Boost loss @ 4500-5500 rpm ...WTF?

[RagtopRon]

04 NB with APR + KO4
Jump on this car first thing in the morning and she screams. Give her a couple of miles to warm up (seemingly more evident when outside temp is above 70) and she'll abruptly lose boost anywhere between 4500 and 5500 rpms. Frustrating and dangerous.
I can sometimes feather it to bring it back on, but most times not. Boost loss is so abrupt it'll throw you forward.
Also blown 2 hoses (diverter to turbo) in the last 12 months.
Anyone gotta clue?

[FarrisK]

Originally Posted by RagtopRon

04 NB with APR + KO4
Jump on this car first thing in the morning and she screams. Give her a couple of miles to warm up (seemingly more evident when outside temp is above 70) and she'll abruptly lose boost anywhere between 4500 and 5500 rpms. Frustrating and dangerous.
I can sometimes feather it to bring it back on, but most times not. Boost loss is so abrupt it'll throw you forward.
Also blown 2 hoses (diverter to turbo) in the last 12 months.
Anyone gotta clue?

Could be that the boost is spiking in that range and "burping" one of the hoses off temporarily. Do you have a boost gauge? Can you verify that the boost goes to zero?

Also, have you checked to make sure all your hose clamps are tight?

[RagtopRon]

No boost gauge. I can hear and feel the leak but can't pinpoint it. I've scheduled a Dyno exam for this week...will this locate the culprit?

Thanks

[noR]

It'll help. It's probably overboosting or some such. You'll need to be ready to get APR on the phone w/the local shop so they can correctly diagnose it.

The shop will hopefully hook you up to a boost gauge. It's a very simple matter of 1 hose tap, and a gauge. No tool necessary except maybe a knife.

[NEauto09]

there is a vacuum operated regulator about halfway down the intake pipe. take it off and put a vac guage on it and you can see the diaphragm move if it doesnt then its faulty

[alexvilla]

N75!!!!