final drive ratio choice - ideas please gents.
Turbo Mini Forums

A pick your brains question. I need to decide what final drive to use for my project, basically supercharged about 150 bhp, 10 inch wheels with 165 70 10 tyres. Not a daily driver, just a weekend toy. Only likely to see a motorway on the odd run to a mini show. But I want it to be a nice drive, not just wanting to take off like a scolded cat all the time revving its nuts off. I have the standard turbo 3.2 at the moment in the box, but also have a 3.1. I don't mind buying other ratios if any others would be better. So the question is what ratio do you think I should go for.

I think a 3.1 would be very nice with that engine. I don't know if you've already seen this but check out the ratio calculator on johns site, it'll help you compare ratios. http://www.guess-works.com/Gearbox/Technical/ratio.htm

if it were me id go for the highest ratio you can get, supercharged motors seem to make lots of torque and dont like to rev too much.

a highter ratio would mean you can take advantage of the torque
plus your less likely to overstress the engine with revs

but this is only my opinion, and im no expert

i have 10's and a 3.44, i wish i had gone for a 3.2 or 3.1 as i think it revs to high on a run

I've gone for 3.2 with 10's on my clubby. I would have put a 2.95 in there but I have metro challenge gearset which has a very long first.

If something is worth doing, it's worth doing half of.

I'd go for the 3.2, or 3.1, deffinately no lower. Should give you about 120mph at 7k. Anything else in my opinion would be wasting the potential of the engine.

3.1 should be about 80 at 4.5k.

I have 10's and 3.44 with sc drops on my daily. Its fun, but loud. Revs top out too early on the motorway, fun getting there though. im going to 3.2 id say next time the engine comes out. Just for some more legs, but i like the scalded cat bit !!!!! hhmmm
second fast cruise mini for me i think!!

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Just leave the 3.2 in IMO

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Dear god not another one of these topics. No offense to anyone, but really only YOU can decide what FD ratio to choose. One mans perfectly acceptable ratio is another mans pain in the arse, and that works for pretty much any number you choose.

If you really really hate the choice you do make, then its not a difficult thing to change it next time you have the engine and box out.

Stay away from the extremes of either end of the scale, e.g. 4.1 and 2.7 and you won't go that far wrong with any of them for a road car.

I have to say that I was not going to comment on this thread for the above reason, but when someone recomends a 3.6 for a road forced induction car you have to say something.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Lol, this is like the other topic

What makes a road going car not a track day car and a track day car not a road car?

road tax

Edited by wolfie on 11th Feb, 2010.

Yes and no, there are some that cross over more than others. For example my white 205 is a trackcar that has now developed to the point that its horrible to use on the road for any distance. OK its taxed and MOT'd but it is definitely more "track car" than it is "road car".

My red 205 on the other hand is a road car primarily, but I have done a track day in it. However I have to say although it certainly has the beans and also the brakes and suspension, with the standard seats and belts by the end of the afternoon my upper body and arms were aching like fcuk, just from clinging onto the steering wheel for grim death trying to hold myself upright in the seats. So that one is more "road car" than it is "track car".

i cant stand my 3.4 on 10's im fitting a 2.9,
but,
i do alot of motorway miles, and my truck isnt really that heavy so i dont think it will be too bad, as it always seems to feel like i need another gear when im cruising.

straight cut box 2.58 1st gear ..,3.2 ....helical box 2.9.

editted to make it understandable for moz ...

if you have a gearbox with the straight cut teeth ,which has a 2.58:1 ratio 1 st gear ,thats the one you use to drive off from a standstill ,then i would advise advocate and utilise a differential gear ratio of 3.2:1.

if you are using a standard unmodified helical box ,with a much lower 1st gear ,thats the one you pull away with ,then i would install,fit,emplace,a 2.95:1 ratio differential gear .

Edited by robert on 11th Feb, 2010.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

rob, what does that mean?

yep 3.2 or the 3.1 both will be good

always looking for them bigger bunches of bannanas