this was on my mind..

Eric_Odie

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Apr 17, 2005
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well awhile i ago i shimmed my wastegate by two shims. And a week after i had that my turbo started to whine really bad, but about a month ago, i started to run Open Downpipe, and since then the whine is no longer existing, and i was actually holding boost. before when the whine would come on my boost gauge would drop to zero, not boosting. Could it possibly be just because it was so restrictive with the Cat and the Exhaust there?
 

Afunk

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Jul 12, 2005
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Well, I do know I could turn my boost controller up to max and shim the wastegate and the turbo would not boost past 5 psi with clogged cats and restrictive stock exhaust. When I went full 3 " turbo back, I can easily hit fuel cut with 2 shims and barely any increase on the boost controller.
 

mkiii222

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Mar 31, 2005
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Troy, MI
Afunk said:
Well, I do know I could turn my boost controller up to max and shim the wastegate and the turbo would not boost past 5 psi with clogged cats and restrictive stock exhaust. When I went full 3 " turbo back, I can easily hit fuel cut with 2 shims and barely any increase on the boost controller.

Just curious, what advantage is there to having a boost controller and shimming the wastegate? I thought shimming was just the 'poor mans boost controller'?
 

Joel W.

Just A Jedi
Nov 7, 2005
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i had the complete sleved cats 2.5 inch full exhaust and it made a huge difference, then i went to full 3" w/ no 90 elbow and boost went way up again...had to turn it down due to boost creeping up... from 4 to 5.5k rps its amazing now...
edited. it pulls hard past 5.5krpms but i dont do that often..:icon_bigg
 
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Eric_Odie

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Apr 17, 2005
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anyone know of a way to hollow out the cat on the downpipe? to hollow out the 2nd cat i just took a pole and a hammer. but i'm not sure abotu the 1st cat if i can get a pole in there since it sits the way it does. anyone done it before. and i would like to add i know i can't pass smog with no cats, but that's why i have a spare cat that i and some friends use when it comes to test days haha =P
 

Joel W.

Just A Jedi
Nov 7, 2005
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i took a grinder and ground some marks into the top of the bend going into the cat and cut my lines in half with a bandsaw or sawsall so i know where to reweld it. smashed the ozone saver out of it, and sleeved it with 2.5 inch pipe, may not be needed,(i just did it to make it flow better) then welded the pipe inside and welded the top of the cat back on... not recomended if you get smog tested or anywhere ever really lol..
 

jaydm16

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May 2, 2005
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I had a bad cat (which i found out from MD state emissions). Well actually it was clogged. It caused my turbo to boost terribly AND have the death whine.
 

Joel W.

Just A Jedi
Nov 7, 2005
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i think thats called "surge" or air trying to be forced back out through the turbo,, my first turbo did that just before it died... lol

im looking for a good 3" hi flow cat...
 

Loki

The Future is Unwritten
Mar 30, 2005
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aaronc222 said:
Just curious, what advantage is there to having a boost controller and shimming the wastegate? I thought shimming was just the 'poor mans boost controller'?


You want to shim the wastegate when you are running higher boost, so the boost doesn't fall off at redline. I know when my car was running, I had my MBC set at 12psi, it would fall off to about 10 at redline. If you shim the wastegate it makes it stiffer so it holds the boost better and doesn't fall off closer to redline.
 

mkiii222

Member
Mar 31, 2005
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Troy, MI
Loki said:
You want to shim the wastegate when you are running higher boost, so the boost doesn't fall off at redline. I know when my car was running, I had my MBC set at 12psi, it would fall off to about 10 at redline. If you shim the wastegate it makes it stiffer so it holds the boost better and doesn't fall off closer to redline.

Thanks, I'm still not 100% up on turbo systems yet. +1 to Loki.