compression on cold engine
#1
compression on cold engine
I have asked this question in another thread but I never had a real answer. I have found a jspec s5 engine and I will do a compression test on it. The engine is out and the transmission and the starter still connected to the engine. The engine is inside. How accurate would be the compression test if the engine is not warmed up ? Will the compression be lower or higher than a warmed engine ?
Thanks for help guys!
Thanks for help guys!
#3
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If the combustion chambers still have an oil coating (i.e. OMP is still working with oil still in the oil pan), the compression numbers will actually be *higher* by about 5-10psi.
-Ted
-Ted
#4
The AUTO DOCTOR
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the results i have gotten when doing tests with my mazda tester is cold motors give lower #'s 10-20lbs or in that area. if the motor has sat a long tim e and the oil coating has gone away it will give really bad #'s and if you put atf/mmo or oil in the motor its going to give you a faules reading... being higher
#6
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i just did a compression test on my engine. I got 50 in the front and 45 in the back. this is on a cold motor by the way. This is from a jspec motor i got shipped to me, so who knows how long it has been sitting in the junk yard. Do you think that these are ok #. As soon as i get it running i will post back so everyone can see the difference from a cold motor to a warm motor.
thanks
thanks
#7
Originally posted by pinkfloyd
i just did a compression test on my engine. I got 50 in the front and 45 in the back. this is on a cold motor by the way. This is from a jspec motor i got shipped to me, so who knows how long it has been sitting in the junk yard. Do you think that these are ok #. As soon as i get it running i will post back so everyone can see the difference from a cold motor to a warm motor.
thanks
i just did a compression test on my engine. I got 50 in the front and 45 in the back. this is on a cold motor by the way. This is from a jspec motor i got shipped to me, so who knows how long it has been sitting in the junk yard. Do you think that these are ok #. As soon as i get it running i will post back so everyone can see the difference from a cold motor to a warm motor.
thanks
-Joe
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#8
Originally posted by RETed
If the combustion chambers still have an oil coating (i.e. OMP is still working with oil still in the oil pan), the compression numbers will actually be *higher* by about 5-10psi.
-Ted
If the combustion chambers still have an oil coating (i.e. OMP is still working with oil still in the oil pan), the compression numbers will actually be *higher* by about 5-10psi.
-Ted
Not to doubt you, but in my experience the opposite is true. Cold = lower. Did you get this info from experience or from someone who told you that? I know you have ALOT more rotary experience than I do, but its strange that we get different results.
-Joe
#9
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This I have seen with my own eyes, and I've confirmed it with others with extensive rotary engine experience even more than mine.
This can be dependent on oil injection versus pre-mix and even down to oil viscosity...
-Ted
This can be dependent on oil injection versus pre-mix and even down to oil viscosity...
-Ted
#10
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i know someone that did a cold compression test and got ~50+ and when he did a worm test after it was running had 110+ on both. mybe his tester is fubared but i used the same tester so i feel good about my #'s.
#11
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The really only meaningful numbers are done under Mazda specifications, which require a warmed up engine and cranking RPM's within the Mazda spec.
It really doesn't matter what the engine does cold.
-Ted
It really doesn't matter what the engine does cold.
-Ted
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