Just finished my first track outing with the Z06. Now there's a whirring noise coming from the left rear fender well, like a noisy motor running. Happens only when the motor is running. Is there maybe a fuel pump back there that could be having a problem? Any other possibilities?
Also, the car seems to be rougher than before. Maybe not quite a "miss" but not smooth either. Do these things eat plugs or valves under hard driving?
Lastly, my exhaust pipes are deep black. After weeks of street use, the insides of the Borla Stinger (quad) pipes are usually squeaky clean. After one day on track they're full black. Do these cars tend to run over-rich at WOT?
BTW, car is a 2002 with 12k miles, all street until today.
jim
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2002 Millennnium Yellow Z06
1992 white Spec Miata race car, for quick cornering
The only thing that's located back there that would make the sound you describe would be the in-tank fuel pump. The whirring noise is not uncommon in vettes although it's somewhat unusual that you'd hear it now and not before.
As far as the black exhaust tips yes, at WOT catalytic converter overtemp protection is enabled which richens the air-fuel ratio in order to protect the CATs.
Have you done any mods to the car that would affect the air-fuel ratio such as an aftermarket intake, headers, etc.?
Nope. Other than the Borlas and CAGS eliminator, dead stock so far.
Gotta do some suspension mods, though. The car feels less than planted in curves over about 130, which is really a limitation. I'm figuring T1 bars and 04 shocks, plus lower a little.
Well, at speeds over 130 it's going to be less planted in turns. There isn't much you can do to alleviate that. Race rubber will help tremendously and is the single best thing you can do for lateral grip but even then at that speed you can't defy the laws of physics.
The T1 bars won't help much in that regard and in fact may decrease lateral grip, especially with street tires. A good improvement would be the 04 shocks in combination with lowering about 15 mm's and a slightly more aggressive alignment, ie: more negative camber. However, this will cause the inside shoulders of the tires to wear. It's a compromise.
It's not really a grip issue. The turns (kink and T1 at Pacific) are gentle. It's more a feeling that the car wants to float around and not go just where it's pointed. It dances around under you just a little, enough to tell you it's not fully cooperating.
I realize the bars can decrease ultimate grip, but I think they'd help the stability. I did a similar number on my 300ZX (stiffer bars with stock springs), and was pretty happy with the results.
I haven't gone back to check the tire wear after today's sessions. If I'm wearing the outsides, I might add a little camber. BTW I have just a touch of toe-out at the front, which might also affect the stability at speed.
Yes, the toe-out , although it improves turn-in (more responsive) it will tend to make it darty at speed. I think you'll find the 04 shocks a very good upgrade over the 02's
"PIR" (as in Portland International Raceway), or Page Ranking (as in Pacific Raceways)? Or both? Good day at Speedware's track day today -- you should've come! Only 2 Z06's, and all those Porsches and BMWs. For a dead-stock car and my first time in the Z06, it held it's own just fine.
The kink being a fairly high speed left then right transition causes some lateral weight transfer and the 04 shocks with their improved valving should help there as well as the right turn onto the front straight out of T10.
Turn one at Pacific is, as you know, a slight dropoff and there is some unweighting of the rear that occurs there so that does result in a bit of instability. Don't let off the throttle as you cross it.
No, never been to Spokane. If I ever get into Conference racing I'll probably end up trying it out. Didn't know about the super-long straight; think I'll try in in the Miata first!
Turn one wasn't where I was finding the problem, but more in the straight (or long arc) before it. If you're really turning (as in One), the suspension has some load and it's not too bad.
I was also seeing some interesting non-linearity of the steering at speed. I'd turn the wheel "a little", and get "a little" bit of turn. Turn the wheel "a little more", and I'd get "much more" turn. After the transition to "much more turn", it seemed linear with even more steering. One of the Speedware guys suggested that it might be due to the front end lifting, which made some sense. I tried lifting slightly at turn-in, which seemed to get rid of it, so I'm guessing he was right.
So now I guess I gotta look at aero stuff too. One thing is that I took out most of the stock rake by lowering the rear maybe 3/8". Might have to rethink that. I can't lower the car too much in front, though, since I've got a nasty driveway entry.
The lack of rake will certainly lead to more lift. You need at least 1/2" with 3/4" being even better. A splitter would help but with driveways etc. that's not always an option.
I forgot to mention it (it's late) but your alignment might be part of it as well. Especially the front toe. It does have a tendency to change as the camber plates are known to slip and frequently do.
The black pipes are normal... at WOT these cars spit all kinds of stuff out. At least it's not oil. You should have seen my car after romping it before the re-ring. It was nasty, now after two VIR events it doesn't burn any oil on the streen and 1/2 quart per VIR weekend.
As for suspension I'm doing the '04 shocks next then maybe T1 bars later. I want to be ready to kick some Viper ass at Viperdays in July @ VIR
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But both, yes.
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