When talking about compression ratios I hear ppl talk in numbers such as:
11:1, 10:6, etc and then in compression tests the numbers are 215, etc

What's the relationsihp between them and what do the individual numbers in example 10:6 mean?


Sorry if this is a noob question...i just always wondered

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EF8_SiR &raquo;</TD></TR><TR><TD CLASS="quote">When talking about compression ratios I hear ppl talk in numbers such as:
11:1, 10:6, etc and then in compression tests the numbers are 215, etc

</TD></TR></TABLE>

11:1 means the amount of air when the piston is at the bottom, 11, is compressed into the space of 1 when the piston is at the top.

Compression test numbers of 215 mean the piston has compressed the air/fuel inside the cylinder to a pressure of 215 PSI.

 

So these two figures are totally irrelevant to each other (ie lower air compression ratio would not necessarily correspond with low compression test numbers)?

Also how can one go about in raising compression test numbers? new pistons, gaskets, etc?

 

they are related.

pistons
headgasket
deckplate
cranks
rods
milling
decking
valves
combustion chamber size

thats pretty much all the ways to change it

 

Theyre related but not to an exact degree. If your engine has 0% leak then you could do the math and figure it but most of our engines have some leak around the rings or valves, guides etc so that means a drop in psi but not in compression ratio. Plus carbon buildup = higher numbers. Follow me? If you could find a conversion factor for an engine with no leak, no carbon and then find out what % your engine is leaking and some way to measure carbon buildup you could theoretically figure it all out. But I say **** that.

 

DAmn the theory behind compression and restoration is a lot deeper then I thought it would be.
Anyways, thx ppl for all the help

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hybridvteceg &raquo;</TD></TR><TR><TD CLASS="quote">they are related.

pistons
headgasket
deckplate
cranks
rods
milling
decking
valves
combustion chamber size

thats pretty much all the ways to change it</TD></TR></TABLE>

and cam overlap as well ...

greg