CA18DET low cylinder compression???

Thread in 'Technical Questions' started by TnF, Jan 20, 2012.

  1. TnF

    TnF Member

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    Hello. Just a quick question about a problem i can't investigate right now. I have a CA18DET with 135K miles on it. Last summer i did a compression test with a quality tester(british brand-draper i think) and i got ~9 kg/cm^3 across all 4 cylinders.

    FSM suggest 10 kg/mm^3 min to 12 max. The engine has stock internals. No oil/water leaks, no smoking at all. NO HG leaking. Engine is open breathing from a cusco can. What i suspect is that the exhaust cam is a tooth(2-degrees off) from the last belt change. I'm not sure if it is retarded or advanced. Also during the compression test i poured some oil in the cylinders though no change. Valves can be a bit clocked since the engine was running a bit rich for some time. Also what i experience is when i'm running 15 degrees as the manual says (with a light strobe) i don't get any near the stock power. Also by datalogging using map sensors exactly after the turbo and at the manifold i see a great pressure loss (though i've still haven't checked for air leaks)

    I know that there are much to do, and i know how to do them, but since i will not be working on it until this summer can anyone suggest the reason of such low compression?-or at least validate me if 1 tooth from the cam could be having such an effect? (btw on second thought i believe the way the cam belt was installed if the exhaust cam i one teeth off, the intake cam must be too!)

    ps. I'm running 10w-60 castrol synthetic competition oil, which seals better coz it's thicker than other oils at the same temp. In addition, i don't remember when this happened but my engine starts extremely easily..as i flip the key to the on pos for 3-4secs, walbro powers up and as i start it, the engine starts immediately...

    ps2. Since i've got tomei adjustable gear cams as well, what should be nice to try?

    ps3. Where i can find speciallity clamps for fuel hoses that are a bit smaller than the stock 6-8mm hoses? I need something about 5-7mm since normal clamps can't provide enough force to stop the walbro pissing fuel before and after the fuel filter;p

    Cheers, Ken
     
  2. r3k1355

    r3k1355 Well-Known Member

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    Firstly if you think the belt is a tooth out take the covers off and count the teeth between the pullys, you have the manual and it tells you the number of teeth you need on each run.

    Secondly if you've fitted adjustable cam pullys you must have them setup on a rolling road, if you fiddle with them yourself you'll toss it all up.

    Thirdly you shouldn't need smaller clamps for the fuel hose, no-one else does - are you old one's completely fucked or something?
     
  3. TnF

    TnF Member

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    Actually you didn't tell me something i don't know. If i had my hands on the car of course i would already check, but since i have to wait much i was asking if a teeth off is the reason i have lower compression.

    I haven't yet fitted the pulleys, and of course i would fiddle them on a dyno, i'm asking general how much benefit there is tuning them with stock cams. (Also does anyone knows how much i can play with the timing without hitting the piston?)

    And lastly, because after 19 years the nissan rubber fuel hoses degraded, cracked and started spilling, i've replaced them with higher quality fuel hoses (up to 30/50bar pressure--something like this/i don't remember now but certainly better than the oem ones) The problem is that even with the internal diameter being the same, the external one is about 1mm smaller and at the fuel filter nipples i've got problem (hard-line is ~5mm in diameter, fuel filter ~4mm-that's why it leaks with the stock clamps)

    And btw, i'll do a leak-down test next time to see exactly where the problem is
     
    #3 TnF, Jan 20, 2012
    Last edited: Jan 20, 2012
  4. Dori-points

    Dori-points Member

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    It seems a little knowledge is more dangerous than no knowlege at all?? If you knew compression was low a year ago, checked timing etc etc and you know how to check everything - why not check the timing? I suspect at 135k internals are worn and valve seats may be coaked up but then this is all purely guess work and irrelevant if you haven't checked, can't check and won't check for 6 months?? My suggestion is, pull the covers off and check timing and then as it's got 135k on the clock pull it out and rebuild it with new bearings rings seals and lap the valves in. Chances are your due a belt change anyway. If your looking to fit the Pullys, I've heard that fitting a CA exhaust cam on the inlet side will increase torque slightly?? True or not I don't know? I'm not sure how much you will gain from the pulleys but I'm sure the cost of the pulleys plus rolling road time won't be worth the bhp you gain on a standard engine set up?? Finally - I'm not sure where your coming from with the pipe?? Have you bought a pipe with too large an ID?? In which case replace it?? If the clip is too big for the OD buy a smaller one?? I suspect you need a smaller pipe??
     
  5. TnF

    TnF Member

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    Haha. It seems i've cause a great deal of confusion here;p I'm from Cyprus, and i'm studying in Uk. Which means only every summer i get to work or drive my car. Though last summer i had a big problem with insurance and some more things happened, that's why i'm in a position of a car with unmapped piggyback, gt2871r, ets fmic and more stuff to be fitted, and then i'll go for dyno tuning.. Since in Cyprus i can't really find any of specialty parts i get to buy everything from here. That's why i was asking about the clamps. I know what i'm doing, just need a smaller fuel-type clamp, and asked where i can find some;p

    About the timing belt change was done 2 summers ago, which afterwards i've blown up the oil seals in my gt28r coz i was running just a hair bigger oil restrictor...last summer i did the compression test when i've changed to denso iridium spark plugs and changed to 510cc/min injectors.
     

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