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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Procede Datalogged: Constant boost off throttle...



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      01-27-2013, 09:51 AM   #1
Eric335
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Procede Datalogged: Constant boost off throttle...

Hey everyone,

I have been having pretty bad wastegate rattle at idle/acceleration lately, so i decided to mess around with the WGPositions. What i noticed when i datalogged my car was that i was getting a constant 1.8PSI of boost, even off-throttle/idle. When i played with the throttle a little, the boost built to 1.9 PSI and then fell back to 1.8PSI. When heavily on throttle, the car built boost normally and stopped building boost at 17PSI (the dead-line i set it at).

I recently installed AA DPs. Is it possible that one of the turbos is building boost constantly due to the v-band clamp stopping the actuator? Could this also be the cause of my rough acceleration/idle/wastegate rattle?

BTW- The car didnt throw any codes, and im on 9-10 Aggressive maps

Thanks everyone!
-Eric335
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      01-28-2013, 12:31 AM   #2
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N54's are designed from factory to have slight pressure at idle IF the wastegates are closed. The software keeps the wastegates open during idling. Change that and you have boost. Small turbos bro.
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      01-28-2013, 12:48 AM   #3
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Try setting the wastegate position to 30 in the global user adjustable parameters and see if that helps. If so, adjust it back 5% at a time until you have issues again so you know where to set it. Good luck.
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      01-28-2013, 09:58 AM   #4
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I think it might be the barometric compensation. Im not sure if Shiv incorporated this into his tune. Later in the day i datalogged again and at idle it was -0.2.
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      01-28-2013, 10:16 AM   #5
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Quote:
Originally Posted by BMWN54tech View Post
N54's are designed from factory to have slight pressure at idle IF the wastegates are closed. The software keeps the wastegates open during idling. Change that and you have boost. Small turbos bro.
Actually depends on the software level. The later cars have the wastegates closed at idle for less turbo lag. My early N54 (1/07) has the wastegates open at idle, as I have the lovely 6mm-pin early turbo design that likes to rattle.

Regardless of wastegate position, the bypass valves should be pulled open by the vacuum in the intake manifold at idle. BMW definitely didn't engineer the car to have positive pressure in the manifold at idle and cruise.
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      01-28-2013, 10:53 AM   #6
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You are right, I was referring to pressure in the charge pipe measured via the tmap as SLIGHT pressure over atmosphere, but yes diverter valves will dump the pressure.
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      01-28-2013, 08:53 PM   #7
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Quote:
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You are right, I was referring to pressure in the charge pipe measured via the tmap as SLIGHT pressure over atmosphere, but yes diverter valves will dump the pressure.
Gotcha.... I've noticed that as well, but it's very slight as you say. This guy says he's seeing a few psi of boost, which definitely wouldn't be normal. Probably a Procede thing.
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      01-29-2013, 12:58 AM   #8
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My guess would be a simulated Map signal to offset the increased fuel pressure and not set tuner faults...
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