1990 Accord DX 5 Speed with 314,xxx. Got 175 Psi on each cylinder. God these cars are great.

 

 

whats considered good? and bad on these engines, also when doing a compression test isn't consistency important while cranking? not just peak psi

 

Consistancy really is the key, I believe AWESOME is above 200,

so 300xxx+ miles and at 175 i'm going to say pretty darn good lol

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TheMuffinMan &raquo;</TD></TR><TR><TD CLASS="quote">Consistancy really is the key, I believe AWESOME is above 200,

so 300xxx+ miles and at 175 i'm going to say pretty darn good lol</TD></TR></TABLE>

Yes it doesnt matter as far as PSI as long as they're all close to the same. 130 130 130 130 is f'ing fantastic

 

weird, how does psi not matter?

 

psi will depend on the gauge, compression, how many times you crank the motor over, etc.

As an example, a compression test on an F23 should yield about 175 psi in each cylinder. 135 psi is considered the minimum amount, but the key is the variance between cylinders, which should be no more than 28 psi. (According to the Haynes manual, that is.)

If one cylinder is off too much than the others, you have problems. Either the rings are toast, the headgasket is leaking, a valve is leaking, etc.

If you get 200+ psi, you probably have a ton of carbon deposits in the cylinders and you need to clean them out.

 

Hmm, phil I saw some numbers in the ITR forum once and someone was thrilled to get those......

maybe just a crazy built motor or something?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by philadd &raquo;</TD></TR><TR><TD CLASS="quote">If you get 200+ psi, you probably have a ton of carbon deposits in the cylinders and you need to clean them out.</TD></TR></TABLE>
I was thinking the same thing...last time I checked I had 205psi +/- 5psi at each cylinder. I've gotta get the carbon buildup removed soon....my instructors at school say I can run water through manifold vacuum, a little at a time...and it'll blow the carbon off the pistons. My NOx is also too high, almost borderline. I'm guessing lazy O2 sensor and I should probably replace the cat converter.

Anyway, for the OP...you've got some good numbers there....you should also do a leakdown test while you're at it...

 

how do you do a leak down test?

 

Ok, for the n00bie, how do you test the compression of the cylinders? I am about to buy a used honda and want to be able to test this type of stuff.

thanks
scott

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TheMuffinMan &raquo;</TD></TR><TR><TD CLASS="quote">Hmm, phil I saw some numbers in the ITR forum once and someone was thrilled to get those......

maybe just a crazy built motor or something?</TD></TR></TABLE>

Different engine, w/ higher compression. An engine with a high compression ratio will show higher numbers when you do a compression check.

 

how does carbon build up gives you a higher reading when doing compression test? so when the air enters thru the cylinder.. when it seesa carbon.. carbon will try to eat the air up sotherefore its gonna require alittle bit more air to accomodate what was eaten up or what? maybe i'm nuts..

 

its carbon build up reducing the volume that the air can fill

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by street_accord94 &raquo;</TD></TR><TR><TD CLASS="quote">its carbon build up reducing the volume that the air can fill</TD></TR></TABLE>
Yup.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Gsir8 &raquo;</TD></TR><TR><TD CLASS="quote">how do you do a leak down test?</TD></TR></TABLE>
You need shop air (compressed air) and a leak down gauge set. Those can run between $100 to $300 or more. Anyway, you take out the spark plug, put that piston at top dead center of compression stroke so both intake and exhaust valves are closed. they you apply shop air and see how much and where the cylinder is leaking from. if you hear it at the exhaust, it's from the exhaust valve; if you hear it from the intake tube it's from the intake valve and IIRC if you hear it from the oil cap it's the rings.

 

so why would the compression be higher if its take less air due to carbon.. wouldn;'t it be less amt of psi because the carbon is in the way

 

think of it sorta like this...

with the same amount of air, as the piston comes up to compress the air the carbon build-up is taking up a little extra space which compresses the air a little more giving a slightly higher compression reading.

 

i'm so lost..

 

on an f22 normal is 170, and 130 or lower is the service limit. Like was probably said a leakdown test is a a lot more important then a compression test. a leakdown tells how well your rings and seals are sealing I got mine done and I got 10-12% loss through the rings and 200-205 psi on the compression. my engine has 219kms on it and thats very good results.

 

if the valve has carbnon and its not sealing all the way the compression will be lower because the air will escape and your get a compression of like 60 or 70psi right?


now how does it work when u have higher compression number i heard higher compression number is good.... i know touring accord explain it but i just can;t understand it maybe somebody can reword it differently so i can understand..

 

its doesnt make the valve close less, it builds up in the chambers thus creathing less volume and more compression.

-E