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Compression Test... Low Psi analysis.. help!

Discussion in 'General Tech and Maintenance' started by JDMnoob, Feb 8, 2012.

  1. JDMnoob

    JDMnoob New Member

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    So some background info.. I bought a jdm gsr swap from a more shady vendor a few months back. I bought it because they had a video of them doing a compression test to it and it showed a strong 225 psi across the board - vin# on the block was included.

    Received the engine and found out it had severe water intrusion :eek:. Had to pay to get the gunk cleaned out of manifold, tb, oil pan. New cometic 3 layer headgasket, h22a LMAS, and valve lash to spec. Had it dyno-tuned on Hondata... put out a decent 163 whp on a dyna pak with shitty 89 gas because thats what the tank in my civic was filled with when the b16 blew up, (later topped off with 94 on the way home). It had I/H/E and msd ignition during tune.

    Recently noticed it was lacking power, and I later saw 2 wires were not secured to dizzy cap, which I fixed w/ snap ring pliers... and ran good once again after fixing that. However, I concluded that I had been driving the engine for about a week with a bad misfire (wasn't really pronounced, just ran weak), and worried about possible fuel wash of cylinder walls. Sure enough the crankcase smelled of gas. Thought it would be a good idea to do a compression check.

    The other day I rented a OEM compression tester, and did a dry and wet compression test, with disappointing results:

    Cyl 1: Dry-152, Wet-152
    Cyl2: Dry-170, Wet-190
    Cyl3: Dry-170, Wet-190
    Cyl4: Dry-172, Wet 182

    Notes: Engine fully warmed up, fuel fuse pulled, msd coil wire disconnected, throttle body held wide open, about 7 cranks per test. All cylinders not being tested had spark plugs threaded in.

    I realize a leak down test is perhaps necessary, and I will do that as soon as I get time and money (college sucks)...

    But in the meantime do any of you experts have any input for this data? Considering its a 10.6:1 compression ratio, are these numbers low enough to worry about? And finally, would any of the given information falsify the test (i.e. spark plugs of all other cylinders still being threaded in, or maybe a lower-reading tester)??

    Thanks
     
  2. TurboMirage

    TurboMirage YEEAAAHHH VIP

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    have you tried to change the oil?
     
  3. JDMnoob

    JDMnoob New Member

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    I'm going to do that after class tonight around 6. I just checked the level though, hasn't dropped at all in the 800 miles it has seen..
     
  4. TurboMirage

    TurboMirage YEEAAAHHH VIP

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    no, but if you suspect the cylinder washed out a bit, there may be gas in the oil?
     
  5. JDMnoob

    JDMnoob New Member

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    Yeah there definately is gas in there. Do you think that could affect the numbers?
     
  6. JDMnoob

    JDMnoob New Member

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    Or could having spark plugs in the other 3 cylinders affect the numbers?
     
  7. TurboMirage

    TurboMirage YEEAAAHHH VIP

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  8. Taco15

    Taco15 I wear stretchy pants VIP

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    TI i'm digging the new avatar. :lol:

    it shouldnt make a difference. but when I did mine ALL plugs were out and fuel still sprayed. now whether you have gas in the plugs or not i don't think it would make a big deal. I would think the rings would still do there job...if.... they are damaged.

    did you have a battery charger hook up? you need to have a consistent batter charge so each tuen is the same.
     
  9. civicious

    civicious FüK-VTEC VIP

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    Battery charge wouldn't make a difference. Having the fuel on or off doesn't make a difference. Opening the throttle body doesn't make a difference (as long as the test conditions are the same for all 4 cylinders). Having plugs in or out on the other cylinders won't make a difference.

    Cylinders 2-3-4 are fine; minimum spec is 135. 'Perfect' is 270, but there are hundreds of factors (temperature, humidity, altitude, etc) that could affect that. You using a different head gasket could affect that as well.

    Cylinder 1 is too low though, all four of 'em should be within 6ish psi of each other. The problem with Cylinder 1 is most likely not on the piston or bottom end, unless there is a hole in the piston - if it were an issue with the rings being washed out, pouring oil (what I'm assuming you refer to as a 'wet test') would cause the reading to raise. More than likely you've got something improperly installed or misadjusted; otherwise you might have a bent valve or a cracked/broken guide. It's also possible, since the cylinder that's lowest is on the outside, that you didn't properly torque the head studs OR you fudged the gasket somehow - not doubting your ability at all;'I'm a professional Bosch and ASE master technician, and I spend my days working on cars that cost more than most peoples' houses, and I still make mistakes.

    Well, actually, I don't make mistakes...but other people with my level of experience make mistakes from time to time.

    Pull the valve cover, re-check everything up top.




    also, how did you use snapring pliers to fix a loose wire?
     
  10. JDMnoob

    JDMnoob New Member

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    Thank you guys for the support. And yes cyl 2 and 3 jumped up 20 psi from added oil, so I didn't know if that was a big enough jump to cause concern. Until I do the leakdown test I'm assuming low psi on cyl 1 is a bent or burnt valve, more than likely an exhaust valve but who knows until I search further (exhaust crackles every so often on idle)... but the fact that psi in cyl 1 didnt jump whatsoever with added oil is a little re-assuring.

    And Civicious, I used snap ring pliers to open up the msd wire terminal so that it fit more snugly inside the dizzy cap terminal. Two wires were loose on the cap and nearly falling off causing a misfire, and I think is the reason unburnt gas got into the oil.... because the fear of fuel washed cylinders was the motivation for the comp test to begin with.
     
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