S14 DE's compression in psi

[red240ne]

Are all KA24DE's stock compression 179psi in the cylinders? I was wondering because the salvage yard by me claims that they have 3 DE's from 95-98 240's with compression readings of 180, 185, and even 192??

[WDRacing]

WHen doing a static compression test its important to make sure all the cylinders are within 5 psi of each other. As far as what the factory specs are, i'm not sure. You can always call Nissan for the info. I'll copy this to the Tech section.

WD

[:: orion ::]

IIRC, 179psi is the 'standard' reading...i.e.your engine is in just fine (normal) condition with 179psi.

Anything better, and that's great. I have a spare motor with 192 across the board.

Anything less, down to 155 is bad (but not horrible per se). You're looking at a rebuild with anything less than 155psi...

Later - Brian

[hannibal]

from huguetpj's sitehttp://www.geocities.com/huguetpj/stats.htm

I think these are the factory specs...

Engine Compression in PSI

standard 179 @ 300rpmminimum 151 @ 300 rpmdifference limit between cylinders 14 @ 300rpm

Jay

[huguetpj]

yep I got that from 240sx.org, I believe it to be right.

[oi138]

IIRC, 179psi is the 'standard' reading...i.e.your engine is in just fine (normal) condition with 179psi.

Anything better, and that's great. I have a spare motor with 192 across the board.

Not necessarily. High compression readings can also be caused by bad rings or anything else that would let oil in the combustion chamber. Also carbon diposits will cause abnormally high compression readings. Leak down tests are a much better way of reading the engines conditions.

[:: orion ::]

High compression readings can also be caused by bad rings or anything else that would let oil in the combustion chamber. Also carbon diposits will cause abnormally high compression readings. Leak down tests are a much better way of reading the engines conditions.

That's true, but with respect to a compression test, 179 indicates 'normal' for a KA, and higher is *usually* better.

I've never seen worn rings cause a high reading...?

Leakdown tests are usually used as a followup to a compression test - If the motor is warmed up and a compression test is done correctly..and the results check out, you can skip a leakdown test - 99% of the time...

Later - Brian

[red240ne]

Those aren't my readings. Those are readings from the salvage yard.

I meant that they have an engine with 180psi. They have another engine with 185psi. And they have another with 192psi.

3 different KA24DE's. Sorry I wasn't very specific.

[WDRacing]

I think we understood that part Red, either way, all of the above engines are good.

WD

[red240ne]

they want 350 bucks for each of them, which really isn't that bad for a salvage yard. all of them have under 90k miles as well.

[WDRacing]

I'd buy all 3...

[oi138]

That's true, but with respect to a compression test, 179 indicates 'normal' for a KA, and higher is *usually* better.

I've never seen worn rings cause a high reading...?

Later - Brian

Oil in the combustion chamber will cause high readings. I can't really explain why but I have seen it before.

[WDRacing]

Well, I don't think it will cause higher then normal readings on a cylinder with very good rings, but on a cynder with bad rings or a bad piston pouring a small amount of oil in the spark plug hole and redoing the CR test will yeild higher CR. The oil simpl;y takes up some gaps between the ring/piston. I also use this method to determine if I have a bad valve or a bad cylinder. If the CR stays the same when you add oil, you have a valve/gasket problem.

WD

[Smurf6x6]

Oil in the the combustion chamber takes up space, so the is less space for the air in the combustion chamber, therfore make the compression ratio higher.

[mikesloud]

I have a rebuilt kadet with 3600 miles on it daily driver, I have all stiff etc,valvetrain and jim wolf cams, 8:5 to 1 ross pistons and I was worried about my comporession my readings ,maybe because of vaccum loss (cams,valve springs)of starter 300 rpm , my results were 139,140,140,141 and I was way worried, I called Ivan at SP Racing and he said don't worry about it as long as they were all close, I thought it may be to low , but it is new motor driving for 6 months 1200 miles no boost,1500 more with 5 lbs boost , now have 12psi I t pull great, drives great. should i be worried , how can I get compression higher?

[Structure240sx]

old post you are bringing back.

klattr1 has similar compression number. around 155 in each with a motor very similar to yours. i think he figured it was the jwt cams that both of you have. no need to try to get better readings if everything is working great

[crzycav86]

Well, don't you think the lower compression ratio would effectively lower the compression of each cylinder?

KA guys with 11:1 CR have compression in the 200 something range..

[hannibal]

I followed the FSM directions with the exception of removing distributor plug). It did take me awhile to perform the test after warming up the car cause I couldnt get the plugs out of the hole I got 190psi in all cylinders. Thats kinda high, but I think consistency is more important. I think the high numbers came from my flawed method.

With 8.5:1 pistons, you should expect lower numbers...

[crzycav86]

Nah. You would get lower numbers on a cold engine. You probably did it right anyway. How many miles do you have? You might have a little carbon buildup or something unimportant like that.

[EXIST tm]

ok so i can tell you that high is 179 psi, standard is 155 with a +/- 12 psi, as from what alldata says about compression, i had to learn this because my engine fired at from 1 - 4, 105 psi, 165 psi, 117psi, 153 psi. that says it has bad rings, and to prove it, put some oil in the cylinder head and see if it brings all the piston up to the regular psi (wet test)

[hannibal]

Its got 86k miles on it. I wondered if a cold motor would give me high or low readings. I couldnt come to a conclusion either way...