morto86 Posted November 11, 2013 Share Posted November 11, 2013 Hey im about to buy a RB20DET motor with a compression test of 230. Not sure if that's good. I thoight stock would be around the 160 mark Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/ Share on other sites More sharing options...
Ben C34 Posted November 11, 2013 Share Posted November 11, 2013 Sounds wrong. That's too high. Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7103369 Share on other sites More sharing options...
Missileman Posted November 11, 2013 Share Posted November 11, 2013 150-160 psi would be excellent Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7103378 Share on other sites More sharing options...
morto86 Posted November 11, 2013 Author Share Posted November 11, 2013 Yeah I thought so. The bloke is going to re do it and send photos of the results Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7103380 Share on other sites More sharing options...
R.3.2.G.T.R Posted November 13, 2013 Share Posted November 13, 2013 done cold or warmed up? Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7105557 Share on other sites More sharing options...
Missileman Posted November 13, 2013 Share Posted November 13, 2013 (edited) On a warmed engine with all sparkplugs removed, with accelerator fully depressed and a charge on the battery capable of cranking the motor at 300rpm. RB20DE/T/26DETT New = 170psi Low Limit = 128psi Max cylinder difference 14psi ...from engine workshop manual. Edited November 13, 2013 by Missileman Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7105598 Share on other sites More sharing options...
Missileman Posted November 13, 2013 Share Posted November 13, 2013 probably a good idea to unplug the cas and pull the fuse on the fuel pump too Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7105604 Share on other sites More sharing options...
morto86 Posted November 13, 2013 Author Share Posted November 13, 2013 I just got the reply 210. Cold. Does this mean the head has been shaved previously Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7105811 Share on other sites More sharing options...
StevenCJR31 Posted November 13, 2013 Share Posted November 13, 2013 Doubt it would make that much difference That figure seems very "optimistic" at best Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7105865 Share on other sites More sharing options...
Ben C34 Posted November 13, 2013 Share Posted November 13, 2013 I just got the reply 210. Cold. Does this mean the head has been shaved previously No as the comp ratio doesnt effect the compression test. it just ensures the rings and valves are sealing as they should. Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7105869 Share on other sites More sharing options...
Missileman Posted November 13, 2013 Share Posted November 13, 2013 I just got the reply 210. Cold. Does this mean the head has been shaved previously That seems wrong, do name the person/ workshop who did the test. Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7105881 Share on other sites More sharing options...
Ben C34 Posted November 13, 2013 Share Posted November 13, 2013 Maybe it was meant to be 120. thats more realistic Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7105933 Share on other sites More sharing options...
Josh080691 Posted November 13, 2013 Share Posted November 13, 2013 210 :// my newly built 25/30 only has 168 across the board. Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7105936 Share on other sites More sharing options...
MagicMikeZ32 Posted November 13, 2013 Share Posted November 13, 2013 I am guessing the gauge is way out of spec Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7105941 Share on other sites More sharing options...
StevenCJR31 Posted November 13, 2013 Share Posted November 13, 2013 Maybe it was meant to be 120. thats more realistic Better hope not 130 is rebuild time Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7106067 Share on other sites More sharing options...
morto86 Posted November 13, 2013 Author Share Posted November 13, 2013 Def 200 all round with snap on gauge and warmed engine. With researsh this proves the comp ratio therefor is 10:1. As for the knob who said the comp is not relayed to the ratio. Actually write out the equation. 1 Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7106158 Share on other sites More sharing options...
Ben C34 Posted November 13, 2013 Share Posted November 13, 2013 Def 200 all round with snap on gauge and warmed engine. With researsh this proves the comp ratio therefor is 10:1. As for the knob who said the comp is not relayed to the ratio. Actually write out the equation. Settle down. explain to me how an engine when built has a certain compression test result, then when worn had a lesser compression test result? Did it's comp ratio drop? can you run more boost cos it has less comp ratio? NO. explain how comp ratio effects the comp test results please Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7106205 Share on other sites More sharing options...
Ben C34 Posted November 13, 2013 Share Posted November 13, 2013 please provide link to your researsh Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7106208 Share on other sites More sharing options...
GTR-N1 Posted November 13, 2013 Share Posted November 13, 2013 Anyone try LiquiMoly Engine Detox to remove residues/deposits and then find comp test improvement? Might be worth a go! Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7106678 Share on other sites More sharing options...
KiwiRS4T Posted November 14, 2013 Share Posted November 14, 2013 Settle down. explain to me how an engine when built has a certain compression test result, then when worn had a lesser compression test result? Did it's comp ratio drop? can you run more boost cos it has less comp ratio? NO. explain how comp ratio effects the comp test results please Well personally I would have though it was obvious that the higher the compression ratio the higher the expected compression test result . The value of the compression test for measuring wear depends on knowing the original compression so as above if the stock factory figure was 170 psi then yes 130 psi indicates a lot of wear which can be confirmed with a leakdown test. My engine had 130 psi compression when built because of the choice of pistons (CR about 8:1) and leakdown test is within limits at 5% Link to comment https://www.sau.com.au/forums/topic/434844-compression-test/#findComment-7107171 Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now