Tintin, you're right, compression is a ratio. What I am planning on doing is to install the pistons and attempt to test the compression of the engine. This will give me a rough estimate of the compression ratio. My prediction is about 20:1 right now (without machining the pistons). This means I am figuring that the psi I measure should be more than the 1.9 TDI, but less than the 1.6 IDI numbers.
After I have machined the pistons to my liking, then I'll measure the actual cylinder volumes to get a compression ratio.
Has anyone here measured cylinder volume before?
Wow...
We need a sticky note program to post into this thread for extremely dumb comments or such observations. For example... Martin, I don't think he quite "gets" what your asking. LOL. However...he did express that compression ratio is a "ratio". Good thing we have that nailed down.
Prothe... volume is an elementary measurement....here, I'll help you out...
http://msnucleus.org/membership/html/k-6/as/scimath/3/assm3_5a.htmlthat would be good practice...
Otherwise...
Volume of a cylinder = Pi * R^2 * H, where
Pi = 355/113
R = radius of the base circle, and
H = height of the cylinder
and for Compression Ratio...
Among other things as well you need...
To accurately calculate compression ratio, you must know several things:
1. Bore measurement
2. Stroke of the cylinder
3. Volume of combustion chamber (in the pistons on a DI motor, including valve depressions) This is where that "CC'ing" comes in that I was talking about...
4. The compression height of the piston
5. The dome/dish volume of the piston (gasser) on DI's, combustion chamber is in piston... no dome/dish measurement
6. The piston-to-deck clearance (protrusion)
7. The thickness of the headgasket
8. The bore of the headgasket
All this and you want to market what you slap together and have to ask the questions to figure out? Wait...it'll actually be on someone else's acct. Gotcha...
Oh....umm...ah...yes, got it.
Oye vey...guessing always works too i suppose.
Joe