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This one may be more accurate. I searched more numbers. What is the cc of the turbo piston? 25.7 or 33? If it's 33 I just dropped below 7:1CR not good. Would have to buy Wiseco 25.7cc 8:1 turbo Pistons.
Interesting project
This thread by a reliable technical source on the 928 forum has the various piston volumes for 944/951/968 and 928 models, as well as head volumes for the various 928 heads:
951 pistons are 25cc apparently, as are early 928S4 pistons (87 to midway through 88MY) which will also have the 4-valve cutouts in them already and are also 100mm (951 ring packs fit them).
Erkka also cc'ed the 928 S3 heads (85/86 32V) as 56.5cc so slightly smaller than your calcs.
I has thinking Porsche gave us all the parts to make a modified version of the 81 la mans 944 turbo race car 2.5 DOHC engine. Someone needs to copy Porsche's equal exhaust headers!
So if you take SFR stage 2 exhaust runners 3 and 4 then take broadfoot racing's stage two number 1 and 2 exhaust runner you will have what Porsche came up with in 1981! And your heat shield for your oil filter can still remain untouched. Bonus!!
So if you take SFR stage 2 exhaust runners 3 and 4 then take broadfoot racing's stage two number 1 and 2 exhaust runner you will have what Porsche came up with in 1981! And your heat shield for your oil filter can still remain untouched. Bonus!!
333pg333 there is only one thing I would change on the header setup, I would have them more oval running under the oil pan for more clearance due to the heat generated. And a bigger pipe if the oval design restricts it too much. And I would white lightning the exhaust and oil pan also. Has anyone used jet coat or white lighting on the oil pan yet? Looks like it would help a lot to reduce heat transfer. Everyone talks about oil coolers so I was thinking of another way to cut down heat for the engine oil. I'm sure someone has.
I personally would try to get as close as possible to 9:1 compression for good off-boost performance. With 951 rods and cast 944S pistons, you should be able to safely run up to about 16-17psi of boost. Racerboy's thread shows you can get very close to 400hp with relatively mild mods.
Racerboy's thread shows you can get very close to 400hp with relatively mild mods.
It is 400hp at the wheels. And that was with boost leak and hot dyno room. At 20c evening VirtualDyno showed 447 whp (during dyno run, VirtualDyno showed 389 whp, Dynojet gave 393 whp, so it is quite accurate).
I'll vote for higher compression plus a good tune.
FYI the early version of the 930 did not have a knock sensor, so it needed low comp ratio just to survive.
08-25-2015, 07:01 PM
