bagodoosh

trying to diagnose a mild stuttering that happens while keeping the throttle constant, i logged my commute to work one morning. it's only about 5mi and the engine barely warms up. so i try to keep the RPMs under 3000 and no boost (at least according to the boost gauge).

what i noticed was that i'm building boost, yet the N75 is not even active. at some points the boost is up to 4psi and the ECU's not requesting any.

i was thinking at -5 or 0 PSI the BPVs are probably closed, but isn't the boost primarily controlled by the N75/wastegate?

i dont understand:
1) where the boost is coming from
2) why the ECU is not throwing a deviation code
3) why the boost gauge & MAP readings differ

<img src="http://us.i1.yimg.com/us.yimg.com/i/mesg/emoticons7/39.gif">

<img src="http://bagodoosh.home.comcast.net/s4/Boostage.gif">

PSmalls::AnalRetentiveNumbNut

Wastegates are shut until you hit ~5 PSI.

Mihnea

MAP sensor is before the throttle body, so you could have some boost there but still vacuum in the manifold because of the throttle plate position.

HTH,

mihnea