Opinions on shift points

[Pit Man]

I ran my 2003 Z06 at SGMP on Saturday and had my son doing the tuning. One thing that I'm trying to perfect is the shift points.

Here is my dyno graph.




I can't get my SAE graph to load which put out 430/400 est., so this will do. Anyhow, you can see peak HP is reached at a RPM of 6250, than slowly falls. What shift point would give me the best ET?

Below is a picture of the log we recorded on Saturday. The car ran a 11.7 @ 121 on a 1.88 60'.

Mods are :
AFR 225 heads
224/224 109LSA
LG long tubes
2.5'' stock exhaust, cats removed
stock mufflers
Vararam
FAST90, LS2 TB
Then, the little bit of tuning we have done.... 30* of timing, 13.0 AFR.

Here is the log:
http://i10.tinypic.com/2nrfsjn.jpg

Pics have to be a max of 640X480

I was watching my tach and I was appr. shifting at 6600RPM. Looking at the log, I was shifting at 7100, each gear!
Luckily my son knows I'm a little slow on the shifts and set the limiter at 7200.

Anyways, most of this is just details and my question is where do I need to shift at to get the best ET out of this car?

Thank you,

Bob

[robz]

I would shift right at the limiter if you are running good sticky tires.
The only shift that you can short shift slightly is the 1-2 to prevent excess wheelspin. But I don't see a big spike in your mph so it may not be necessary.
The slow shifting is hurting your times probably by about .1 on each shift. If your limiter is at 7200, then you should be able to powershift it with the light being set at 6800-6900 without hitting it. Since you are not powershifting then I would work on shifting at 6900 on the tach and that will also get your speed up.
I would also rev a little higher in the burnout to get those tires hotter.
What psi/tires?? I would be happy to give you feedback on anything related to any part of the run.

If you notice, coming off the throttle affects many things.(injector dc,maf, etc..) Provided traction it would benefit in many ways to keep the pedal planted. But, I do understand it will take some seat time to get the timing figured out.

[Pit Man]

Rob,

I can see the slow shifts hurting ET. You can see that TPS is dropping very low inbetween the shift points and this probably isn't a good thing. My son was explaining to me that if I let out of the throttle too much during the shift, AFR is going back to stoich (14.63) and then having to jump back into PE when I get back into the throttle. All of this is probably taking up precious time.

I'll also work on the burnout a bit more.

Tires are Nitto R2s @ 18psi.

Tune is in open loop, SD. No MAF.

Any and all tips are greatly appreciated.

Bob

[Pit Man]

Also, I'm assuming it's more about the speed of the shift, rather than at what particular RPM?

[Top Cog]

It would be interesting to get Ranger's comments on this. Anyone know if he's still active here? I see him on CF regularly.

[robz]

Ranger doesn't post here but his philosophy is to shift at redline without hitting the limiter.
Bob, your son is right about the negative effects of lifting.
The big limiting factor is the nitto r2's.(I'm assuming your talking about the road racing tires). I use them as my street tires. I ran them at 14psi on a few passes at the strip with my cam only setup(419rwhp). My best 60' was 1.70. I think they are good for high 1.6x's with some finesse. You may want to run them around 15-16 to give a bit more grip. Mid 11's on those tires is a great run. You will have better results with drag radials like bfg's or mt et street radials.

The big dilemma to getting the best et with those tires is to prevent WHEELSPIN.
One way is to shift slightly early moreso on the 1-2,
The second way is to slow down the shift especially on the 1-2.
I imagine you are gettting alot of wheelhop on the 1-2.
Ranger would suggest keeping your shifting near the limiter and slower shifting the 1-2.
I believe your best results with those tires would be to not powershift the 1-2 but shift it up near the limiter.
The 2-3 should be a faster shift near the limiter.
The 3-4 I would maybe powershift it near the limiter.
Although there are negatives to lifting off the throttle,the wheelspin that powershifting will create will hurt you more on those tires IMO under most conditions.

Your run was very nice for those tires. You guys are doing everything right.The best bet is to get better drag tires.
Make sure your slipping the clutch somewhat on the launch. You would probably have an easier time if you were only making 400rwhp with those tires.
Another thought is to run on a day where there are alot of fast cars with slicks. The track conditions will make a big difference. Keep us posted.

[Pit Man]

I'll be at the track again in early January when the surrounding tracks reopen.

Thank you for the help and the tips.