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Default Under Boosting After Turbo Rebuild Looking for Advice - 10-17-2017, 05:22 PM

Hi all, just got done swapping out my CHRA turbo cores for some nice new RB ones, took about 3 weeks in my garage with say 30-40 hours of labor. My issue now is very bad under boosting about 5-7 PSI off target and PWM is pegged at max, I checked for boost leaks tightened down all the clamps checked all the vacuum lines that I had just replaced all looked fine. Maybe a smoke test from my charge pipe to see if something is leaking, possibly the end of the outlet at the rubber section. However My belief is when I setup the waste gate actuators before I put the turbos back in I applied -200 mbar of vacuum to the solenoid as per BMW manual and internet instruction and made sure the flapper could just barely spin in the waste gate seat in the housing. Now anyone who has done this knows its not exactly a science I could go a quarter turn more and get 0 movement or the other way and get excessive play. I spent about an hour adjusting it just to where I thought was perfect but now I'm under boosting meaning the flapper isn't tight enough to the housing to fully spool the turbos IMO. Now that they are on the car adjusting the front turbo is gonna be a major PITA so I'm looking for any other opinions or if anyone has had same trouble adjusting the arms, also I got the upgraded Vargas waste gate assembly installed not that it should effect any of this, ill post some logs and pics.
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Default 10-17-2017, 08:25 PM

As mentioned, WGDC is maxed out...looks like you have a boost leak or hardware issue.

Smoke test won't do much, I'd suggest a pressure test.



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Default 10-18-2017, 04:52 PM

Ill shoot some compressed air in my chargepipe meth bung and listen for any leaks and spray some soap and water around my intercooler connections tomorrow. If nothing then I guess ill have to do some rod adjustments thanks for the response!
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Default 10-19-2017, 11:44 AM

I'd suggest reviewing this.

http://www.n54tech.com/forums/showthread.php?t=13114



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Default 10-19-2017, 04:10 PM

haha had that tab open all day, did the tests outlined, pressurized the intake system and found no leaks or hissing. Next went out bought a vacuum gauge hooked it up at the T going to the actuator got consistent 20 mercury inches of vacuum at full waste gate pressure (5 on the tach) so no vacuum line issues as I suspected. Last I got a hold of the rear waste gate rod (made custom 4 mm wrench) and did 1 full turn then went out for a drive. Huge difference I had my phone monitoring Boost and target as well as PWM live with the JB4 app, I hit almost 13 PSI instead of maxing around 10 but PWM still pegged at 99 as soon as I put my foot down in 3rd and boost came in slowly not hitting full boost at 3000-4000 like it should. So now the rear turbo is most likely being over worked while the front is not spooling, gonna have to get that front one adjusted a turn or 2 and go from there see where I'm at. Wish I could go back in time when I had the turbos out a week ago and just turn that rod a few more times now I'm stuck with these major headaches, whoever says at 5.5-6 mercury inches of vacuum the flap should still be able to spin slightly is full of it, the flapper should be sealed tight against the housing at that pressure, endless I have some odd ball exhaust manifold lol.
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Default 11-01-2017, 09:25 AM

Update - adjusted waste gates and car runs perfect, turns out my mighty vac was way off when reading 5 Mercury inches it was more like 20, so make sure your gauges are reading accurately lol.
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Default 11-01-2017, 09:47 PM

Quote:
Originally Posted by BoostedSedan
Update - adjusted waste gates and car runs perfect, turns out my mighty vac was way off when reading 5 Mercury inches it was more like 20, so make sure your gauges are reading accurately lol.
Glad you got it sorted, thatís got to be a relief



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