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[RSAE]

Hi Everyone,

We are in the midst of designing and installing an MP90 supercharger on a 3.0L. We have the ability to set it up to run enough boost to blow something up. The question we have been shopping around is: how much power can this drivetrain take before something fails? I know there are a million variables, but this is sort of a "poll the [knowledgeable] audience". Assume hp will be about the same as torque. Please vote on the poll then post up what will break. A reason would be even better if you're feeling particularly generous. Thanks.

Edit: Good point raised by Mef- this is a full race car (although with some tweaks to make it barely legal to drive on the street). It will be on road courses, drag strips, auto-cross. Full boost for extended periods of time. Driven hard...

-damen

[Mezevenf]

Well it *really* depends on how you drive it

I could kill a standard 3L if I drove it like my friends drive their cars, haha.

I forsee either driveline or heat issues being the problems.

[Greg Gordon]

Provided you don't go up over 6000rpm and avoid detonation the engine will hold up fine. I don't see heat as being a big problem below 10psi, about that it will start to be a bigger factor.

I do worry about the driveline. We have all seen or heard about Guibo failures on standard cars. I think they hold up well to at least 300 horsepower if they are in good shape. My biggest concern is the transaxle. I have seen one first gear break and two pinion gears brake, all on stockish 2.5 cars! For what it's worth I have has zero driveline failures on my supercharged cars, go figure....

Greg

[5yearplan]

AS far as the tranny, depends on how you shift

[Daniel]

I have heard from a very knowledgable alfa man (he races them and has for years) that 300 lbft is the limit for absolute reliability. From there it depends on how you treat it. His opinion was that you could shift a transaxle as fast as you like as long as it had good oil in it and was well warmed up.

Personally I have shattered a diff planetary with a slightly hotted 2.5 but it was an alfetta box with 2 planetaries, not a 4 planetary 75 box.
There are a couple of guys in Sydney running 75 turbos with 500 ish hp but I don't know what driveline is behind that.

Jules, what did Mark Paps car run ?

[zambon]

A full race car will be significantly lighter than a stock Milano with a full interior, AC, and power everything. That should help to give the ring and pinnion gears a fighting chance...
It is really a matter of what kind of replacement period you want to expect. With stock power, I wouldnt expect the diff to live through 20 years of track events. More power should speed up fatigue.
A guy with a supercharged 3.0 told me that he changed his driving style on standing starts and his transaxle has been doing fine since. He runs wide 18in wheels and slicks, I believe, and it is a race car.
That said, he had been having issues with the driveline when he was dumping the clutch.

[Alfettish]

That said, he had been having issues with the driveline when he was dumping the clutch.

As you would with a stock car too.

[SydneyJules]

Mark Paps turbo was doing something like 270rwhp. But I personally, dont think his box was built to the best standard- the clutch never lined up properly- constant clutch issues- not the box!

Paul K on the other hand, turned 330whp, and I can tell you straight out that if he had the balls to launch it, that thing was a high 11 sec 1/4 car.

But he drives it nicely- it spun third at about 1/4 throttle after a redline 2-3 change.

I think 400hp nicely driven is what it will take. Mine has been driven hard with 250 odd and 8k, and shows no signs of letting up.

Then again, a boosted 1.8 or blown 3.0 is a bit different to mine!

[zambon]

I think that as long as you have a spare gearbox in the garage, the one in the car will prove to be very tough. The moment you are without the spare, the car will sense your weakness and punish you for it.

But he drives it nicely- it spun third at about 1/4 throttle after a redline 2-3 change.

Whoa!

The convetional wisdom is that the ring and pinnion are the weak point here, but the RSAE car has a lightened gearset. Anybody ever run lightened gears in a high HP car other than race teams? (The race teams most likely serviced the box for every race).