So my EVO X has 10,000 miles on it now with an FP Red, AMS everything, etc... so I thought it'd be a good time to baseline compression test the car after a spirited run to see how my gauge reads on all 4 cylinders.

I was a bit surprised in my results. I had 160, 160, 160, and 150. Cylinder #4 kind of upset me.

I went online and found a post by Eric, a technician at AMS in Chicago. He said that based on his experience with compression testing numerous 4B11T's, he's seen big variances from one cylinder to the next, from one motor to the next, and even in the SAME cylinder taken at different times. He attributes this to probably having something to do with the MIVEC on both the intake and exhaust cams.

My question for you guys is... have you encountered the same thing? Or have all four of your cylinders matched approximately across the board? I might try to retest that cylinder today after driving it again... although I think I'm going to buy a leakdown tester kit as I'm pretty paranoid. Haha...

Thanks for any input!

Lou

 

That's actually well within the normal variance although I bet if you test again it might turn out differently. You definitely want to do the test on a hot motor. You can also add some oil into a cylinder that is reading lower and see if it raises it or not. If the oil helps then the rings are likely the culprit and if it's the valves leaking then the oil won't help compression go up at all of course. There is something about the MIVEC creating some odd results but the main thing is to make sure you don't test on a cold engine.

 

Less than 10% variance in the numbers. Looks good to me.

 

I know the motor is within spec, but on a motor this new, I'd expect a more uniform reading across all four. I'm trying to figure out whether or not the MIVEC may cloud the true numbers.

Will be doing a full leakdown test this week and will report back to this thread. Really curious to see if cylinder one leaks any more than the other three. Fingers are crossed.

Lou

 

Not a good update.

I re-tested compression, and got the same exact thing, 160, 160, 160, 150.

I put a capfull of oil down cylinder #4, and the compression shot up

Don't know if the car came like this from the factory, or if a bad fuel pump relay is to blame... I know most of you will say the motors totally fine and within spec... but on a $35K "new" car, I would expect the numbers to be the same across the board. Very frustrated.

Will be doing leakdown as soon as my kit shows up, and will report back then.

F^$%K.

Lou

 

Interesting. Pre-oil, you were still within normal limits. I'm willing to bet that if you did the oil test on your other 160 cylinders, you would see higher numbers also. Just my .02

 

Good point made.

My first test on the "bad" cylinder with the oil reported 175psi... Like you said, the others might hit 185psi or so with oil in them.

Still, I'm determined to figure out what's going on with the 4th cylinder. In the engine failure thread, it seems that cylinder #4 craps out before any other cylinder on a majority of these motors.

Lou

 

You need to do a leak down test, it can tell you if you have a pin hole leak on a intake valve on cyl #2. A compression test will never show a pin hole leak it was designed in 1920's

 

whats the difference between the two?

 

A compression test uses an air hose that's screwed into the spark plug hole that is attached to a gauge. The engine is cranked over with the fuel injectors and ignition system disconnected.

Each time the piston travels up toward the top of the bore, it compresses the air, and the max reading is held by the gauge. Usually it takes about 5 full revolutions of the motor to reach its max compression number.

The leakdown test is a much better indicator of overall cylinder health. The way it works is similar to the compression test in that a hose is screwed into a spark plug hole. Then, compressed air from an air compressor (usually at 100psi) is injected into the cylinder and held there. A second gauge on the leakdown tester measures the amount of air that is escaping through leakage in the cylinder. It's represented as a percentage. 5% and lower is a very healthy engine usually. As the test is being administered, the person has the ability to listen to the air and where it's escaping through.

Tailpipe = exhaust valves
Intake manifold = intake valves
Crankcase = pistons, rings, or cylinder walls

With this test, you can also test for headgasket leakage as well. Hope that helps.

Lou

 

The motor is flipped on this car from the 4G63. Is #4 on the passenger side?

 

#1 is on the passenger side, where all the accessories are.

 

Thanks GG!

 

No, #4 is on the driver side. Doesn't the order go 1, 2, 3, 4, starting from the timing chain side (passenger)?

 

Yea let us know what you find. It seems like Cylinder 4 keeps taking a dump on some of these engines.