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Diff ratio against engine revs
Garyd - 14/9/12 at 06:44 PM

Was after some help on how I can calculate how much engine revs will change by changing the diff ratio over a given distance.

Example: 7000 revs reached over a given distance with a 3.5 diff
So if I changed to a 3.9 ratio over the same distance what would the engine revs be?

Does anyone know if it's a given difference between each ratio, meaning 500 revs from a 3.5 to a 3.7 or is that too easy?

Taking that same gearbox and tyre and wheel size stay constant.

Hope this makes sense

Gary


ian locostzx9rc2 - 14/9/12 at 07:01 PM

Does depend on tyre size a bit but with 185 60 14 ,1 to 1 ratio ie 4 gear in a type 9 gearbox
3.5 ratio approx 20 mph per 1000 revs
3.7 ratio approx 18mph per 1000 revs
3.9 ratio approx 16mph per 1000revs
hope this helps


tul214 - 14/9/12 at 07:05 PM

Gear calc


Xtreme Kermit - 14/9/12 at 07:27 PM

Top programme. Makes it all so easy.


Garyd - 14/9/12 at 07:29 PM

Thanks


snapper - 14/9/12 at 07:58 PM

Shows how wide standard car gearboxes are.
For me it also explained why ford used the 3.6 with an MT75 and why the 3.9 works better with a type 9
Ratios are still far to wide for our applications


tul214 - 14/9/12 at 09:44 PM

quote:
Originally posted by snapper
Shows how wide standard car gearboxes are.
For me it also explained why ford used the 3.6 with an MT75 and why the 3.9 works better with a type 9
Ratios are still far to wide for our applications


Buy Caterham 6 Speed Gearbox | eBay NTDWM


Xtreme Kermit - 15/9/12 at 06:56 AM

Mmmm. Shiny