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Old 12th June 2012, 17:51   #31
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Default Re: What is engine compression test ??

Bumping up an old thread. If in case its found that your engine compression is around 150 - 175, does it mean that the rings and gasket is gone? and if in case one needs to improve the figures, does it take a lot to replace the rings and gasket? is that an easy job? is it recommended? I had read a thread on using some lubes in each cylinder to improve the compression but not really sure if that is the correct way to achieve it.

Please advise gurus. My 2001 Vtec is not in its full elements. I am in 2 minds to keep it or sell it. Depending on the work required it will be decided on what to do next. Overall its behaving satisfactorily (slightly sluggish) but the Vtec punch is no longer there.
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Old 26th August 2012, 00:28   #32
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Default Re: What is engine compression test ??

again, trying to revive an old thread. just for curiosity, any proactive comp test done by Xylo (or even Scorpio) owner ? where is it done in Mumbai & cost ?

more curious: by changing engine oil, will u see bit different (+ve) parameters ?
thanks,
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Old 26th August 2012, 01:29   #33
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Default Re: What is engine compression test ??

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Originally Posted by pcpranav View Post
again, trying to revive an old thread. just for curiosity, any proactive comp test done by Xylo (or even Scorpio) owner ? where is it done in Mumbai & cost ?
There is no harm in carrying out a compression test in Xylo/Scorpio. A correct result will ensure, good condition of piston rings, head gasket & Valve seat.


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more curious: by changing engine oil, will u see bit different (+ve) parameters ? thanks,
In compression test? No

It is always advisable to get the oil changed after 10K kms. Specially for diesels where it gets contaminated with soot and operates in higher temperatures. You can get a slight benefit in FE but the real benefit is in the engine durability.
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Old 26th August 2012, 02:09   #34
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Default Re: What is engine compression test ??

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Originally Posted by Desmosedici View Post
Bumping up an old thread. If in case its found that your engine compression is around 150 - 175, does it mean that the rings and gasket is gone? and if in case one needs to improve the figures, does it take a lot to replace the rings and gasket? is that an easy job? is it recommended? I had read a thread on using some lubes in each cylinder to improve the compression but not really sure if that is the correct way to achieve it.

Please advise gurus. My 2001 Vtec is not in its full elements. I am in 2 minds to keep it or sell it. Depending on the work required it will be decided on what to do next. Overall its behaving satisfactorily (slightly sluggish) but the Vtec punch is no longer there.
What's important is the variance between cylinders. I believe anything upto 15% is within spec, but old Honda VTEC engines from 00-01 have been known and observed to have a variance of not more than 5 psi between all cylinders. Once the localisation increased, the quality went down.

I've observed anything between 190-210 psi in Mumbai, 250+ on my friend's high-comp engine.

175 is perfectly fine, 150 means a tired engine that needs, if nothing else, atleast new rings and a hone.
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Old 26th August 2012, 08:29   #35
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Default Re: What is engine compression test ??

I have a (stupid?) question. If we are removing the spark plug / injector of a cylinder to plug in a gauge, ain't the overall power / compression compromised due to the un-firing cylinder?
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Old 27th August 2012, 09:10   #36
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Default Re: What is engine compression test ??

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I have a (stupid?) question. If we are removing the spark plug / injector of a cylinder to plug in a gauge, ain't the overall power / compression compromised due to the un-firing cylinder?
The engine isn't firing during a compression test. Its just turning over (cranking). You should run a compression test with all spark plug leads entirely removed.

So in terms of "power" - there is none being made by the engine. Its just the electric starter motor that is turning the engine.

What you are measuring is the sealing capability of all the parts that make contact in your combustion chamber. This is done for each cylinder one-by-one. The more 'leaky', ill-fitting and worn out the parts are - the lower your compression will be.

The quality of compression affects the engine's final power delivery by:
(a) Getting the fuel-air mix to ideal pressure before the spark plug ignites it (ie not leaking).
(b) Not 'leaking' any of the power that is created by the expanding (/exploding) charge during the ignition stroke (preventing extreme blow-by, etc)
(c) Anything else i missed??

cya
R
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Old 27th August 2012, 09:25   #37
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Default Re: What is engine compression test ??

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Originally Posted by Rehaan View Post
You should run a compression test with all spark plug leads entirely removed. (c) Anything else i missed??

cya
R
By this did you not mean remove all the spark plugs from the cyl head of the car/engine you're testing. And the need to keep the throttle fully open while cranking the starter. And I think one has to unplug the wire which goes from the coil to the distributor.
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Old 27th August 2012, 14:42   #38
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Default Re: What is engine compression test ??

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Originally Posted by pranavt View Post
What's important is the variance between cylinders. I believe anything upto 15% is within spec, but old Honda VTEC engines from 00-01 have been known and observed to have a variance of not more than 5 psi between all cylinders. Once the localisation increased, the quality went down.

I've observed anything between 190-210 psi in Mumbai, 250+ on my friend's high-comp engine.

175 is perfectly fine, 150 means a tired engine that needs, if nothing else, atleast new rings and a hone.
Thanks Pranav. If one wants to change the rings and other stuff to improve compression, how much of an effort will it take and what would the costs be. Is it really really required to do that or is there any other way (read easy and cost effective to do the same)
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Old 27th August 2012, 14:52   #39
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Default Re: What is engine compression test ??

The correct way will require removal of the engine and its disassembly. Then take the block to Mahesh Powale near Shivaji Park and get it honed as per Honda specs (60 degree crosshatch, 400 grit stone). The major expense will be labor, as the rings cost about 1600 and the honing procedure isn't expensive.

The easy way would be to hone the cylinders with a flex hone and a hand drill by lifting the head, removing the crankshaft, rods and pistons while keeping the engine in its place. Getting the correct crosshatch is difficult with this method.

Cost will wary from mechanic to mechanic. New set of OE rings cost about 1500-1600, last time I checked.

What compression readings are you getting, btw? And how many kms has the engine done?
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Old 27th August 2012, 15:17   #40
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Default Re: What is engine compression test ??

Thanks Pranav. I am getting 2 cylinders on 175 and 2 on 150. The car has done about 55000 kms till date. The compression was checked 2 months back by Sunil Shanbag at Dadar but i was not there personally to see it. I can feel more and better acceleration post 2500rpms but the engine does feel a bit strained. I never felt it when i had brought the car in Nov 2010 though.
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Old 27th August 2012, 18:08   #41
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Default Re: What is engine compression test ??

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Originally Posted by oxyzen View Post
There is no harm in carrying out a compression test in Xylo/Scorpio. A correct result will ensure, good condition of piston rings, head gasket & Valve seat.




In compression test? No

It is always advisable to get the oil changed after 10K kms. Specially for diesels where it gets contaminated with soot and operates in higher temperatures. You can get a slight benefit in FE but the real benefit is in the engine durability.
thanks. infact, what I meant to ask: regular oil changes would be one of factor to show better results in a compression test ?
(ofcourse, rash handling would be considered as a damaging factor, even with fresh oil!)
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Old 27th August 2012, 20:57   #42
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Default Re: What is engine compression test ??

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Originally Posted by Desmosedici View Post
Is it really really required to do that or is there any other way (read easy and cost effective to do the same)
A cylinder leakage test is much more illuminating.

Before rushing into an overhaul, take off the head, visually inspect (carbon deposits, glazing, scoring), feel (ridges), measure (out of round, bellmouth), and then take a decision. 55K is too early for an overhaul.

Regards
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Old 28th August 2012, 03:50   #43
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Default Re: What is engine compression test ??

In a true 55k Honda engine, like Sutripta said, you still don't need an overhaul unless it hasn't been maintained properly. Get the test done in front of you. For the record, which ones were 175 and which ones were 150? #1 cylinder is the one closest to the timing belt and #4 cylinder is the one closes to the transmission.

Do a leakdown test to find out whether it's the valves or the rings. If it's the valves, you'll need a fresh valve job done on the seats and cleaning up the valves. If it's the rings, and if the cylinder clearances aren't too bad, you can do a re-ring and a hone.
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Old 25th September 2012, 19:09   #44
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Default Re: What is engine compression test ??

I have a question..I'm getting a Maruti EECO which has done 140K on the odo & I wish to get the engine compression test done before buying it. How do I get to know if the compression the cylinder has is upto the mark? What minimum value is acceptable? Kindly suggest.
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Old 12th October 2012, 22:23   #45
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Default Re: What is engine compression test ??

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Originally Posted by Shan2nu View Post
I just got the compression checked on my 2001 VTEC.

These were the results (tested at 2,200ft above sea level)

C1 - 185psi
C2 - 185psi
C3 - 190psi
C4 - 175psi

The numbers are within 10% of each other, but i need to find out why the 4th one is lower.

Maybe a wet comp check will give me a better idea of how the rings are holding up.

"A wet compression test should be used when cylinder pressure reads below the manufacturer's specifications. It helps you to determine what engine parts are causing the problem. Pour approximately 1 tablespoon of 30-weight motor oil into the cylinder through the spark plug or injector opening, then retest the compression pressure.

If the compression reading goes up with oil in the cylinder, the piston rings and cylinders may be worn and leaking pressure. The oil will temporarily coat and seal bad compression rings to increase pressure; however, if the compression reading stays about the same, then engine valves or head gaskets may be leaking. The engine oil seals the rings, but does not seal a burned valve or a blown head gasket. In this way, a wet compression test helps diagnose low-compression problems."


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Shan2nu
Shan2nu, my 2002 1.5exi OHC has run almost 2,00,000 kms, and for the past several months it's not been performing as good as it should. I have a freeflow, and changed to semi-synth last year.

Would you recommend a compression test? Please let me know if there is any place in bangalore which does it good, and an estimated price would help too..
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