compression

rotorgem · tinkerer Joined: 04 Oct 2001 Posts: 80

just wondering if you can convert your psi reading to the ratio or how to you find out the ratio (eg 8:1)

HELP

TXcoupe · petrol head Joined: 05 Oct 2001 Posts: 1675

you divide the psi reading by 14.7 to get a ratio

Fastgem · tinkerer Joined: 04 Oct 2001 Posts: 166

are you sure about that? my old 2ltr was running between 200-202 psi on all cylinders which divided by 14.7 works out to be around 13.6:1, considering i could run it on super and it wouldnt ping i think the result from the formula is a tad high.

rotorgem · tinkerer Joined: 04 Oct 2001 Posts: 80

fastgem are you sure it was 200psi not kpa because if it is psi that sounds very high

tx_shitbox_thrasher · rice boy Joined: 13 Nov 2001 Posts: 13

yeah mine was at 40 psi with a blown head gasket.. lol

Fastgem · tinkerer Joined: 04 Oct 2001 Posts: 166

200kpa is like 29psi so i would bloody hope not. I built the motor with hi comp in mind, have the specs for it somewhere. i though it was around 10:1 or there abouts and I seriously doubt the cam in it at the moment would have enough overlap to let it run at 13:1 so fuck knows.

Tooleeda · tinkerer Joined: 04 Oct 2001 Posts: 93

I always thought CR was the ratio between the bore volume (to the deck of the block) and the combustion chamber. If so you really need to know the specs on both, which usually means having the chambers CC'd. Otherwise shaving the head, or boring the block will affect the CR and we all know it does.