Gear Ratios : Speeds In Gears : When To Shift a Skyline GT-R
This post is all math. If you don’t have some math, to fill into the blanks, you can’t figure any of this out. What you need to know:
- Tire Height – can be calculated from
- Aspect ratio
- Wheel size
- Transmission in the car
- Is it stock?
- Is it modified?
- 5 speed
- 6 speed
- Overall Gear ratio
- 4.111 is stock R32/R33 GT-R
- 3.545 is stock R34 GT-R
- It can be something else
- Shift Point
- If you shift with the stock tach you are shifting at 7600 rpm
- If you shift at the limiter then that is most likely 8000 rpm
- If you shift at a different point, the links are below to figure that out
One example, my bluecar. It has a 275/35/18 tire on it, which is 25.58 inches tall. It has a stock 5 speed transmission. Overall/Final gear ratios are 4.111. It is shifted at 8500 rpm.
|4.111, stock transmission, shifting at 8500 rpm.|
|4.111. stock transmission, shifting at 8000 rpm on the stock tach, aka 7600 rpm.|
So you can see that by shifting at a higher RPM, you fall into a bit better point on the dyno chart for this car, and this turbo combination. https://www.gtrusablog.com/2019/10/finally-running-bluecar-on-dyno-results.html
So about if we swapped to a Getrag? Well actually the bluecar used to have a Getrag in it, but we sold it to a friend, that needed one. So add a 6th gear, keep the 4.111 gear vs the 3.545 gear of the R34. Then we get:
|5242, nearly that magic number.|
Now onto a sequential. My Nismo has(had, till I stole it out for Big Bird 2) OS88 sequential transmission, and 4.3 gears. The OS ratios are:
|4.3 gears, OS88 transmission. 58 mph in 1st gear|
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Index and Start Page
Published at Sat, 16 May 2020 01:37:00 +0000