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C6 Corvette ZR1 & Z06General info about GM’s Corvette Supercar, LS9 Corvette Technical Info, Performance Upgrades, Suspension Setup for Street or Track
30 minutes later I dropped tire pressure from 22psi (oops!) down to a more appropriate 16psi and headed back to the lanes for another pass. In hindsight, I should have taken a lap or 2 around the lot to get air moving through the HX to get the IAT2's stable. With a little cruising they will sit in the mid 80's but I had an immediate opening for lane so I took it. As a result, starting IAT2 was 106°...! A short burnout, 5000RPM launch and full-lift shifts resulted in knocking .280 off my previous PB:
I was totally shocked and elated..! I knew the car had at least a high 10.20 in it, but didn't think I'd also pick up 3MPH over my previous best trap. I was really tempted to let the car cool and make a true glory run, but decided against it as the IDC's were a little scary.. Not to mention DA was rising and my main intention for this track day was to get some shakedown passes in my Supra. The rental organizer was kind enough to let me make a few passes in the ZR1 as a 2nd car, so didn't want to wear out my welcome.
Still stock/original clutch with absolutely no issues after I removed the over-center spring --- I highly recommend that 'mod' for anyone that does any hard driving. I had issues with the pedal sticking to the floor on a hard launches the first time I went out on a drag radial. Flushing the fluid every few passes, etc.. All that BS ended after I pulled the spring out; never an issue since. I flush the fluid, only for posterity's sake, before each track visit.
Still stock/original clutch with absolutely no issues after I removed the over-center spring --- I highly recommend that 'mod' for anyone that does any hard driving. I had issues with the pedal sticking to the floor on a hard launches the first time I went out on a drag radial. Flushing the fluid every few passes, etc.. All that BS ended after I pulled the spring out; never an issue since. I flush the fluid, only for posterity's sake, before each track visit.
That is one healthy z. Great mph and great driving
It only takes a few seconds to remove with a pair of needle nose pliers. It's pretty self explanatory once you contort yourself under the dash. It's probably slightly more complicated to re-install, but I can't think of any reason you'd want to. Pedal pressure is only marginally heavier, and it's more consistent/linear. All goodness, IMO, and the results speak for themselves...!
Thanks, it looks easy, except I don't think I can cram myself under the dash anymore! I use to do all my wrenching, but I've gotten older and fatter! I plan to follow your mod receipt, in another year. One thing I do not like about the shifter, is how sensitive the 2-3 shift is, easy to grab fifth, instead. I use to drag race every weekend, not so much any more. I'd love a ten second slip, just don't know if I can get the technique down, without blowing it up.
Ha, fair enough! Short term pain, long term gain on this one, though..!
I'm super impressed with this mod formula and would recommend it as the first round of go-fast to anyone. Absolutely zero sacrifices and it will run 10's all day long, even an regular tires. Injectors are the limit at this point; IDC's now over 100% in this good weather.. I think my next step will be injectors and the next smaller pulley. If I can get that done before the good weather goes away it should go 9's with only those changes. After that it's cooling mods, ported blower, etc..
Luckily I've never had an issue on the 2-3, but the gates are noticeably closer than some other gearboxes, so can see how you could 2-5 it. Much better than 2 back into 1, though!
Just shakedown runs on this outing, so nothing too exciting/impressive to report. It went 9.9 @ 154MPH with a lot of power left on tap and haven't even scratched the surface on getting the car to leave. It's a full-weight street car that was previously set up for 1/2 mile. It should go bottom 9's ~160MPH once it's sorted out.
Thanks, guys. I'm reallllly tempted to drop in some injectors and a smaller pulley and try for 9's in this weather. I think I can get away with a few 1/4 mile passes without any cooling mods as long as I can get the starting IAT2 low.
11-21-2018, 10:40 AM
Basic bolt-on ZR1 drag results - REDUX
I plan to follow your mod receipt, in another year. One thing I do not like about the shifter, is how sensitive the 2-3 shift is, easy to grab fifth, instead. I use to drag race every weekend, not so much any more. I'd love a ten second slip, just don't know if I can get the technique down, without blowing it up.
Short term pain, long term gain on this one, though..! 
I think my next step will be injectors and the next smaller pulley. If I can get that done before the good weather goes away it should go 9's with only those changes. After that it's cooling mods, ported blower, etc..
