14 replies to this topic

[cian]

I am at a stage now where i have done all the perfomance mods i wanted to my engine and it is quick enough ( for now lol ) But i am finding it hard to get the power down off the line, i just put on a set of yoko a048 tyres which have cured it to a certain extent but still spins up and jerks, i was told that putting a set of close ration gears gives a longer first with less chance of spinning, is this correct? Any advice would be great

Engine spec

1275 MPI
stage 3 head
1.5 roller rockers
Sw5 cam
SC 5 port management
3.4 ratio

Edited by cian, 07 September 2012 - 10:30 AM.

[rally515]

Im no extpert on gearbox ratios yet but are you settting off in first as apposed to second gear on these aggresive starts.
Just some minor input to start the topic rolling a bit.

--experts feel free to type below.

Regards
Clifford

[freshairmini]

setting off in second?? Surely you would destroy your clutch in no time?

[rally515]

setting off in second?? Surely you would destroy your clutch in no time?

I admit as above im no expert (covering my own a*se) but 1st is for normaly setting off speed which is why it shoots up too 3000rpm in no time.
Iagree that a few clutch parts may (will) be needed after a few digins but prosuming the setup is sensible ie upgraded engine=upgraded clutch gears ect.
other than that go for it ( rover p6 in 2nd HEAVY right foot start gets you going like that 2.5 bugatti

Regards
Clifford

p.s. hope this hasnt gone too off topic.

Edited by rally515, 07 September 2012 - 12:52 PM.

[cian]

No im definatly not setting off in first, when the engine was rebuilt there was a new clutch kit put in so i dont have to worry about that, i had a rummage through previous threads about this kind of thing and some people seem to ride the clutch in first then nail it in second

[rally515]

some people seem to ride the clutch in first then nail it in second

[cian]

Hahaha!!!!! I can only go part throttle in first, if i nail it it will spin up

[rally515]

Get an f1 traction control system along with the 30,000 pound steering wheel which hamilton threw out the car at "monaco 2011" (i think)


to be frank cooperman or similar expierenced persons would be your best bet as here done licorice allsorts with minis mostly rally.
Drop him a PM with your concerns.

Regards
Clifford

[Cooperman]

From the engine spec the gearing you have looks ideal.
The Straight-Cut Close Ratio (SCCR) gears are for very highly tuned engines where the power band is higher but with a narrower power band. For example, a 286 cam will give its best power from about 5000 up to 6700 rpm. With a SCCR box 1st gear is very high and you need a low Final Drive Ratio (FDR) to get off the line.
All Minis will give a lot of wheelspin off the line. It's not the gearing, it's the weight transfer from front to rear due to the vehicle's inertia.
When I do a 0 - 60 test it is necessary to do around 4 runs in each direction and the way the power is controlled when letting in the clutch is the key to the optimum time.
Personally I would not consider a SCCR gearbox on any engine with a softer cam than a 286 or equivalent.
What size tyres are you using? If you have 13" wheels with 175 section tyres you may well get more wheelspin as the bigger tyre area onto the road will reduce the contact pressure and allow more wheelspin, but a 165 section tyre is about optimum.
It's really a question of practice to get away cleanly. The 1275 engine has a lot of torque at your spec.

[cian]

Hey cooperman thanks for your reply! Great advice! Im running 7 x 13 inch wheels with yoko a048 tyres, i just cant get the power down consistantly in first, i have to go part throttle in first, the torque is fantastic but its taming it off the line

[Cooperman]

You might do better off the line with 12" wheels and 165/60 x 12 tyres, but if you already have 13" that may not be an option of course. See if you could borrow a set of 12" just to try out.. In fact, on wet, gravel or icy roads the narrower 145 section tyres are always better for pulling away.
Just a thought really. Wheelspin is a problem with all powerful Minis and the real cure is a Limited Slip Differential (LSD), but they are not at all nice to drive with on the roads, although essential for racing and hill-climbing. Personally I've never felt comfortable driving with an LSD, but maybe that's just me and my driving style.

[cian]

Yeah i agree i dont think i would be comfortable with an LSD on the roads, i have a 4 pin in it and thats strong enough but yeah an LSD would be the way to go, so would a close ratio gear set be a good start? Oh and im running metro 4 pots would they clear 12 in wheels?

[Cooperman]

A close ratio box is not really suitable for an engine with a fairly mild cam like an SW5. It would raise 1st gear and you would find 1st a very 'long' gear with the rest all very close together. That's one reason why such a box is normally associated with a very low FDR. You could pull a SC CR box with a 3.44:1 FDR, but your initial acceleration would suffer and the clutch would have to be slipped even more when pulling away.
With your engine spec the gearing you currently have is about right. In all honesty, rather than spending the money on different gesring which will give you as many disadvantages as advantages, probably more, you might be better getting a set of 5" x 12" wheels with 165/60 x 12 tyres. Your brakes will clear a 12" wheel OK.

[Midas Mk1]

I've got a 3.44 diff with around the same power, even on 165 yokos on 12" rims traction in first is still a big problem, especially when trying to cross traffic, entering a main road on t junctions.
That said full throttle in 2nd usually has great traction.

I wish 1st gear was longer on mine.

If the Mini in question is your avatar pic, then fitting skinnier 12" wheels imo won't help aesthetics with the current wide arches.

Edited by Midas Mk1, 08 September 2012 - 10:29 PM.

[cian]

Hey midas yeah thats what im thinkn it just wouldnt look right! I guess im just guna have to practice and keep at it! But its the same with me a junctions too! Mayb wen the engine is out next il put close ratios in