My first post I know guys but I need some help from the kit car guru's which I believe to be you,
Basically I own a MK Indy which we've built for the track (was a road car). The main info I'm after is gearing, diff ratios etc it runs a
2.1 pinto
kent FR32 cam
Big valve head
ported
Vernier
wiseco pistons
cossie rods
lightened flywheel
twin weber 45's
this is attached to a type 9 gearbox which I believe is the 2.0 version not 2.8, then onto a 7" push fit drive shaft 3.38 lsd diff 15"
wheels with 195/50/15 tyres (r888's), seems fine off the mark 1st 2nd 3rd gear but once you change up into 4th it seems to just lack any get up
and go so would this be down to the diff ratio ?
[Edited on 22/8/16 by mkindypaul]
[Edited on 22/8/16 by mkindypaul]
With that gearing it's likely by the time you change into 4th you are experiencing the supreme aerodynamic ability of a seven.
quote:
Originally posted by theduck
With that gearing it's likely by the time you change into 4th you are experiencing the supreme aerodynamic ability of a seven.
3.38 diff is too high a ratio for a pinto a bike engine or v8 rover maybe you would be better with a 3.64 or even a 3.9 diff
quote:
Originally posted by ian locostzx9rc2
3.38 diff is too high a ratio for a pinto a bike engine or v8 rover maybe you would be better with a 3.64 or even a 3.9 diff
Yes ideal for a bike engine (or rover v8 due to lots a torque )
quote:
Originally posted by ian locostzx9rc2
Yes ideal for a bike engine (or rover v8 due to lots a torque )
3,62 is what you need and what happened to 5th gear
quote:
Originally posted by mkindypaul
quote:
Originally posted by ian locostzx9rc2
3.38 diff is too high a ratio for a pinto a bike engine or v8 rover maybe you would be better with a 3.64 or even a 3.9 diff
I was under the impression the 3.38 was the choice for the bike engined cars or so I was told
quote:
Originally posted by jacko
3,62 is what you need and what happened to 5th gear
quote:
Originally posted by Ugg10
quote:
Originally posted by mkindypaul
quote:
Originally posted by ian locostzx9rc2
3.38 diff is too high a ratio for a pinto a bike engine or v8 rover maybe you would be better with a 3.64 or even a 3.9 diff
I was under the impression the 3.38 was the choice for the bike engined cars or so I was told
For the bike engines it is not an issue of torque (pretty small usually compared to a car engine) it is the 10k+ revs and the fact that after the inbuilt gearbox they have the sprocket / rear wheel ratio to take into account that you do not have when driving a car diff.
I found this calculator pretty useful for calculating speed/gearbox info -
http://www.subarugears.com/Ratios/Ratios.html
and this for calculating wheel diameters
http://www.willtheyfit.com/
As has already been said -
3.38 will give you a big top speed, compounded by the 15" wheels, which is currently compensating for the type 9 low 1st gear but then over extends 4/5th at which speed (possibly 100mph+) you are hitting the proverbial aerodynamic brick wall of the seven car.
Ideal is a long 1st type 9 plus 3.9 or 3.6 diff depending on the track (3.9 for short twisties, good acceleration, 3.6 for longer where top speed is needed).
[Edited on 22/8/16 by Ugg10]
quote:
Originally posted by mkindypaul
quote:
Originally posted by ian locostzx9rc2
3.38 diff is too high a ratio for a pinto a bike engine or v8 rover maybe you would be better with a 3.64 or even a 3.9 diff
I was under the impression the 3.38 was the choice for the bike engined cars or so I was told
Ok cheers then guys, so I suppose my next move is to find someone to fit a 3:9 crown wheel and pinion into my diff, I have a pic of mine is it defo a
lsd and can a 3:9 be fitted to it?, also can someone tell me if its going to make a difference to 4th gear driving ?
It will make a difference, but only because you will get to 4th at a lower speed.
Theoretically if you max out 3rd gear at 6500 rpm and change up to fourth (which is a 1:1 ratio in the type 9) and then max that out then subarugears
suggest that approx -
3.38 diff max 3rd is 106mph, max 4th is 137mph
3.9 diff max 3rd is 92mph, max 4th is 119mph
The down side is you max 1st gear goes from 38mph down to 33mph. Long 1st (2.98 or lower depending on box vs 3.64 for stock) will sort this out and
also reduce the possibility of bogging down between 1st and 2nd which is a wide gap on the stock 2.0l i4 type 9.
Hope this helps.
I run similar spec Pinto,s and trust me the 3.9 diff gives you usable performance and an achievable top speed in 4th
Granted 80 in 5th is 4K
I run the V6 gearbox which is the best option but could do with a longer 1st
quote:
Originally posted by theduck
With that gearing it's likely by the time you change into 4th you are experiencing the supreme aerodynamic ability of a seven.
I would say your rear diff
is "over geared" though, as already suggested, a 3.62 or 3.92 would be better suited if you can find one.
Think my best bet would be to buy a 7" push in shaft diff off eBay for example but a 3:6 or 3:9 and just fit the crown wheel and pinion into my current diff that way I can keep the lsd which I know works and the bearings etc are all nice and quiet.
I've got a 7" 3.92 going spare - it was a bolt-on (the stub axles have already been robbed off it so its now a push-in 
) but if all you
want is the CW&P that won't make any odds
quote:
Originally posted by mcerd1
I've got a 7" 3.92 going spare - it was a bolt-on (the stub axles have already been robbed off it so its now a push-in
don't know what its worth - it would need a full rebuild and a rear cover to ever be used again - so maybe £25 +p&p ?
I'd guess the p&p will be quite a lot given the weight, but I'm happy for you to arrange collection if you like
the case was fine when I last looked at it, but had a bolt stuck in the top mount (I'm sure that would come out when its cleaned up properly) -
and the gears looked ok, but all I've done was pull it off the donor car and shove it in a corner so can't guarantee its condition
here's the old pics I've got for now - I can take some fresh ones if your interested
your other option would be to buy a working open centred 3.92 diff first just to try in the car - then you wouldn't need to pay for rebuilding
your LSD until you were happy with the ratio
also bare in mind that a 3.38 LSD with push-in shafts could be desirable enough to sell for some decent money as is - although I doubt it would pay
for a complete new 3.92 / 3.62 LSD it may have got a good second hand one with cash to spare
if it helps each step in the sierra diff ratio is about 8% higher or lower gearing - so 8% higher or lower revs for whatever combination of speed and
gearing
- with 3.38 to 3.92 being 2 steps giving you about 16% difference
[Edited on 23/8/2016 by mcerd1]
@adamirish
What wheel and tyres size do you run ?
run some numbers through the gear calc program if it helps
based on the stock 2.0 type 9 ratios and your 195/50 R15's
3.92 ratio
At 70mph in 3rd you’d be doing 5572rpm - changing to 4th would give you 4067rpm
If you hung on in 3rd till 90mph you’d be doing 7163rpm and forth would give you 5229rpm
And in 4th you’d get 5810rpm at 100mph and 6972rpm at 120mph
3.38 ratio
At 70mph in 3rd you’d be doing 4804rpm - changing to 4th would give you 3507rpm
If you hung on in 3rd till 90mph you’d be doing 6177rpm and forth would give you 3697rpm
If you hung on in 3rd till 100mph you’d be doing 6863rpm and forth would give you 4108rpm
And in 4th you’d get 6011rpm at 120mph and 7013rpm at 140mph
Based on that I’d guess the 3.38 is too much for you, but you’ll know yourself were your power band is within your rev range and what your rev limit /
max safe revs are and the sort of speeds that you likely to be doing (or at least revs for any given gear)
[Edited on 23/8/2016 by mcerd1]
Going by those numbers for us to achieve any decent pull from 4th gear the 3:9 looks the best as I don't think 3:6 would be enough of a jump
^^ edited the above to show the highlights as the format went a bit weird....
have you got any more details on the rev limit / power band that you want to work within ?
[Edited on 23/8/2016 by mcerd1]
God it's a nightmare, I don't think there is going to be any definitive answer it needs a 3:6 and 3:9 to test. The track we used it on was a short track with just one longish straight and I only put it into 4th for a short period of time and this was from 3rd at about 6200ish rpm so maybe I was wrong and the 3:6 would be the most practical answer, that way I don't destroy first with such a short diff as a 3:9 and I also bring the speed down enough with the 3:6 to the point where I needed 4th the engine is gonna be revving harder so once slotted into 4th it's more into the revs and power band.
Hi
You answered the question in Post 1 really, as you're running it as a track car cruising ability is irrelevant, so you're looking at the
following scenario:-
On the longest straight you're ever likely to see you should want to hit the rev limiter in 5th just before you get to the point of hitting the
brakes
Or
Around the same point the car hits the aero wall - yes?
Even with a 3.9 in it, you'll not do that you'll either run out of straight well before it gets to the red line or it'll hit the aero
wall - either way out of the choice of a 3.6 or a 3.9 it'll certainly be the latter.
HTH
Hell Jim,
Basically yes I think it hit the aerodynamic wall in 4th and with the straight not being massively long I ran out of road to pull through but with
more power I'm sure it would of done so. some people reccomend the 3:6 and some say 3:9 so it's confusing. I may just get the 3:9 crown
wheel and pinion off mcerd1 and fit that to my current diff and just take it to a track day at the same one as I used last time, I mean fitting the
3:9 shouldn't hamper the day should it ? Won't be to much that we can't use it
Mcerd1,
Would you be able to remove the crown wheel and pinion to save posting such a bulky item as I don't think I'll use anything else from the
unit itself ?
[Edited on 23/8/16 by mkindypaul]
quote:
Originally posted by mkindypaul
@adamirish
What wheel and tyres size do you run ?
Cheers for all the help guys I think I'm gonna go 3:9 route first and see how we get on, I just have one other question though as I've read on here you can't get a 7" push in shaft lsd diff ? Mine is 7" with push in shafts and on the first page I put a pic up with the back off?
quote:
Originally posted by mkindypaul
I've read on here you can't get a 7" push in shaft lsd diff ?
quote:
Originally posted by mcerd1
quote:
Originally posted by mkindypaul
I've read on here you can't get a 7" push in shaft lsd diff ?
you can't get an OE ford LSD with push-in shafts - but you can get any of the aftermarket LSD's
Looks after market judging by the difference in materials?
Google the numbers on it
If you can fit 13 inch wheels over your brakes these make for much better track driving than 15's,and you can use the smaller wheels to alter
your gearing too.
^^ my pics above are fords bog standard open diff - so yours looks like an aftermarket of some kind...
doesn't quite look like a tranX one either:
Tranx fitted 1
or a quaife atb:
some googling throws up some pics of supposed ZF plated diffs - but they aren't that common (no longer in production) and I don't know much
about them, but I believe they are still quite sought after by some folk
I'm sure someone else will know exactly what it is...
[Edited on 23/8/2016 by mcerd1]
My bro googled the last lot of numbers with the s25 and the quaiffe website came up but that's as far as we got, maybe it's a discontinued version either way it's in perfect working order and fits lol
Cheers mcerd1 & nickP
Looks like it's a zf Motorsport plated lsd diff, quite a capable unit by all accounts
Mcerd1, did you get my message about your 3:9 bits and if needed whether you'd mind splitting them because I only really need the cw&p
[Edited on 23/8/16 by mkindypaul]
quote:
Originally posted by mkindypaul
Mcerd1, did you get my message about your 3:9 bits and if needed whether you'd mind splitting them because I only really need the cw&p
As discussed here's a pic of my 3.9 Quaife LSD innards. It's got 26 spline push in shafts. U2U me if you want to go ahead.
here's the current state of my spare one:
obviously could do with a clean, not sure when I'll get a chance to split it though
drop me a u2u if your interested
Cheers mate I'll message you if I need it.
Well it's been a while I know but I've had the diff changed from a 3:38 to a 3:92 by road and race transmissions which was a really good hastle free turn around by them, all installed today so fingers crossed at the next track day we notice a difference
If it's just for track days then I would fit a 3.9 ratio if you do some road / motorways then 3.6 would be best as said 7s aero is a big issue so the lower gearing will help to get the most out of it
I run a 3.9 all the time and it's a good diff for a mid power Pinto
I have a high power Pinto and the higher rev limit makes the ratios feel closer.
I run a V6 type 9 which has slightly higher 1st and longer 2nd & 3rd
But still not ideal
If I had a 2.7 1st that would be ideal for road and track
quote:
Originally posted by snapper
I run a 3.9 all the time and it's a good diff for a mid power Pinto
I have a high power Pinto and the higher rev limit makes the ratios feel closer.
I run a V6 type 9 which has slightly higher 1st and longer 2nd & 3rd
But still not ideal
If I had a 2.7 1st that would be ideal for road and track
(probably more road than track for me) Well did my first track day of the year in the Indy today after changing the diff ratio to a 3.92 and all I can say is jesus what a difference, its
like a completely different car. Flys up the box now constantly in the power band so thanks to everyone for all your help and info on here.
[Edited on 28/4/17 by mkindypaul]
I ran a 3.9 ratio in my striker with a Toyota 4age and I found it the best ratio when it comes to a car which is going to be used for trackdays more than a cruiser . I've done trackdays at Abingdon for years and that was the ratio which I found best suited.
You'll soon be looking for a higher 1st gear trust me
quote:
Originally posted by snapper
You'll soon be looking for a higher 1st gear trust me