracted.

FINALLY, the question of whether/how this new step will get applied to EXISTING listings is still an unknown. We started using it during last night's call for NEW listings and will continue to do so. It will also get applied to any "please review" cases we have on our current agenda. What happens after that is not yet decided (e.g., another Great Realignment) and is the topic of ongoing discussion.

So there you go. We figured that we kind of owed you all some news about a step forward - particularly those of you being patient about requests that are tabled pending clarification of our internal processes...

K

[shwah]

Interesting. Thanks for sharing.

It wasn't clear to me though. Do you apply the % adjustment to the 'process weight' of the car, or use the weights you show above based on class average? I think the former, but maybe I missed it.

Was this used to derrive my 10?

[jimmyc]

So Lapsim seems to indicate the higher the weight, horsepower, and grip get, the larger the percent of weight that needs to come off in order to balance FWD and RWD.

<----Why do I have a FWD car again......

Because even at it's current weight, i bet that sucker will do a 2:00:xx at T-hill USING the crows nest!!!! ITR has a lot of growing room!!

After seeing what a ITR ITR can do on toyo's and 7 inch rims...