Low Boost Problem!!

[Matt_Steel]

Hi Guys. Having had my car on the rolling road to check it's power output, I discovered it to be running about 40HP short of it's suggested 265 standard. After a days diagnostics, the guys at the garage think that the wastegate actuators are knackered. Do you know where i can source some replacement actuators as the people at the Audi garage have told me i need to replace the turbos!!
Cheers!!

[JonnyX]

Well, 'apparently' this is true. Whether it's really true or not I don't know. More to the point, how
was this discovered -> what fault codes did you have?

[gavsteryoung]

Are you sure this is the case?

Have you tried using a VAG Com to look at AirFlow? Sounds like the MAF to me!

Neverheard of the actuators dying?

[Matt_Steel]

MAF has been replaced. No fault codes shown to indicate actuators. But a process of elimination lead to them. The car was reading a lack of boost and fueling, so the guys at the garage bypassed the boost control valve to try and increase boost to bring on the extra fuel but could not get the boost above 5 psi, which suggested that the actuators are passing or just weak. Tried to adjust the actuator but it was seized.

[jeffw]

I assume that a full pressure test has been done ?

[JonnyX]

Have you pressure tested the intake? (you could just have a ripped hose or a hole in an IC)

[Nige_RS4]

I agree 5psi is typical when the car is in 'limp mode'. I would investigate further before spending the best part of £3k on new turbos. Check the TBB and F hose as a starter for 10.

[Matt_Steel]

The guys at the garage said it was not a leak as this would cause the engine to run rich and not lean, as it is doing.

[jeffw]

Yes....but have they done a pressure test.?..

If they haven't then get them to do a full pressure test. It is very common to have TBB & F hoses fail as well as the DVs ....

[KayGee]

I'd try emailing jacob (at) BuehnEngineering dot com and ask his opinion, I've never heard of a busted wastegate and I've owned turbo cars for five years. Have heard of heatshields coming loose and stopping the wastegate actuator rod from working.

Lastly the wastegates aren't adjustable AFAIK, they are preset at the factor and matched as pairs.

Limp mode is favourite and a burst or split pipe.

[gezzerS4]

Check the MAF, When I took mine for an AMD stage 1 upgrade, it was 40hp down from standard, they replaced the MAF did a run, and it when straight up to 269 bhp.

Then they added the stage 1.

[snbS4]

I agree with GezzerS4 et al.
I'm on my 4th MAF - the 3rd lasting all of 70 miles. I've heard stories of new cars at Dealers with faulty MAF's so it's worth changing again!
Assuming no unusual 'whooshing' noises?
Take it for a second opinion - my dealer diagnosed noisy wastegates which they guaranteed GBP3K +VAT 'ish for new turbos would fix it - it was actually a loose collar on the exhaust manifold!! Hence new manifolds and K04's etc for me!
DV's GBP80 each and don't last forever. MAF GBP200 ditto. TBB GBPcheap ditto again. F hose cheap if relevant - is it an early car?
You don't say if you had the RR at a specialist who is very familiar with these engines and I think you need to find one in Scotland.
Good luck!
Simon

K04's, Forge DV's, Tanoga, full Milltek, H&R, Samco TBB&F!

[JonnyX]

A bad MAF would normally give lean codes on banks one and two. You could also log block 003 on vag-com.
However, the stated problem is low boost. If you are satisfied that there are no leaks in the intake system then
log block 115. This will tell you how much boost the ECU is actually requesting. If you are requesting a normal
amount of boost ( 8 - 10 psi if unchipped - a bit more on overboost) then it's not limp mode. You could try using
an MBC instead of the N75 valve - it could be that your ECU wastegate control is fubar'ed - however, I would
expect a fault code for this (short to ground or something).

[Nige_RS4]

A bad MAF would normally give lean codes on banks one and two.

For what it's worth, I had a bad MAF which never gave any lean fault codes, but I did get a boost deviation fault code and I specifically remember the car going into limp mode on a regular basis.

I picked it up by logging with VAG-COM, as I knew that my car wasn't as quick as it should be.

Nige.

[Matt_Steel]

Thanks for the comments guys. I'll get the intake pressure tested before I proceed. If all turns out to be well, does anyone know who does aftermarket actuators, as 3.5K on new turbos really isn't an option!!
Cheers.
Matt.