DIY : Compression testies :)

[bennjamin]

Its that time of the month again....DIY JOBBY !


Disclaimer: The following is provided as a GUIDE ONLY, and neither myself nor Ozhonda take any responsibility for the outcomes of someone else doing the following. You follow these steps at your own risk!


Aim: To test the compression of a engine - that is , basically see the internal condition of piston rings , valves , valve seals etc. Handy when purchasing a second hand car or if you are just paranoid like myself :D




http://www.ozhonda.com/gallery/watermark.php?file=2/7921-med.jpg



Required: Car. atleast 2 hands - only one foot is needed though. Compression tester tool , and spark plug remover.



Steps:


http://www.ozhonda.com/gallery/watermark.php?file=2/79naked-med.jpg


1. Open bonnet. Pull out all spark leads , then use removing tool to take out all 4 spark plugs.



2. Open fuse box in engine bay ( upper should be right corner) - take out the fuse marked ECU ( 15a i think ?) ( to disable the fuel and ignition)


http://www.ozhonda.com/gallery/watermark.php?file=2/7911-med.jpg

3. Place the compression tester tool into the 1st cylinder (any is ok) and tighten up. Either get a friend to hold it and read the reading OR leave it atop the engine bay. YOU MUST FOLLOW ALL STEPS IN THIS PHOTO....



http://www.ozhonda.com/gallery/watermark.php?file=2/7931-med.jpg

4. Jump into the cabin , apply WOT ( wide open throttle/ full throttle) and turn over the engine 6 times. Jump out , and read the top reading OR get ur associate to tell you the maximum psi reached. Record down and write the cylinder number/location.



5. Simply repeat for each cylinder - once all recorded pack up in the opposite fashion , reinsert sparkplugs + leads, then reinstall the ECU fuse and away you go.



Other comments

Results of the compression test will vary engien to engine - but apparently the wanted norm is a MAXIMUM variation of 28 PSI between all 4 cylinders hot or cold .

If there is a substantial change in PSI perhaps a bent valve might be to blame - or worn piston rings or even a bad head gasket.
IF in doubt , take it to a professinal to get a leak-down test + more to find the source of crappy boost :D


http://www.ozhonda.com/gallery/watermark.php?file=2/79Ywood.jpg

Thats it. Go honda :)

[revNhevN]

Very good write up. :D . Do you know what the pressure should be for a B16a? like, what is good and what is bad.

[bennjamin]

Very good write up. :D . Do you know what the pressure should be for a B16a? like, what is good and what is bad.

i have no idea - my totally stock d16a8 - pulled 220 psi ( quite high) - while HOT ( that is , with the car warmed up properly). So , im sure your car could pull a similar number.
As long as each readout is within the 28 PSI range there shouldnt be a problem.

[egSi]

cool write up ben, i should do this :thumbsup:

ur the diy king y0! ;)

[ProECU]

yeah, just on this, ideally, the cyllinder pressures should not vary by greater than 5%.

Excellent writeup

[_FeRiO_]

cool write up man!! i might give it a go when i have time

[Q_ball]

http://www.ozhonda.com/gallery/watermark.php?file=2/7931-med.jpg

LOL @ step 3

always lookin to make revenue huh bren ;)
nice write up mate

[pgclee]

how much 12.5:1 if it were to convert to Psi?

[bennjamin]

how much 12.5:1 if it were to convert to Psi?

thats the compression ratio of an engine. This test is to judge the maximum compression in psi , to test for internal leaks etc.

[**Ghost**]

few queries

1. "turn engine over six times"... i wanan know what this means? as in rev it 6 times?

2. also another thing...where and how much does it costs to get a compression testing tool?

3. does low compression indicate a dying headgasket

[revNhevN]

1. "turn engine over six times"... i wanan know what this means? as in rev it 6 times?



I think he means to try to start the engine 6 times per cylinder.

[bennjamin]

few queries

1. "turn engine over six times"... i wanan know what this means? as in rev it 6 times?

2. also another thing...where and how much does it costs to get a compression testing tool?

3. does low compression indicate a dying headgasket


1. "6 times" means , you will hear the engine "crank" 6 times. Its an obvious noise/situation. This is to judge the maximum compression of each cylinder.

2.The tool is about $40-60. You will hardly use it so i suggest to borrow a mechanics ( like i did) or get them to do it for you. Cost = $20 or $30 i guess . It takes only 15 minutes or so.

3.Low compression could indicate a dying headgasket , or bent valves , or worn / leaking piston rings amoungst other things. The most important thing as said before - is that the compression between cylinders does not vary more than +/- 5%.

[**Ghost**]

thanks for that but how do i "crank" it? kinda noob with this stuff.... do i turn the car ON? or something else? completely lost here

[bennjamin]

thanks for that but how do i "crank" it? kinda noob with this stuff.... do i turn the car ON? or something else? completely lost here

arrgghh dont worry. Just turn it "over" - liek you would to start the car normally. The engine will make a " dun dunnnnn" noise and kep the key in the same position until it does it 5 or 6 times.

[JDM.Power]

nice write up ben! top job

[**Ghost**]

arrgghh dont worry. Just turn it "over" - liek you would to start the car normally. The engine will make a " dun dunnnnn" noise and kep the key in the same position until it does it 5 or 6 times.

hahhahahahha rolf... thanks ben i'll do that!! : ) see u shoulda been more simple in the first place :p

[Nuttz]

when my car was warm/cold(i left it for about 20 mins) i got 135 165 135 180. but when i redid the test after starting the car and made the engine hot it got pretty much 180 psi across all pistons.

so does the warm/cold reading mean anything??

[Surrufus]

where do u get said item in step 3? :p
i mite just get one lol

[chartinael]

nice write-up. really appreciate it :-) especially the explanations given to ghost.

kristin

[SiR JDM]

Nice write up Benj... get some pants! :p

[michael_antoi]

i plan to do the test on a ZC tomorrow, is it hard to get the spark plugs out?

Ie. is the spark plug remover necessary to get them out?

[michael_antoi]

this test work on carby engines?

tried it and the compression tester keeps sitting on zero for some reason...

[michael_antoi]

well the problem was that the compression tester wouldn't screw in properly, still cant get it to

[bennjamin]

well the problem was that the compression tester wouldn't screw in properly, still cant get it to

Which part wont screw in ? The actual head which goes into the engine/spark hole ? Or the top which connects to the gauge ? Try running alittle fresh oil around the head to "seat" it in - and make sure all the gauge lines and screws are tight. Good luck !

[michael_antoi]

not sure what u mean about gauge lines

but the end of the compression tester wont screw in where the spark plugs usually go...

[SKREMN]

will the temp of the engine vary the read outs?
better to be done when its COLD or WARM

[bennjamin]

will the temp of the engine vary the read outs?
better to be done when its COLD or WARM

yes - at COLD the engine will sometimes give varying compression results ( carbon and very slight dimension differences etc ) But once the engine is at operating tempreture - compression should not vary with +/- 5% of each cylinder. That is , best result = at warm :)

[ProECU]

Errmm......

What is the situation with injectors and fuel in this procedure ? ;)

[bennjamin]

Errmm......

What is the situation with injectors and fuel in this procedure ? ;)

a big 0 since its all disconnected lol :confused:

[ProECU]

Yeah True

I should learn to read gooder...

[spardikis]

with my build up-b18c block-ctr pistons and b16a head- i broke in my engine where at 1000km's i tested it...
i read something like 240-225 psi... would you guys think that the compression is too variable?? if i remember how to do my maths right the +/- is variable is about 6.5% differance!

would this efect the tuning and timing or perhaps cause one cylinder to have pre dettanation while the others didnt??

lol i dont want to reseat the rings....mabey i should just close my eyes to it and keep driving coz it runs sweet! just pretend i didnt do the test in the fiorst place;)

[ProECU]

I think you should re-try the compression test.

I would be concerned with those numbers you posted...

It might be a case of still requiring to run th emotor in further.

I'd keep an eye on it, and recheck the compression later down the track.

[spardikis]

will do :)

I will have to do a leak down test to get a propper diagnostics i think

[MWAKU]

whys all the pictures the same, a civic

[lilthug]

considering u bumped a thread thats almost 5 years old

im thinking the images arent on the server anymore

[MWAKU]

yea obv lol. just pointing out it should be changed :P

[grifty]

maybe pm bennjamin and ask him nicely to re-upload the photos?

[Sir_vtec]

Bump for an old dog.

Does anyone know how to perform a compression test for a motor thats our of a car?

[grifty]

apply power to the starter motor?

[mytfoz]

awesome write up.
great tip for someone buying an second hand car :)