i have been looking at the different gear ratios between all the different models and i have noticed that the P1 have got almost very similar gear ratios to UK cars however it has a final reduction of 4.444 like the sti v,vi etc compared to 3.9 for UK cars. i have been in coupel of P1s they felt like they had a shorter gearing than my uk car. can some please explain all this to me.


cheers

sam

 

Sam,

Stelios is right.

It is the reduction ration, given by how many times the engine turns for one rev of the wheels.

UK cars are 3.9. Jap cars are either 4.1 or 4.44. my car has a shorter ratio type r gearbox and a final drive of 4.44, the uk 22b has the same gearbox but a final drive of 3.9. I believe the P1 ditches the standard type r gearbox and goes for a normal sti one with the same final drive of 4.44 as per any other jap car

Can someone confirm their rpm at 80mph?

 

Not an expert Sam but as far as rpm go its something like this: Engine RPM -> Gearbox (each gear different reduction from 1st to top)-> Axle (final reduction) so total reduction ratio is Gearbox ratio (per gear)*final reduction ratio

 

Sam,

the final drive is pretty much what it says... it is the ratio of the number of teeth on the crown wheel to the number of teeth on the pinion inside the front and rear differential, and thereby gives the number of revolutions of the prop shaft per revolution of the wheels.

Adam, you also need to take into account the gear ratio, as this will affect the number of revolutions of the output shaft of the gearbox with respect to the engine.

The figures 4.444 and 4.111 come about from the following ratios:

40:9 crown inion on the 4.444 (ie actually 4.444444444...) and 37:9 for the 4.111 (actually 4.11111111....). The 3.9 I have yet to have a close look at but suspect it is 39:10 as no integral :9 ratio will work.
There are many different final drives, 3.9, 4.111 and 4.444 being the most prevalent among the turbo cars, but there are also some around 3.5 is on others (NA, auto etc).

UK gearing is probably taller, even with the final drive taken into account, so there is more to it. I'm sure all the ratios are available somewhere on the Internet.

Hope this helps,

Pat.

 

I realise that pat but unlike you I think it is best not to try to confuse people unnecessarily!

I also find it funny that you tried to write crown : pinion ratio but neded up with crown inion ratio.

 

pat,

Don't mind Adam, he's just young...

Moray
(Retiring to safe distance now blue touch paper is smouldering )

 

thanks guys for your help.

so does that mean if i change the diffs to an import on i will virtually reduce ( shorten ) the gearing on all the gears ? so is this how the P1 achieve its shorter gearing. and will using 4.44 diffs with the taller UK gearing ( ratios very similar to the P1 ) make the car slightly more suitable to motor ways.

when i looked at the FAQ section mentioned that all the imports have 4.444. so which cars have 4.1.

what i am trying to achieve is faster in gear acceleration while maintaining good motor way behaviours. i am not really interested in the 174MPH theortical speed at 7000rpm in 5th that my car seem to be capable off !!!!!

 

come on guys any more info ? surely some one must have looked into this in detail that can answer my question


sam

 

Sam

The 2 door cars have the 4.444, 4 door imports have 4.1.

I thought the 22BUK went to 4.1, not 3.9

If you change your UK box to an import box, you will also have to change the rear diff to match. Later 4.444 diffs can only be used with their own drive shafts... and these also need the later 2 pot hubs. This is what I did with my 94 RA.

Early RA's also had 4.444 rear diffs and these can be used with non 2 pot rear hub set ups. I changed so I could also fit the 2 pot rears.

 

Sam/ My max speed in a UK car at 7000 was just over 160mph but I believe the car was only doing 158ish mph on the rev limiter.

P1/ 5th gear cruising at 90 mph = 4000 rpm.

 

bob i have just used the ratios given for the subaru in the FAQ section. so i am not sure if they are right or not.

thanks pete
but this adds to the confusion now. so sti 4 doors and P1 are running 4.1 final reduction ? since the extra short 4.444 is for the type RA and 22Bs.

if i get a 4.1 diff from an sti V 4 doors will it fit my car ?

the other thing, due to the slightly longer ratios of the UK gear box will the gearbox oil get hotter ? hot enough to start causing problems


cheers

sam

 

Pete,

I could have sworn that the 22B Type UK was running on a 3.9 final reduction.... that gives about 78 MPH at 3500 RPM in top which is about right, IIRC. But I' ve been known to be wrong before, and I'm sure I will be again....

Also, while you are correct in saying that 4 doors have 4.1111 final drive, this was only, AFAICT, up to 1997 when the EJ20K was introduced, With the higher 8000 RPM redline on the STi, the final drive could be dropped down to 4.4444 and still maintain a "sensible" top end, about 170MPH (or 156 in a Type R).

It would appear that all early WRX and STi cars have got 4.1111 final drive though, everything up to and including STi II anyway With one or two exceptions like your Type RA which had 4.4444 (lucky that... ).

As for the later rear diff, I *think* that is an R180 diff, the others are R160 diffs. You are spot on with regard to the drive shafts... basically you CANNOT mix'n'match I have got a solution, which is basically a completely custom driveshaft that has the R180 spline pattern at one end and the R160 spline pattern at the other end, and is about 10mm shorter to accomodate the extra width of the R180 diff. This would allow the ABS rings to be retained if using the R180 (which appears to be a mechanical, not viscous coupled, LSD). Watch this space


Sam,

Although I am not 100% certain, I think the STi IV has a 4.4444 final reduction, have a look at something like an STi II or '1994 to 1996 WRX for a 4.1111 final drive. I know that Pete has some 4.11111 R160 (and a couple of R180 4.4444, one of which is mine ) diffs lying around, so should be able to sort you out with one. That leaves the front.

This could cause you a bit of grief. You *could* get an older 4.1111 'box, but in 1997 they revised the 'box casing to strengthen it somewhat. Also the gearset was revised, with better synchromesh, so ideally you wouldn't want to go for one of these if you can avoid it. This does mean that you have to fit a 4.1111 crown and pinion to your 'box. This is a very highly skilled operation, if it's anything like a "normal" diff... to get it done properly you'll need to dig deep into that wallet. Again, Pete will be able to arrange for this work to be done... his gearbox man is a bit of a perfectionist, errr, actually that is like the understatement of the decade!

Not sure of the P1 final reduction, but I'de try to stick with "standard" stuff, UK or STi rather than "special" stuff which Prodrive have made for a limited production run... more chance of getting hold of spares should you have the misfortune of breaking something.

In fact an STi 4 transmission would probably work quite well, give you roughly 80MPH at 4000 RPM in top, 140MPH at the redline, and it will almost certainly pull all the way (look on the bright side, my current gearing maxes me out at 130, but it doesn't half get there quick!).

Hope this helps,

Pat.

 

Try this, this might be helpful in the future.