Achieving 3.2 FD
Turbo Mini Forums

Hi guys did a search, but got a bit confused as to how ago about achieving this final drive with my setup!

Ive got a s/c clubman gearset from minispares, a set of 1:1 trannex s/c drops and 13" wheels.

Will simply fitting a 3.2 crownwheel get me a 3.2 FD? I understand that standard FD is 3.44 is this correct?

From what ive read a 3.2 is a tidy FD for track/road use? What are your opinions? Lower?

Also, i bought the gearkit a while ago now http://www.minispares.com/Product.aspx?pid=36035

Ive only just realised it says for "A+ engines", have I made a mistake by getting these because ive got a metro turbo engine and have a feeling they're not "A plus" engines.

I hope to god ive not got the wrong kit as I cant find the receipt!!

Cheers

Edited by richminiturbo. on 18th May, 2008.

Metro turbo is A plus, gears should be fine.

The crownwheel and pinion must be fitted as a matched pair to get the final drive ratio. Which FD you have depends on what you want to use the car for. Most people run between 3.444 and 2.9

Nice one tom cheers!

Car is going to be primarily regular road/motorway, and as many circuits as I can make it to, aswell as Avon etc.

So im looking for a general all round usable car really, but would prefer ripping away from a stand still but nothing silly which will see me bouncing valves at the end of the strip!

Will fitting a certain crownwheel+pinion to my setup mean the resultant FD being the ratio of the crownwheel+pinion itself? As I have 1:1 drops? Am I correct in saying that there isnt a huge difference in FD effected by the wheel size?

Ive been calculating road speed with 3.2:1 FD and my wheel size, in 4th, 4000rpm giving me a nice 73mph. From the figures i've been playing around with, a ratio higher than this doesnt really sound ideal for the road and track.

Ive tried 3.2, 3.1 and 2.95:1 and cant really see what would be best.

Edited by richminiturbo. on 18th May, 2008.

your pretty much right on everything,

the rolling diameter of 10s and 13's isnt normally hugely different, the 13's will be a tad "taller" by about 10% IIRC

I would say for all round use either 3.1 or 3.2 shouhld be pretty good. If you don't do any track and quite a bit of motorway then a 2.9 might be more suitable. also you'll get away with a 2.9 better if you have a helical box as 1st is lower.

one thing that might be helpful is.... the no of teeth on the big gear divided by the no on the small gear will give the ratio.

Great thanks for the info!!

Edited by richminiturbo. on 18th May, 2008.

AHEM!

Edited by richminiturbo. on 19th May, 2008.

I agree, now I haven't got my calculations back to front! cheers Joe.
Metros run 3.9 for racing...be quite crap for road use.

Hmmm ok.

Will the car be nice on the 3.44:1 if i leave it alone? Im not too bothered about it being abit silly on the road as i wont use it that regularly.

According to the haynes destruction manual...3.44 is standard 1275 diff

Yeah, im wondering if i should stick with the 3.44 ratio that it has as standard at the moment, but im not sure what will be best for my situation really

What are you planning for the car?

Track day and weekend car mainly!

then go for 31 but no higher than 3.2 this will use the torque curve of the engine better

always looking for them bigger bunches of bannanas

Milamber what do the metro top out at on the track then with that diff??

m

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
Split Rims? - http://www.force-racing.co.uk/

Honestly couldn't tell you. 120ish. Thats sreaming it though, well into the 7000+ rpm . Thats with challenge gearset & 13" wheels

assuming 175/50/13's I "calculate" 7k with a 3.9 as 105Mph,

what are the tyres? i'll double check it

it would just be crap because at at 60 in 4th your going to be doing circa 4k rpm which is going to drink petrol and get irritating,

with a 3.44 @60 you'll be doing 3500, which will just take the edge off the "buzz"

with a 3.2, 3250

3.1= 3150

2.9 = 3k

for circuit work you need to find out what top speed your likley to BE ABLE to hit and gear accordingly, ie gear just below this to balance aceleration against top speed.

Yeah true, im almost tempted to stick with a 3.44 just because thats what i already have in there so wont have to buy one.

And thats what originally fitted to the engine so its obviously an all round good ratio otherwise they would have fitted something else as standard!

might be a good option,

as you say it wont cost anything, then you can decide if you want it taller geared or not.

If your not using it on the road tooo much then the 3.44 might be quite good.

Yep thats the size. Rev limiter set at 8000 rpm

And as Rob says...you don't want it screaming constantly down a motorway. Circuits its it up & down.

Edited by Jason G on 20th May, 2008.

Oki doki thanks for the info. I think i'll see what its like with a 3.44 for minute and maybe change it once ive gotten a firm idea of how i want it to behave.

Cheers!