Compression test done.. numbers REALLY high??
#1
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Compression test done.. numbers REALLY high??
Bought an Autozone compression tester.. pulled out the valve on the dial so it wouldnt hold a reading.. warmed the motor to normal Op temp and tested my compression. Pulled the EGI fuse, held the throttle wide open and cranked the motor.
I saw about 115 psi rear rotor and about 118-120 front! The motor is a j-spec used motor with about 60k miles on it... now i hear most people saying they have about in the 90's to low 100's.
What gives? Is this normal compression?
I saw about 115 psi rear rotor and about 118-120 front! The motor is a j-spec used motor with about 60k miles on it... now i hear most people saying they have about in the 90's to low 100's.
What gives? Is this normal compression?
#3
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Sounds good to me. I wouldnt believe what I was told about the mileage on the engine. Jspec resellers quoting mileage on their engines are like boyfriends wondering about their new girlfriend's sexual history...they have no clue what all was done by the previous owner before they got their hands on it.
#4
well, you never know what shape the engine is in when you get it. maybe someone did some internal work.. i just got a jspec engine and did compression check, the rear has only one good face on the rotor. the others dont read any compression..did you start it yet?
#5
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The thing that bothers me is that you said you took out the valve, so the tester wouldn't hold a reading. Usually, that would mean you just get the needle bouncing to 30 psi or so as each sealing face makes compression.
You leave the valve closed for a total reading and open it to get individual bounces...
BTW, I recently did a test and got even higher than those numbers.
You leave the valve closed for a total reading and open it to get individual bounces...
BTW, I recently did a test and got even higher than those numbers.
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#8
Sharp Claws
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depends on conditions mainly, i do notice the difference quite often and it isn't because the internals are in bad shape. most i have seen on n/a is 115 really but 120 isn't impossible. i don't compression test FDs much because theyre a bitch to get to the plug holes so i just do the poor mans compression test on them often because they have blown seals and is quite obvious.. S4 TIIs are the lowest of all generally ranging around 90-100 often because the housings are semi worn already but the compression is still average.
i am kind of skeptical about this jspec 125psi TII motor though, that is rather high, i thought it was an n/a at first until i re-read the post. an S4 would have to be pristine surfaces to get that reading, at least on my gauge.
i am kind of skeptical about this jspec 125psi TII motor though, that is rather high, i thought it was an n/a at first until i re-read the post. an S4 would have to be pristine surfaces to get that reading, at least on my gauge.
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Ive bought 2 jspec 13b-re's, both came with compression readings, and where in the 90-100 range. The one I am using now the compression has gone up he first time I tested it it was around 90 a few months later under the same conditions it was around 105. I did the water treatment on it, but thats all I can think of.
#11
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Well i just checked mine the other day but now Im not so sure I did it right. My gauge only has a valve with push button on the side that you cant remove. I checked it without venting the valve so I guess i just got an overall compression. How many times do you turn the engine over? I let mine do about 5 full rotations or 15 puffs. About right? If I didnt hold open the throttle how would that have effected my #'s? Higher or lower? I only read around 75psi
Last edited by FCKing1995; 12-04-06 at 12:09 AM.
#12
Originally Posted by alexdimen
The thing that bothers me is that you said you took out the valve, so the tester wouldn't hold a reading. Usually, that would mean you just get the needle bouncing to 30 psi or so as each sealing face makes compression.
You leave the valve closed for a total reading and open it to get individual bounces...
BTW, I recently did a test and got even higher than those numbers.
You leave the valve closed for a total reading and open it to get individual bounces...
BTW, I recently did a test and got even higher than those numbers.
If I'm wrong, someone please correct me.
#17
Originally Posted by fusion-turbo
Bought an Autozone compression tester.. pulled out the valve on the dial so it wouldnt hold a reading.. warmed the motor to normal Op temp and tested my compression. Pulled the EGI fuse, held the throttle wide open and cranked the motor.
I saw about 115 psi rear rotor and about 118-120 front! The motor is a j-spec used motor with about 60k miles on it... now i hear most people saying they have about in the 90's to low 100's.
What gives? Is this normal compression?
I saw about 115 psi rear rotor and about 118-120 front! The motor is a j-spec used motor with about 60k miles on it... now i hear most people saying they have about in the 90's to low 100's.
What gives? Is this normal compression?
I've seen 125psi on an s4 n/a engine, I don't remember the ALT, but I believe it was around 1100ft, can't remember cranking RPM either, it was 5 years ago.
2psi difference between rotors to boot.
#18
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Originally Posted by RotaryResurrection
Sounds good to me. I wouldnt believe what I was told about the mileage on the engine. Jspec resellers quoting mileage on their engines are like boyfriends wondering about their new girlfriend's sexual history...they have no clue what all was done by the previous owner before they got their hands on it.
That's so wrong...
#19
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Originally Posted by alexdimen
The thing that bothers me is that you said you took out the valve, so the tester wouldn't hold a reading. Usually, that would mean you just get the needle bouncing to 30 psi or so as each sealing face makes compression.
I dunno, it just seemed really high. I was surprised cause first i tested it when cold and got REALLY low numbers and i thought my motor was bad.
#21
Originally Posted by classicauto
meh.........
My DD 86 N/A with approx. 50,000kms on a re-man has 113 front (all faces) and 116-113 range on all faces on the rear rotor.
Thats nothing out of this world.
edit: no idea what the cranking RPM was and these were on a warm motor.
My DD 86 N/A with approx. 50,000kms on a re-man has 113 front (all faces) and 116-113 range on all faces on the rear rotor.
Thats nothing out of this world.
edit: no idea what the cranking RPM was and these were on a warm motor.
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Originally Posted by darktritium
Yeah, how would you find out?
#23
Originally Posted by fusion-turbo
Count I guess you can do math? 250RPM is what it says in the FSM, so 250 revolutions equates 250 RPM at the ROTORS right? If so, there should be 750 puffs. Divide that by 60 (seconds in a minute) and 750/60=12.5. So you should see 12.5 puffs a second if the motor is rotating @ 250RPM. Hmm, that seems like alot.... this is of course, theory... HAH