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How can you get 300hp?

 
Old 01-27-2019, 09:31 AM
  #31  
Isaacsracing
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My 968 motor is a Michael Mount build from 2014 and was then tuned by John Behe. The prior owner did it and I think it has RS Barm cams. 11:1 ratio still, but John set it for 100 octane and being a track car, that's fine, but not what you want PF as a 924 RS for the street. Also has a 2.5 inch free flow exhaust, oversized fuel injectors, Lindsey fuel rail, Canton accusump, oversized radiator, no heat or AC, underdrive pulleys, and likely a bunch of other things that I don't know about or aren't thinking of. I have performed a compression test, but leak down is absolutely 0% on all cylinders - still after 30+ hours on the track.

I spoke with Michael about a year ago and he said that he will still build heads, but doesn't want to do the rest of the motor. John Behe is very much in business and works well with Michael Mount. A good route would be to have John oversee the thing and send the head to Michael. Pete at RS Barn is mostly out of the office taking care of other matters, but hopes to be back full time soon; last I spoke with Pete was in December.

Redline is over 6800, but the power really comes on between 5000 and 6000. While Michael Mounts says that the valve springs will keep up at higher revs, John Behe says that the power won't increase that much. With the HP increasingly slightly while the torque decreases slightly, the sweet spot is in the low 6000 rpm range. That's what John told me and from driving the car I would agree with that. The power feels flat in that general range. The dyno sheet is below.

With 250hp at the rear wheel, do you figure the actual engine is producing 280-290??





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Old 01-27-2019, 03:01 PM
  #32  
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next big step is an intake manifold - stock 968 is similar in runner length to the 944S2 which 'tunes' right around 4000rpm for a nice surge of torque.
968 gets that too but the curve is spread out wider via variocam advance and the "dual path" plenum.

long runners at high rpm suffer from simple pipe friction and can actually get into "negative tuning" (resonance tuning is sine waves, 4000rpm is the 'peak' but at certain points you're in the valleys lowering dynamic pressure)

design the intake to tune at a higher RPM (shorter runners) and you'll see your power curve shift "right" (higher HP with flatter/slightly lower torque line below the tuned RPM)
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Old 01-27-2019, 04:50 PM
  #33  
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engine is producing 280-290?
Impressive (if the motor dyno readout is to be believed).

My understanding was that the 968 motor, based on the 944S2, already was a well-developed motor, and that Porsche did not leave much on the table for more hp.

Last edited by MN; 01-27-2019 at 05:38 PM.
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Old 01-27-2019, 09:37 PM
  #34  
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Just to satisfy my curiosity and memory I went back and looked at the dyno results on my red 968. It was a car with a stock engine with around 150,000 miles on it . It was equipped with a design 1 supercharger. It dynoed at 254 wheel hp. The drive train drains 35 hp to the rear wheels. So it was close to 290. Again this was a stock engine.
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Old 01-29-2019, 04:24 PM
  #35  
PF
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Originally Posted by Isaacsracing View Post
My 968 motor is a Michael Mount build from 2014 and was then tuned by John Behe. The prior owner did it and I think it has RS Barm cams. 11:1 ratio still, but John set it for 100 octane and being a track car, that's fine, but not what you want PF as a 924 RS for the street. Also has a 2.5 inch free flow exhaust, oversized fuel injectors, Lindsey fuel rail, Canton accusump, oversized radiator, no heat or AC, underdrive pulleys, and likely a bunch of other things that I don't know about or aren't thinking of. I have performed a compression test, but leak down is absolutely 0% on all cylinders - still after 30+ hours on the track.

I spoke with Michael about a year ago and he said that he will still build heads, but doesn't want to do the rest of the motor. John Behe is very much in business and works well with Michael Mount. A good route would be to have John oversee the thing and send the head to Michael. Pete at RS Barn is mostly out of the office taking care of other matters, but hopes to be back full time soon; last I spoke with Pete was in December.

Redline is over 6800, but the power really comes on between 5000 and 6000. While Michael Mounts says that the valve springs will keep up at higher revs, John Behe says that the power won't increase that much. With the HP increasingly slightly while the torque decreases slightly, the sweet spot is in the low 6000 rpm range. That's what John told me and from driving the car I would agree with that. The power feels flat in that general range. The dyno sheet is below.

With 250hp at the rear wheel, do you figure the actual engine is producing 280-290??




Looks like a great package😀

Thanks for your info and results. I have some hooks out there now so I will see what that comes down too.

Again Thanks to all for your inputs
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Old 01-29-2019, 10:34 PM
  #36  
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The dyno sheet shows that that 968 engine has not yet reached peak power at 6800. Perhaps the car feels great in the low 6000 range, but power is actually greater at higher RPM if you choose to go there.
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Old 01-29-2019, 10:46 PM
  #37  
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Nice torque range.

-Y
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Old 01-30-2019, 12:33 PM
  #38  
V2Rocket
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those cams look meaty.
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Old 01-30-2019, 01:27 PM
  #39  
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Originally Posted by Isaacsracing View Post
My 968 motor is a Michael Mount build from 2014 and was then tuned by John Behe. The prior owner did it and I think it has RS Barm cams. 11:1 ratio still, but John set it for 100 octane and being a track car, that's fine, but not what you want PF as a 924 RS for the street.
Isaacs: how does your motor idle with those cams? On cold starts and when the motor is warm?

I am considering hotter cams but thereĺs a fine line between civil street-ability and significant power gains.
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