In my ZO6, and I don't autocross but I do "roadrace" it depends on the size of the track and the length of the heat (session). And of course how far the nearest gas station is or how much they are charging for 100 octane at the track.
On tracks under 2 miles and heats under 20 minutes I run less than 1/2 usually around 3/8....cuts down on the weight. And my ZO6 runs fastest when it's lightest.
On tracks between 2.5 and 3 and a 25 to 30 minute heat I have to run at least 5/8 tank, because my car (stock) will suck almost 1/2 tank during that time. And on more than one occasion, I been reminded by the computer, which cuts the engine, that I'm on reserve fuel. BTW, I've driven so far a max of 13.6 miles on reserve fuel. Anybody know the max range?
The additional oil is a good idea, I usually run 1/2qt over.
Hey are those CCW wheels on your red car? Do you have the 12's in the back.
Warning: Don't race with the stock brake pads, they're dangerous. They just heat up and fade away.
Maybe I'm missing something here but you did say autocross. I take this as short timed events(100 seconds or less) and at speeds usually under 70 mph.
The answers before this refer to road courses.
Weight is critical in autocross.
Fuel is around 6 pounds per gallon. If you run with a full tank, you will be carrying about 100 pounds more weight than necessary.
Fill the tank with only as much fuel as it takes to keep the car from starving in turns.
1/4 tank should be close.
Stock brake pads are very good for autocrossing.
I don't think extra oil is necessary unless you have long sustained corners. 1/2 quart over will not hurt anything.
Again if you are doing road courses and not autocrossing, then forget what I just said.
I don't know now why I've never done AutoXing.....less than 100 seconds, under 70 miles an hour, and they do those in a parking lot, with cones, right?
Wow, that sounds exciting:
The Supercar tires don't even heat up until after 3-4 minutes. Sorry, I'm being sarcastic....it would probably be pretty fun in a shifter-kart.
I agree with the brakes...hard to imagine you'd see substantial heat and fade after 100 seconds....but watch out after 5 minutes.
I read your Web-sig, and saw the answer to my question on your CCWs....but I have another....Did you have to modify your rear brake ducting or anything else to run those 12s back there. I just got mine (18s with 335/30s), haven't put them on yet, but John said I'd have to mod the rear brake ducting...we'll see.
As I haven't had the car that long and I'm certainly not an expert. When the cutoff occurs though it feels artifically induced, as if the computer were doing it to get my attention. It only lasts for a second or so, but I've never had it repeat during exiting off the track for some fuel. You'd think if it were starvation it would occur intermittently until I refueled.
I just ordered that book on Corvette fuel injection....maybe that will shed some light.
Either way, I just love the ZO6 on the track, so much so that I sold my race prepped 993, affirming my commitment to the ZO6. I simply love the way it eats $150K tt porsches.
Depends, but absolutely NOT a 1/2 full tank. Too much schlossing around causing unwanted weight transfers Rt.>Lt.>Rt. in turns. This phenomena is deminished somewhat in the C5 as it actually has 2 "saddle" tanks. But still the weight transfer can occur just at the wrong moment.
As gas weighs almost 7lbs./ gallon a full tank 18 + 2 unusable = 20 gal x 7 #'s /gal.= 140 lbs. Since 100#'s is worth 0.1 sec. in the 1/4 mile under CONSTANT acceleration, you would be at an advantage running an almost empty tank. Actually even more in autocross because of the many acceleration runs you make out of each corner. You would think the difference would be miniscule but it is really exponential. Some races are won or lost by a .001 second! In actallity a 100 # difference in AutoX is a ton and might mean a 1 full second! That's an eon in AutoX. Some Pro Soloists add a gallon after each run that's how empty they are running.
I'm on a diet BTW, I can probably save a couple of seconds there!!
A lighter car is usually a faster car. That's why most qualifying runs are made on nearly empty tanks and why F1 teams use 1/2 tanks at the start of some races where the course is tight with little passing....to get out front and stay in front.
However there are times when a full tank might be advantageous in AutoX. A full tank may aid weight transfer Ft.>Rr. and increase traction on a slippery or wet course.
In addition adding weight as in running a fuller tank may be used to fine tune a car for a particular course or track. Adding weight to the rear will generally effect the moment arm applied to the sway bar. How will additional weight in the rear effect understeer/oversteer??? That is the ultimate question in AutoX.
Personnally I have found that adding weight in the rear of the Z06 aids traction and adds oversteer.
I usually run on 1/8 of a tank and no more than 1/4 of a tank on dry "sticky" concrete. I play with the fuel load on asphalt and usually run a softer shock setting in the rear.
Wet is a different animal. I always run a full tank in the wet, regardless of surface, and set the shocks on their softest settings being very careful with brakes and power into and out of corners. I try to "SET" (or preload the suspension) car into and out of a corner and modulate the brake and power to keep it balanced in the "SET" position.
One further tip: when you get that competition alignment be sure the tanks ARE 1/2 full; and the driver is sitting in the seat.
Thanks for all the info, Speedmon, I did not need to modify my brake ducts. My 18s do stick out, and would rub if I went to a high speed high bank course. Texas World would be a problem for me. John may have changed the offsets for you to keep this from happening for your race style.