R1 STRIKER
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| posted on 30/5/06 at 12:37 PM |
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3.38 OR 3.92?
Hi all,
Have just finished converting my Striker to R1 ready for Le Mans. The only thing I haven't had time to do is change the diff.
I know the 3.38 will be the better diff but is the 3.92 that is currently in the car going to drive me mad? How much difference is there with normal
road driving, the car is on 14 inch wheels.
I've already got the 3.38, just don't see me getting chance to fit it in next two weeks!
Thanks.
Ben.
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Peter M
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| posted on 30/5/06 at 12:45 PM |
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gearbox/diff calculator
my previous cars
my westfield build
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jimgiblett
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| posted on 30/5/06 at 12:50 PM |
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Depends how much motor way driving you do. A 3.92 with 185-60-14 tyres give a top speed of approx 116mph at 11,250rpm. 70mph will be a shade under 7k
revs. A 3.38 will give a top speed of approx 135 (although aeros will probably lower that) and 70mph will be just under 6k revs.
Acceleration with a 3.92 will be blistering though 
A diff swap shouldnt take long on a Striker (3 hours ish) if you can get to it without taking the tank out.
- Jim
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smart51
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| posted on 30/5/06 at 03:06 PM |
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My R1 BEC will do 50 in 1st and 70 in 2nd with a 3.62 and 195/50/15 or 185/60/13
A 3.38 will give 53 and 75 in 1st and 2nd
A 3.92 will give 46 and 65 in 1st and 2nd
Acceleration in each gear will be 16% better with a 3.92 over a 3.38 but the top speed in each gear will be 16% lower.
If you want a sprint car or the best 0-60 then a 3.92 is for you. If you do lots of long straight roads or long straight track days then the lower
revs of a 3.38 might be nicer.
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R1 STRIKER
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| posted on 30/5/06 at 03:22 PM |
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Thanks guys,
From your reply's I think I'll leave the 3.92 in untill I get back from france. Was just a little concerned that it might be a complete
nightmare on way over. But should be ok with helmet.
Might see some of you over there.
Ben.
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JoelP
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| posted on 30/5/06 at 04:27 PM |
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id swap it myself, bearing in mind that you're off to le mans in it. If it was just a trackday or something i wouldnt rush swapping it though,
but to be honest i find that my helmet doesnt do much to reduce noise, and i suspect that a long trip will get tiring.
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R1 STRIKER
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| posted on 30/5/06 at 04:52 PM |
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Joel,
You might be right but unfortunatley taking the week off for Le Mans means i'm rushed off my feet for next couple of weeks. Shouldn't of
taken so long changing engine but never mind. MOT in the morning, then the real fun can begin.
Ben.
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ChrisGamlin
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| posted on 30/5/06 at 05:02 PM |
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I was forced to do Le Mans 2 years ago with a 3.89 diff after my 3.54 started making noises 2 days before departure. This was with a blade and
185/60-13" tyres. The overall gearing meant it topped out at ~110mph and although it was not ideal, it stangely didnt feel too bad cruising at
9k/90mph, so although Id recommend swapping if you can, its not the end of the world if you cant. Also it wouldnt be as bad as I had it if
you're not part of a convoy that treats the entire drive much like a British road (ie driving on he left hand side of the road virtually all the
time!  )
Chris
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Bouldy
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| posted on 30/5/06 at 06:56 PM |
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Can you work out for me what a 3.26 and 3,16 diff will achieve .
Engine rover v8 peak revs 6500 (tuned) currently running 3.62 still very quick but still to low have loads or torque so can afford to come down a bit.
Cheers
Paul
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smart51
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| posted on 30/5/06 at 07:11 PM |
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3.16 is 14.5% taller than a 3.62
3.26 is 11% taller than a 3.62
Your top speed in each gear will be higher than now by these percentages and the acceleration in each gear will be lower than now by these
percentages.
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G.Man
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| posted on 30/5/06 at 09:07 PM |
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Smart
Thats not actually always right...
Speed in each gear will be 14.5% different but other factors affect the acceleration, especially thru the gears, and matching the diff to the weight
and the gear ratios can yield a better overall acceleration.. you can also find with the wrong diff you are always between gears in corners etc
etc...
Look to gear a locost for around a 130-140 top speed, much faster and the front goes light.. then you should be about right...
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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ChrisGamlin
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| posted on 30/5/06 at 11:33 PM |
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Yep Id agree with that, I found with the 3.89 compared to the 3.5 that although the actual in gear acceleration was very slightly stronger, because
you were going through gears quicker and using more gears for any given acceleration increment, the overall acceleration didnt really change at all.
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smart51
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| posted on 31/5/06 at 07:13 AM |
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quote:
Originally posted by G.Man
Thats not actually always right...
Speed in each gear will be 14.5% different but other factors affect the acceleration
OK, OK, I was trying to keep is simple. I bet most people cant tell the difference between 10% more and 11% more acceleration anyway.
Acceleration at low speed will be the quoted percentage better but as speed increases, the effect of aerodynamic drag and rolling resistance vs
available engine power will mean that the percentages drift a bit. You do get the general idea though.
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G.Man
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| posted on 31/5/06 at 11:29 AM |
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But for a given speed you will be making more gear changes as well with a higher ratio...
ie 3.92:1 more changes than 3.38:1
With a kwikshifter tho, this wont be an issue..
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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Bouldy
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| posted on 1/6/06 at 02:13 PM |
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ok all a bit too technical for me so....
i have a tuned 3.5 v8 in an indy, 270 hp approx. Tyre size 205/40 17. current diff 3.62 want to go to a 3.16 or 3.26 .so can any one work out what my
speed will be in 1st 2nd 3rd 4th 5th ???? with the respective diffs?
Paul
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gregory75
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| posted on 1/6/06 at 10:08 PM |
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diff ratio catalog
can anyone point me towards a "catalog" of sierra differentials with ratio?
I'm particularly interested in the available LSD diff ratios
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cossey
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| posted on 2/6/06 at 08:16 AM |
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the lowest lsd is the 3.62 in the 7" lower than that requires hybriding a loer ratio diff with an lsd. (ie you put the lsd into the diff with
the right crown wheel/pinion.)
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gregory75
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| posted on 2/6/06 at 06:40 PM |
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quote:
Originally posted by cossey
the lowest lsd is the 3.62 in the 7" lower than that requires hybriding a loer ratio diff with an lsd. (ie you put the lsd into the diff with
the right crown wheel/pinion.)
is it really feasible to do? can you point me towards any guides/websites where this is done?
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