Somethings not right

J

Jehri

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Jul 26, 2007
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185
I have just completed upgrading my 57 mm super b to a billet 362, & also upgraded my 471 to a 475 on the compressor side. Now for some reason I have a slow spooling, low boost situation, no power & a ton of black smoke. I did a boost leak test, & all is good.
Normally I would see 6-7 lbs. boost driving @ 70 mph, & now I have o lbs. Was very snappy before, now it's a dog. The machine shop that did the work had never done a turbo compressor cover. Is there a possibility the covers were cut to large, ( to much clearance between wheel & cover).
I was expecting more & ended up with less! With all the knowledge on here I'm sure someone can point me in the right direction.
All knowledge is appreciated,
Thanks.
 
That setup should still spool plenty fast, sounds like a gate issue as mentioned unless someone royally screwed up the machine work
 
What size turbines and housings?

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Nevermind, I didn't see that you didn't change turbine size the first time I read it.
 
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Yes the gate is hooked up, it's a spring gate.
Compressors to big just by moving that little?
It does measure .012 from wheel to bore. Not sure on the inside cover measurement. If machined to big, would that make for a slow spool? I take that the inside should also be within .012?
62-65-14
75-83-1.25
Also, I didn't gain any boost with the bigger wheels, if that matters at all.
 
Jehri said:
Yes the gate is hooked up, it's a spring gate.
Compressors to big just by moving that little?
It does measure .012 from wheel to bore. Not sure on the inside cover measurement. If machined to big, would that make for a slow spool? I take that the inside should also be within .012?
62-65-14
75-83-1.25
Also, I didn't gain any boost with the bigger wheels, if that matters at all.
Click to expand...

You arent going to gain boost with bigger wheels.
 
DDually said:
You arent going to gain boost with bigger wheels.
Click to expand...

That's why I had mentioned it. I wasn't looking for more boost. The turbo's needed rebuilding, thus the upgrade while I had everything apart. I now wished I would have left them alone.

I was just outside & took the outlet off the 62 mm to feel if there is any air coming out. There is no airflow until I take it up to 1600 rpm's. It's almost like they are have to fill something before the boost comes on. Doesn't even hear like they are spooling, until, then everything is there. Wished I had 2 factory machined covers to try.
 
.012 is a pretty good number as long as the cover follows the contour of the wheel.

You should see a little slower spool and a little more boost. Nothing huge though. My old 62/75 would do 90psi+ with 5x16s and spool pretty dang quick.

If you checked for boost leaks and have none. Then it's probably an exhaust leak or wastegate issue. I'd lean toward the wastegate. Unless.... you left a rag or something in the piping.
 
Got it fixed, prepare for liftoff!
I got to measuring things up today & discovered that the 475 cover was over cut. So I found a lathe & somebody to run it, (the owner) & we ended up cutting .013 off the mating surface for the band clamp to bring the cover closer to the wheel & the .012 I wanted to begin with, plus had to do a little hand massaging on the contour to get it just right.
It now spools pretty much the same as the old 57/71, but comes on a lot harder. :woohoo:
 
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