NJFBOA - Home of New Jersey's Camaros and Firebirds - View Single Post - Determining best launch and shift points, using math and datalogs

IROCZman15 · 10-19-2020, 06:26 PM

a friend sent me this link:

https://glennmessersmith.com/shiftpt.html

I put in the numbers I have from the engine dyno sheet and it is telling me to SEND IT higher into the rpms.

I am unsure with my mph is during the 1->2 shift, but I think the mph given by the calculator (86 mph) is pretty close, because I have usually shifted 2->3 just a little bit before the 1/8th mile cones, and I am typically trapping 91-94 mph in the 8th, so that number seems to mathematically make sense.

Additionally, if that set of mph numbers is correct, I will probably never need to shift into 4th gear even when on the nitrous because this calculator says I should make the shift to 4th around 140 mph... and it is very unlikely this car will get to 140mph in the 1/4 even with the 200 shot. So, keeping this rear gear ratio and tire height seems promising for the nitrous setup, while a switch to 3.73 might indeed put me too deep into 3rd where I would have to shift into 4th (on the bottle).

10-19-2020, 06:26 PM	#7
IROCZman15 10 Second Club / Meet Coordinator Join Date: Dec 2004 Location: Roxbury, NJ Posts: 2,101 iTrader: (8)	a friend sent me this link: https://glennmessersmith.com/shiftpt.html I put in the numbers I have from the engine dyno sheet and it is telling me to SEND IT higher into the rpms. I am unsure with my mph is during the 1->2 shift, but I think the mph given by the calculator (86 mph) is pretty close, because I have usually shifted 2->3 just a little bit before the 1/8th mile cones, and I am typically trapping 91-94 mph in the 8th, so that number seems to mathematically make sense. Additionally, if that set of mph numbers is correct, I will probably never need to shift into 4th gear even when on the nitrous because this calculator says I should make the shift to 4th around 140 mph... and it is very unlikely this car will get to 140mph in the 1/4 even with the 200 shot. So, keeping this rear gear ratio and tire height seems promising for the nitrous setup, while a switch to 3.73 might indeed put me too deep into 3rd where I would have to shift into 4th (on the bottle). __________________ 1987 IROC-Z - modified Last edited by IROCZman15; 10-19-2020 at 11:59 PM.