R32 Gtst Compression Test

[johnny_boi85]

hi guy im just wondering what psi i should get from a compression test from each cylinder on my rb20det motor

[mad082]

from memory, new they would read 155 to 160psi. generally anything over 140psi is reasonable, but the biggest thing is to have all cylinders within a few psi of each other.

[johnny_boi85]

ok cool thanks for that i will test them tomorrow arvo and just another question how do you do timing on them. ive only ever done timing on cars with dizzys and leads

where do you connect the timing light to sorry if that sound like a dumb question

[johnny_boi85]

forget that question i just figured it out

[odessy]

Ive been told RB20 will have a lower comp ratio than the 25. 130-140psi is a good result. See below from when I did mine and the comments that followed.

http://www.skylinesaustralia.com/forums/topic/407291-rb20-compression-test/#entry6493262

[Missileman]

the manual says 170 psi is new and 130 psi rebuild time, 15psi or less difference per cylinder is acceptable

[odessy]

Looks like you are right. Which doesn't make sense. Atmospheric pressure being 14.7 PSI and compression ratio 8.5 does not equate to 170PSI.

Also found this:

http://www.webbersrbguide.com/index.php?option=com_content&view=article&id=74

[Frosty]

if you want to get technical it would only 14.7 if at sea level

[johnny_boi85]

I got 140 140 135 135 140 140 so all round good then

[mad082]

Looks like you are right. Which doesn't make sense. Atmospheric pressure being 14.7 PSI and compression ratio 8.5 does not equate to 170PSI.

Also found this:

http://www.webbersrbguide.com/index.php?option=com_content&view=article&id=74

compression ratio x atmospheric pressure doesn't = combustion pressure results.