I competed in the Sport Compact Car Mag "Ultimate Street Car Challenge" last week in my 2800lb (full tank of gas without driver) 439rwhp/385rwtq LS1 powered RX-7. 49.5% front/50.5% rear weight. Cross weighting was within 1lb of each other with me in it.

I just got off the phone with SCC Mag and they said I can post at least my skidpad numbers.... I can't post any other results as the issue won't be published for many months.

1.13g's going one direction (one of the highest they have ever recorded) and 1.06g's going the other on a 200ft skidpad. Avg is 1.09g's. You can guess how I did in that particular challenge with those numbers.

This was on 18x10.5" CCW's with Michelin Pilot Sport Cup 285/30/18 (unshaved) tires at all corners and used 550/450 Eibach coilovers with used GAB Super R shocks, used TriPoint adj front bar, used stock rear bar, new zerk fitting'd JimLab bushings.

And who says the LS1 kills the handling of the FD now?

I put a similar thread up in the race car section:
https://www.rx7club.com/race-car-tech-103/ls1-fd-pulls-1-13gs-skidpad-431720/

 

Just FYI, skid pad numbers are more indicative of tire grip than handling. Slalom numbers are more indicative of handling ability.

BTW, how are those bushings working out?

 

the bushings rock and don't squeak.... I have about 1K miles on them. I am unable to post my results on the road course since the issue won't be out for a while.... but to say the least I'm very very pleased . The car posted some good results even with me driving against 8 professional drivers and only the 5th time ever on a road course (3x in a 140hp FC with road race suspension/RA-1's and 2nd time ever in the 500hp ls1/fd).

 

Good for you. Glad you got your car together in time!

 

I would love some info on how you got 285/18's up front.. I know coilovers are a major part of the equation. Glad to hear the car did well... I was very impressed with my Ls1/FD on the road corse, so I am sure with that kind of grip it was sensational. And Jim, just for your information.. I made the "MaxAir" box that you had/have, on your supra!!!

Jonathan

 

??? I never had an air box on my Supra. Just a K&N filter.

 

Congrats Mark.
I knew that thing would do well.
It's about time you roll it over and let me drive it.
btw, my nose is doing better after your car 'bit' me.

Since I know the results, can I disclose them

 

Hmm... Steve Jarvis said that you had one on your supra, And I am the one who assembles them all for steve and MVP motorsports... Oh well my mistake. And GNX: never mind the explanation on how the wheels and tires fit... I just saw your response in the Race car tech Thread.

Jonathan

 

Mark, congrats! Hope my project works out as good as your did!

 

RX-Heven- my car knows a true rotaryphile and had to nip you a little . Thanks for lending me all the tools and your help during the build. As we both know our projects will never be done as they progress into better machines as the years go on.

Can't wait to play chase on the NorCal road race tracks in '05.

 

Congrats!! I'm guessing you are happy with the conversion? Can't wait to read about it in the SSC..

 

WHat month's issue does this start? The challenge I mean.

 

Oh come on, you put Michelin Sport Cups on the stock suspension, and the car will do close to those skidpad numbers.

Skidpad #'s don't mean squat in my book.
They doing a slalom test?


-Ted

 

You're always so cheery ted...like a ray of sunshine in everyone's life.

 

Ted maybe you just don't get it. People have corner weighted LS1 FDs and they aren't much different than stock.

People have run LS1 FDs at the track, they WORK.

 

Actually, Ted's right. You can match a Z06's skid pad numbers with a C5 Corvette just by swapping the tires.

I don't think Ted was questioning that a converted car would handle well. He was just bringing up the fact (belatedly, since I already did in the second post of this thread) that skid pad numbers don't necessarily mean good (or bad) handling, and it's very easy to improve skid pad numbers just by getting better tires.

 

In this case you both are right and wrong. Depends on the point you are trying to make.

If you take a car with crummy tires and put R-compound tires on it the skidpad numbers will go up. You are right, tires make the difference.

Take a car with the same tires on it and change the weight distribution significantly you might find that the skidpad numbers change. You are wrong tires don't make a difference.

Which variable do you want to hold constant? Tires or weight balance? I think the original poster was trying to point out that the LS1 converted car's skidpad number did not do into the toilet.

Car and Driver or Road & Track tested a Impala SS (several yrs back) with a GM installed BBC, skidpad numbers went down...

 

You'd have to significantly change weight distribution when a stock Ford Lightning with all the weight on the nose (55.8/44.2) can manage 0.85-0.87g. Improve the tires and you could easily get one into the 0.90-1.00g range.

Skid pad numbers are basically tire grip vs. vehicle weight... not weight distribution. Slalom numbers would be far more indicative of whether the vehicle's handling was unbalanced by a change in weight distribution.

Of course not, because the overall weight did not increase significantly.

As you'd expect, with another 200 lbs. of engine.

 

My point exactly.

1. The LS1 does not significantly change the handling of a FD.
2. A FD does not significantly handle better with the 13B-REW.


Like I said, that is what I think the thread is about.

 

Not quite true either. I've seen quite a few Saleen or other tuner Mustangs tested with "upgraded" suspensions running 275 or 285 width R-compound tires and they could barely get over 0.9G. A Viper running the same width street tires, a little less weight, but with MUCH better weight distribution gets 1.0+ G. Hell, look at Ferraris and Porsches, they typically run 225-235 width front tires and pull 0.95-1.0G.

A front-heavy RWD car is hampered on the skid pad, as it will tend to plow forward or power oversteer too much. I sincerely doubt you could hit 1G with a Ford Lightning, even with 285 R-compounds up front, for example.

There is more to skid pad performance than just really big sticky tires.

 

Yeah, weight... as I believe I stated. Besides, a difference of 0.10g or less is basically irrelevant.

It is, but a skid pad number isn't necessarily the right performance measurement to really drive that home, and that's what Ted and I pointed out.

 

There is more to it than big sticky tires and the weight of the vehicle. Weight distribution and suspension tuning play a significant role in the "steady-state" handling numbers. Two vehicles hitting the same skidpad number may feel extremely different from each other doing so.

I agree. Even the combined use of skidpad and slalom times don't fully describe how a car handles, but at least give a decent idea.

 

Um, I'm not dissing the V8 conversion.
I'm questioning how useful the skidpads numbers are?


-Ted

 

OK, sorry for the confusion.

 

In a previous SCC Mag USCC running there was a Caterham with a 13B-REW motor that pulled the highest number they have EVER recorded. 1.133g's....

I understand skidpad numbers certainly aren't the end all tell all meaning they definately mean your car handles well.... but they certainly mean the car is doing something right I'd say.

BTW- everyone was running R-compound tires that posted good skidpad numbers.

Ted- Do you ever visit Northern California? You should come out on the road course this summer. In NASA HPDE Group 4 there isn't much that can touch the car... I was being chased by Evan Ginsberg (instructer) in a C4 Vette with 500hp+ motor, lexan everything, major roll cage/chassis stiffening, 315/17's all around R compound tires and he didn't pass me for a few laps until I let him by due to getting hot coolant temps. Modified Evo's and Sti's I could close the gap closer even in the corners and in the straights it was good bye time.... I was roping in a Lotus Elise at Thunderhill every lap until coolant temps made me do a cool down lap. I have no radiator ducting or belly pan right now... or hood venting. I'm curious how the car does at Sears Point (Infineon) in August. I would love to have a professional driver sort my car out and see what kind of lap times it could pull at the 10/10 full out level.

Jim- I'd love to see a Lightning with stock style suspension (upgraded of course) and no significant weight added to the rear pull 1.0g on the skidpad. Not going to happen "easily."

Ferrari's and Porsches being mid and rear engine'd cars can run less tire up front due to the weight distribution.... we all know that. Get a Porsche into oversteer and then let off the gas and kiss your *** goodbye. Those cars have killed many many race car drivers that aren't used to the style required to push them to the limit.