Help! Slow Spooling + Not Holding Boost N54 (logs included)

[thetaobear]

Hi Everybody,

Recently I am experience these symptoms:
1. at low RPMs, there is a low rumble at WOT (just doesn't feel right, especially with higher gears 4+)
2. not much torque
3. slow spool up (see below)
4. some strangle whistling noise from engine bay under WOT

I recently changed to new
- turbos to new dinan remanufactured turbos
- new sparks
- new coils
- new vacuums
- new solenoids

Mods:
stock boost
Upgraded chargepipe and intercooler

The vacuum lines measure at 26Hg during idle (normal). However, under acceleration, the vacuum lines drop to 5Hg- what does this mean? My logs see my pressure hits target but then tails off to 5-6 PSI with slow spool- 30ff pops up at long WOT. Replaced both solenoids and vacuums- didn't change the behavior.

My mechanic says next is to smoke test; however, I already did a spot check and tightening in the whole intercooler, charge pipes, and diverted valves. My question is why would the intake areas be the problem if the vacuum lines go below specs- would the intakes affect vac pressure under WOT bringing it down to 5Hg? Any other components I should check before sending the car in? What is the best way to go from now?

This is becoming a headache and expensive. Seems like the mechanics are having troubles diagnosing the problem.

Suspect: Could it be the diverter valves? Any help will be appreciated!

[ErvGotti]

Post a log of one long continuous pull WOT in 3rd from 2500 RPM to 6500 RPM.

But to me with symptoms 3 and 4 it sounds like a vacuum leak or your boost solenoids going bad. That's assuming you don't have boost leaks, which I don't think you do as you would throw a code.

Pull off the engine cover and closely examine all the vacuum lines, paying close attention to the one's that run to the boost solenoids and canisters.

I replaced my solenoids not to long ago, not a hard job just a pain in the ass cause there's not a lot of clearance. I bought the generic one's off ECS and they've worked great and way cheaper than the BMW one's.

[AZN54]

When did you start noticing the lack of boost, after a particular mod or just randomly? I second the vacuum leak or boost solenoids; at least start there. It very well could be a nice leak in the diverter valves, too. Double check all piping is connected and clamped as well (intercooler/chargepipe, etc.). I ordered some nice vacuum hose from Amazon with 3.5mm inner diameter. I was a little leery about an Amazon purchase for this, but it's very strong and I don’t see it collapsing. A buddy used same hose to replace entire vacuum lines and it’s been great. http://www.amazon.com/High-Performan...=AZZUFLYGX73QL

[thetaobear]

Thanks guys.

I have replaced all my vacuum lines (using silicone) and solenoids about 2 years ago. I think I will check again.

This happened after track day, which caused one of my turbos to die (which is why I got them replaced). 1+3 started to show up

After turbos replaced, 1+3 still existed (but held boost at higher PSI), then started to degrade from there through time.

Thanks again for the suggestions.

[ErvGotti]

Check to see if the two black vacuum canisters on the turbo side aren't cracked. They can cause the symptoms described.

[thetaobear]

Just an update
- canisters OK
- whole intercooler, chargepipe plus connections OK
- diverter valves OK

My mechanic claims that my after-market vacuum tubes may have caused this problem (they are attached correctly and brand new) because they collapse and bend different from OEM.

Is this even possible? Has anybody experienced this?

I got mine from Verocious Platinum Cured Silicone Vacuum Hose Kit - Black Mini Kit

[all4bspinnin]

Do you have the ability to post a log?

[SSSnakeman]

I just put the verocious ones on without issue. Did they get hard or soft over time? Or was one cracked or something?

[thetaobear]

Sorry- it was not the vacuum lines. Went WOT and got 30FF, with the same behavior.

However, during the last diagnostics, we figured there was low vacuum pressure during WOT.

Does this mean the waste-gate actuators are leaking? I am running out of ideas.

[thetaobear]

The vacuum lines measure at 26Hg during idle (normal). However, under acceleration, the vacuum lines drop to 5Hg- what does this mean? My logs show my pressure hits target but then tails off to 5-6 PSI with slow spool- 30ff pops up at long WOT (see log above). Replaced both solenoids and vacuums- didn't change the behavior.

My mechanic says next is to smoke test; however, I already did a spot check and tightening in the whole intercooler, charge pipes, and diverted valves. My question is why would the intake areas be the problem if the vacuum lines go below specs- would the intakes affect vac pressure under WOT bringing it down to 5Hg? Any other components I should check before sending the car in? What is the best way to go from now?

This is becoming a headache and expensive. Seems like the mechanics are having troubles diagnosing the problem.



Thanks again!

[Blue335xicody]

Did you ever solve this?