Just got S4 Turbo engine compression tested, just wondering how to interpret this correctly...



From what I can see, both rotors are way above 85 psi, so its not doing too badly?

The difference between the 2 is not too much either, and all peaks are pretty much even.

Thoughts?

Cheers!

Paul.

 

looks ok, all the pulses are even so the seals are ok.

one rotor has a bit higher compression..but it doesnt look like enough to worry about.

 

from my calculations:

even compression over rotor faces. Rear: ~100psi / Front ~108psi (min spec is 85psi)
difference between rotors ~8psi (max allowable spec is 21 psi)

So im thinking it looks good.

Went to a dodgy guy to do a look over on the car and he said this was poor compression lol.. i think he is messed up

 

for some 4 cylinder piston engines, it might be.


but not in this situation...most old engines sit around 100psi.

weaker are 90psi...and the ones about to go are 85psi and below.

 

Here's mine!

I think those are good numbers...it's an SE engine, I'm hoping for at least 200,000 miles.

http://brownmound.com/engine03/itstarts.html

Right on.

 

brownmound, I noticed that "ATF" raised your compression numbers, but there was talk that ATF (or any oil really) only raised comp temporarily. I'd be interested to know if your numbers stayed that high on the rear rotor. If they did, it could be imperical proof that using some form of penetrating oil or cleaner can help a tired old engine!

Jon

 

Good question....i tend to think it was a temporary increase as well...however it did unstick the seal that was causing the no start. Maybe next time I head up to my mechanic's shop I'll bug him for another test, without atf.

Right on.

 

wow, those numbers are pretty damn good.

it's weird that the rear rotor is much lower (8psi) than the front, but it shouldn't really be much cause for concern.

that motor is in better shape than probably 90% of them out there.

 

Now that the image finally loads for me, I'd say that's a forkin' awesome test result.

I'm absoloutely amazed at how EVEN your points are between the three faces of each rotor. The 8psi difference between the two rotors isn't very large, and definitely within spec. There was a thread at one point speculating that there must be some different forces at work on the rear rotor because someone had blown three engine, all rear rotors! Either way, with comp numbers that high, it looks great.

But I will say that I don't know what the compression ratio or expected numbers are for an S4 Turbo engine. Those numbers are as high or higher than what I'd expect to see off an FB engine. I thought the turbo engines were supposed to have low comp rotors, and if that's a test with low comp rotors, I'd want to know what high comp rotors looked like on a test!

You sure it's not an N/A engine?

Jon

Edit: I'm going to make a copy of this and send it to the 2nd Gen Forum because it's a second gen engine, they'd know more about what the comp test should look like for this engine. I'll leave a copy here since people seem to be interested. So head over there and take a look-see.

 

those numbers are decent . its not brand new and its not worn out either. its pretty normal to have one rotor a lil diff than the other, in every motor ive tested i generally see a 5 psi difference between front and rear....

 

Cold or hot test?

 

Car was warmed up when the test took place.. had been sitting for ~10-15 mins before it after a long drive.