Straight Cut Gears & Turbo/NA???
Turbo Mini Forums

Hi guys,

I have two questions to ask regarding turbocharged engines before i go ahead with ordering all the parts for the build:

People on here have said that turbo engines become unreliable if you run more than 130bhp (give or take)! The main problem being the strain on the gearbox at higher power outputs! ideally, i would aim to run anywhere between 160bhp & 200bhp and according to many people on here necessitates frequent gearbox re-builds!

From these comments i wondered why having good quality straight-cut gears is so essential if they are only going to have to be replaced again! can i not get away with using gears that don't create the whine of straight-cut gears.

This chap seems to be running non straight-cut gears from what i can hear : http://www.youtube.com/watch?v=eSgPt8z3Nbw

any help on this topic would be appreciated.




My SECOND question is this:

Which would require the most frequent rebuilds and cause the most problems:
---1430cc N/A producing 135ish/140 bhp?
---1293cc/1380cc turbo producing anywhere between 160bhp and 200bhp?


Again, any help regarding this issue would be appreciated.

Cheers,

Mike

lsd, hardy spicers, straight cut gears and straight cut drops will help with the strengh issues. other than that it has to be built with new bearings new syncros etc all help towards it. but lets face it a gearbox designed to take 30bhp isn't at its best at 200bhp.

"Cars are a lifetime of pain"

If you can get 140bhp from an N/A 1430 you will be spending more than double what a 200bhp turbo engine will cost you!!!

Also such a highly stressed N/A engines lifespan would be measured in hours not miles!

Edited by John on 30th Apr, 2009.

If something is worth doing, it's worth doing half of.

Depends what you are going to do with the car and how much power you use.

A 200 hp turbo Dyno queen will last for ages if all you do is run it hard on rare occasions and then just tootle about.

A 1430 will not last long if thrashed.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

thanks for the replies!

are you saying a 140bhp N/A will cost twice as much as a 200bhp turbo? i was a little confused by that comment!

yes, i will be tootling around pretty much all of the time apart from special occasions when i want to let it rip!

when i have asked before, everyone has assumed i will be thrashing it 24/7 and saying it will need rebuilds every couple of months!
surely if you dont thrash it, even on high boosts, it will last for quite a while!

so a good, strong straight cut set-up should last for quite a while then?

Cheers,

Mike

A 140bhp N/A engine will have to have very high compression, very well modded head with massive valves, racey camshaft which will need you rev it hard to make it go anywhere.

For the high revs you would need a trick bottom end which if you are planning a stroked 1430 unit will cost you an absolute arm an a leg.

And this is before we get to the fuelling and fuel consumption!

Where as a turbo engine you don't need an expensive bottom end as you arent revving it as hard, you don't need such a wild camshaft etc.

Also with a turbo you can turn the boost down when you want to plod around and just crank it up for fun times.

Edited by John on 30th Apr, 2009.

If something is worth doing, it's worth doing half of.

That mini has an Uno turbo engine in it. look at his other vids.

oh yea....my bad! ha!

So, from this i gather the bottom line is that a turbo engine will be more reliable than a 140bhp N/A engine as long as it is driven senisbly most of the time (and at low boost) and only hammered once in a while!

if i did drive a turbo mini like this, how long would you expect a good quality straight-cut gearbox to last before a rebuild is necessary?

am i right?

cheers,

Mike

The June Mini World features a 138 NA engined mini.
The text says the engine cost 2000 pnd without gearbox.
Engine built by Mini Speed.

Owners comment: "It could be a bit more if we play with the cam timing, but then it becomes more undriveble - at low revs it's already a bit of an animal to drive"

So I suppose not suitable for tootling around.
I would agree with the others; turbo.

Han

Dazed and Confused....

with a highish powered turbo lump the torque spike is the killer in the transmission, buy using sc drops and gear set along with a 4 pin diff then the drive train will last a long time aslong as its built with new bearings layshaft ect.

depending on what it is being used for then once every 2 seasons thne restrip and check layshaft and bearings, no real major hassels.

on occasions of heavey use then the layshaft can bend if not checked and you can end up braking teeth on the lay gear, happened to me and mini williams but now we know the cause not to much hassle

always looking for them bigger bunches of bannanas