928S4 head CCs
Thread Starter
Rennlist Member
Joined: Dec 2001
Posts: 25,186
Likes: 105
928S4 head CCs
Does anyone know what the cc's are of the head on an S4? I am trying to fiddle with a CR calucation for my engine, and I will not be ccing the head in person any time soon, so....
This is what I was trying to follow:
[quote]
V1+V2+V3+V4+V5
______________
V2+V3+V4+V5
Where V1 is the swept volume
V2 is the piston to deck
V3 is the volume of the head gasket
V4 is the combustion chamber
V5 is the top of the piston
<hr></blockquote>
Any ideas?
This is what I was trying to follow:
[quote]
V1+V2+V3+V4+V5
______________
V2+V3+V4+V5
Where V1 is the swept volume
V2 is the piston to deck
V3 is the volume of the head gasket
V4 is the combustion chamber
V5 is the top of the piston
<hr></blockquote>
Any ideas?
Instructor
Joined: Nov 2001
Posts: 243
Likes: 0
From: Riyadh
Brendan,
Based on
CR= (Swept+unswept)/ Unswept
You can derive
Unswept = swept/(Cr-1)
How the Unswept is made up is another matter, and which parts you can do much to change is problematic. If you know the bore and compressed gasket thickness you can calculate volume there. If you know area of chamber face at gasket, you can work out effect of skimming head.
HTH
jp
Based on
CR= (Swept+unswept)/ Unswept
You can derive
Unswept = swept/(Cr-1)
How the Unswept is made up is another matter, and which parts you can do much to change is problematic. If you know the bore and compressed gasket thickness you can calculate volume there. If you know area of chamber face at gasket, you can work out effect of skimming head.
HTH
jp
Thread Starter
Rennlist Member
Joined: Dec 2001
Posts: 25,186
Likes: 105
Thanks for the info JP. I am specifically trying to calculate whether or not I can use chevy 5.7 rods with my 928intl stroker crankshaft. I suppose that I would probably need the piston hieght, but I was trying to figure out a estimate. See, if I can use the chevy 5.7 rods, I am much better off price wise, and may be able to afford Ti rods. Anyway, I looked at a 928 chamber, and it looks not as big as a chevy head, and those are about 63cc, right?
So maybe 50cc in the head?
Any opinions?
So maybe 50cc in the head?
Any opinions?
Instructor
Joined: Nov 2001
Posts: 243
Likes: 0
From: Riyadh
Not having seen a 928 piston in the flesh I cant be sure, but I think they have a dome of some sort to achieve a 10:1 CR. This makes it difficult to calculate the actual head chamber volume - have to be measured with a pipette or similar method. Are your new pistons flat or domed, or even concave tops? Getting tricky now.
You will need -
Vol of chamber
Vol of concave piston crown (Add to above), or volume piston crown ABOVE flat (subtract from above) - zero if piston flat
VOlume of gasket thickness
Swept volume of cylinder
Assumes piston crown stops exactly at block deck level - if lower, add volume below deck to chamber volume, then you can calculate CR. YES you need piston height to find out where crown reaches in cylinder.
jp
jp
You will need -
Vol of chamber
Vol of concave piston crown (Add to above), or volume piston crown ABOVE flat (subtract from above) - zero if piston flat
VOlume of gasket thickness
Swept volume of cylinder
Assumes piston crown stops exactly at block deck level - if lower, add volume below deck to chamber volume, then you can calculate CR. YES you need piston height to find out where crown reaches in cylinder.
jp
jp
Thread Starter
Rennlist Member
Joined: Dec 2001
Posts: 25,186
Likes: 105
Thanks for the assistance JP (and Sterling 
I have not purchased pistons yet. That is kind of a problem, as I need to calulate what I will need in the piston design from what compression ratio I get with a 95.25 crank stroke, possible 5.7inch chevy rods, and the basic head chamber. If I can get the Deck Height and CC of the head chamber, I can have good numbers to work from with the piston makers.
I have not purchased pistons yet. That is kind of a problem, as I need to calulate what I will need in the piston design from what compression ratio I get with a 95.25 crank stroke, possible 5.7inch chevy rods, and the basic head chamber. If I can get the Deck Height and CC of the head chamber, I can have good numbers to work from with the piston makers.
