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Old 10-27-2007, 10:50 PM   #1
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Default How can i lower my boost?

OK, now with my new Shore Motorsports intake my car is making 17.2 lbs of boost(woulda been higher but i noticed it and took my foot off). As you can see in my sig i run a stock 99 motor with an MSM turbo. Any immediate suggestions to keep the boost from going that high? I've heard anything over 12 is dangerous with this bottom. Gonna have Tim elongate the wastegate arm to help but was looking for something quicker. I know the easiest way is to not keep my foot in it but I have a heavy foot.

for reference the car was making 12.0psi before the intake.

i have plenty of fuel, max duty cycle was 73%

air intake temp max was 76 F
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Old 10-28-2007, 01:20 AM   #2
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Boost controller?
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Old 10-28-2007, 01:56 AM   #3
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you can only go as low as the wastegate will allow. taking some preload out of the arm will help, that's about all you can do.
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Old 10-28-2007, 02:22 AM   #4
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I really don't see how just an intake would make you start boost creeping that bad all the sudden.
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Old 10-28-2007, 02:48 AM   #5
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just checked to see if the "Vacuum" line(sees boost only so should i call it a boost line?) to the wastegate actuator had blown off.

it didn't

so that means 1 of 2 things.
1. the actuator diaphragm is shot
2. the system is now so efficient that the small size of the wastegate on the MSM turbo is so restrictive that the system is still building boost while the wastegate is open.
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Old 10-28-2007, 02:52 AM   #6
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Are you sure the wastegate arm isn't somehow getting pinned open? Intakes do not cause 5psi jumps.
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Old 10-28-2007, 02:55 AM   #7
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#2 is possible, but you would have see that happen after you installed the exhaust most likely.
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Old 10-28-2007, 08:10 AM   #8
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i gotta figure out a way to apply some air pressure to it to see if it's responding.
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Old 10-28-2007, 09:48 AM   #9
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Take a bycicle pump and cut off one end then stick it on the WG nipple. with a boost gauge teed in not the pressure at witch the WG moves and then if you notice any problems go from there. If the WG moves fine and has full motion then a simple reverse helper spring can do the trick just fine. Also the boost is not the problem with the NB bottom end it is the tune if the tune is good then the motor will hold together. GL bud
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Old 10-28-2007, 01:10 PM   #10
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I assume you weren't at redline to be at only 73%DC at 17.2psi on the 460cc injectors?
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Old 10-28-2007, 11:09 PM   #11
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Quote:
Originally Posted by magnamx-5 View Post
Take a bycicle pump and cut off one end then stick it on the WG nipple. with a boost gauge teed in not the pressure at witch the WG moves and then if you notice any problems go from there. If the WG moves fine and has full motion then a simple reverse helper spring can do the trick just fine. Also the boost is not the problem with the NB bottom end it is the tune if the tune is good then the motor will hold together. GL bud
i'll have to borrow a bike pump


Quote:
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I assume you weren't at redline to be at only 73%DC at 17.2psi on the 460cc injectors?
hell no, i had to take my foot out of it for fear of breaking something.

actually that max DC was at 15.0psi and 5666rpm.
at 17.2psi my DC was 65% and 4874rpm
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Old 10-29-2007, 12:57 PM   #12
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ok. did some testing.
  1. line to wastegate actuator not leaking
  2. wastegate opening under pressure. 12-15psi to open fully. Has anyone ever tested an msm turbo wastegate actuator to see how much pressure is needed to open it? i know the MSM's run like 7.5psi from the factory. My guess is the system(intake and exhaust) is so restrictive that the turbo cannot build more than 7.5psi so the wastegate never even opens fully. Can anyone tell me otherwise?
  3. i locked the wastegate completely open and went for a drive. car still building 15lbs of boost before i wisely took my foot out of it. so that confirms my original suspicion that the intake/exhaust combo is too efficient for the turbo, specifically the wastegate opening size. So my next question is this: Has anyone with an MSM turbo gone to a similiarly setup intake and exhaust and then hogged out the wastegate opening and had success with reducing the boost creep?

so to response to Savington & neogenesis2004: intake design changes can make a 5psi jump in boost pressure if the original was too restrictive, the exhaust is unrestrictive enough, and the wastegate is too restrictive.
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Old 10-29-2007, 01:53 PM   #13
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Some further testing.

So as not to JUMP to any conclusions about the new intake being responsible for the 5 lb increase in my boost pressure I removed it and reinstalled the stock MSM intake.

Results: I stand by my earlier statements.


IOW, Boost max=12psi.
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Old 10-29-2007, 02:08 PM   #14
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Sell it and go garrett like I told you in the beginning

-Attempt to enlarge/smooth the internal WG passage.

-build a MSM replacement manifold with an external WG (probably around $350 in parts)

-find a welder (BEGI maybe?) who is willing to weld a external WG flange and/or pipe to the MSM manifold

The following will restrict that killer spool you now have:
-you reinstall the MSM intake (I threw out the MSM exhaust a few weeks ago)

-I can weld a 1" restrictor plate into that new intake.

-Perhaps that muffler/restrictor gizmo you were considering to quiet your exhaust may restrict it enough to bring down boost
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Old 10-29-2007, 02:13 PM   #15
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Quote:
Originally Posted by Savington View Post
Are you sure the wastegate arm isn't somehow getting pinned open? Intakes do not cause 5psi jumps.
I call my line of intake and exhaust components "absurdflow". TM and copyrighted.
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Old 10-29-2007, 02:16 PM   #16
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Quote:
Originally Posted by TurboTim View Post
I call my line of intake and exhaust components "absurdflow". TM and copyrighted.
I like it. Now can I get a sticker that says that?
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Old 10-29-2007, 02:19 PM   #17
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Quote:
Originally Posted by neogenesis2004 View Post
#2 is possible, but you would have see that happen after you installed the exhaust most likely.
Paul's still using the MSM upper cast iron downpipe elbow. His downpipe is sorta kinda like the FM, just blends to 3". Besides cost concerns, we were worried the divorced WG DP would lead to creep. I don't know how much more boost the exhaust alone made, Paul?

That on that particular MSM, clamping the WG fully open produced around 10 psi. That was with FM's intake kit, stock intercooler & plumbing, and my 3" turboback/divorced DP. With the WG rod lengthened to removed basically all of the preload, it makes 11psi.
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Old 10-29-2007, 02:28 PM   #18
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with the stock msm exhaust and stock intake it was making 10psi

with the 3" exhaust and stock intake it was making 12psi and getting there a hell of a lot quicker

now with the new intake and the 3" exhaust i'm hitting 17+ and again spool is reduced.
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Old 10-29-2007, 02:35 PM   #19
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so why are you complaining
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Old 10-29-2007, 02:51 PM   #20
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Too close to BOOM, maybe
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