Low boost issues

4.2 V8 40v biturbo - 450 bhp
4.2 V8 40v biturbo - 480 bhp (plus)
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MattyRS6
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Low boost issues

Post by MattyRS6 » Fri Aug 19, 2016 3:41 pm

As a new owner of my rs6 I've just given the car a full major service including a gearbox overhaul with new filters and sump, got the car back the day I went on holiday a few weeks ago and literally drove a few miles and parked it in the garage.
Yesterday a took the car out for a spirited drive and after a bit I noticed I was seriously down on boost, especially on the lower rev range, no fault codes and it still drives fairly well, just down on power?
Reading through the forum I've now read the N75 sensor is probably the culprit, or DV's or possibly the N112 and N249.
Firstly where's the cheapest place to get these sensors and shall I just do the N75 first and see how it goes ?
Any advise would be great guys
Cheers.


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Shoppinit
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Re: Low boost issues

Post by Shoppinit » Fri Aug 19, 2016 11:09 pm

You're gonna need a Vagcom to diagnose properly.

You could chAnge the N75 and DVs but that's no guarantee that you'll revolve the issue.

You could do a boost leak test.

Everything much easier with a Vagcom.
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."

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RoyK
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Re: Low boost issues

Post by RoyK » Fri Aug 26, 2016 8:53 am

I've had a similar issue(s) and ended up changing the following:-

N249
N75
DV's
Vacuum hoses (under the air box)
Both Intercooler resealed by MRC and pressure tested.

the car drives allot better but not like i used to remember it to drive.

might just be the case of having the ECU remapped.

as i did have a separate issue of my TCU failing and replaced that with a second hand TCU that isn't mapped so now the ECU isn't mapped to the current TCU.

not sure if that would make a difference but will be getting the car remapped with the TCU and see if that solves the boost issue once and for all.

over all by chaingthe parts mentioned it has made a huge difference.

only t hing is i change everything at the same time so never found out which of the part was the actual culprit?

TPS would be the best place to get the parts.

forgot to mention that it might be worth checking the MAF's too or at the very least the MAF seals.

you are better off buying those form ECP.
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RS6 C5 - M3 E46 - Fiat 500 Abarth

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RSMOJ
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Re: Low boost issues

Post by RSMOJ » Tue Aug 30, 2016 11:01 pm

Had similar issue with mine 3 or 4 years back.....car laid up whilst on holiday, started up and no boost on driving. Sadly one exhaust manifold had fractured and a bit went through one turbo! Hope yours not the same issue? TTS in Bedford fixed after long and tricky diagnosis!

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