Nissan 370Z Forum - View Single Post - 3.9 upgrade worth it, dedicated track car?

BGTV8 · 01-05-2017, 09:00 PM

Mike, I have 3.9 with 677mm tall tyre *275/40R18) for road use and SRM still works a treat .... 4.08:1 is noticeably out though ........

I will go to 4.08:1 diff with new engine and Quaife box on short tracks and still use the 3.9 on longer tracks. Engine and box should be in the car by March.

3.9 with 1:1 top gear and 280/655R18 slick @ 8500rpm is 272kph
4.08 with 1:1 top gear and same tyre @ 8500rpm is 260kph

Difference between 3.7 and 3.9 pulling out of turns can definable be felt, acceleration with 4.08 is proportionately better but with OEM rev-limit (still have std oil pump), you run out of revs with 4.08 and my little (650mm diameter) R-Spec tyres

01-05-2017, 09:00 PM	#2 (permalink)
BGTV8 A True Z Fanatic Join Date: Dec 2009 Location: 03350 Australia Posts: 1,514 Drives: 09 Nissan 370Z M6 Rep Power: 39973	Mike, I have 3.9 with 677mm tall tyre 275/40R18) for road use and SRM still works a treat .... 4.08:1 is noticeably out though ........ I will go to 4.08:1 diff with new engine and Quaife box on short tracks and still use the 3.9 on longer tracks. Engine and box should be in the car by March. 3.9 with 1:1 top gear and 280/655R18 slick @ 8500rpm is 272kph 4.08 with 1:1 top gear and same tyre @ 8500rpm is 260kph Difference between 3.7 and 3.9 pulling out of turns can definable be felt, acceleration with 4.08 is proportionately better but with OEM rev-limit (still have std oil pump), you run out of revs with 4.08 and my little (650mm diameter) R-Spec tyres Last edited by BGTV8; 01-05-2017 at 09:03 PM.*