Daffy

I would have to assume that one would want as close to equal wieght on all four wheels with driver(or equivilent weight) aboard and a full tank of gas(on a C4)...Would this be correct? Or am I gonna be wrong as usual when I think I have an answer...

gonzalezfj

Yes to corner weighing. No to a full tank of gas: weight it your enemy in autocross and any other form of racing. Run your car with the least amount of gas that will allow it to run dependably without fuel starvation.


20 gallons at 6 lbs a gallon is 120 lbs you don't need to carry.

Frank Gonzalez

Daffy

The full tank seems the be the only option on the C4 due to the slosh(weight transfer) and starvation factor.

RAFTRACER

, but you need to do something with the pick-up so that you have the option to run a low (or lower ) fuel load. There is no way in hell when those cars were running the Corvette Challenge they had these problems. They would have had to stop for gas every ten laps.

Unless this is a dedicate race car (scca-prepared or nccc rp) you can not purposely ballast the car to have all corners equal or left to right equal for that matter. When you corner wieght your car you are looking to have your diagnals being 50% of the total wieght. IE; LF+RR=RF+LR. Since wieght always transfers diagnally in a turn , if the diagnals are equal then the car should be balanced. In a non-race car the left side wieght will always be more, there are more neccesities on the left side including the driver.................................. moving the battery to the right rear will help alot on the C4.

ghoffman

Not that I would ever disagree with Lord Raftracer of Auto-X anyway!
This is further complicated on a C4 by that lack of a spring adjuster on the front of a stock C4 spring. A Vette Brakes spring or coil-overs would change that but obviously class considerations might prevent that option. On a C5/C6 there are threaded height adjusters on the end of the spring, but not on a C4. I suppose you could shim the spring but that would be a PITA.

Daffy

Could I not make some adjustments from the rear on the C4??

VetteDrmr

Well, it's not that much ballast. Don't get me wrong, I understand about unnecessary weight, but you need some gas to get your best time in!

So, how much do you run (I actually just started another thread with this question)?

Have a good one,
Mike

RAFTRACER

More fuel creates more forward bite which helps when on low frictions surfaces (no grip). I thought fuel was a little over 7lbs a gallon anyway?? Wieght is the enemy, but if it helps you put power down which is worse????
If the car is a group 3 car (nccc) you can use the VBP front flat spring with adjusters. group 2 car , this was made illegal last year or the year before based on a "witch hunt" for Don Smith from down in the south. Yes you could shim front spring, and the rear even as stock has some wieght shifting ability. I can scale even group 1 and AS c4's and keep them legal ( and still achieve 50.0% cross )

Daffy

Thanks guys,at least I can get in the ball park now.

69427

You're not going to get equal weight on all the tires without a lot of juggling around of components in the car. And, depending on the course, you may not want to. Most road courses are run clockwise. If the majority of your corners are right hand turns then it isn't a handicap if your car happened to be a bit right side heavy. However, if it is an autocross course running CCW, then hopefully your car is left side weight biased. Also, a little additional rear weight sometimes helps traction to launch the car out of a slow autocross corner but additional weight is certainly not helpful on a long high speed straight. You just need to be aware of what helps you, and what doesn't. This can change for every type of course.
The suggestions offered by the other members are also definitely worth considering when you have the opportunity to weigh your car and then see what the impact of CW or CCW circuits does to your car. It's a long learning process, and rarely will anybody say they don't keep learning new things as they get more track time. Have fun!!

RAFTeRACER

Most C-4's begin to sputter in hard cornering around 3/4 of a tank. It's not worth the time lost to save on a few pounds. My car runs best full.

RAFTRACER

No sh## ??!!!! The masked marvel reveals himself again.....I'm wandering if you would actually know and if your car is black ????

It's defineatly worth someones time to modify the pick-up and save the wieght of all of the extra fuel. Weight is the enemy remember no matter where it is . Lighter is always better ..........

If your car does happen to be black, I think you have some forward mounted wieght that needs to be removed (ie: exhaust manifolds )

gonzalezfj

You are right, Danny. How soon we forget!!!

The C5/C6 tank and pick-up system is so good it makes you forget past foibles of the brand.

Frank Gonzalez

RAFTRACER

Frank, note you have quoted the RAFT "e" Racer, the masked marvel........................

C4's stock have severe fuel starvation problems , my dads 86 with the LT4 will do this @ 3/4 -5/8 of a tank if there is enough grip, poor fuel tank/pick-up design that I am sure the Corvette Challenge racers of the late 80's-90's did not deal with ( they would have been in the pits for fuel way to frequently ).

Generally I run my C5 stuff "light" unless I cannot put any power down. The C5's will not fuel starve unless you are damn near empty, happens a little sooner on the roadcourse do to spending longer time a max lateral g's, but still can run very low.

Daffy

With the tank in the C4 being mounted the way it is it also (if half full) will transfer the weight of the fuel in the corners and cause a very annoying snap oversteer situation.Did the Corvette challenge guys run stock fuel tanks??

RAFTRACER

Yes, fuel "slosh" is upsetting to the rear of the vehicle. Typically you either want to run full or empty, especially when the tank is mounted aft and high of the rear axle.

I believe the Corvette Challenge car used stock rear tanks, anyone have any insight ?????

VetteDrmr

I did some digging but couldn't come up with any definitive results. However, considering how they were raced, I would think they would be required to use a fuel cell for safety reasons.

stairman

Danny
I have no insight for you, I know a guy here in town that worked on A challenge car team, I will see if i can catch up with him.
I can tell you in mine that I like a full tank, I know the weight is not good but it helps balance the car, and it minimizes the slosh. I think to fix the problem you have to have a pickup that will draw from both sides. The problem is the fuel running away from the pick up.

By the way, what is the deal with this 'MASKED MARVEL', I think he just wants to be like you.

Good running this weekend, it is always a pleasure to lose to you.

Mike

Daffy

A fuel cell is starting to look like a good idea.Make the car faster in the name of safety.

racerwannabe

having been the "other party" to said witch hunt..i had an adjustable spring too,,the flat adjustable spring puts you all the way to RP..that's why i removed it..it's for sale if anyone can use it..my C-4 allways ran better times with the tank full...
johnny