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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > Regional Forums > UK > UK Technical Forum > Strange boost issue



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      06-01-2018, 04:38 PM   #1
gaz_ball
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Strange boost issue

Evening,

Had my E91 335d in to the garage last weekend to have DPF deleted, swirl flaps blanked, EGR deleted & a new intercooler fitted along with a GBW remap. It made good stock figures before any work was carried out but when they had it on the dyno after the remap it only made an extra 8bhp (!). All 335d's mapped at this particular garage using GBW maps have made between 350-375bhp so something is amiss. The boost logs from the mapping session (see attached) show a difference/lag between what the ECU is requesting (bottom) & the actual (middle) with quite an obvious jump between the high pressure turbo & low pressure turbo. We have a few ideas of where to start looking and it needs to go back to the garage to hopefully find the issue but I wanted to ask on here in case anyone has seen or experienced similar symptoms.

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      07-17-2018, 09:00 AM   #2
Mus22
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If you have the Bosch pressure control valves they are prone to fail maybe unrelated but check them.
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      07-20-2018, 08:51 AM   #3
MooLard
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What mileage on your car? Are you happy with the vacuum system? Any leaks will slow the car right down.
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2016 435xd GC, MTC intercooler, centre and back box deletes, GKR stage 2 remap, methanol injection, H&R lowering springs. To do: wash it.
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      07-23-2018, 07:33 AM   #4
gaz_ball
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Thanks for the replies.

We changed out the turbo pressure control valve, the pressure converters & most of the vacuum lines which solved the issue. Got a pretty decent increase from the stock dyno run in the end. A bit frustrating but worth the wait!
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