Occasional overboost cutout?

[newsh]

Every now and then, maybe once a week or so, ( yesterday I drove about 500 miles it happened 3 times), I get a cutout at full throttle.
Because its so rare I always miss what rpm and boost pressure, I always back off and or change up when it happens. I think yesterday I saw the boost gauge hit 30lb once just after it did the lurch,(car is mapped for about 25-27lbs, I think, Mihnea?) usually happens in a high gear and I think usually at around 3.5 - 4k rpms. If you floor it again immediately after, it is fine, so its not going into limp mode.

Any ideas guys?

[porkkis]

Sticky WGFV? You using the standard breather system or modified one?

[audiman]

Or a small boost leak.

[newsh]

WGFV new (ish) will give it a clean tomorow. Stock breather yes, but again all new parts since I blew the cam cover gasket out a few weeks back..

Will pressure test again tomorrow too, didn't have time today. Have the Mark H mod to fit too.

Strange that its so irregular, didn't do it at all today and I really tried

[newsh]

Tom your avatar is really naughty

[Bibby]

When this happens, does the car just feel like it's accelerating like it has no turbo?

[newsh]

When this happens, does the car just feel like it's accelerating like it has no turbo?

No, it stops accellerating like the fuel pump or ignition has been swithed off for a second. I dont think it can be ignition though or it would backfire.

I think it happens if I run up to quite high boost, back off a bit then floor it again.

[Crawford_S2]

I had this and still do occasionally, i clean the MAF connector with switch cleaner and it stops doing it.

[audiman]

It sounds like 'MAF cutout' or fuel pump shut off. It is triggered by the MAF having more than the expected amount of air going into it. This is normally casued by a boost leak.

Do you still have the IC o-ring with 30psi of boost???

Ask Mihnea what level he set your MAF. I know that mine is at MAX so it wont do that even with a pipe off.

[Jonas_R]

It sounds like 'MAF cutout' or fuel pump shut off. It is triggered by the MAF having more than the expected amount of air going into it. This is normally casued by a boost leak.

Do you still have the IC o-ring with 30psi of boost???

Ask Mihnea what level he set your MAF. I know that mine is at MAX so it wont do that even with a pipe off.

Audiman:

Is this the same as overboost protection? And does this register as ECU fault code?

/Jonas R.

[newsh]

Yes still have the IC O-ring, and its not leaking (yet)...
Did the pressure test today. With all the pipes connected and pressurising via the MAF hose I get a small leak at the throttle butterfly pivot. With the tube and IM blanked off I get a creaking noise from behind the throttle body at a certain pressure and the crankcase pressurises, oil filler will start to seep air.. Undo oil filler and you get a large PAAHHH... So this is happening via the small side hose from the MAF to turbo hose. I think this is normal yes? Cos the MAF hose never sees pressure IRL.

Anyway I've decided I need a catch tank... Cos I still dont understand the breather system, eg. what exactly is the little saucepan shaped thing in the breather hose below the IM?? Is it a valve or just a vapour trap?

Washed out the WGFV with WD40 and went for a spin, SH*T what a lot of smoke!! Some old guy waved his hand around in front of his face as I went by as if to say "what a stink", sorry mate. Couldn't get it to cut out and boost was slightly reduced from before so maybe the WGFV was sticking a bit.

I wonder if it'll do it again?


@ Mihnea what do you think? How is my MAF set?

It sounds like 'MAF cutout' or fuel pump shut off. It is triggered by the MAF having more than the expected amount of air going into it. This is normally casued by a boost leak.

Do you still have the IC o-ring with 30psi of boost???

Ask Mihnea what level he set your MAF. I know that mine is at MAX so it wont do that even with a pipe off.

[porkkis]

Anyway I've decided I need a catch tank... Cos I still dont understand the breather system, eg. what exactly is the little saucepan shaped thing in the breather hose below the IM?? Is it a valve or just a vapour trap?

It's a combined restrictor and check valve.

[newsh]

It's a combined restrictor and check valve.

Right, well I'm going to take it off again and have a look then, when I looked the other day it had some condensation / mayo in it so maybe its gummed up.

[audiman]

Its a crappy valve John, just change it, not expensive. Stops the turbo dragging oil from the sump!

[newsh]

Its a crappy valve John, just change it, not expensive. Stops the turbo dragging oil from the sump!

Ok, yes, I see how it works now, if there's a lot of vacuum it pulls the diaphragm in and shuts right down to a small hole. At low vacuum (idle?) it opens up for the sump to breath easily.

Well at least its not supposed to hold boost..