Final Drive change for cosworth supercharged 86

[Rtb 4]

Hi Guys

Some advice please.

My car is supercharged....use it for both road and odd track day......not to bothered about the whole economy bit just interested as to final drive swap for that "better out of bends" "more in power range" stuff...any advice please.

[Ade 517]

I was tempted but ultimately decided the money could be better spent elsewhere. You'll find on some corners stock gearing is better and vica versa. 

 @DanJ has one on his Harrop supercharged BRZ. 

[Church 209]

Optimal gearing is very track specific. What may add some acceleration on some, may add extra gearshifts on others, as result even slowing down.

Given you already have supercharged, i'd keep it at that. Would think a bit more about FD change on NA stock power though.

[Lauren 2259]

We did comparisons on different final drives a while ago. They offer no advantage was the consensus. Better to stick with stock gearing I would say. I've driven a car with the shorter final drive, the 4.67 and it was quite annoying in how short the gears felt, particularly first whilst seemingly offering nothing more really. 

[Foulsmell 120]

We did comparisons on different final drives a while ago. They offer no advantage was the consensus. Better to stick with stock gearing I would say. I've driven a car with the shorter final drive, the 4.67 and it was quite annoying in how short the gears felt, particularly first whilst seemingly offering nothing more really. 

It’s only by 300rpm.

 

 

On an NA car I’d say yes it makes a worthwhile difference on a road car. 12% more torque being but through is noticeable especially in 3rd 4th and 5th gears. Mine has never felt short geared and I have 4.67.

Like said before a final drive would be track specific so not worth it.

[Lauren 2259]

Yes,  I know. I guess it's personal preference. Gearing is fine as it is, was my finding. 

[Church 209]

Lauren: but what i was thinking about for a while - combo of final drive change AND close gear ratio set (from trd/cusco, or some cheaper alternatives, eg. mfactory). As in - so that 1st & 2nd stay somewhat same, but 3-4-5-6 get closer/shorter. If only gearsets had been cheaper, sigh.

I find current 2nd rather optimal for many tracks i was at, letting me stay above torque dip even in slowest-tight hairpins and lessen gearswitches. But would have prefer a bit better geared gears above it.

[Lauren 2259]

Church, that would be great if all you did was drive your car on track, though it would be very expensive to do. I find that your mileage varies in terms of the gears being optimal for the track as it very much depends on the track. When sprinting I've sometimes found I'm inbetween 2nd and 3rd in some corners and that Kev who was at the time running the shorter final drive ratio of 4.67 had an advantage, this has been the other way round at other tracks/corners. So you can't win really. I've tried the shorter final drive. I didn't like it, so quite happy with what I've got. My car is driven on the road 99.9% of the time though. 

[KevinA 695]

I now run 4.44 and it's better on the road and fine for track, there is no perfect solution.

[DanJ 374]

In road driving the extra torque at the wheels when pulling away from junctions can be useful.

Track wise I've found that typically I'm a gear higher than cars with the std FD in most corners, less across the gate downshifts to second is a bonus but otherwise there isn't much in it.

I imagine there'd be a small advantage on some sprints pulling away from the line, but that depends on how far it is to the first braking point and whether you'll have to make an extra shift with the shorter ratios.

If I had my time again I would spend my money elsewhere, but don't regret it as I've learnt plenty from doing it.

[Foulsmell 120]

I think the value of them are on the road. I’ve no need to drop gears to overtake for instance like before. You don’t have to work the engine as hard.
The extra torque reduces the feeling of the ‘dip’.
And on the motorway it appeals to my lazy side. Overtaking in 6th no problem.

[Kodename47 446]

Just to throw something different to the mix but if you have more torque then it could be advantageous to run a longer, rather than shorter, FD. Now the Cossie SC might not be of a big enough torque jump to make the best of it but plenty of guys in the US running a 3.9 or similar. This will keep you in the torque band for longer. Most Porsches are a good example of this where the gears are so "long," this is so that they make the most of the torque available.

[Rtb 4]

cheers guys.....I think i will leave as is re: FD.....after comments.