danglerb

I bought a copy of PipeMax Pro, a fairly advanced engine calculation program that figures out optimal intake and exhaust pipe sizes among other things.

http://www.maxracesoftware.com/pipemax36xp2.htm

The software is designed to take some known engine details, and combine that with the results of some dyno runs to fine tune things like vol efficiency. Half the stuff in my first swing at the parameters I don't know, and I need some dyno info from some of you, and I will update as people correct my mistakes and data is added, then I will post some of the calculated results.

To keep it simple I would like to use numbers for a stock 4.7 US 928S.

Engine Data
Volumetric efficiency 75% (wild guess)
Engine Bore size 3.940
Crankshaft Stroke 3.106
Rod Length C-C 5.906
Cylinders 8
Peak HP RPM 5250
Compression Ratio 9.3

Intake Data
Number of Valves 1
Valve Head Diameter 1.750 (wild guess)
Valve Stem Diameter 0.250
Camshaft Valve Lift 0.434 (wild guess)
Duration @ .050 220.0 (wild guess)
Degreed Centerline 90.0 (wild guess)
Lobe Center Angle 90.0 (wild guess)

Exhaust Data
Number of Valves 1
Valve head Diameter 1.400 (wild guess)
Valve Stem Diameter 0.250
Camshaft Valve Lift 0.434 (wild guess)
Duration @ .050 210.0 (wild guess)
CenterLine Length 3.200 (wild guess)

Corrections greatly appreciated, and I will look up more stuff myself as well.
Thanks

toofast928

ooh input Tri-Ys

blown 87

The VE will be higher than 75%, and at times (RPM's) may be close or actually over 100% on some motors.

hernanca

And I didn't have to say a thing!

Looking forward to what Pipemax says vs. what folks are running.

Would be even better to know, IMO, where to find the needed data (little Porsche Tech booklets, WSMs, Owners Manual, etc.), and what conversions are needed on this data (some not simply a units conversion), for all the pieces of information needed.

Vilhuer

Rods are 150mm which is 5.906".

IcemanG17

Dangler
Couple things

97mm bore is 3.8188"
Intake valves are 43mm
Exhaust valves are 38mm (Euro is 45-40)

Cam specs are .435 lift intake .395 exhaust

I don't have cam duration in right now but its LOW....I will look it up

I estimate the peak flow of a USA 16V head around 180cfm....the euro is around 210cfm..... I also have many dyno runs of my engine (84 USA automatic) if they will help you?

IcemanG17

Found it