brent_G

Well i have always wondered how to get the compression ratio. Lets say a b18b1 with 190 across the board...whats the ratio on that? 10-1? anyone can give me an idea of how that works that would be cool.

Mista Bone

can't be done.

civickiller

you kind a can but not too accurately because the more the psi goes up the higher the comp ratio so yeah but idk if anyone knows the exact ratio to psi

keebler65

i think it can be done, however, it requires more numbers than you want to deal with. you're better off finding out what the rating is when they come from the factory, then find out the percentage, like this:

(your psi)/(factory psi) * 100 = percentage of original

blah13

It is nearly impossible to determine. First you would need to do a leakdown test and find that percentage, as that will lower the psi of the compression test. Then you have to determine the ammount of carbon buildup in each cylinder as excessive buildup will increase the psi. Then you need to know the psi for an engine with no leakdown and no buildup....so yeah, pretty hard.

Mista Bone

then how do you factor in the cam timing?????

If you retard the intake cam, you get a low cranking psi.

I stand by my original statement.

MrTodd

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mista Bone &raquo;</TD></TR><TR><TD CLASS="quote">then how do you factor in the cam timing?????

If you retard the intake cam, you get a low cranking psi.

I stand by my original statement.</TD></TR></TABLE>

Agreed.

You could get over 200 PSI with a 9:1 CR, if the ring seal was excellent and if the vavles were sealing just as effectively.

Compression testing isn't going to tell you anything regarding the actual compression ratio.

civickiller

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blah13 &raquo;</TD></TR><TR><TD CLASS="quote">It is nearly impossible to determine. First you would need to do a leakdown test and find that percentage, as that will lower the psi of the compression test. Then you have to determine the ammount of carbon buildup in each cylinder as excessive buildup will increase the psi. Then you need to know the psi for an engine with no leakdown and no buildup....so yeah, pretty hard.</TD></TR></TABLE>

u dont have to determine anythign because thats the compression ratio, carbon buildup, ok as the carbon builds up your compression ratio increase, i mean if your trying to find stock compression ratio then that would be hard, but if yoru tryin to find out the compression ratio you have now, u dont have to do that because right there you would be finding out hte compression ratio you have right then.

fourthgenhatchB17

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

u dont have to determine anythign because thats the compression ratio, carbon buildup, ok as the carbon builds up your compression ratio increase, i mean if your trying to find stock compression ratio then that would be hard, but if yoru tryin to find out the compression ratio you have now, u dont have to do that because right there you would be finding out hte compression ratio you have right then.</TD></TR></TABLE>

Yep.

brent_G

yeah i was trying to thnik of a way to figure it out myself...but couldnt thats why i came to you guys maybe someone knew of a way to figure it out...seems to be there isnt much of a way.