Managing Handling Balance Change

Interested to hear from those of you who have done endurance events in thier car and how your car generally performs as the fuel load burns off.

We just did another 4 hour enduro in the weekend (ran as high as 2nd and finished 6th in strong field) and the car tended to over steer or "step out" on turn in as the fuel load got down to half a tank or less.

There were a couple of adjustments that were not quite right on the car but it was not far off so curious how other have found this trait in enduros.

Kel.

I set my car up for sprint races and let it push with a full fuel load.

Kel that's when you start drifting the turns for extra style points.

No experience with endurance racing here, just sprints. I have my Z06 setup so that I start every race with a full tank and come in 10-15 lbs over my minimum competition weight after a 40 minute race. I have no in-car adjustablity of anything.

It seems to me the thing to do would be a way to have an adjustable rear swaybar to try and combat some of the tendency to oversteer on turn-in. Anything more than that sounds fairly complex to implement.

I just changed my springs in the front and rear to try and help with the oversteering issue I been experiencing during long runs or on older tires with many heat cycles. I have stiffened the front by going to 750 lb/" springs (started with 550's), and went softer in the rear by installing 200 lb/" springs (started with 350's). I don't have a sway bar in the rear. Front bar is set full stiff. After the spring change I corner balanced with ride height at 3 3/4" up front and 4 1/4" in the rear. The heights are measured from the frame (in line with axles) to the ground.

After my weight reduction effort from the past three seasons I'm happy to report that the car is down to 2550 lbs with 1/2 tank and no driver. I think the car started at over 2750 lbs (w/out driver) when I bought it.

That's impressive! I'm shooting for mid 2500s w/o driver as well. LS1 swap with much less/lighter accessories, manual steering, smaller fuel cell, much simpler wiring etc. etc.

Jerry, please tell me what you did to shed those pounds. I am looking at big expenses to shed very little. The best is for me to shed 25lbs :-)

The stuff I had considered are braille battery, aluminum rear end pumpkin......

Kel that's when you start drifting the turns for extra style points.

No experience with endurance racing here, just sprints. I have my Z06 setup so that I start every race with a full tank and come in 10-15 lbs over my minimum competition weight after a 40 minute race. I have no in-car adjustablity of anything.

It seems to me the thing to do would be a way to have an adjustable rear swaybar to try and combat some of the tendency to oversteer on turn-in. Anything more than that sounds fairly complex to implement.

Yup, there was plenty of drifting going on Brian, in fact I had 2 spins in the race as it was........... Have considered an adjustable rear bar but will probably try a slightly lighter rear spring first and soften the rear shocks up as well.

Kel.

I just changed my springs in the front and rear to try and help with the oversteering issue I been experiencing during long runs or on older tires with many heat cycles. I have stiffened the front by going to 750 lb/" springs (started with 550's), and went softer in the rear by installing 200 lb/" springs (started with 350's). I don't have a sway bar in the rear. Front bar is set full stiff. After the spring change I corner balanced with ride height at 3 3/4" up front and 4 1/4" in the rear. The heights are measured from the frame (in line with axles) to the ground.

After my weight reduction effort from the past three seasons I'm happy to report that the car is down to 2550 lbs with 1/2 tank and no driver. I think the car started at over 2750 lbs (w/out driver) when I bought it.

Jerry, have you run the car with the 200lb rear springs with a full 32 gal fuel load? If so how did you go regards scraping/bottoming in the back of the car over bumps?

One adjustment we made just prior to the race after oversteering issues in quallifying was to drop the rear ride height. That helped but we still had some fun in the race. Nothing radical but tricky on the limit.

Remid me Jerry, what block are you running in your car? Reason I ask is that I was down around 2550lbs when I had the 5.0 blocked engine in the car. No chance now with the Dart block but the price you pay for the reliability at the hp required to beat GT3's.

Kel.

Jerry, please tell me what you did to shed those pounds. I am looking at big expenses to shed very little. The best is for me to shed 25lbs :-)

The stuff I had considered are braille battery, aluminum rear end pumpkin......


Easy Brian, during your engine rebuild, just stump up the $4K for an aluminium Dart block and you will be in the magic 2500 - 2600 lb range!! Next drop the 105 - 110lb TKO for a center shift Mid Valley Engineering NASCAR 4 speed (65 - 70lbs) and you will be lighter all round......wallet included :evillol:

On the engine rebuild front, are you using the AFR225's or the new 220's coming out from AFR very soon? Seems the flow figures are way up on the new heads. The new 200cc head flows more than the old 225 according to published AFR figures. I am looking at the 220 as an option.

Kel.

Very Easy indeed. I am emailing you wiring instructions for the block, labor, and tranny. I will cover the installation in the car no charge. Your name and picture will be all over my car for your generous contributions. :-)

The motor was barely hurt. The high pressure radiator cap blew out the gasket on the intake from the inside. Filled motor immediately with water. Luckily I filled the motor with WD-40 so nothing rusted and it didnt have to come completely apart. My AFR heads are still good. Bought new ones last year so no I dont think I will get the 220 heads.

As it turns out the ford intake gasket doestn have bolts between the sections. The chevy does and can run much higher pressures. We had a 30lb cap and have backed down to 24lbs. Hopefully that works.

Any other GREAT ideas? hehehe...

Very Easy indeed. I am emailing you wiring instructions for the block, labor, and tranny. I will cover the installation in the car no charge. Your name and picture will be all over my car for your generous contributions. :-)

The motor was barely hurt. The high pressure radiator cap blew out the gasket on the intake from the inside. Filled motor immediately with water. Luckily I filled the motor with WD-40 so nothing rusted and it didnt have to come completely apart. My AFR heads are still good. Bought new ones last year so no I dont think I will get the 220 heads.

As it turns out the ford intake gasket doestn have bolts between the sections. The chevy does and can run much higher pressures. We had a 30lb cap and have backed down to 24lbs. Hopefully that works.

Any other GREAT ideas? hehehe...

Brian, I struggle to fund what I want to do with my own car so for all that coin, you missed out the most important bit about my name being on the entry form where its says ........"Driver"!! (not doubting your driving ability, just a value for money thing)

On a more serious note, yes, wouldnt it be nice to have a sponsor with all that gold. I consider myself to be very very fortunate this season to have a very good tyre sponsor in Alert Motorsport/Federal tyres. With thier help and assistance we have logged 2nd in the DOT class in the NZ Endurance Champs and run/finished in the top 6 of the 2 rounds of the North Island Endurance Series that we have run.

Not quite sure what the next step is though. Looking at the AFR 220's with a view to picking up another 50 - 80hp so that we have the mumbo to run top 1 - 3 on the faster high hp circuits. We need to pick up around 1 - 1.5 seconds and I figure we will be on the money with around 480 - 500rwhp. Last dyno run was 466rwhp so AFR 220's a Super Victor and shorten up the header primaries should get us there. Sounds easy if you say it quickly but the header shortening job is probably 30 - 50 hours of work alone!!

Good to hear your engine rebuild was no drama and good tip on the gasket failure thanks.

Kel.

Jerry, have you run the car with the 200lb rear springs with a full 32 gal fuel load? If so how did you go regards scraping/bottoming in the back of the car over bumps?

One adjustment we made just prior to the race after oversteering issues in quallifying was to drop the rear ride height. That helped but we still had some fun in the race. Nothing radical but tricky on the limit.

Remid me Jerry, what block are you running in your car? Reason I ask is that I was down around 2550lbs when I had the 5.0 blocked engine in the car. No chance now with the Dart block but the price you pay for the reliability at the hp required to beat GT3's.

Kel.

Kel;
I have the 5.0 block stroked to a 347. It dynoed at 350 HP. I removed the 32 gal fuel cell and have gone with a 12 gal Fuel Safe unit. I figured I have taken over 100 lbs off of the rear of the car (behind the rear dif) with the change in fuel cell. I don't run any long races any more, so 12 gal of fuel is more than enough. The reduced the weight in the rear is why I thought I could get away with 200 lb/" springs in the rear.
I have not driven the car since the mods were made, but I hope to in the next couple of weeks. I'll post after I drive it with impressions. I'll use indicators on the shocks to see if I bottom them. THere are a couple of big humps in my home track as you cross the banking of the oval, and I would expect that if the car is to reach the limit of t ravel, it will occur over these humps.
Jerry

That's impressive! I'm shooting for mid 2500s w/o driver as well. LS1 swap with much less/lighter accessories, manual steering, smaller fuel cell, much simpler wiring etc. etc.

Brian;
You can get to 2500 lbs (or lower) with the all alum motor and going with manual steering, etc. That should be 50 to 75 lbs less that where I am with the steel 5.0 block and with power steering.
Your Dad's car will be killer with the mods you're making. I wonder if it will be faster than your Z06. My car is now 1 to 2 seconds faster than my '02 Z06 at my home track. Taken a bit of work to get there. The Vette was a very well engineered car and very capable.
Jerry

Jerry, please tell me what you did to shed those pounds. I am looking at big expenses to shed very little. The best is for me to shed 25lbs :-)

The stuff I had considered are braille battery, aluminum rear end pumpkin......

The biggest savings have come from mods to the motor. I've gone to alum heads, and removed the EFI system for a carb. Alum flywheel and light weight clutch. I've stripped off the large coolant overflow tank and went with a small bottle. Removed the ECU and wiring harness. That saved ~10 lbs. On the rear of the car I went with a 12 gal fuel cell. That saved over 100 lbs. I've removed wiper motors (inside and out side) as I only race in the sun here in NM. I cleaned up the roll bar up front by removing the steel tube between the supports. Taking out the passenger seat and belts also saved 35 lbs. I'm sure there was more little things, but I can't remember them all.
I thought about going with lexan wind screen, but that didn't seem to save more than a pound or two once all the added supports were considered.
Jerry

I've got the VIR track record for my class with a 2:03.65. Years ago (2009 time frame) I had the Panoz in the low 2:06s on 275 R6 Hoosiers with 315 rwhp (heads/cam mods to the stock driving-school 5.0). Car was around 2750lbs; 2970 with me in it.

My Z06 makes 365 rwhp and my minimum comp weight is 3101 lbs with me in it. I ran the 2:03 on 245 A6s. I think the Panoz will have slightly more potential due to the superior aero, but the power/weight will be the same as they're both being built to 8.7:1 NASA classes.

Full aero C5Z06s @ 8.7:1 have run 1:59s at VIR... flyin! I think the Panoz could do that just fine with a proper front spliter, revised rear wing, and big tires.

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I was thinking about this thread tonight working on the car. I pulled the fuel cell out of the car. Was able to pick it up and out with the fuel still in it, sucker is heavy! All that weight at the far rear of the car will make fuel level have a serious effect on the handling characteristics of the car. My Z06 had "saddle bags" tanks; one on each side of the tunnel. They're in front of the rear suspension/tires and just behind the driver; more centered in the chassis.