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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??
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)
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.
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.
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.
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.
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 there’s a fine line between civil street-ability and significant power gains.
Just to tell what I am planning. Goal is to build a "what if Porsche did a 924 RS"
I am using a - 86 924 S as a base and I am looking to create a really sleek, light and nimble car in true Porsche RS style. Goal is below 1100kg and 280+HP 968 engine. Should be a real blast and a true sleeper. Love the slim body of the 924.
This sounds like a really cool project. I have something very similar in the backburner. Please keep us posted!
This sounds like a really cool project. I have something very similar in
the backburner. Please keep us posted!
Yes I hope it will turn out great 😀Mr Mount is preparing a head for me together with hotter cams other headers and custom chip.
This car is a long term project. Just now I am trying to finish my 968 Turbo S/RS tribute build. When that car is done I will just enjoy myself before I start on the 924.
Yes I hope it will turn out great 😀Mr Mount is preparing a head for me together with hotter cams other headers and custom chip.
This car is a long term project. Just now I am trying to finish my 968 Turbo S/RS tribute build. When that car is done I will just enjoy myself before I start on the 924.
Cool!
Do you post updates about your 968 build in some other thread?
I've heard a few times about Michael Mount but have never been able to find a website of his. Does he have one?
I have a 1991 944S2 Coupe with about 120,000 original miles. I have a chip that I bought from DME Shoppe in Germany, my car didn't come with an airbox just an aluminum tube with a cone air filter and a cat less original exhaust. I have been reading as much as I can about gaining power. The stock cams on the S2 are a pretty mild profile. I have read that guys use the 944S cams and gain 10 to 15 HP. Although the profiles are only 3 to 4 degrees different when I read the profiles. Also, as per Racer's Edge, the S2 only has about 10.5 to 1 compression. Not the 10.9, 11 to 1 advertised compression. If the 944S can make 188-190 HP, you would think the S2 could make more than 208, 211 HP. The consensus seems to be that the S2's intake ports are too large and has poor intake air velocity. I just checked Web Cam's site and they now sell brand new camshafts for the S and S2. So you have more options than just sending in your stock cams and have them welded and reground. I honestly don't know what lift, duration and overlap is the best for the S2. I don't want to tear into the bottom end, so I will rebuild the head, investigate cams, shave the head for a little compression bump and I don't know if it's worth buying the Bursch headers that Lindsey sells. I have heard that a 2.5 inch exhaust may be too big and the original exhaust or DANSK cat back minus the cat may be the best way to go. It's a street car and that's probably all it's ever going to be unless I do some time attacks. I would appreciate any input. Thank you! Kevin Anderson
01-27-2019, 08:31 AM
