With 1250mi. on the rebuild I'm getting even pulses of about 90psi-90psi, which is only incrementally better than what I got at 80mi. on the rebuild (85psi-90psi).

I've been having hot start issues during the break-in, which is annoying because I know it's related to my low compression.

Thing is, the housings I used in my s4 TII are from my s4 N/A that was making 100psi-100psi before the coolant seal failure made it undrivable.

The housings had 60k-65k mi. on them before being swapped.

Should I expect my compression to get any better? Or am I pretty much screwed? The fact that I've only gained 5psi during the whole break-in period is a bit perplexing. You'd think that with good housings and new seals I'd be making a lot better compression...

Also, this is an important question:

I've been boosting since passing the 1000mi. mark (250mi. ago) I'm hitting around 5psi at 4k RPM's, I've seen 6psi-6.5psi in 4th gear shifting at around 4.5k.

WILL I WEAKEN THE MOTOR BY BOOSTING TOO MUCH LIKE THIS??? Can I boost as much as I want as long as I keep my RPM's below 4.5k and 5psi?

thanks guys

 

What's max compression if you let it build up? That's another thing to look at and compare than just pulses, it's nice to know sometimes.

 

umm lets seee thats kinda low... but it still may be breaking in because you used the same seals from the other housings and they may have not seated correctly yet... give it to about 1750-2000 befire u get really worried i would say...


Peace

Dustin

p.s check your pms..

 

He used new seals, old housings. From lots of what I've read, heard, and experienced full compression is reached by 1000 to 1500 miles, depending on the housings and how worn they are (if used). It can even come sooner than that. Basically once compression plateaus its pretty much broken in excluding the bearings if they're new.

 

Didnt you post somethign about using seals that had been run on another set of housings, with these housings? See, what you did just doubled your breakin. Each housing has unique wear patterns. The seals that you'd used had ridden on the first set, and worn to match them. Now, you put them riding against a different set, with different wear patterns. OF course the patterns dont line up, so you're actually worse off than as if you'd used a brand new set of flat seals that had no wear. It'll take twice as long for the used seals to seat against this second set of housings, but this will eventually happen. I'd allow 2000-3000 miles for full seating of the seals in this case.

Even on a rebuild with good housings, we usually say breakin is complete between 1000-1500 miles. IN reality, you can usually measure a slight compression increase all the way up to 4 or 5000 miles. It's just not enough to worry about, maybe an additional 5-10psi.

 

Interesting. I didn't know he had swapped housings once but that would make sense now.

 

word ^, that was what I wanted to hear... thanks, that makes perfect, logical sense...

Oh, and dDub I'll do what you suggested just out of curiousity. Thanks guys