mkindypaul
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| posted on 22/8/16 at 03:00 PM |
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MK Indy pinto and gearing
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]
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theduck
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| posted on 22/8/16 at 03:06 PM |
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With that gearing it's likely by the time you change into 4th you are experiencing the supreme aerodynamic ability of a seven.
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mkindypaul
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| posted on 22/8/16 at 03:14 PM |
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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.
Really? I don't run a speedo in it so not sure on what speed I'm reaching but it did cross my mind about their aerodynamic ability, Im
just not sure on the best move forward with it to be honest.
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ian locostzx9rc2
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| posted on 22/8/16 at 03:15 PM |
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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
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mkindypaul
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| posted on 22/8/16 at 03:24 PM |
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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
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ian locostzx9rc2
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| posted on 22/8/16 at 03:28 PM |
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Yes ideal for a bike engine (or rover v8 due to lots a torque )
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mkindypaul
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| posted on 22/8/16 at 03:30 PM |
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quote:
Originally posted by ian locostzx9rc2
Yes ideal for a bike engine (or rover v8 due to lots a torque )
Oh sorry I misread your reply, what sort of torque do the bike engines produce then in comparison to my spec of pinto?
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jacko
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| posted on 22/8/16 at 03:32 PM |
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3,62 is what you need and what happened to 5th gear 
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Ugg10
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| posted on 22/8/16 at 03:48 PM |
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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]
---------------------------------------------------------------
1968 Ford Anglia 105e, 1.7 Zetec SE, Mk2 Escort Workd Cup front end, 5 link rear
Build Blog - http://Anglia1968.weebly.com
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mkindypaul
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| posted on 22/8/16 at 03:48 PM |
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quote:
Originally posted by jacko
3,62 is what you need and what happened to 5th gear
It was a track day at Abingdon in Oxfordshire so I ran out of road on the back straight its not very long.
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mkindypaul
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| posted on 22/8/16 at 03:55 PM |
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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]
Ok thanks for that, so if I was to fit a 3.9 with the rest of my current set up I would have better acceleration through the gears but what would it
do to 4th gear would it make it any better ?, also Ive seen the long first gear kit for the type 9 but beings I'm not actually racing off a
green light would I actually benefit much from the first gear ?
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mcerd1
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| posted on 22/8/16 at 04:00 PM |
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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
bikes and V8's - most seem to suit a 3.38 or 3.14 depending on the wheel size etc...
pintos, zetec's and other normal ~2.0 engines seem to like 3.92 / 3.62 ratios better - the bonus is these ratio's are cheap compared to
the 3.38 so you could make some cash back if you sold your existing one 
if you compare real world figures to the theory most sevens end up with a drag coefficient of 0.6 all the way up to 0.75 to make the numbers work
(depending on windscreens, tyre and arch widths etc)
I don't expect my pinto to produce much more than 140bhp for now (about 25-30 more than the donor it came from), but based on other peoples
experience that probably will have a top speed in the dax of around 125mph - which is only the same as the donor car
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mkindypaul
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| posted on 22/8/16 at 04:10 PM |
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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 ?
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theduck
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| posted on 22/8/16 at 04:13 PM |
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It will make a difference, but only because you will get to 4th at a lower speed.
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Ugg10
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| posted on 22/8/16 at 05:55 PM |
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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.
---------------------------------------------------------------
1968 Ford Anglia 105e, 1.7 Zetec SE, Mk2 Escort Workd Cup front end, 5 link rear
Build Blog - http://Anglia1968.weebly.com
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snapper
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| posted on 22/8/16 at 07:56 PM |
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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
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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Adamirish
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| posted on 22/8/16 at 07:56 PM |
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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.
This.
Mine is running a 140bhp Xflow with a 3.62 and a standard type 9. It's f**king rapid(as rapid as a 140bhp car can be anyway) to the top of 3rd
and into 4th. It's still pulls really well until I hit 3 figures. Then it's like trying to push through a brick wall. I have had over
120mph out of it but it took a long circuit(!) to do it on. It wasn't pleasant either so won't be doing it again!
The answer to more speed is more power. Or if it's lap times you're after then just be braver in the corners! 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.
MK Indy 1700 Xflow
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mkindypaul
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| posted on 23/8/16 at 11:46 AM |
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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.
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mcerd1
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| posted on 23/8/16 at 12:02 PM |
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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
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mkindypaul
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| posted on 23/8/16 at 12:08 PM |
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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 ) but if all
you want is the CW&P that won't make any odds
Ok mate I'll bare that in mind as I think it's my best option, if I pay a company to install new it's gonna be £500-£600 and then if
it turns out a 3:9 is to much I'll have to do it all again with a 3:6. How much was you looking for ?
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mcerd1
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| posted on 23/8/16 at 12:41 PM |
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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]
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mkindypaul
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| posted on 23/8/16 at 02:32 PM |
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@adamirish
What wheel and tyres size do you run ?
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mcerd1
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| posted on 23/8/16 at 03:00 PM |
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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]
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mkindypaul
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| posted on 23/8/16 at 03:12 PM |
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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
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mcerd1
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| posted on 23/8/16 at 03:15 PM |
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^^ 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]
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