FIXES! Boost Control (N75) and Suspension (DRC)

[R1NGA]

Folks,

Apologies for starting yet another thread about Boost and DRC issues, but I thought I should share yesterdays' experience at QSTuning in Haywards Heath.

My RS6+ came from the Approved Audi stock and therefore still has 9 months of its 12 month warranty remaining, which is a good thing. But the car has thrown a repeated engine fault for some time and (maybe coincidentally) was associated with what felt like a loss of boost and somewhat intermittant performance. Sometimes it felt like a 480bhp rocket, other times I'd say about 300bhp. All very frustrating. The most difficult issue was convincing non-RS6 afficionados that it was not going as fast as it should - everyone who went in it thought that even the '300bhp' mode was quick. Didn;t expect much sympathy from an Audi tech used to 1.9Tdi's....

To cut a long story shirt, I didn't have faith that the local Audi dealer would be able to help initially, and with good info from Grant G on the list, established that the N75 boost control valve was a likely candidate. And for less than £40 for the part, seemed worth changing all the same.

QST have done work on my previous allroads (Tdi and then a V8) and they have always been top notch. So I booked in there yesterday for an N75 and their opinion on my troubles.

Whilst waiting and talking Audis in general, I mentioned that the offside rear shock was also leaking (handling was going to pot) and my list of issues to pass over to Audi was growing all the time. I have had a towbar fitted to the RS6 (a normal dealer-fit S6 kit went straight on, no worries) so that I can tow my small 500kg limit trailer (ie: it's tiny, so no problem for the car). As a result, I knew only too well that the sight of a fitted towbar on my car would have made their warranty dept roll over laughing, so knew I would eventually have to fund the DRC repairs myself.......

.... which is when Kim showed me the Bilstein B16 PSS9 kit he just happened to have on the shelf! All Nurburgring tested and everything (have been going there since 92 and have nearly 3500 laps under my belt, so know how good suspension needs to be if it to excel on the Nordschleife), so I took the plunge there and then. Really wasn't expecting to do it, but the price was good as far as I was concerned and like I said before, I trust their judgement and I was sat there working anyway!

So, I've now done 120 miles with new N75 valve and a PSS9 kit. Boost restored to full health and it now consistently does that 480bhp thing as it should, no faffing around, no there-one-minute-gone-the-next issues that I had before. And the PSS9 is utterly fabulous. Set on number 5 out of 9 all round (1:Hard, 9:Soft), more compliant than standard (although I think I've had creaping DRC issues for a while, so a little difficult to confirm), better control and just proper sure-footed progress as I'd always hoped. I've actually never left a car's suspension standard, ever, so I should not really be surprised. Aftermarket suspension is 9 times out of 10 going to be better than factory, as suspension (and brakes) are hugely expensive items pound-for-kg, so they are always left as a compromise by the swine bean-counters.

Big thanks to QST for sorting things for me so painlessly.

Sorry for the ramble, but the car is now as it should be again. And now I can go back to Audi about the other 'small' problems I still have - Steaming up A/C, dead TPMS, Oil fumes when hot etc etc!!!

Thanks,

Phil G
Guildford

[GardinerG]

Glad to hear your boost issue is fixed Phil.

Steaming up A/C...

Do you have the Solar Sunroof - cuz there is a tech bulletin about a fix that Audi should have done.

Re TPMS - the voltage measurements/life expectancy via VAG-COM is oft wrong - mine said 30 months remaining and I still kept getting intermittent coms. One of my current sensors is iffy and in need of replacement for this reason.

HTH

Grant

[R1NGA]

Grant,

I do have the Solar Roof - do you have access to that Bulletin by chance? What was it about? My issue is that when I switch the A/C off (ie: onto ECON when it's just not needed), I get a full steam-up within a couple of minutes and it needs full heat and windows open to clear, which is a nuisance!

Re; TPMS - I get no bad comms messages or anything, in fact nothing at all, even when tyre was completely flat as I carefully drove onto the back of the flatbed that came to collect me. It's like the system is not fitted. Have done the Store Pressures thing too, no errors, just a general OK. Bit rubbish really!

[GardinerG]

The bulletin was about the car steaming up when parked after you turn the engine off. I think they added a temp sensor to the front of the car. I've just re-read it and I doubt it will apply to your car (or mine). I will email you a copy, it's only 10 pages after all.

I know what you mean about Econ causing a steam up in wet weather, it happens on mine too. Works fine when dry. If you get a fix, it would be interesting to know what it was.

TPMS: Do you have VAG-COM? Have you checked the sensor readings (voltage/pressure/stored pressure/temp) for each sensor?

G

[Rupert]

Hi Phil, I have had the "Pressure Control Solenoid" replaced on my standard 6 about 2 years ago. 300BHP is exactly what I estimated with my butt-dyno when there is no boost. Thankfully the tech experienced the fault, diagnosed and fixed it easily.

[R1NGA]

By all accounts there is an updated N75J valve available, but my replacement was just your cooking N75. All the same, fixed it nicely. I till look at VAG-COM later and see if I can find the TPMS section - do you know which TAB it's under (I can see the categories, but none look like containing TPMS stuff)?

Thanks,

Phil

[GardinerG]

Module 65 Tire Pressure - Under the Chassis tab, or just enter the module number 65.
E.g Measuring blocks - Group 004 = Front Right
Group A: '004
------------------
Block 1 - Wheel Sensor Position
Block 2 - Wheel Temperature °C
Block 3 - Wheel Pressure (actual) bar
Block 4 - Wheel Pressure (specified) bar

P.s. you can get the TPMS for £65 from http://www.alloywheelsdirect.net/option/other IIRC.

HTH

Grant

[Rek]

How recently did you get the PSS9's fitted. They are in short supply so I am told.

[L14MDP]

How much did the PSS9's cost?

[ewill]

And does anyone know the spring rates on the PSS9s and how they compare to OEM?

[R1NGA]

Kit fitted 2 days ago for about £1700 all up, fitted, with VAT. If I paid over the odds I don't want to know! I suspect this might have been the only kit they had in stock, although it's worth a check (01444 451542). Not too sure of the spring rates, but by the feel of things, I'd say less. Overall ride quality fundamentally better.

Phil