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u63af · Posted: Sun Nov 19, 2006 8:19 am Post subject: Fuel cutting at 0.95 bar?

Hi,
I raised the boost on my car the other day and it seems to be stuttering at 0.95 bar. It feels like its fuel cutting. Can anyone think of a reason for this as I thought the boost cut off was at 22 psi? Car is running a standard turbo with a front mount.
Cheers
Sandy

Smoothie · Posted: Sun Nov 19, 2006 10:05 am Post subject:

Might you be hitting the rev-limit?

Of course the problem could be a faulty overboost cutoff switch. As long as your wastegate is working and boost is being reliably limited, there should be no harm in grounding the wire to the overboost switch as a quick test.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Smoothie · Posted: Mon Nov 20, 2006 2:09 am Post subject:

Another possibility - A vacuum (/boost actually) leak that only opens up at the higher pressure level. My car did this (hesitation, stuttering while under boost, but not quite as severe as the fuel cutoff) when the bracket that holds the lower charge tube to the block came loose. This allowed the charge tube to seperate from the turbo when a certain level of boost was attained because there's only an o-ring joint between the turbo and the lower charge tube. It took a long time to diagnose because the joint would slip back together as boost decreased - so everything seemed fine when looking at it with the engine shut off.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

u63af · Posted: Mon Nov 20, 2006 3:01 am Post subject:

I dont think it is a vacuum leak as all my pipes are silicone hose now. Will try earthing the boost cut off switch.
Cheers

u63af · Posted: Mon Nov 20, 2006 3:02 am Post subject:

Dont think its rev limiter as only taking itup to about 5000 rpm