EGk20pro

Hello, I just did a compression test on my k20a2 the readings I got have me at a little bit of a concern. 114,117,117,119 is what I got without oil in the chamber. 152,148,147,153 is what I got with a cap full of oil. Test has been done on a warm engine. I just rebuilt it last year with all forged internals. 9.0:1 compression, ferrea 6000 valves (stock size), supertech springs and z1 stock cams. Car runs perfectly fine. It made 623whp on the dyno a few weeks ago. I also did this test with 2 testers just to make sure it wasn't my gauge. Any input would be great. Thanks.

viper_boy403

iTrader: (1)

what were your ring gaps? any smoking? very consistent #'s, and it obviously makes power just fine. I wouldn't sweat it

Muckman

iTrader: (2)

Could also be your testing method. How many times are you cranking it? Are all the spark plugs removed when you are testing? Are the numbers consistently repeatable?

EGk20pro

No smoking at all. Gaps are fine.

EGk20pro

I'm cranking it over 10 times each time. All plugs removed. Pedal to the floor. Did the test the other day with the same exact numbers.

Car does not smoke. I never need to add oil. I did a leak down test on it and the biggest drop I got was 3%. Car runs and idles perfectly fine.

phaphon

Motor sounds pretty healthy

EGk20pro

Here's a dyno video. If say it sounds pretty damn heathy to me lol.


Dyno video:
http://www.youtube.com/watch?v=y3Ihk...ature=youtu.be

Muckman

iTrader: (2)

I dont understand how a "healthy" 9:1 motor could produce such low compression numbers.
Are you sure its really 9:1? Maybe your valves aren't sealing well? Did you get a valve job with those new valves?

wantboost

iTrader: (2)

numbers should be within 10% of each other and when you add oil (should be just a cap full, just enough to get around the 1st ring) and the numbers jump that high, it's pretty indicative of a problem. I bet if you did a leakdown test it would show fairly high leakage in each cylinder.

Also the numbers could be low because mechanical cam timing could be off. My K series knowledge memory sucks but do you have one of the variable cam timing heads? that could throw the numbers off as well

EGk20pro

Yes it's 9:1. Got the pistons from JE. Head was tested before I installed it.

EGk20pro

Read the replies please. I already said I did a leak down. Biggest drop I got was 3%. And I did theses tests multiple times with the same results. Car does not burn oil nor do I have to as any.

Timing is dead on according to the manual. It does have the VTC too.

wantboost

iTrader: (2)

Oh sorry, I missed where you said that.

it could be burning a small bit (most honda motors do, especially the vtec b series motors)

It could be something like valvestem seals, which for the most part the leaking oil would be burned off regardless of intake or exhaust placement.. it could affect compression but it is unlikely

What do the plugs look like? Do you have a borescope so you can look down in the cylinders and see what the walls look like? The ones from Home Depot and Lowes that they sell in the tool department are perfect... thin (fits through a spark plug hole) is very flexible, has an led light on the end with the camera and the built in display is pretty good.

They are cheap, I would suggest buying one (if you can) then return it when you are done lol.


Have you done any datalogs once you found out the compression was weird? That might show an issue that you might not be able to even know is happening. Maybe post one if you have it or try to drive the car and do one.

oh, did you do a compression test when the motor was fresh and new? That way you could at least have a set of "control" numbers from which you can base your current results off of because with that compression that low and so far off between cyliders (10% between cylinders is the accepted normal) and even more so when you add oil nd it jumps but still remains so uneven between cylinders makes me think about ring sealing.

Maybe some of the rings have spun around as the motor runs, that could cause serious issues if the rings are not staggered properly.

I'm also worried that the VTC is playing with cam timing during cranking, causing those goofy results. Can you disable the system and try the test again? (oil, no oil)

EGk20pro

The plugs look fine. I don't have a borescope but investing in one sounds like a great idea. I can post data logs later today to see what you think. The pressure between the cylinders is well under 10%. The highest gap between the cylinders in oiled is 5psi and oiled its 7psi. That's well under 10% am I right? When I installed the rings they were staggered. Not sure if there's a way to check to see if they spun around without opening the motor. I'll disable the VTC and see what that does

Freemananana

iTrader: (3)

10% would be greater than 5~7 PSI. Even at 150 PSI, 10% is 15 PSI. But your motor should be much higher compression wise, 220 PSI or something like that.

WantBoost, he said he did a leak down test before you suggested that (maybe at the same time, but his post was first) and he said it was very low, 3%.

wantboost

iTrader: (2)

yea I saw where he did it and mentioned it in my next reply

I was super tired last night, don't know why I couldn't see they were less than 10% different from each other.

What kind and thickness headgasket are you using? your low compression pistons, if paired with a thicker than stock headgasket could lead to very very low compression, this would be reinforced by the test numbers you got

yea disable the VTC and try the test again. *hopefully* the numbers go up. I know the K series with VTC do strange things to cam timing for the best fuel mileage and also for maximum torque and horsepower. Not sure if the VTC system alters cam timing during startup cranking or not.

I know the VTC k series with drive-by-wire do some wacky things, like at cruising speed it will open the throttle 100% (to reduce pumping losses) and alter cam timing to keep the motor at a certain rpm

EGk20pro

Head gasket thickness is a valid point. It's a cosmetic head gasket. I honestly don't know the thickness I just know that it's a 3 later type. I thought it was oem spec and you just throw it in and go.

I'll try disabling the VTC and redo the test again when I get time.