More power from RS-spec 2.4 engine

[993TT]

Hi,

I have a 2.4 T engine converted to 2.7 RS-spec with MFI, which currently needs rebuilding. During rebuild I'd like to get more hp and torque from it.
Which would be the best setup bearing in mind that it would be mostly for street use and some club track days?

I'm open to all ideas as long as it won't cost me my arms and legs.
Weber's (40 IDA, 40 IDS, 46 IDA) or MFI? Would I gain anything by using carburetors or should I stay with MFI?

Emissions are not a problem in this case.

Would a std 915-gearbox be able to handle that extra power?

I've read B.Andersson's and W.Dempsey's books, but would very much like to get your feedback as well.

This engine would be installed in a '70 911ST replika.

Thanks in advance,

[edmayo]

Compression ratio,,,,,you only have 8.5 to 1,,,,if that,,,

[RSTarga]

Mahle used to make a 9.5 to 1 piston and cylinder set
I think Chuck has those

[Frank Beck]

What the heck is an RS spec 2.4?

[edmayo]

Frank, he did say it was converted to 2.7 RS spec, which is usually the common low compression piston set.

[Gearby]

You shouldn't have a problem with the 915 gearbox. You couldn't produce a 2.7 liter normally aspirated motor that could push a 915 past its reliable limit. I believe Porsches general rule of thumb was that the gearbox can handle twice the power of the motor. Which if you look at it they used the 915 through 1986 when the 3.2 was putting out 200 horses. Which that obviously means it could handle reliably up to 400 horses. ROW models were putting out 231hp. they didn't go to the G50 until the power increased slightly in 1987.

[Frank Beck]

Sorry. Did a quick Drive-By.

I would go with 92mm 2.8 conversion with MFI and a hotter cam profile.

240-250hp and your 915 won't break a sweat.

I have all of the parts in case you want to go this way.

[91133]

If your car is to 2.7RS spec on MFI then it should already have S cams and the RS cam in the Bosch MFI pump as well as the tapered intake stacks etc. Assuming that, a good rebuild with some reduced rotating mass - Carillo Rods, RSR flywheel and judicious port and head clean-up should see 235 hp without any trouble....at least that's what I have and that's really all we did. On the other hand, if your car is an MFI T with just the extra capacity....there's quite a bit to do.

And rather than worrying about the 915 transaxle - which will be fine as others have said although a limited slip diff will be as good an addition as extra horsepower - you need to think about oil circulation - 964 or 3.2 oil pump and a front cooler.

Good luck

[Chuck Miller]

Mahle used to make a 9.5 to 1 piston and cylinder set
I think Chuck has those

- Yep...Built my 2.4S/2.7RS+ project around a set of Mahle 90mm RS 9.5 pistons and barrels...
- Also replaced my S cams with WebCam S Mod regrinds (#120-104)... Much fatter middle
- Also an MFI RS space cam replacement...
- And LOTS of intake head work...

That's about it........ Probably about 230hp ... but never dynoed so who knows?

About 75000 miles on the rebuild in 13 years and still go'n strong.........

Hope this helps

[cmcfaul]

More compression, twin plugs, should get you 10+ HP. Not sure whats involved in upping the displacement.

Assume you have the 7R case. Will need strengthening (shuffle pins, case savers) and cooling.

Chris
73E