Cold compression data worth anything?
Cold compression data worth anything?
Unfortunately, this was before I was aware that you are supposed to do the compression test with the engine warm. I plan on redoing the test, but I thought I would ask if there is any value in the cold numbers.
The results were: 330 to 340 for cylinders 1,2,4 and 290 for cylinder 3. After doing some more reading it seems 290 is marginal. The harbor freight 90 degree fitting broke on cylinder 5, so I have no data for that one.
Over the holiday break I reamed and replaced my glow plugs, and performed a compression test while I had the fuel lines off.
Unfortunately, this was before I was aware that you are supposed to do the compression test with the engine warm. I plan on redoing the test, but I thought I would ask if there is any value in the cold numbers.
The results were: 330 to 340 for cylinders 1,2,4 and 290 for cylinder 3. After doing some more reading it seems 290 is marginal. The harbor freight 90 degree fitting broke on cylinder 5, so I have no data for that one.
ForcedInduction
01-05-2010, 08:42 PM
#2
Cold numbers are more useful. Warm numbers are artificially high from the tighter clearances and won't give any insight into how well it will start in cold weather. 330psi cold is good.
I thought I would test the difference between a hot and cold compression test, I adjusted my valves and charged the battery and this is what I got. I warmed the engine for 1/2 hour & spun out the glow plugs and compression in #1 was 410#'s, then I let the engine cool overnight and found the compression to be 360#'s so in my test I found a 50# difference between hot and cold. I may do other cylinders to see the difference.
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