ka compression?

[freakyjason]

hey guys!i accidentally posted this same question unde "y guys" so i decided to make another one just in case.i was wondering what is considered good compression for a 92 ka24de? also is there some way of testing the compression when the engine is off?

[TheOne]

FSM states 150-170 no less than 14 psi between each piston.

you may get higher compression numbers depending on if the head has been milled, or if there's carbon buildup and other misc things.

you have to do the compression test with the engine off as you have to pull all spark plugs, but you do have to have the engine warmed up as you will get other compression numbers when engine is cold.

[freakyjason]

is this a hard test to administer on an engine that has been taken out of the car? would warming it up be a problem? what kind of numbers would you expect if the engine was not warmed up? lower or higher?

[benemorius]

It's pretty much a no-no out of the car. Certainly doable, but probably not for most people. You'd have to mount the engine firmly or it could twist itself and the engine stand over. You'd also have to either bolt a transmission to it or find a ghetto way of getting the starter lined up properly by itself. Compression will be lower with a cold engine. Exactly how much is hard to say. 10-20 psi maybe?

[freakyjason]

the reason im asking is because im trying to buy a ka from some guy and i asked him to do a compression test and he said he would. he already told me that the engine was out of the car and that he was unable to start it. i was wondering if i should be suspicious of the numbers i get back from him.

[benemorius]

Well, like I said, it's certainly possible for someone who knows what they're doing. I suggest casually remarking in person or over the phone that he must have gone to a lot of trouble putting the motor back in a car and taking it out again just to test the compression for you. Do your best to judge his character by his reaction to this.

[zero_gripS13]

..

do a leak down test.. thats the easiest way to test the engine out of the car..u might not get the most accurate readings but itll twell u if its ok

u will be able to tell if ur rings are leaking or anything inbetween...

its safer than ghetto riggin a contraption to run the engine for compression test
Modified by zero_gripS13 at 7:52 PM 5/12/2006

[pregmantis]

there is a tool that blows air into the cyl and measures compression leak. I dont think that it will give you compression #s but it could tell you percentage of leak through rings, valves etc.

[pregmantis]

zero, I think compression results are higher when hot, atleast in my experience. I would think its from the pistons expanding and maybe even from tighter tolerances from vlvetrain expansin...who knows?

[benemorius]

there is a tool that blows air into the cyl and measures compression leak. I dont think that it will give you compression #s but it could tell you percentage of leak through rings, valves etc.

That's what a leakdown test is. I agree it's a good idea, but once again only if you know what you're doing. Not because there's any danger in this case, but just because you won't get any useful results if you don't know wtf you're doing.

And yeah - a cold engine will give lower compression.

[zero_gripS13]

sorry about the nmisinfo..

i must of had it back wards..

ive never comp tested a cold engine, but i was told till read higher...

[freakyjason]

thanks a lot for the input. ill talk to him tonight and see what he says. im inclined to think that he is an honest man since i met him in one of these threads.