gday,
as the topic says, is this good compression? I've had a s4 13bt rebuilt and have been told compression will be around 80psi. And that 60psi is getting low for a s4 13bt.

cheers,
heb.

 

80 psi is getting pretty low, 60 psi is dead.

 

Quoted from Rotary Ressurrection:

"115+ is like new, 100-115 is healthy, 90-100 is getting weak(1 year or less in most cases) below 90 could blow at any moment."

 

omg, I'm gonna go rank! This motor has 'apparantly' been rebuilt. I was hoping coz the s4 is a lower compression motor, 80 was alright. Thanks for the feedback.

 

If it was JUST rebuilt I think it takes a while for it to break in and great higher compression numbers. Don't quote me on it though.

 

It's kind of like the speed of light- it's all relative...

If she starts up without a problem, runs well, and doesn't smoke, then 80 is fine...

If she's hard to start, is running with noticeably less power than she was a couple of months ago, etc, 80 is too low...

I started noticing power losses at about the 88 to 90 level...

 

yeh its just been rebuilt. Hasn't even been started yet as the transplant is still taking place into my s2.

 

OK- why are you taking compression readings on a fresh rebuild that hasn't had the chance to even "seat" the seals yet?

 

Fresh rebuilds will have low compression, like 80, for the first 500-1000 miles and then will slowly build up higher compression. Break in procedures and what to expect:

http://rotaryresurrection.com/rotary...r/breakin.html

 

lol, it hasn't been tested yet, but he said it WILL be around 80 psi once the motor has been started. I didn't ask whether thats after a 1000km run in, or if its gonna be the same day as when the motor is first started. But I certainly will be asking that tonite.

heb.

 

hmm....i did a check on mine and right above 90 and i have 100k and motor is nice and strong

 

i also have an s4 na

 

I'd relax.. There are two possible scenarios going on here:
1 - All new/rebuilt motors have low compression for a bit until the seals seat themselves. And that's what he's talking about in reference to the 80 PSI (Most likely!)
2 - The guy is good enough to know exactly what compression he will get from the engine he's rebuilding, in which case I'm sure he's smart enough to know that 80 PSI is not acceptable on a fresh rebuild with, say, 3-5,000 miles...

Either way, I wouldn't sweat it.. I've heard of people having as low as 50-60 on a rebuild (I think I read that here, maybe not?) immediately afterwards, and the same people ending up with 110 after it breaks in...

 

yeh, I spoke to him tonite, and he did mean 80 psi before its been run in, and around 100 once its been run in. Thx for the feedback. Now I can sleep tonite