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compression and cylinder leakdown test results..

Discussion in 'General Tech and Maintenance' started by D16SiHatch, Jan 30, 2009.

  1. D16SiHatch

    D16SiHatch New Member

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    I'm placing this here cause i figure i'll get better answers than in the general crx/civic forum, and my main concern is whether or not these numbers would be acceptable to throw some boost at.

    Ok so my only concern with the testing is the engine was not at operating temp. i wanted to warm it up more but my friend said it would be alright. i guess you guys can tell me if he's right about that or not. it was warm because it was running like 2 hours or so previous, but it certainly wasn't hot enough to even register the slightest on the temp gauge. regardless he said it'd be fine.. you tell me.

    ok so here's the readings: this is with the psi on the input gauge reading around 25 psi i think, and the shop hose still connected to the unit. now i trust my friend with being able to do many things (2jz w/ 6spd into a mkIII swap), but i'm uncertain if i should trust these leakdown results : /

    cyl 1: 176 leakdown: 35%
    cyl 2: 175 leakdown: 30%
    cyl 3: 182 leakdown: 35%
    cyl 4: 178 leakdown: 30%

    On alldata it said anything from 135 psi to 199 psi was considered normal, with maximum variance between cylinders of 28 psi. also it occurs to me we forgot to hold the tb open while doing the compression test. whoops :/

    Now from what i've read anything over 25% leakage is supposed to require a major rebuild? which certainly concerns me, and is making me wonder ok what the hells going on here. That aside the engine runs really well and doesn't burn oil *knocks on wood*. also what i found interesting is on the gauge itself anything less than 40% was in the green and considered low. 40-70 ish was moderate, 70+ was major leakage. i mean if the leakdown is accurate would it honestly even be running as well as it is?

    It seems odd to me that the compression is pretty decent and yet the leakdown test showed terrible numbers.. i guess i'm hoping that he screwed up the test somehow but im just not sure. i read on another site that the pressure coming into the cylinder should be like 80-100 psi, and from that you gauge how much loss their is. now if thats the case i'm not sure why the inlet pressure gauge was reading around 25psi or less..

    So what do you guys think? i'm going to try and convince him to retest it later and see what happens. i'll make sure to get it up to proper operating temp this time. and i guess if it is leaking i'll try and isolate where from.
     
  2. DickBswapn

    DickBswapn New Member

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    Your engine was cold after two hours, this time of year for sure. And having the throttle open should make a difference in results. I also would recomend having the car on a battery charger during the testing for consistent cranking.
     
  3. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Which engine were you testing? Your D16? That's about right for a D16A6, and you really just want all the numbers to be as close as possible. You have a range of 7psi from lowest to highest, which is a maximum of 4% variation based on the lowest value. I think you're fine.
     
  4. D16SiHatch

    D16SiHatch New Member

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    ha no i got rid of the d16 ages ago. i have a b18b1 in there now. like i said im not concerned with the compression numbers, its the leakdown results that are of concern to me. from what i've read matco suggests you pressurize their CLT from 50-150 psi before starting the test. i know his inlet pressure gauge never read that high so i'm fairly certain something wasn't done right.

    my concern here is because i want to boost it with a 57 trim t3/t4 at around 10-12 psi, and i don't want the engine to fall apart on me lol.

    Here is something i read on another site i thought also was kind of interesting..

    "The overall point is that a leakdown tester is a great diagnostic tool to identify real (or imagined) cylinder pressure difficulties. But don't be alarmed if you get 15 to 18 percent leakdown on all cylinders. If the cylinders perform within a couple of percentage points of each other, it's time to look elsewhere for major power gains.

    Don't be shocked if you see leakage from an otherwise good-running street engine around 20 percent. You could do an excellent rebuild and still not pick up appreciable power even if the leakage was substantially reduced."

    from here How to do Cylinder Leak Down Testing- Car Craft Magazine

    the cylinder leakdown percentages were all pretty consistent, all within about 5% of eachother. The thing is i just dont believe that all 4 cylinder are getting terrible results like that. i'm thinking he must of screwed up the test somehow, because from what i'm reading if i have an engine leaking that much on all 4 cylinders, it would not be running very well at all.
     
  5. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    At stock compression, you'll get numbers like that. My 13:1 compression engine was pushing 295+psi on the compression tester, but it's all going to depend on cam profiles, pistons, port work etc... worry about the consistency between cylinders.
     
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