Compression Ratio's????

[drft86]

hey all

just wondering if someone would know how to convert a compression figure into a ratio thanks.

eg 190psi = 9.5:1 compression or whatever


would be a bit of a useful thing to know if someone could help please

thanks jason

[SprinterTRD]

I dont think it can be done as the compression you measured is effected by to many things, like cam profile,
you will also have to know what temprature you did the test at.

[aaaaah]

Compression ratio is the ratio of the total cylinder volume to the volume of the compression chamber. Plain and simple.

[Hen is a total nutcase]

TRD man is on the money. Cam overlap will affect the psi reading you take during a compression test, as will many other things.

Maybe you should ask what is a typical reading for whatever engine you have. However consistency across the cylinders is more important than the absolute value.

Hen

[biggo]

Yair and what happens when u add boost?

Does the compression multiply it or what?

[Drift Love]

to get an exact compression ratio u need to know the area in the chamber at bdc and tdc

if the motor is stock u should b able to look up the compression ratio from toyota or somewhere like that

the psi reading has nothing to do with compression ratio cos if u have a dead ring or a stickey valve u may have no compression but it will still have the same compression ratio

hope it helps

[AE86GT]

you can get a reading by doing a compresion test psi or kpa

[SprinterTRD]

You can get a pressure reading but you cant work out the compression ratio

[Drift Love]

yeah u can get a compression reading but not a raitio from doing a compretion test

[shift_rook]

Also there is a percentage leakage test for non static compression testing , but yes you cannot work out the compression rate from any of these tests .