Hey Guys,

Wanted to see if I could get some input on a compression test I just completed on my B16A. I did this compression test because I was noticing steam escaping from both the valve cover breather and the catch can breather (2 10ans off valve cover to filtered can). It does this at idle (not a ton, but noticeable). Disconnected the lines to the can yesterday, and I also drained the can. Seemed like all that was in there was a watery liquid which seemed to be condensation. Wasn't a lot. Anyways, I just wanted to check the compression (because of the steaming from the breathers) to verify that there wasn't an issue internally, with rings, etc. Even though, other than this, there were no other signs that would lead me to believe that there was a problem internally. Car is SUPER STRONG RUNNING and has always seemed to be a healthy motor.

The car's setup is B16A (JE 9.1 pistons, eagle rods), B16 head (crower valvetrain, itr cams), top-mount v-band inlet precision 6266 setup. Here were the results:

Cylinder 1: 141
Cylinder 2: 140
Cylinder 3: 140
Cylinder 4: 141

The test was done with the distributor connections disconnected, the throttle open, and the injectors clips disconnected. Each cylinder was cranked until the gauge would not climb any higher. I couldn't find the damn fuse to take power from the fuel pump, and didn't have a lot of time to look for a relay, etc, so there was fuel going to the rail. Not sure if that could have affected the test or not, but I didn't think so.

As you can see, the results are pretty damn consistent from cylinder to cylinder. While this is true, I wasn't sure if these results were lower than what they should be. Also, I thought, if there was a ring problem or something like that causing blow-by and the steaming, there would be a fair amount of oil in the catch can. There wasn't any. This was after several 3rd gear full-boost pulls.

Let me know if this seems to be something to worry about. I'm just really paranoid about my stuff, and I wanted to get some input.

Thanks in advance,

Toby

 

Do a leak down test and get back to us.

 

Ok. So the results seem low, even though they are so consistent? Would a slight valve-cover gasket leak cause a lower result with the compression test? There is a small spot on the front of the cover that I need to put some honda bond on. It leaks a little oil at the valve cover because I believe it is ever so slightly bowed. I didn't think that this would alter a compression test though (probably just a leak down test). Also, would the fuel getting to the rail affect the results? I didn't think that it would.

 

You have low compression pistons so the compression will be lower than stock. Your numbers are fine. The only thing that a compression test checks is the health of your combustion chambers (rings, valves, head gasket) it has nothing to do with a leaking valve cover.

Same thing with a leakdown test, the only difference is it pinpoints where you're losing compression.

 

Also, the plugs were taken out one at a time. The battery was not on the charger during the test, although it had a full charge. The test was done dry. I had the car running for a while before I did the test, although I didn't do the test until probably 15-20 minutes after I already turned the car off. So I don't know how warm it would have been.

 

Thank you for your reply. That is what I was thinking. I knew that the results would be lower with the lower compression pistons, I just didn't know if they were too low. I was happy with the consistency, just not the numbers. I guess they may be fine. Everything else leads me to believe that this motor is in great shape. The car made 422 wheel on 93 octane on the old turbo setup (6262 with a small e cover) and 17lbs. That's on a b16a, stock bore, stock sleeves.