For road course usage, 4.36:1 makes 1st gear redundant and in effect gives you a 5-speed gearbox with reduced Vmax.
With 4.08:1, I don't use 1st to start, which gives me a single gear from zero to 100kph. 4.36:1 would be crazy short ...
Speed in gears with Nissan box and my DD tyres at 7200rpm is:
1st 40mph
2nd 64mph
3rd 91mph
4th 117 mph
5th 148mph
6th 156mph ** at 6000rpm ***
With my 645mm tall track tyres, speeds are
1st 35 mph too slow to be any use, so I start in 2nd
2nd 57mph
3rd 82 mph
4th 110 mph
5th 140mph
6th 159mph *** at 6500rpm ***
In my case, I used to see redline in 5th at Phillip Island GP circuit with the 3.7:1 OEM ratio but ith the 4.08:1 ration I have to use 6th and pull somewhere between 6300 and 6400 rpm down the chute into T1, so the 4.08:1 has made a very significant difference in acceleration and Vmax.
I would reckon that unless you can safely turn your engine to 8000+ rpm (means dry-sump) then a 4.36:1 diff will not help on the track - might be useful on the strip though
I am now playing with options as I have a box with a much taller first gear and a 0.878:1 OD 6th .... so looking at tyre sizes to suit (650mm tall vs 665mm tall vs 675mm tall Dunlop slicks).
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