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

[ekim952522000]

OK I am getting ready to do some more simulations looks like I am goiong to go with RWD 50/50 - FWD 65/35 2500lbs 100-300 IT HP

Only variables will be FWD/RWD power and Weight balance. I will will see how much weight you have to take off each FWD model to make the lap time equal. Should have some interesting results.

Any other suggestions?

Last time I used a RWD car and made it FWD this time I will use the BTCC FWD model and make it RWD this should give the FWD car the biggest "advantage" for the purposes of this test.

EDIT: I will just be expanding on my original model the BTCC car is turning up similar results so I see no need to have to rerun all the simulations I already did.

[Ron Earp]

I used 130 for the CRX and 225 for the 944. The shapes of the curves are obviously different as well. It's a couple of cars I have a bit of info on and already had models for.

Alex

130 and 225??!

I think you have the 944 a over rated and the CRX under rated. There isn't a 100hp difference between these cars in IT trim.

Besides, we're talking about S cars and they will have similar hp levels. With Greg's ITS Integra and a good ITS build on brand X we're probably only talking about a 15hp difference if that. Greg and his boys don't build crap so I'm sure it has beans.

My 260Z makes about 168 rear wheel hp and some is on the table. I bet we can get it to hit 175 rear wheel hp at least, or about the same or more than a good 240Zs. I'd say I'm a committed IT racer who crosses ts and dots is on the engine. Isn't a well done Integra around 170 to 175 whp? I remember Ira telling me his was somewhere in the ballpark and it was knocking down some 2:16s at VIR, so he has some juice.

Ron

[dj10]

How about the Egg? Looking at some of the RWD'ers, I would say using 50-50 is fine. Cross weights are not relevent to the discussion - correct? Everyone should be able to achieve 50-50 cross weights - even though its not neccessarily the best thing.

AB, looks like those front drivers are going pretty well @ Daytona. How do they do it? There races are a lot longer than our's are.

Good job on qualifying btw, I'll be rooting for you......good luck tomorrow. Damn, I wished I was down there!:cool:

[Andy Bettencourt]

130 and 225??!

I think you have the 944 a over rated and the CRX under rated. There isn't a 100hp difference between these cars in IT trim.

Besides, we're talking about S cars and they will have similar hp levels. With Greg's ITS Integra and a good ITS build on brand X we're probably only talking about a 15hp difference if that. Greg and his boys don't build crap so I'm sure it has beans.

My 260Z makes about 168 rear wheel hp and some is on the table. I bet we can get it to hit 175 rear wheel hp at least, or about the same or more than a good 240Zs. I'd say I'm a committed IT racer who crosses ts and dots is on the engine. Isn't a well done Integra around 170 to 175 whp? I remember Ira telling me his was somewhere in the ballpark and it was knocking down some 2:16s at VIR, so he has some juice.

Ron

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.

[esuvee]

130 and 225??!

I think you have the 944 a over rated and the CRX under rated. There isn't a 100hp difference between these cars in IT trim.

Besides, we're talking about S cars and they will have similar hp levels. With Greg's ITS Integra and a good ITS build on brand X we're probably only talking about a 15hp difference if that. Greg and his boys don't build crap so I'm sure it has beans.

My 260Z makes about 168 rear wheel hp and some is on the table. I bet we can get it to hit 175 rear wheel hp at least, or about the same or more than a good 240Zs. I'd say I'm a committed IT racer who crosses ts and dots is on the engine. Isn't a well done Integra around 170 to 175 whp? I remember Ira telling me his was somewhere in the ballpark and it was knocking down some 2:16s at VIR, so he has some juice.

Ron

Well, I'm pretty sure on the CRX so we'll have to agree to disagree on that one and I mentioned I was talking about an ITR 944.

Alex

[Ron Earp]

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.

So what we're talking about are S cars here and there isn't going to be any difference in hp for this comparison. Torque, yes, but hell I'm only 160 ft/lb versus say 130 ft/lb with the Integra. A difference for sure. Torque is better, helps hide my lack of driving skillz.

Anyhow, hp wise a good S car is going to be around 175-180 whp FWD or RWD.

[Ron Earp]

Well, I'm pretty sure on the CRX so we'll have to agree to disagree on that one and I mentioned I was talking about an ITR 944.

Alex

There aren't any 944s in ITR.

We're not trying to balance ITR cars with ITA cars. I was thinking we were looking at ITS cars here.

[Knestis]

...I could then do that for wheelbase.

I cold then do that for aero.

Is that where we want to go? I FULLY ACCEPT that FWD is a disadvantage. But why are we choosing to address that one versus others?

...

Is that where we want to go? How many times is it necessary to say no? No. NO. No means no.

Why? Because that's what we've chosen to do for a long time.

K

[Andy Bettencourt]

Try these cars:

Crank hp: 212

One rear wheel, one front wheel.

Then this one:

Crank hp: 255

One rear, one front.

[Knestis]

"I FULLY ACCEPT that FWD is a disadvantage. "

Not necessarily in the shorter races we run.
Why are the ST FWD dominating in Grand AM?

Because they make up their weights reactively, in an effort to "get it right." They wobble back and forth between advantages, season by season.

K

[Andy Bettencourt]

Is that where we want to go? How many times is it necessary to say no? No. NO. No means no.

Why? Because that's what we've chosen to do for a long time.

K

And while this is hard, I think this is more do-able than trying to quantify wheelbase or aero...fo-sho!

[Andy Bettencourt]

Because they make up their weights reactively, in an effort to "get it right." They wobble back and forth between advantages, season by season.

K

And they do NOT have the same prep rules. Each car has it's own mini spec line. Daytona is a GREAT HP track...

[esuvee]

OK I am getting ready to do some more simulations looks like I am goiong to go with RWD 50/50 - FWD 65/35 2500lbs 100-300 IT HP

Only variables will be FWD/RWD power and Weight balance. I will will see how much weight you have to take off each FWD model to make the lap time equal. Should have some interesting results.

I still think that even if you don't intend this data to be used you are putting it out there and it will influence the discussion. Especially since you are now calculating actual weight differences that people will begin to quote.

Whatever time delta you see will be wide or narrow by ~1 second due to setup problems on one car or the other, this translates into 50's to 100's of pounds that you are guaranteed to be off.

My already optimized RWD 944 converted to FWD with no changes was running 2:04.3 around the MRC. After revising springs, bars and brake bias for the FWD config it ran a 2:03.48 which narrowed the amount that needed to be made up with weight by ~1sec.

Again, imagine throwing a FWD drivetrain in a 944 and making no suspension changes! You are figuring out how much weight would need to be removed from this bastard car to make it as fast as a good RWD 944, it's going to be a much bigger number than makes any sense to the real world.

Alex

[JeffYoung]

It's a different question this time Kirk.

Why is FWD more important of an issue to address than others? Meaning, why do we say yes to one and no to the others.

Greg has given me a plausible explanation, but I still don't have any real numbers to back it up. But I am still concerned by the groupthink that we need to address FWD because it is a disadvantage and not other just as easily provable disadvantages.

I'm rapidly coming to the conclusion that the best result, for me, for logical consistency is to vote (and it's just one vote) to simplify the process to power and weight, with a torque modifier.

[esuvee]

There aren't any 944s in ITR.

We're not trying to balance ITR cars with ITA cars. I was thinking we were looking at ITS cars here.

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

[Knestis]

But everybody looks at on track performance. Had Greg finish on the podium every race this year, this thread would not even exist. Is it a good gauge? NO. Should it be used to make adjustment to rules? NOT in IT.

With respect, you don't actually know of what you speak. This topic is in the top five, I think, right now in the IT rulez biz.

K

[ekim952522000]

It's a different question this time Kirk.

Why is torque more important of an issue to address than others? Meaning, why do we say yes to one and no to the others.

Jeff has given me a plausible explanation, but I still don't have any real numbers to back it up. But I am still concerned by the groupthink that we need to address torque because it is a advantage and not other just as easily provable advantages.

I'm rapidly coming to the conclusion that the best result, for me, for logical consistency is to vote (and it's just one vote) to simplify the process to power and weight, with a FWD modifier.

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?

[Andy Bettencourt]

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?

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.

[Knestis]

It's a different question this time Kirk.

Why is FWD more important of an issue to address than others? Meaning, why do we say yes to one and no to the others.

Greg has given me a plausible explanation, but I still don't have any real numbers to back it up. But I am still concerned by the groupthink that we need to address FWD because it is a disadvantage and not other just as easily provable disadvantages.

I'm rapidly coming to the conclusion that the best result, for me, for logical consistency is to vote (and it's just one vote) to simplify the process to power and weight, with a torque modifier.

To this point, we've collectively (the ITAC) thought it mattered enough as a variable influencing performance, that we could include it WITHOUT lots of headache. Good upside, low downside.

In reality, what we think of as "front wheel drive" is probably a composite variable that includes the influences of both FWD and weight distribution, since they go hand in hand. And lower driveline losses might play a role, albeit probably the other direction.

Now, I agree with your basic premise for low power/lightweight cars. The idea of giving otherwise equal cars (say the Corolla FX16 GTS vs. the RWD Corolla GTS) a break ONLY because it's a front-driver seems qualitatively silly.

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

[ekim952522000]

I still think that even if you don't intend this data to be used you are putting it out there and it will influence the discussion. Especially since you are now calculating actual weight differences that people will begin to quote.

Whatever time delta you see will be wide or narrow by ~1 second due to setup problems on one car or the other, this translates into 50's to 100's of pounds that you are guaranteed to be off.

My already optimized RWD 944 converted to FWD with no changes was running 2:04.3 around the MRC. After revising springs, bars and brake bias for the FWD config it ran a 2:03.48 which narrowed the amount that needed to be made up with weight by ~1sec.

Again, imagine throwing a FWD drivetrain in a 944 and making no suspension changes! You are figuring out how much weight would need to be removed from this bastard car to make it as fast as a good RWD 944, it's going to be a much bigger number than makes any sense to the real world.

Alex

I agree 100% that the numbers will be too big for any real world use what I am looking to see is if the relationship for removing the weight to make the times equal is linear or not, that is all. If it takes 350lbs to match up the time I am not going to suggest that 350lbs should be taken off a ITS prelude. I also openly admit that there is flaws in the system I am using BUT as of right now it is the best method I have for doing repeatable controlled tests to try and see a pattern.