Intermittent boost...what to check

[willg54]

Make sure you haven't got any air in the cooling system too.

Good point, I have just redone the rad! I'll do it again in the hotel car park tomorrow. I've only notice this after about 30-40mins drive I think

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[newsh]

If its a problem with the MFTS then unplugging it will give you back full boost.

Strange noise sounds like you might have a boost leak.

I was running a stock ecu, when boost was reduced it would drop to 10psi.

Pull the vac line that goes to the Diverter Valve and suck on it, the DV should hold a vacuum, if not the diaphragm is split.

[martinws]

I've boost leak tested a few times and all seems fine. When I test it from MAF straight into the engine it seems to pressurise the oil catch tank so it could be a leak past rings or I guess the stem seals maybe?

The noise i get is a kind fffffrrrrr noise and boost kind of stalls and power goes flat.

[willg54]

If its a problem with the MFTS then unplugging it will give you back full boost.

Strange noise sounds like you might have a boost leak.

I was running a stock ecu, when boost was reduced it would drop to 10psi.

Pull the vac line that goes to the Diverter Valve and suck on it, the DV should hold a vacuum, if not the diaphragm is split.

I'll give all these a try today if the problem returns.
Am I right in thinking the Mfts is on the water rail? But which one?

Thanks for all your help

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[willg54]

Search actually worked on my phone....found out which one

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[UrS4boy]

MFTS Info

I'll give all these a try today if the problem returns.
Am I right in thinking the Mfts is on the water rail? But which one?

I know you figured it out but for future reference:

MFTS info:

http://forums.quattroworld.com/s4s6/msgs/22584.phtml

One of the many live label links in this diagram:

http://members.shaw.ca/speedtek/UrS%20Engine%20Bay%20Device%20Map.html

[willg54]

it's still playing up and completely random it seems...5 seconds and it'll completely change! im not sure if there's an airlock, i dont think so.

I need to get another ecu in or make a blinker and see what happens, hopefully figure this out asap!

also noticed the afterrun didnt work tonight...maybe connected?!

[Drummer87]

I think I have this problem now. First I had the whole kangaroo feeling when full throttle past 4k rpm. Would go after turning the car on and off. Yesterday after a spirited drive when full boosting it goes rough, like juddering nothing violent like the kangaroo feeling which must be the hall sensor.

I've cleaned up the maf sensor to no difference. Starting to annoy me. I'm thinking is it my dump value playing up.

[willg54]

Sounds very different to mine...might be worth a diff thread to not confuse things

Not an ignition problem for you ? Coils playing up?

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[UrS4boy]

I think I have this problem now. First I had the whole kangaroo feeling when full throttle past 4k rpm. Would go after turning the car on and off. Yesterday after a spirited drive when full boosting it goes rough, like juddering nothing violent like the kangaroo feeling which must be the hall sensor.

Not likely the G40 Hall sender. More likely a boost leak or bad coil or you've got the wastegate spring turned down too far (or a 1.9 Bar WG spring with even a bit of spring turn in down).

[newsh]

Ground connections on the IM?

[newsh]

WGFV plug not fully home or wiring intermittent , WGFV sticking?

[willg54]

WGFV plug not fully home or wiring intermittent , WGFV sticking?

Who are these suggestions pointing towards?

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[newsh]

Who are these suggestions pointing towards?

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They're for you Will! I think the other chap has a boost leak or bad MAF connector.

[willg54]

Cheers!

All good points to check, wgfv sticking sounds like a sensible thing.

Is it just a coincidence that this has started after my rad change? Maybe I caught some loom while doing it?

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