I did a comp test today and my numbers were 270 across...Now my ?? is can these numbers tell me my comp ratio?? Ive heard different stories about this and any help would be great


Ps: the motor is a b18b with endyne rollerwave high comp pistons.

 

you can get it around about.like my ls is 285 and guesstamateing 12:4-5 im sure there is a formula

 

The pistons I got are supposed to be 12:5

 

then thats about right cause i have 82mm,im sure mtber knows the answer to this

 

my stock b16 was 160 across before i hydro locked it

 

It can get pretty complicated to attempt to get back to a SCR from a compression test. It is much easier to judge SCR based on cumbustion chamber volume/cylinder volume and then guessing what your compression test results should come to.

Here's a good java calculator you can use to get your SCR http://www.csgnetwork.com/compcalc.html

Then you can judge how close your compression test results are to the actual ratio.

All things the same, say you have a SCR of 10:1 and that atmospheric pressure is 14.7, given cylinder should compress 147psi of air. That's a minimum. Normal compression is about 17-20 times the value of the ratio depending on other variables/engine condition.

The important thing is that all cylinders are approximately matched to determine a problem cylinder. Or a leak down should be performed to judge the condition of wearable parts.

 

but as you can see the higher the numbers jamie the better the chance of your compression being closer to where it is supposed to be, now was the compression calculated for your motor based of a vtec or non vtec head? headgasket? this is also where some of it gets tricky. but with numbers like 270 i would say its pretty close. was this done with the throttle held wide open while cranking the car over???

funny my civic only reads 155!

 

That's because NA IS GAY, lol. It's all in a good day's ribbing....

 

I almost buried the needle on my compression guage back around to the pin at Zero. 375ish I think, no #'s on that part of the guage. NA is not gay at those pressures ; ) .

 

still GAY!

when you max an autometer boost gauge and your motor still purrrrrs like a kitten, let me know! hahahahah JK.