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Longest Diff Ratio Available? https://ausmini.com/forums/viewtopic.php?f=5&t=33941	Page 1 of 3

Author:	WasabiPimpNinja [ Tue Jul 17, 2007 9:25 am ]
Post subject:	Longest Diff Ratio Available?
Hey guys, Thinking about heading over to Lake Gardiner for the Dry Lake Racing next year. Probably just heading over with a few mates to watch some real speed. But then I started thinking that it might be fun to road trip in the Mini. Then of course, the next "logical" step in the thought process was, maybe I should RUN the Mini and see what kind of speeds I could get. This was partially inspired by the "Top Speed" thread from a bit earlier, but helped by a few cold brews Now I know the Clubman has all the aerodynamics of a service station, so it'll be like pushing a soft smelly brown substance up a hill with a pointy stick, but it could also be a laugh and another story for around the campfire. So the next obvious question is, diff ratios. Being that it's a timed "Flying Mile", and you have 1 mile or so to build up speed before the timed run, acceleration is not of too great a concern. So what's the longest Diff Ratio around that's "commonly" available for the Mini? What about special order stuff? It's sort of opposite end of the scale stuff for Mini's I guess so I'm thinking there wont be much around.. This is all sort of Pie in the Sky stuff at the moment, but if it turns out to be possible to do without spending too much coin, I'll be out there in a flash. So any advice or info will be taken onboard. Possibly some info on a "Dream Setup" with cam choice, head choice, and other engine setup ideas wouldn't go astray Peace

Author:	Spaceboy [ Tue Jul 17, 2007 9:51 am ]
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2.76 from a late model rover mini, also 2.9 is available.

Author:	dove grey 64 [ Tue Jul 17, 2007 10:45 am ]
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which rover mini had a 2.76? what year?

Author:	cush [ Tue Jul 17, 2007 10:57 am ]
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one of the coopers wasn't it?

Author:	Wombat [ Tue Jul 17, 2007 12:27 pm ]
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Author:	KLAS [ Tue Jul 17, 2007 4:27 pm ]
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1970 mini K wrote: which rover mini had a 2.76? what year? the MPi, from end 1996 till 2000

Author:	drmini in aust [ Tue Jul 17, 2007 5:41 pm ]
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I'll stick my neck out here, and say for a high performance N/A A series, with ANY diff taller than a 3.44 you will NOT get maximum speed. Aerodynamics are the killer. You are not driving a locomotive with unlimited torque. Stock Minis with a 2.76 were faster in 3rd than 4th. OK so flame me... Nb racers don't even run with a 3.44 on 99% of tracks.

Author:	Spaceboy [ Tue Jul 17, 2007 5:54 pm ]
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but the cooper S came with 3.4!

Author:	drmini in aust [ Tue Jul 17, 2007 7:42 pm ]
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Spaceboy wrote: but the cooper S came with 3.4! Yes, and if it had a taller one, it would have been slower....

Author:	9YaTaH [ Tue Jul 17, 2007 8:17 pm ]
Post subject:	Doable??
drmini in aust wrote: I'll stick my neck out here, and say for a high performance N/A A series, with ANY diff taller than a 3.44 you will NOT get maximum speed. Aerodynamics are the killer. You are not driving a locomotive with unlimited torque. Stock Minis with a 2.76 were faster in 3rd than 4th. OK so flame me... Nb racers don't even run with a 3.44 on 99% of tracks. I suppose you would have to fit 13s as well...not necessarily fat ones, just 12 or 13s as anything smaller may not get the full benefit from the diff as fitted to Rovers. With a powerful enough engine (anyone got a calculator??) and the big run up you get on the flat....the Min is likely to do OK. If it runs out of puff and don't get to reach peak revs in top...it will still be a hell of a hoot

Author:	drmini in aust [ Tue Jul 17, 2007 8:40 pm ]
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Rover Cooper MPI with 13x6 Sportspacks was a full 5MPH slower than the stock Rover Cooper MPI wearing 12s. For speed, you want skinnies..... `cheese cutters' would do fine. The 2.76 ratio was only fitted to UK-made Minis reduce drive-by noise figures.

Author:	gafmo [ Tue Jul 17, 2007 9:08 pm ]
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Hmmm...do you get a number of Runs

Author:	Mini Mad [ Tue Jul 17, 2007 9:19 pm ]
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Isn't the mini aerodynamically limited to around 122MPH or so?

Author:	Morris 1100 [ Tue Jul 17, 2007 9:34 pm ]
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Mini Mad wrote: Isn't the mini aerodynamically limited to around 122MPH or so? Yep. So fitting a taller diff will not add anything to top speed but it may help to save some fuel.

Author:	drmini in aust [ Tue Jul 17, 2007 9:47 pm ]
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Lesson in overgearing- I had a Fiat 124AC sports coupe, 5 speed. 4.11:1 diff, 13" wheels. Nice car... pretty quick back then, good for 106+MPH on the flat, more downhill. Note that was in 4th gear. 5th was only good for 99 MPH. Moral of story- Taller gearing does not make more speed, if engine can't get to its max power rpm.

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