Intake/MAF resonance?

[Wangspeed]

I'm not getting much traction on help elsewhere, so I figured I would ask here. I get compressor stall, only under vacuum, around 10inHg. Seems to happen if I back off the throttle under cruise conditions, but I can also provoke it sometimes by blipping the throttle. Is this intake/MAF resonance, or an issue with getting vacuum to the BPV? In a nutshell, you can see the MAF jitter in the graphs, and you can hear the BPV/turbo flutter.

Things that I've tried so far.

• bypass vacuum tank, still happened
• clean and lube Forge BPV
• swap back to stock BPV
• checked line from solenoid to BPV

sidenote: yes, I know EGT and FP logging is broken. It's on my TODO list. I don't really care at the moment since I only run 93, and I only have a modest tune with no fueling issues.

Things that I can think of. I've not tested the boost solenoid. Could it be contributing? I doubt it since it's always 0% DC when this occurs. The valve holds boost even after the car is off, until I disconnect the tube going to it. One last thing. The MAF pretty much rests against the K&N heat shield. I was concerned about this when I first installed the intake, but didn't see any issues, so I didn't think about it. Just a few weeks ago, this cropped up. I suppose that could be contributing, but MAF resonance shouldn't cause the BPV to flutter, at least I wouldn't think so...

[Iam Broke]

I had something similar with the AEM intake and an early Dejon. Do you feel it hesitate & surge at part throttle sometimes?

What intake and filter are you running? If aftermarket, look for rubbing/vibration. I see it in the MAP as well though.

[Wangspeed]

I had something similar with the AEM intake and an early Dejon. Do you feel it hesitate & surge at part throttle sometimes?

What intake and filter are you running? If aftermarket, look for rubbing/vibration. I see it in the MAP as well though.

K&N. I think I hit the heat shield because of my stage 1 rotated mounts. I'm going to need to cut the shield, or do something else to move it away. I saw the K&N on someone else's car that didn't have rotated mounts, and it is no where near the shield.

You can see the MAF butting up against the shield here:

[Wangspeed]

Tom, I forgot to answer part of your question. No surge or hesitation at all. The car drives fine. I'm more concerned about long term turbo health than anything else.

[Iam Broke]

I used to get that light flutter on decel like you have, I really don't think it'll hurt the turbo.

If it was surging under boost, then I'd worry.

[Wangspeed]

Ugh. I know it shouldn't worry me, but it doesn't give me a warm fuzzy. I probably wouldn't worry about it if it was a ball bearing CHRA, but under decel, the oil pressure is dropping, so I worry about the health of the journal bearing CHRA. Plus the fact that it suddenly started up a few weeks ago, seemingly out of the blue, worries me too.

Thanks for the input. It's appreciated. I'll try to tweak the shield and see what happens. Either I'll try to redo the bracket for the intake, or I may just dremel out part of the shield.

[roadconetuning]

mine did that horribly with the aem silicone tube on the full cold air and with the stock air box. i havent seen this issue with my K&N this afternoon since i started dialing it in... I honestly wouldnt worry about it. i doubt you're getting more than a fraction of a pound of thrust force on your turbo that these loads... my K&N in the same way with stock mounts and i'm almost afraid to put my rotated mounts on the car because i think it'll only make the issue worse...

[Wangspeed]

I trimmed about a 1/4 away in a small area and tweaked the shield a bit. It's pretty much all gone now. Back to normal! Just used some left and right tin snips and a file, and painted after. I think the biggest issue was that the tube itself was contacting the shield, not just the MAF connector. Looks like one of the bolts for the shield was a little loose, so it moved a bit, which is probably why this started up.

[Iam Broke]

Glad you resolved it.

[cobaltssoverbooster]

there are alot of reports of the pipes causing the sensor to fault like that.