Boost issues

[uds135]

Hello,

The car in question is a 2010 n55 135i with 40,000 kms on it with a procede V5.
COuple of weeks ago the car went in to BMW for a routine service, prior to this it would build boost strongly through the rev range peaking around 15-16 psi.

However recently boost struggles to get past 10psi. As it approaches close to around 10psi you can feel the car shudder and then boost dials down. Anyone experienced anything like this? Also in high gears (4-6) as the boost goes past 7.5 the car vibrates loudly and makes a strange noise. Was wondering if this had to do with spark plugs (no codes thrown)?

[TimMc]

Charge pipe or diverter valve(s) leaking?

[uds135]

Originally Posted by TimMc

Charge pipe or diverter valve(s) leaking?

I checked to see if the charge pipe had blown off, but its still on. This is a noob question but how do you check if a diverter valve is leaking?

[HondaGoneRogue]

How are you monitoring boost?

What did your service summary say was done to the car?

How does the boost come on when slowly rolling on the throttle vs going straight to WOT?

Can you not datalog and send your files to Shiv? That may be the more appropriate step if you know the hard parts are all good.

[HondaGoneRogue]

Also (I am not entirely familar with the n55), check your wastegate for obvious signs of tampering or binding/chaffing.

[BMW86]

Just curious how you are measuring peak boost. 15-16psi seems a bit high for the N55, correct me if I'm wrong.

[uds135]

Originally Posted by HondaGoneRogue

How are you monitoring boost?

What did your service summary say was done to the car?

How does the boost come on when slowly rolling on the throttle vs going straight to WOT?

Can you not datalog and send your files to Shiv? That may be the more appropriate step if you know the hard parts are all good.

Just using the fuel gauge hi-jack. It was just a routine service and they pulled apart the brakes at my request to check for cause of squeaking noise.

Near identical, even on WOT boost doesnt start to build until 4k RPM. I can, just unsure what channels i would need to log?

[uds135]

Originally Posted by BMW86

Just curious how you are measuring peak boost. 15-16psi seems a bit high for the N55, correct me if I'm wrong.

Just using the fuel gauge so i mean the range is between 14-16 psi. A few people in e90 post n55 section do also get these boost numbers. Problem with n55 is that it cant hold boost to the redline, it tapers of to 10-12 psi near the redline (infact after 5k rpm)

[HondaGoneRogue]

Originally Posted by uds135

Just using the fuel gauge hi-jack. It was just a routine service and they pulled apart the brakes at my request to check for cause of squeaking noise.

Near identical, even on WOT boost doesnt start to build until 4k RPM. I can, just unsure what channels i would need to log?

Not familiar with Vishnu but I would guess Throttle Position Sensor, Manifold Absolute Pressure, Wastegate Duty Cycle, etc.

I know Terry will take all values and just pull what data he needs from a log.