Compression test numbers

[Mike Brake]

Doing a compression test on my turbo 1g this weekend but I cant find any info. Any one know what some good numbers would be.

[daniel sanat]

Every motor is different. But probly around 150-170  across the board

[Remi Raymond]

It's also the difference between each cylinder that you want to watch for.

170-165-160-155 isn't nearly as alarming as 170-155-165-160 would be, for example.

[Jason Harwood]

I think the service manual says that the lowest should be 125, highest normally is 175 I think.
Aslong each cylinder is between 10% of each other.

[GlenMartin]

um when you guys are doing yoru compression tests how many engine revolutions are you letting it do?? 3-4-5?

[Marke Bailey]

at least 7. and hold the throttle wide open.

[GlenMartin]

at least 7. and hold the throttle wide open.

holy fuck......reading these posts scared the shit out of me, cause i did a compression test the other day and the numbers were way lower than stated a above.....however from what you say i was doing it totaly wrong. haha.

so the needle on your compression tester is suppose to stroke 7 times? i was doing it three times and not holding the throttle open. opps.

[Jason Harwood]

at least 7. and hold the throttle wide open.

holy fuck......reading these posts scared the shit out of me, cause i did a compression test the other day and the numbers were way lower than stated a above.....however from what you say i was doing it totaly wrong. haha.

so the needle on your compression tester is suppose to stroke 7 times? i was doing it three times and not holding the throttle open. opps.

You can hear the engine make 7 revolutions. but the needle will attempt to move 7 times.

[GlenMartin]

at least 7. and hold the throttle wide open.

holy fuck......reading these posts scared the shit out of me, cause i did a compression test the other day and the numbers were way lower than stated a above.....however from what you say i was doing it totaly wrong. haha.

so the needle on your compression tester is suppose to stroke 7 times? i was doing it three times and not holding the throttle open. opps.

You can hear the engine make 7 revolutions. but the needle will attempt to move 7 times.

Ya ok, cause i was just watching the needle, stroke/pulse three times, and it would end up at 120 all across the board. i was more looking for consistancey than high numers so when i saw it was suppose to be around 170.  i was like oh shit. k i will redo it.

guess dad is totaly off his rocker when it comes to compression tests unless its different with v8's but i doubt it. thanx dad.

[Matt Fredrikson]

hahaa we'll do it again this weekend when we gank the turbo out

[Remi Raymond]

make sure the throttle is open too, that will change your numbers.
By the book you're supposed to do 10 revolutions.

[Ivan Skare]

I bet when you do it again correctly your numbers wont be too far off from 120psi. Holding the throttle open isnt THAT significant.

at least 7. and hold the throttle wide open.

holy fuck......reading these posts scared the shit out of me, cause i did a compression test the other day and the numbers were way lower than stated a above.....however from what you say i was doing it totaly wrong. haha.

so the needle on your compression tester is suppose to stroke 7 times? i was doing it three times and not holding the throttle open. opps.

You can hear the engine make 7 revolutions. but the needle will attempt to move 7 times.

Ya ok, cause i was just watching the needle, stroke/pulse three times, and it would end up at 120 all across the board. i was more looking for consistancey than high numers so when i saw it was suppose to be around 170.  i was like oh shit. k i will redo it.

guess dad is totaly off his rocker when it comes to compression tests unless its different with v8's but i doubt it. thanx dad.

[GlenMartin]

no its going to be different because on one cylinder i turned it over four times by accident at it went to 150, but i was under the impression your only supposed to do it three times, so i did it again and got a 120...might just do it tonight again cause now i am curious.

[Jason Harwood]

I bet when you do it again correctly your numbers wont be too far off from 120psi. Holding the throttle open isnt THAT significant.

at least 7. and hold the throttle wide open.

holy fuck......reading these posts scared the shit out of me, cause i did a compression test the other day and the numbers were way lower than stated a above.....however from what you say i was doing it totaly wrong. haha.

so the needle on your compression tester is suppose to stroke 7 times? i was doing it three times and not holding the throttle open. opps.

You can hear the engine make 7 revolutions. but the needle will attempt to move 7 times.

Ya ok, cause i was just watching the needle, stroke/pulse three times, and it would end up at 120 all across the board. i was more looking for consistancey than high numers so when i saw it was suppose to be around 170.  i was like oh shit. k i will redo it.

guess dad is totaly off his rocker when it comes to compression tests unless its different with v8's but i doubt it. thanx dad.

I disagree, having done it before, I had 90PSI on my old mx6 and nearly pooped my self, realised it wasnt WOT. Re-did it and went up to 145.

[John Hartman]

3-4 times by the book that they made me read    I got shit for doing it 5-6 times in school.

and in addition to WOT, unplug your injector harness so it can't spray fuel in there.  That will alter the results and dilute your oil. Make sure your battery is fully charged so that the last cylinder you test gets the same piston speed as your first one.

1g specs are minimum of 114psi and max of 14% difference between cylinders.  In reality, while the car will run at 114psi, its not gonna be that great.  Mostly you want to have 145-160 on a 7.8:1 motor.  Too high and you will have to change timing and boost to keep detonation in check.  To low and obviously its gonna have power and mileage issues.