compression test

[sugz]

hey guys,
i have my eyes on this H22A, and was wondering what sort of result would i expect if i do a compression test on them?

if the 'brand new' H22A compression ratio is 11:1; and the results come up say 10.9:1 would that be a reasonable result or would that be a no go zone?

[JasonGilholme]

a compression test usually comes back as psi read cause its testing the pressure.

Compression has to do with the lenght of the stroke and the volume of the cylinder.

Usually its ok if all the cylinders are close to the same PSI if theres a big different in one or two cylinders it'll need new rings and or valve seals etc.

[Drew]

Compression test and compression ratios are different

Compression test basically measures the actual pressure within the combustion chamber be it psi or kpa

Compression ration basically measures how much the mixture is compressed from when the cylinder is at the bottom and when its at the top... if that makes sense

You want the compression to be pretty much the same across all cylinders with maybe 10psi max difference between them... If one or two cylinders are drastically different then you have a problem

IE

Cyl 1 190psi
Cyl 2 189psi
Cyl 3 192psi
Cyl 4 191psi

= All Good

Cyl 1 190psi
Cyl 2 54psi <--- PROBLEM
Cyl 3 53psi <--- Leaking
Cyl 4 193psi

[sugz]

thanks jason and drew, youve made it very clear to me

[EK4R]

what psi should you been looking for in a say b18cR 200?

[bennjamin]

for comparision - my B18c7 (r) puts about 250 psi across all four cylinders HOT and WOT.

[EK4R]

for comparision - my B18c7 (r) puts about 250 psi across all four cylinders HOT and WOT.

ben do you know if the jdm or the auspec are similiar ?

[bennjamin]

ben do you know if the jdm or the auspec are similiar ?

From testing , (healthy engines) they are exactly the same compression test result.
But this isnt relevant to these engines as my old D series had about 240 psi too.
Or do you mean the actual compression ratio ?

[Menthu Rae]

I have 11:1 CR pistons from Prelude Type S, along with shaved head and H22Z1 bottom end.

Previous compression test results (10.0:1, shaved head, ~80,000km):

196
196
190
196

New compression test results (11.0:1, shaved head, ~10,000kms):

215
215
215
215

Your results depend on more than just the CR of the pistons, they depend on ring seal, cylinder/bore wear, head clearance (don't know exact term for that?), piston compression ratio, and most importantly atmospheric pressure at location of testing.

If you test at sea level, as opposed to 100m above sea level - your compression results will vary.

Edit: You can also do a leak down test, which involves adding oil to the combustion cylinder... this will help seal the rings and determine if you have any blow-by or leakage past the rings. You will observe the compression results go up by a reasonable amount if there is any kind of leakage/problem.

[EK4R]

ahh ok . yeah well i was just curious if higher PSI means healthier engine , because i know some engines do like 250 like ben stated and some do mere 190-200 ish. even though they are similiar engines and was wondering if its caused by a internal problem or doesnt mean much at all as long as 4 cylinders are similiar in PSI

would say doing internal work like shaved head, knife edged, blueprinted work INCREASE or DECREASE your PSI?

[fatboyz39]

as long +- 10psi within each cylinder it should be fine. Number don't mean shit cause different gauges gives different reading. If you want a accurate way to examine the engine health, do a leak down test.

[JasonGilholme]

Yes higher PSI means better seal/compression however the main thing you're looking for is a descent average across the cylinders.

[paps02]

time to revive this thread instead of starting a new one..

on the weekend im going to visit a h22 front cut which after i get a leak down or compression test done on it and it passes my mechanics check, i will hopefully BUY!!!

firstly should i ask him to do a leak test? or a compression test? or both??

what results should i expect in terms of a stock h22a sir with 80000k?

[CB7_OWNER]

have a read of this:

http://autos.yahoo.com/maintain/repairqa/engine/ques057_1.html

[paps02]

dam good information right there. thanks

[dudeling7]

a leakdown test will give you a more comprehensible readout of the health of the engine and point you in the right direction if there is a problem with it.

also when doing a compression test numbers will vary if the engine is HOT or COLD. reading being higher when HOT. Either way as said before you want the number to be consistently within a close range of each other is of most concern.

[paps02]

went to have the test yesterday. got around 225 across all 4...

[migoreng]

225 huh..
can't believe it...i paid $30ish a while ago to be told 140-150 across all 4 is normal...
they probably only cranked it 2 or 3 times...
i didn't know much myself back then so yeah

haven't be bothered to go back and ask for a proper one to be done...

[peejayy]

where in melb is a good place to get a leakdown/compression test done?

And also, if a leak-down test is done, is a compression test neccessary? Or does a leak-down test tell you everything you need.

EDIT:


A leakage test can also be used in conjunction with a compression test to diagnose other kinds of problems.

A cylinder that has poor compression, but minimal leakage, usually has a valvetrain problem such as a worn cam lobe, broken valve spring, collapsed lifter, bent push rod, etc.

If all the cylinders have low compression, but show minimal leakage, the most likely cause is incorrect valve timing. The timing belt or chain may be off a notch or two.

If compression is good and leakage is minimal, but a cylinder is misfiring or shows up weak in a power balance test, it indicates a fuel delivery (bad injector) or ignition problem (fouled spark plug or bad plug wire).

I will be looking to do this in a month or so.

[paps02]

225 huh..
can't believe it...i paid $30ish a while ago to be told 140-150 across all 4 is normal...
they probably only cranked it 2 or 3 times...
i didn't know much myself back then so yeah

haven't be bothered to go back and ask for a proper one to be done...

i didnt believe 225. i thought they rigged it personally but i'v bought it now. at least i know theres nothing wrong with the valves!! if anything it will be rings...

i asked him if they lined the cylinders with oil.. he said no... so dunno what to believe.. 225 is just so high...

but $30 wtf. places do it for free! its a 5minute job

[bennjamin]

i didnt believe 225. i thought they rigged it personally but i'v bought it now. at least i know theres nothing wrong with the valves!! if anything it will be rings...

i asked him if they lined the cylinders with oil.. he said no... so dunno what to believe.. 225 is just so high...

but $30 wtf. places do it for free! its a 5minute job


its not that high. my old d16a8 did 220 across all 4 at HOT and WOT.

higher compression motor will yield higher results too. b18c7 type r puts about 240 psi across all 4