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

[ekim952522000]

We DO add for torque in some cases. 100lbs right onto the min weight to those V8's in the proposal. What we don't do is have a formulamatic part of the equation for it.

Correct and (correct me if I am wrong) some cars recieve a 50lb add and some a 100lb add. This is the same thing we are talking about doing for FWD cars here. If it is a low powered FWD car it gets - 50 a very high powered FWD car -100. A really high powered one -150.

Is there a difference?

<----Mke who is very impressed that this conversation is remaining so on topic and focused, It does show how many people care about the category and that's a good thing no matter which side of the FWD line your on.

[JeffYoung]

Fair question/point.

For me, torque is a part of the power/weight process that is missed and must be accounted for to complete the one basic calculation we have to perform.

Plus, my car gets a torque adder, and it has to in order to account for its oddball motor. I simply think it fair we leave the torque modifier in to account for odd low hp/high torque motors like mine, the GM 3.8s, the AMC 4.2s (and yes there is at least one running in ITA, the 325e (a potential class killer in ITA) and the V8s in ITR.

I also agree this has been a great, mostly civil discussion. Appreciated all around.

Bold = changed by me


Jeff do you see how the same argument can be made for not factoring in torque that you are using for not factoring in FWD? How is a Torque adder any different than a FWD subtractor?

[Chip42]

Jeff - you know the process better than me, but doesn't your car get a stick axle adder, a drum brake adder, and a strut adder (all negative) and a torque adder (positive), too?

torque is an advantage. yes, when misused it can roast the tires and/or cause dents. when used well, it helps win races. it deserves an adder.

the rest are disadvantages - they deserve the negatives weights. as does FWD. are those adders adequate? I don't know. throw the argument out there. these are all characteristics that, like FWD, can be simplified to "yes" or "no" without going into make/model. FWIW, I think that solid disks deserves a negative adder, too, if it is not in play.

Also (not related to anything in "the shape of things that break") we have to stay focused on the reality of the fact that the weights of (mostly) the smaller (higher specific output) cars being classified (ITR in particular) are often impossibly light (or unwisely light given the 1.5+ ton "tanks" on course and the safety skimping that will undoubtedly accompany a full-on lightweight build). Newer cars weigh a lot. why make a rule that no one can use?

how about a new Power/weight multiplier, at least in ITR (less established, less people to upset) that might allow for the adders to take effect (in real cars, not on paper) and THEN see if they are adequate. until they are achievable, there's little sense in arguing about it.

[JeffYoung]

Chip, not at all. I get no deductions for live rear, or crap brakes, or for mac strut vs. double wishbones. I do get and should get a torque adder.

Well, step back. My car has actually not been through the process. If you run it at any normal IT power gain it comes out ridiculously low due to its low stock hp. But if you run it through wtih teh standard adders/deductors, you would just get one torque adder.

We don't do anything for live rear cars (nor do I think we should), or BAD brakes (just good ones), or for mac strut cars in ITS (that I am aware of).

Chip, we did know when creating ITR that some of the tweener cars were going to be at weights that were difficult to achieve. There will always be tweeners, that fall in the too heavy in the lower class, too light in the higher one, that are just hard to deal with. The Celica GTS certainly is one in R -- it could be an S car, but the weight it would require would probably make it entirely unattractive there as well.

[Ron Earp]

Jeff - you know the process better than me, but doesn't your car get a stick axle adder, a drum brake adder, and a strut adder (all negative) and a torque adder (positive), too?

No, it doesn't. The point is if someone wants to argue for a FWD break couldn't a racer argue for breaks for these attributes as well?

[Andy Bettencourt]

At SOME point, IT is just gonna have to be 'what it is'. And currently, many think its the best ruleset in the SCCA.

Finding that 'is what it is' point is tough. Everyone has a different view of where it should be.

[Chip42]

Jeff- out of curiosity, what would the TR8 weight be "by the process". note that I am in no way trying to assail the car or you - I have nothing but high regards for you from the limited face time I have had and I would love to see the '8 do well. I have no vested interest in ITS at all, at most a friendship with Scott Seck, but he holds his own quite nicely, thank you.

ron - I thought that these were active adders. been wrong before, sure it will happen again. my experiences are building FWD ITA and prod cars and MR2s and inspecting, not so much driving and rules making.

but I would think, in the spirit of this discussion, that race-length detriments over "normal" equipment (drums, solid disks, stick axle as it induces odd tire wear,...) should be considered, either way. FWD is just another one to add to the list (albeit a big nasty one)

[Ron Earp]

No ITR 944S2 on pg 344? I must have written my own GCR then.

I was following the discussion about weight and HP and their effect on differences in laptimes of FWD and RWD cars across all IT classes. I also had two convenient models already on my machine.

Alex

Sorry, forgot about that and I actually owned one up until Dec 2008. Was thinking too much about ITS/ITA and the discussion at hand.

Anyhow, I understand what you're saying about the models but comparing an ITA FWD car with an ITR RWD car isn't going to clearly define how much weight, or an approximate weight, should be on the cars to equalize them with a 100hp difference.

Ron

[Ron Earp]

At SOME point, IT is just gonna have to be 'what it is'. And currently, many think its the best ruleset in the SCCA.

Amen.

[Andy Bettencourt]

You for sure want to compare cars from the same class....

[JeffYoung]

Chip, absolutely no offense at all. Ask any and all questions, please -- I'm serous about that. And yes, Scott is damn fast in his car, I finally saw it at Daytona (although the clutch exploded I think) and that is one nice GSR.

Process weight on my car would be:

133 stock hp * 1.35 (highest present IT power modifier) * 12.9 + 50 for torque = 2366, or TWO HUNDRED pounds less than what it is now. I could probably get the car down to 2500 if I had too, but even that weight is too low and, honestly, if the FI motor makes what we think it might then the 35% gain is too low as well. We'll see.

Also, the adders are far simpler than you think. I don't have the specifics right in front of me, but it basically is and adder for torque, an adder for double wishbone (I personally think we need to do away with that) and an adder for brakes (same).

Jeff- out of curiosity, what would the TR8 weight be "by the process". note that I am in no way trying to assail the car or you - I have nothing but high regards for you from the limited face time I have had and I would love to see the '8 do well. I have no vested interest in ITS at all, at most a friendship with Scott Seck, but he holds his own quite nicely, thank you.

ron - I thought that these were active adders. been wrong before, sure it will happen again. my experiences are building FWD ITA and prod cars and MR2s and inspecting, not so much driving and rules making.

but I would think, in the spirit of this discussion, that race-length detriments over "normal" equipment (drums, solid disks, stick axle as it induces odd tire wear,...) should be considered, either way. FWD is just another one to add to the list (albeit a big nasty one)

[JeffYoung]

That is where I am headed.

Stock hp * 1.25 in almost every case with a torque adder, and that is IT. Nothing else. No suspension modifiers. No brake modifiers. No live rear axle modifiers. No aero modifiers. No wheelbase modifiers. Nothing.

I accept Greg's position that FWD is a disadvantage. But I don't see anyway to quantify "how bad it is" versus other disadvantages we don't and have no intention of quantifying.

And this is IT. No guarantee of competitiveness. Build your car, and man up and drive it (and its disadvantages). Most of us do that anyway.

BUT THAT'S WHAT WE'RE TRYING TO AVOID: Making judgments by our guts, pulling numbers out of our butts. That said, I'd endorse your idea of doing away with variables if that's what it took to get consensus around a repeatable, transparent process that considers physical attributes of the car and doesn't allow for butt-number-pulling.

K

[esuvee]

... but comparing an ITA FWD car with an ITR RWD car isn't going to clearly define how much weight, or an approximate weight, should be on the cars to equalize them with a 100hp difference.

Ron

That's not at all what I was doing, I was 'creating' a FWD 944 and comparing it to an as produced RWD 944. Same with the CRX, I took my model of my CRX and 'created ' a RWD CRX. The reason for the two cars was to reinforce that power is a big deal in this equation. I should have included a table:

ITR 944 RWD - 2:01.75
ITR 944 FWD - 2:03.48
ITR 944 FWD minus 250lbs - 2:01.83

ITA CRX FWD - 2:07.9
ITA CRX RWD - 2:07.0
ITA CRX FWD minus 115lbs - 2:06.98

The only difference between my anecdotal examples and Mike's work are that I changed many factors on the 'created' cars that a racer would change to 'optimize' a FWD or RWD car to get an accurate idea of what part of the FWD disadvantage can be made up with suspension tuning.

His table is perfect for comparing trends of weight and power, I am trying to find anecdotal examples of what weights might work. None of this will result in a perfect equation, just more info for everyone.

Alex

[ekim952522000]

Nice job Alex I have a new table that turned out very odd. I left everything the same but started with more of a FWD biased setup last time was more a RWD biased setup and used a 65% bias instead of a 60% and the results were quite different almost linear. The 65% front bias made the changes in lap time much less dramatic then the last table.

I also ran a 200hp FWD car with all different weight Bias to see how lap times were effected.

Here are the results. The only thing I have left to do is to see how much weight I have to subtract from each line in order to get the times to match.

[ekim952522000]

That is where I am headed.

Stock hp * 1.25 in almost every case with a torque adder, and that is IT. Nothing else. No suspension modifiers. No brake modifiers. No live rear axle modifiers. No aero modifiers. No wheelbase modifiers. Nothing.

I accept Greg's position that FWD is a disadvantage. But I don't see anyway to quantify "how bad it is" versus other disadvantages we don't and have no intention of quantifying.

And this is IT. No guarantee of competitiveness. Build your car, and man up and drive it (and its disadvantages). Most of us do that anyway.

Why'll that does not "sound" bad I think it would make people very unlikely to race FWD in anything above ITA.

Jeff I still don't agree with your logic you said "....I don't see anyway to quantify "how bad it is" versus other disadvantages.....How do you quantify the torque adder than?

I could accept your logic if you said IT should be stock hp * 1.25 and that's it. But then you throw in the torque thing...

[shwah]

At SOME point, IT is just gonna have to be 'what it is'. And currently, many think its the best ruleset in the SCCA.

Quoted for super extra maxi truth.

[JeffYoung]

I'd take the torque out too, but it would be a "me" request because it would help my car, so I don't think it right for me to bring it up.

Why'll that does not "sound" bad I think it would make people very unlikely to race FWD in anything above ITA.

Jeff I still don't agree with your logic you said "....I don't see anyway to quantify "how bad it is" versus other disadvantages.....How do you quantify the torque adder than?

I could accept your logic if you said IT should be stock hp * 1.25 and that's it. But then you throw in the torque thing...

[Jeremy Billiel]

Jeremy and Greg can give the details but I think they ran this year with just bolt-ons and an ECU. I think they wanted to do the suspension and then evaluate. Seems as if another thread had that car at around 180whp with all the balls and whistles. Probably 128-130ft/lbs of wheel toque max though.

The TYPE of 944 has to be defined...a regular 944 8V should be about 152whp. The CRX is about 130whp.

The Integra will hit IMO the 25% adder. There will be zero torque, but with a LOT of money you can build a 25% capable GSR motor.

[Ron Earp]

Nice job Alex I have a new table that turned out very odd. I left everything the same but started with more of a FWD biased setup last time was more a RWD biased setup and used a 65% bias instead of a 60% and the results were quite different almost linear. The 65% front bias made the changes in lap time much less dramatic then the last table.

I also ran a 200hp FWD car with all different weight Bias to see how lap times were effected.

Interesting results. Seems to suggest that the times are more dependent on weight distribution than anything else. Also it appears the time difference between the two cars in relation to horsepower doesn't increase as much as it was expected. But, it is just a simulation.

In my opinion this thread has brought up some concerns in our classification process. Certainly one that stands out to me is why single out FWD as the factor that must be corrected for when there are clearly other factors that one could choose - brakes, weight dist, suspension, driveline, etc.

As Andy and Jeff have both stated in various ways, IT isn't broken. Far from it. Maybe it is best to deal with it as is and make the best of it. I do hope that if the ITAC considers the FWD adder that they will bear in mind that IT works pretty well.

[Greg Amy]

...why single out FWD as the factor that must be corrected for when there are clearly other factors that one could choose - brakes, weight dist, suspension, driveline, etc.

Because next to engine output and weight, driveline layout is the most important factor in predicting performance (which is exactly what you're doing with the classification process). Though all this extra non-related stuff is muddying the waters, this fact remains apparent to anyone that understands front wheel drive cars.

I ain't sayin' that suspensions, brakes, axles, ad nausea don't make a difference; of course they do. But they don't make anywhere near the difference that ponies, weight, and the driving end does. I'd take a drum/strut/live axle RWD car long before I'd take a disc/multi-link/IRS FWD car, given equal engine output and weight. And you would, too, I bet.

Bottom line, treating drive layout with the same significance any of these other characteristics illustrates a basic misunderstanding of the vehicles' dynamics.

That's all I'm tryin' to say.

GA