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

[ekim952522000]

The big problem I see with the LapSim results is that no changes were made beyond FWD/RWD and weight bias. I went through and 'optimized' each setup's spring and bar rates for a FWD and RWD ITR 944 and for a FWD and RWD ITA CRX. I found 112lbs needed to equalize the CRX and 250lbs needed with the 944 after working all configs to their optimal spring/bar setup. Both 'fake' setups (RWD CRX and FWD 944) took multiple iterations of roll moment distribution changes to get the best lap time and both gained more than 1 second. I'm still not sure the setups are perfect.

Imagine if you just put a RWD drivetrain in my CRX and left springs and bars alone :eek:

So, 112 and 250 are pretty different numbers, I am in the camp that this is HP related. LapSim allows you to watch the driver inputs including throttle pos. The FWD 944 spends a lot more time at part throttle than either the RWD 944 or the FWD CRX. I am also in the camp that FWD cars like mine are stupid and should be avoided at all costs so I favor no further weight brakes My next racecar will drive the right end of the car.

I also favor rules stability. We're getting close to a nice setup here, again, what specific problem do we think we have? In ITR most 'it weighs too much' complaints are already headed to the RWD rather than the FWD cars.

Alex

Yes you are correct I did not change all those variables but I was trying change as few variables as possible. Again I will repeat my self I am not suggesting we use the weights that Lapsim generates. BUT we can agree that it shows a trend of more power = larger gap from FWD to RWD right?

Note: I am not arguing if the ITS weight is wrong or right I am simply saying given the data if ITS gets a 100lb deduct then ITR should get slightly more and ITA slighty less.

[Greg Amy]

Had Greg finish on the podium every race this year, this thread would not even exist.

Jeff Roussel, not so surprisingly there's more info you don't know.

Like, for example, in '06 (?) when I was racing the NX (getting all those track records, remember?) and the "subtractor" for ITS was only 50# (and I really didn't give two shakes about the GS-R or ITS). I made it pretty clear back then that I thought it wasn't enough and needed to be bumped to 150#, if not 200#, instead of 50#. And I've got the emails to prove that position.

Cut to late '07. The "subtractor" was now 100# for ITS, my buddy was racing a GS-R in ITS and I was still in ITA (and I still didn't give two shakes about ITS) and I told my buddy it still wasn't enough, that it needed to be 150# if not 200#. And I have the emails to prove it.

Cut to 2008. I'm bored with the NX and am thinking about sitting back for a little while. Instead I agree to run with my buddy in the GS-R in ITS; I tell him, however, that the numbers still aren't right, but we can go have fun. I get into yet another email exchange with ITAC member(s) telling them it's not enough (and I kept those emails to prove it); their response was, in effect, "look, just go try it and let's see what happens". And, not so surprisingly, nothing happened to change my position. It was at that point I pretty said we weren't going to put any more development in this car.

Then I wrecked the car in September and I pretty let it be known I had no interest in pursuing it further (don't believe me? Ask my Jeremy how he had to talk me into building another car with him).

Bottom line: I know what I'm talking about. I've picked and prepped numerous winning cars over the last nearly 20 years of racing. I'm rarely wrong on my predictions of performance of vehicles.

Jeff R, I give newcomers a lot of slack, and I understand how the Internet keyboards tend to make heroes out of people. But I would sincerely appreciate it if you would desist trying to imply that there's selfish motivation behind this. I'm not asking you to believe me, I'm simply asking that you cut. it. out. In return I promise to overlook your glaring deficiencies in experience, simultaneously overlooking that you have a massive, and potentially ignorant, conflict of interest coupled to your position as well.

Capiche?

GA

[Ron Earp]

Yes you are correct I did not change all those variables but I was trying change as few variables as possible. Again I will repeat my self I am not suggesting we use the weights that Lapsim generates. BUT we can agree that it shows a trend of more power = larger gap from FWD to RWD right?

Just for sake of interest what are the hp ratings of the theoretical CRX and 944?

[lateapex911]

But everybody looks at on track performance. Had Greg finish on the podium every race this year, this thread would not even exist.

LOL, you don't know the Greg Amy!

What's funny about this is that, for those with long term experience (10 years lets say) in IT, this issue was far far down the list of "issues" just a few years ago.

But, we're racers, and if you are a racer, you better be thinking about ways to improve things, and you'd better be thinking in creative ways.

So, we apply that mindset to the classing of our cars.

IT is MILES ahead of where it used to be. great.

But...it could be better. Of course, we need to tread carefully not to dink up the success we've had.

I think that there is merit and logic in examining a "sliding scale" of adders for FWD. I have no problem with the adder concept for FWD, I think it's certainly needed, but i'm not sure if we apply in the best manner currently.

I'd suggest that, if you all feel strongly about this, that you let the ITAC know. Write a proposal. Add some objective documentation that you feel supports your case. (Clearly, "I had to work my ass off to stay in front of RWD cars" won't cut it there!) And if you like, detail a method to accomodate your proposal.

Personally, I like the concept of choosing a "bogey weight" per class then deviating from that via percantages for heavier or lighter cars. Or if we could work that into the class factor number and it essentially yeilded the same result, that would be cool to.

I've always known the "fine tuning" of the process would be an ongoing project, but everyone needs to be aware of the history, and the big picture.

[lateapex911]

And Greg?? C'mon, be nice...take the high road.

[JeffYoung]

Jeremy, honestly, I think it is an indicator that ITS at least has been a Mazda/Datsun/BMW class. Those cars have been around a long time and are all fully developed and sorted.

I frankly know of several GSRs that run in ITS -- Ivan's (RIP), Scott Seck's (FAST), Cliff Ira (Fast), the two from DC Region that come down to run enduros at VIR (one ran a 2:16 by the way, which I think was the fastest ITS lap of that race), Zsolt's and yours.

So, that's six on the east coast alone, for a car that is still fairly new to ITS in the grand scheme of things.

On your car, sphericals? what shocks? crank scraper? Motec? done testing to find the best place to pick up intake air? worked hard to make the rear brakes do as much work as possible? worked on conserving tires over the course of a 30 minute race? run Hoosiers? etc. etc. etc......

We aren't talking about Greg, or at least most of us are trying not to.

Eric, I agree FWD is a disadvantage. I'm just not sure why we are picking THIS disadvantage out for special treatment, although I understand Greg's position that other than power/weight FWD is one of the most if not the most significant performance factors.

You guys are seriously funny. No seriously....

This is not about Greg, this is about FWD disadvantages.

Why did Greg do "ok" this year?

1. He has above average driving abilities.
2. We put a boat load of money, testing and time into the car to get it where it is.
3. The NER ITS car counts were not there this year. If we went to the ARRC it would be very easy to see how far back we would have been.

I can tell you that since I built this car it has always and will continue to have the same FWD problem that others are experiencing in ITS. The other reason that this has not been talked about previous is simple....

THERE ARE ALMOST NO ITS or ITR FWD cars running out there! Is that in indicator of something?

[Jeremy Billiel]

Jeremy, honestly, I think it is an indicator that ITS at least has been a Mazda/Datsun/BMW class. Those cars have been around a long time and are all fully developed and sorted.

I frankly know of several GSRs that run in ITS -- Ivan's (RIP), Scott Seck's (FAST), Cliff Ira (Fast), the two from DC Region that come down to run enduros at VIR (one ran a 2:16 by the way, which I think was the fastest ITS lap of that race), Zsolt's and yours.

So, that's six on the east coast alone, for a car that is still fairly new to ITS in the grand scheme of things.

On your car, sphericals? what shocks? crank scraper? Motec? done testing to find the best place to pick up intake air? worked hard to make the rear brakes do as much work as possible? worked on conserving tires over the course of a 30 minute race? run Hoosiers? etc. etc. etc......

We aren't talking about Greg, or at least most of us are trying not to.

Eric, I agree FWD is a disadvantage. I'm just not sure why we are picking THIS disadvantage out for special treatment, although I understand Greg's position that other than power/weight FWD is one of the most if not the most significant performance factors.

Jeff - All us Integra GSR guys talk and we, like them, have all the best stuff. Is there perhaps some stones we need to turn sure, but for me to list the mods will do nothing to this argument.

This argument is SIMPLE. In fast, high HP FWD cars, the front tires are asked to do too much and thus additional weight should come off.

[JeffYoung]

I won't dispute any of that except for "and thus the additional weight should come off."

Do you agree that your brakes are better than mine? And thus the additional weight should be taken off.

Do you agree that your suspension is better than mine? Remember, you are putting power to ground through an adjustable, independent suspension. I'm trying to do so via a heavy, unsprung live rear axle with no camber adjustment. That stick axle is being asked to do too much and doesn't allow me to take advantageo f the torque and power that led to my car being classed at the weight it is.

Your car is far newer and has a much cleaner aero profile. And thus the additional weight should be taken off.

etc. etc. etc.

Jeff - All us Integra GSR guys talk and we, like them, have all the best stuff. Is there perhaps some stones we need to turn sure, but for me to list the mods will do nothing to this argument.

This argument is SIMPLE. In fast, high HP FWD cars, the front tires are asked to do too much and thus additional weight should come off.

[Jeremy Billiel]

I won't dispute any of that except for "and thus the additional weight should come off."

Do you agree that your brakes are better than mine? And thus the additional weight should be taken off.

Do you agree that your suspension is better than mine? Remember, you are putting power to ground through an adjustable, independent suspension. I'm trying to do so via a heavy, unsprung live rear axle with no camber adjustment. That stick axle is being asked to do too much and doesn't allow me to take advantageo f the torque and power that led to my car being classed at the weight it is.

Your car is far newer and has a much cleaner aero profile. And thus the additional weight should be taken off.

etc. etc. etc.

We were on the same page and then you brought your pensonal car into this. You have the EXACT same car except one is FWD and one is RWD. By having the same everything else the ONLY difference is RWD. With that said, the question is how much of a benefit should that FWD car get based on its disadvantages that have already been discussed? Currently its #100 lbs. I happen to think its too little.

THAT is the argument. Do not bring cars into the mix. It can be any car...

[JeffYoung]

Jeremy, there are significant differences between your car and mine. Vented rotors v. solid, rear discs v. drums, live rear axle with which I am trying to power down v. independent suspension on drive wheels (probably the biggest advantage you have but I digress), aero, etc.

I'm bringing up "my car" because that is easy thing to do and what everyone is GOING to do (although they will couch it in general terms) if we do/allow this.

I'd rather we let all cars suffer their own disadvantages. Class at power to weight, deal with torque and move on.

[Andy Bettencourt]

Can anyone with a decent IT effort post their actual weight distributions? I stopped at the shop today and grabbed the sheets for my Miata and wasn't too surprised to see a 53-47% distribution from an alignment session (with the amount of gas I would have when I crossed the scales post race)

I am guessing that the Miata is one of the better RWD cars in terms of % so I wonder if we could see the Teg's numbers to insert into the SIM. Maybe 60/40 and 55/45 are better representive of real weights, especially with what clever guys are doing with cages and rear 'sway bars'...

It's also possible that real racing weight % for FWD's should be more like 65/35....but I would love to see the numbers. I have a feeling that with the engineering you can do within the rules, the difference may be smaller than was used in the SIM. Maybe not.

Given the information I have seen so far, I could definately support ekim's:

ITR - 150
ITS - 100
ITA - 50
ITB - 25
ITC - 0

Understanding this is all a 'guess', I would just like to make the 'least stupid' guess!

[JeffYoung]

Ron has cross weights on the Z car somewhere.

[dj10]

[quote=Andy Bettencourt;281556]Can anyone with a decent IT effort post their actual weight distributions?

51/49

[Gary L]

Can anyone with a decent IT effort post their actual weight distributions?

At "perfect" race finishing weight of 2640 and matched cross weights - front 51.0, rear 49.0 on my ITB Volvo.

[Xian]

My CRX was 61.3/38.7 at 2258#'s (spec weight is 2250). I don't have figures yet for the Civic.

FWIW, I think the sliding scale would be the easiest to implement and the least "dangerous" option I've seen (short of doing nothing which has it's own dangers).

Christian

edit:
Crossweights were 51.5:48.5

[Jeremy Billiel]

OK here are the stats for the ITS Integra

Front 63.8%/Rear 36.2%

Cross Weight 50/50

Total Weight 2598 (8 lbs over)

[Jeremy Billiel]

Mike - Re-run those LapSim numbers at 65/35 to see how quickly that gap gets worst. I bet its not linear.

[Ron Earp]

260Z:

52.5 / 47.5 as of last year with me and about 5/8 of fuel. Has a bit of a nasty wedge though.

I think we can improve the weight dist this year because I've lost some weight off the car and will be moving some items about.

[esuvee]

Just for sake of interest what are the hp ratings of the theoretical CRX and 944?

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

[Andy Bettencourt]

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.