I got my motor rebuilt about 5k miles ago and after 1k i did a compression test and it was at 170. I did it again at 3k and it was at 180. I did it just before I boosted my car and it was at 190 (about 4k). They were all across the board on all cylinders and I used the same compression tester each time for all those numbers. Tonight however, after boosting for 3 weeks they came out to 150 across the board. This time it was with a different compression tester but I am not sure if that makes a difference. Please give me some insight on what you guys think.

Thanks-
Corey

 

what compression pistons are you running? There's no doubt that 150 across the board is low. I have 9:1 endyn rollerwaves and get 210-215 across all cylinders. Have you been checking your oil to make sure it's not getting burnt up?

 

warm engine compression at one time ? and cold engine the other time??

that's the only guess i can make

good luck

 

I have 9:1 Je pistons. I seem to have alot of piston clap too.

It was a warm engine the first 3 times i did it. The last time i did it my engine was hot hot.

My oil has been going down quite a bit. Right now i do have to fix my oil return line b/c it is backing up a bit. I don't know if that burns your oil but i do know that it has been coming out my exhaust after 5 min or so of idleing.

Anyone got any more feedback for me...

Thanks- Corey

 

how is your battery. If your battery voltage is low, your motor won't crank at hte same rpm as before- thus giving you low numbers. but corey, you have to remember that its the fact that all your numbers are the same. The compression tester might be different which causes you to have different numbers.

 

I'd have to agree. That the numbers are even across the board is a good sign. Typically one of the two center cylinders will be the most prone to detonation. It is usually but not always the center cylinder furthest away from the fuel inlet of the fuel rail. When your numbers look like mine at: 155-150-127-150 Then you may have issues. Still however, my car doesen't burn any oil. I'm thinking that those JE's are causing problems or the motor wasn't bored correctly. DSM'ers have been having a LOT of problems with JE's so all the really fast guys and even some of the slow guys are using Ross pistons now. Energy dynamics makes good stuff IMO as Wisco is a good manufacturer and the energy dynamics rollerwave design works well IMO.

Time for a leakdown test.

 

What size are your oil send an return lines ? Too much oil to the turbo can burn your seals up an cause it to get coked up pretty fast an I know what that is like , an not enough oil to the turbo...well we all know what that can do to a turbo !

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by danl &raquo;</TD></TR><TR><TD CLASS="quote">I'd have to agree. That the numbers are even across the board is a good sign. Typically one of the two center cylinders will be the most prone to detonation. It is usually but not always the center cylinder furthest away from the fuel inlet of the fuel rail. When your numbers look like mine at: 155-150-127-150 Then you may have issues. Still however, my car doesen't burn any oil. I'm thinking that those JE's are causing problems or the motor wasn't bored correctly. DSM'ers have been having a LOT of problems with JE's so all the really fast guys and even some of the slow guys are using Ross pistons now. Energy dynamics makes good stuff IMO as Wisco is a good manufacturer and the energy dynamics rollerwave design works well IMO.

Time for a leakdown test.</TD></TR></TABLE>

ROSS

 

bump please.

 

I redid my compression with a brand new compression tester and it was ~180 across the board. Then i put a top of oil in the cylinders and the compression came out to ~205. What does that say about my rings....

 

using different tester could be the cause of the lower numbers.

Also make sure you have the throttle wide open and fuel pump fuse disconnected.

As long as your numbers are within 20 psi of each other your fine.

 

Your fine, no matter what shape your engine is in, if you add a little oil and do the test the numbers will jump because your sealing from both sides with oil... your #'s look good...

However if your still concerned I'd do a leakdown test... my comp #s were awesome too, but leakdown ended up telling me my exhaust valves on #2 and #3 cylindars didn't like me all that much with 6 and 9% leakdown... which still isent all that bad, but still its not real happy either

 

still sounds good to me. It all depends on the comp. tester. You have to worry more about 1 or 2 cycl. being low. If they are equal across the boards, your good to go. Remember loosing oil doesnt even have to be in the rings or pistons, it could be in the head. Also, bad oil rings will lose oil, but that wont affect comp. test. Sounds like your fine to me!

 

I got freaked out when my compression went from 190 to 150. I am happy with 180. I will prolly be doing a leakdown in a couple of weeks. I will let you know the results.

Thanks