Engine Compression Question - Cylinder 4 slightly lower but within Spec
10-14-2022, 01:39 PM
#1
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Engine Compression Question - Cylinder 4 slightly lower but within Spec
Hello,
Interested in general thoughts/opinions regarding what can be done, if anything, to keep this healthy engine from declining.
Just back into an S2000 after about 5 years away.
Purchased an '04 with about 68K miles on it. Full service records since new, has had history of oil change every 3-5k.
Had compression test done prior to purchase, shows compression is overall good--within Honda's specs-- but Cyl 4 is slightly low compared to the others.
Mechanic's readings were as follows:
Cyl 1: 155
2: 156
3: 157
4: 140
I did my own with a Lisle gauge:
Cyl 1: 245
2: 240
3: 245
4: 225
These readings are all well within the Service Manual maximum variation of 28 psi.
I then decided to do a wet compression test on Cyl 4 which then showed upwards of 265 psi.... (Maybe piston rings?)
Engine runs strong and valves were just adjusted.
I am wondering, a)Is this something that may "just stay as is" given prudent maintenance and good care when driving
b)is there anything else that I should do aside from keeping an eye on things (and good maintenance), to help prevent this from "getting worse"?
Not going to track the car, will keep it stock, never been supercharged, etc.
Thank you!
Interested in general thoughts/opinions regarding what can be done, if anything, to keep this healthy engine from declining.
Just back into an S2000 after about 5 years away.
Purchased an '04 with about 68K miles on it. Full service records since new, has had history of oil change every 3-5k.
Had compression test done prior to purchase, shows compression is overall good--within Honda's specs-- but Cyl 4 is slightly low compared to the others.
Mechanic's readings were as follows:
Cyl 1: 155
2: 156
3: 157
4: 140
I did my own with a Lisle gauge:
Cyl 1: 245
2: 240
3: 245
4: 225
These readings are all well within the Service Manual maximum variation of 28 psi.
I then decided to do a wet compression test on Cyl 4 which then showed upwards of 265 psi.... (Maybe piston rings?)
Engine runs strong and valves were just adjusted.
I am wondering, a)Is this something that may "just stay as is" given prudent maintenance and good care when driving
b)is there anything else that I should do aside from keeping an eye on things (and good maintenance), to help prevent this from "getting worse"?
Not going to track the car, will keep it stock, never been supercharged, etc.
Thank you!
10-14-2022, 02:36 PM
#2
You're good.
10-14-2022, 02:38 PM
#3
I wouldn't worry about it. It's within the noise of what you'd expect. You're fine.
The only thing you can do about it is do a leakdown and find where compression is being lost. If it's from a piston, rings. If it's from valves, figure out which ones and re-do them. Neither of those things are worth doing with your current compression. I wouldn't go searching for problems here.
The only thing you can do about it is do a leakdown and find where compression is being lost. If it's from a piston, rings. If it's from valves, figure out which ones and re-do them. Neither of those things are worth doing with your current compression. I wouldn't go searching for problems here.
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stock06 (10-14-2022)
10-14-2022, 04:05 PM
#4
Did the numbers change after VA? Was it done cold?
if the numbers come up that much after adding oil that might point to rings but I wouldn’t worry too much. I would have maybe added oil to a good cylinder to get a baseline on the change. Engine runs good? Burns any oil? Maybe scope it to check bores.
if the numbers come up that much after adding oil that might point to rings but I wouldn’t worry too much. I would have maybe added oil to a good cylinder to get a baseline on the change. Engine runs good? Burns any oil? Maybe scope it to check bores.
10-15-2022, 05:09 AM
#5
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Engine runs good. Didn't seem to burn any oil on the 800 mile drive home. Will continue to monitor.
Valve adjustment was done stone cold.
Thanks for the insight!
--Kevin
Valve adjustment was done stone cold.
Thanks for the insight!
--Kevin
10-15-2022, 06:31 AM
#6
Leakdown will tell you where the air is going
But....nothing to worry about, and unless its valves, there's not much you can do without a lot of effort and risk.
But....nothing to worry about, and unless its valves, there's not much you can do without a lot of effort and risk.
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