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

jimmyc said:
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...
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Come out to ITR and prove it! Color me very skeptical.

- Josh "still in the 2:05s in my ITR BMW" Sirota
 
Chris-

it goes like this:stock hp x IT factor x class factor = base weight
(Borgward Special: 160hp * 1.25 = 200 * 12.9 = 2580 base weight).
base weight * percentage = adder. (2580 x5.56% = 142.)
So the Borgward, barring any other adders would weigh 2438

other adders come off that number, or get added to that number.


Clearer?
 
Thanks Jake. It is applied as a % on the individual car's process weight (for all factors except driveline type). This is a good evolutionary step.
 
shwah said:
Thanks Jake. It is applied as a % on the individual car's process weight (for all factors except driveline type). This is a good evolutionary step.
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We think so. We like that it is based in real world science, and that it is more granular, and it is very repeatable.

It's taken some work, but these are the kinds of thing s we've been cooking. I consider it "The Process 2.0". It is attempting to fine tune what was already a good thing, remove either real subjectivity or the appearance of subjectivity, increase consistency, and make it more robust going forward.

More to come.
 
Knestis said:
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
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Thank you guys so much this is fantastic and I think will be really good for all us racers!

Just to make sure I have this right

ITR Prelude 190*1.25*11.25 = 2672 - 6% = 2512 correct?
 
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shwah said:
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?
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If I'm following the first question correctly, we are applying the percentage for each class to determine how much to take off of each FWD car run through the new(est) process. We used a class average IT HP as part of the process for figuring out what those percentages should be.

I'm not following the second question, I'm afraid.

K

EDIT - and I should add that some of you might see your influences in what we've decided to do. THANK YOU all for that.
 
JoshS said:
Actually we also agreed to give live-axle RWD cars in ITR a -50 as well. Only cars that qualify are the new pony cars.
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What about the existing V6 Mustang and Camaro? They are live axle cars already in ITR, have been from the beginning.
 
Ron Earp said:
What about the existing V6 Mustang and Camaro? They are live axle cars already in ITR, have been from the beginning.
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Good point. Thanks.

As Kirk mentioned earlier, it's still a topic of discussion about what to do about existing listings when the process changes (and these 'refinements' really are changes.) If we manage to reassign weights, we'll take the axle into account for those listings.
 
JoshS said:
Good point. Thanks.

As Kirk mentioned earlier, it's still a topic of discussion about what to do about existing listings when the process changes (and these 'refinements' really are changes.) If we manage to reassign weights, we'll take the axle into account for those listings.
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I think it is a good idea to hold off on any more re-classing until you guys have the whole thing hammered out since I know you guys have said there are a few more things you are trying to lock down, so future ITAC's will be able to follow exactly what you guys did.
 
I am pretty sure the GSR was run through the process and the subtractor was used in calculating its present weight (or at least -100 lbs, which isn't far off from what it would get using the new formula).
 
We go around and around about that, Mike - it's a real puzzle.

We decided to do a couple of new listings last night even though we are still working on a final aspect or two of the new system, but only after estimating that they would come out pretty much the same even if/when we change what we're looking at changing. On the other hand, we have a basketful of other reviews that we want to be sure we do with everything in place, because we think revised practices ARE likely to influence the outcome.

We feel like we can't simply stop doing our business just because we're working on HOW we do it, but it's a balance that we make decisions about.

K
 
Jeremy Billiel said:
Interesting the GSR would be the exact same weight before adders?
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There may be more surprises for GSR owners....if they are good boys and Santa is nice. ;)

Regarding cars "in the works", (that is, cars we have requests to reprocess) ...we've held back on those cars that have characteristics that might be affected by our refinements. Some cars however don't, and those we are trying to do.

And just to reiterate what Kirk mentioned. Some cars might not get what the owners feel they deserve, and others might get a tiny gift. None of this is F1 level science. We're not trying to balance every car in every class on the head of the pin. There will be winners and losers.

BUT, we're hoping the range between the winners and the losers is kept in check, and we want, more than anything, to be consistent.

We want you guys to have faith that your car got a fair shake, and it was the same shake as a car a year ago got, and one a year from now will get. There may be things intrinsic to certain models that result in better race cars, but we hope our system mitigates those to manageable levels.

On edit: Looks like Kirk has made my point redundant..he types faster!
 
lateapex911 said:
.........

BUT, we're hoping the range between the winners and the losers is kept in check, and we want, more than anything, to be consistent.
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I can only speak for myself but that one word means more to in regards to classing race cars than any other and it is what I want to see the most.

I also appreciate the ITAC letting us know this information I like to hear the updates of what's going on.
 
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