[Mk2] [Turbo] standard boost gauge and juddering issues

[dantheman]

I took my car on a trackday yesterday, and as i was pounding round i noticed 2 issues.

firstly the boost gauge went off the scale under maximum acceleration. is this normal or would it indicate that my car is running more than stock boost?

secondly when i was operating at part load in the higher rev ranges (5000 upwards) the car had a severe judder going on. it was as if it was going from max boost to no boost in a binary fashion, really jerky. this would happen when i was maintaining constant speed then lift off slightly. i have a baileys dump valve mounted and have noticed it venting during the juddering when the car is stationary, but my passenger said he didnt hear it venting when i was on track. however this could be a result and not a cause. is this problem likely to be a dump valve issue? ive had suggestions it could be signs of a blown head gasket, or a leak in a pipe. any ideas?

[willfinch36]

I took my car on a trackday yesterday, and as i was pounding round i noticed 2 issues.

firstly the boost gauge went off the scale under maximum acceleration. is this normal or would it indicate that my car is running more than stock boost?

Normal.

[Marf]

Where you say "juddering" is it like a misfire or are you being thrown forward slightly when it does it?

Could be hitting fuel cut.

The Bailey dump valve will not be helping things either, it'll be open at idle screwing with your fuelling.

[dantheman]

see ive never experienced a misfire so im not sure. but a mate has mentioned that as a way of describing it. it may not be going from max to no boost, it could be that for example only 1 cylinder is exploding. either way it physically shakes your body and the car quite violently maybe 4 times a second.

fuel cut could be a possibility, i hadnt thought of that. should that be happening though if the boost hasnt been increased?

[RobCrezz]

see ive never experienced a misfire so im not sure. but a mate has mentioned that as a way of describing it. it may not be going from max to no boost, it could be that for example only 1 cylinder is exploding. either way it physically shakes your body and the car quite violently maybe 4 times a second.

fuel cut could be a possibility, i hadnt thought of that. should that be happening though if the boost hasnt been increased?

Sounds more like misfire to me. Check all the ignition bit, plugs, leads, dizzy cap etc