BJ67

To all the performance tuners and hard core drag pro's, my question is why shift at 700 rpm over the max horse rpm instead of the usual 500 rpm over in reference to a stock LS7 Z06. I realize Chevrolet says the redline is 7000 and the fuel shut off is 7100. Did Chevrolet underrate the motor by saying it produces 505 hp @ 6300 and if so, does it make more horse @ 6500. Bottom line, for best 1/4 mile Times what RPM should I shift at?. Thank you in advance for any great feeback.

The Highlander

IT will depend on the transmission gear ratios.

Normally the longer you are in the previous gear the more multiplied torque you have to the wheels... the better the acceleration. That will depend on your torque x multiplied gear... if the next gear x torque is higher, you should shift at that point.

Mike@DiabloSport

If shifting at peak power causes rpm to drop below peak torque, you may find better acceleration by shifting a bit higher.

Again, its something that you really need to test to find out, but I am sure there are a few guys here who have figured out where to shift to maximize acceleration in the C6Z.

The Highlander

Mike

If you shift at the point where you drop to peak torque you will be shifting at 6000 or so and that will result in greatly reduced overall acceleration!

I'll post a spreadsheet later on how to calculate your shift rpm

Mike@DiabloSport

I was simply making an example, not saying you had to shift to get the next gear to pick up right at peak torque.

This changes tremendously with a fat torque curve as well. A small displacement motor is much more dependent on exact RPM to get peak performance than say an LS7, or a positive displacement supercharged setup, for example.

8850

Z06 is rated at 470# of torque at 4800 rpm. You would like to not drop below peak torque at shift.

Shifting the 1-2 at 7000 drops the rpm to just above 4600. Not quite high enough.
2-3 shifting at 6600 drops to 4800. 3-4 shifting at about 6300 drops to 4800. So each gear is different to maintain peak torque at shift.

My guess is a 7000 shift would probably net best et.

I was using stock tire diameter for my calculations.

wtb-z

You make more average power shifting above peak power. Only with infinitely close gear ratios (e.g., a CVT) would you "shift" right around peak power.

C7/Z06 Man

Read this somewhere a long time ago for best 1/4 mile times.

*Shift 7-8% above HP peak for best 1/4 mile times.

My Example: LS3 = 430hp @ 5900 rpms.
+8% =.................................472 rpms.
Shift point =........................6372 rpms.

My A6 LS3 shifts approx. 6350 to 6450 rpms from the factory and it runs well for a heavy GS with a stock converter (11.32 @ 125 mph).

*LS7 = 6300 rpms + 504 rpms (8%) = 6804 rpm shifts.

I have seen guys run their cars up higher just because they can and think it sounds better too; but their et usually falls off.

PS: I would start at the 6800 rpm shift point than try moving it up or down some and see what works best for you.

1MEANGS

I always thought you should shift a lil higher then your peak power so that when you slam the next gear you don't bog and be in too low of an rpm?