Boost Wars

[lune]

You know when you think eveythings going fine, then someone lets you drive their car
and it's a case of mine doesn't do that!

My mate purchased a 1995 S6 slipper waggon last night and being as though he was passing on the way back home he thought he'd pop in. Nice fairly standard green with cream leather, few knocks and clunks, knackered calipers but OK for the £
Anyway he'd driven mine previously to get an idea and hence offered me a drive.
First thing I notice W.T.F. he's getting 2.0bar boost and 2.2 overboost in 4th compared to mine 1.6 and 1.8 overboost in 4th Mine holds its boost fine just doesn't get that high

He hasn't checked out if someones fiddled with the WG etc. but after a bit investigating on the Forum his figures seem about right and mine are down. Mine has no fault codes showing and I have checked the hoses for leaks, took top of WG and checked seal and valve seems to move freely. Checked vacuum hoses blown off etc. New Forge re-circ valve

I appreciate there could be 101 things, but where do I start, I'm looking at getting an MRC remap soon, so I want to have it running 100% before they start
One small problem I have in addition is sometimes when you pull up to T Lights etc the revs drop low then pick up again, dont know if this is an additional symtom?
On searching for clues WGFV pops up now and then whats this and where do I find it, bit naive I apologise in advance.

Any help much appeciated,

Cheers

Ben

[stevieyid]

hi my revs do that have a look at a thread called cutting out! I think it was suggested the idle valve was the problem

[GandalfS6]

The OE Boost gauge on the S6 reads total boost - i.e. at 2.2 bar he is only boosting about 1.2 bar which is standard. If it is a aftermarket boost gauge that just reads boost pressure - WOW!

[lune]

Cheers Stevieyid, I'll have a look for that post, I've played with them valves on many a car.
Sorry Gandalf, I should of mentioned that both the readings are being taken of the OE digital boost gauge intigrated in the onboard computer (this gives total pressure=atmospheric+turbo pressure). Therefore I am comparing like for like and theres still a problem with mine somewhere

Ben

[kwlw]

You know when you think eveythings going fine, then someone lets you drive their car
and it's a case of mine doesn't do that!
a drive.

First thing I notice W.T.F. he's getting 2.0bar boost and 2.2 overboost in 4th compared to mine 1.6 and 1.8 overboost in 4th Mine holds its boost fine just doesn't get that high

Ben

If your car is 3b, then it should read 1.8 all the time (no boost/overboost). If it is ABY, then you should get 2.1-2.2 (depending on your gauge). I mean stock aubi gauge, which shows absolute pressure.

However there is one BUT . Electronic LCD gauge is influenced by ground/voltage issues, and it can show lower boost due to low dashboard voltage for example . I was getting only 1.4 bar on my 3B. After changing voltage regulator, boost appeared to be 1.7 bar which is quite normal on cracky hoses and tired engine .

Connect mechanical gauge from hydraulic shop (usual price ~10-15e), there are standard gauges for -1..1.5 bar pressure. They are accurate and suitable for test measurements (not for mounting in the dashboard). Then you will see true boost pressure. If it is 0.8-0.85 for 3b, or 0.85-1.15 on ABY, don't screw your mind on this issue . If NOT - find and destroy that boost leak, or anything else, which is not allowing to BOOST .

Sau

[Greg_S]

On your S6 lune the mechanical boost pressure should be in the same range as ABY engine

[Jamo]

If your car is 3b, then it should read 1.8 all the time (no boost/overboost). If it is ABY, then you should get 2.1-2.2 (depending on your gauge). I mean stock aubi gauge, which shows absolute pressure.

However there is one BUT . Electronic LCD gauge is influenced by ground/voltage issues, and it can show lower boost due to low dashboard voltage for example . I was getting only 1.4 bar on my 3B. After changing voltage regulator, boost appeared to be 1.7 bar which is quite normal on cracky hoses and tired engine .

Connect mechanical gauge from hydraulic shop (usual price ~10-15e), there are standard gauges for -1..1.5 bar pressure. They are accurate and suitable for test measurements (not for mounting in the dashboard). Then you will see true boost pressure. If it is 0.8-0.85 for 3b, or 0.85-1.15 on ABY, don't screw your mind on this issue . If NOT - find and destroy that boost leak, or anything else, which is not allowing to BOOST .

Sau

His car is an S6 not S2 mate.

[iain1067]

That was what my urs4 was doing when i got it, you need to really either pressure test the hoses or take them off and have a look for cracks. I ended up replacing the intercooler to cross pipe hose (michelin man hose) and also the turbo to crosspipe hose as that was cracked, even though i pressure tested it on the car. I also put in a new wgfv and S3 diverter valve. The wgfv is found if you follow the small hose from the wastegate. Your friends is right on the money if it hasn't been played with, if the ecu has been out then for sure the carpet in the passenger footwell will have been cut right by the trans tunnel.

You can also run the ecu output tests which will run the, wgfv, injectors,idle stab valve and the carbon cannister. it's not difficult all you need is a bent piece of wire, the procedure is here http://www.sjmautotechnik.com/troubl...20v.html#outs4

[lune]

Cheers lads,
Sooo,
WGFV or Boost leak are looking like big possibilities.
My action plan is swap WGFV with mates, if no joy pressure test system and find the bloody cracked hose
Then I'll hopefully be rockin on full boost

I hope I bl**dy find the cause, its been like this since I bought it a year ago

I'll keep you updated

Thanks

Ben

[iain1067]

My cracked hose didn't show up when i pressure tested it, i decided to take it off and inspect it. Another thing worth doing is replacing all the hose clips with decent ones aka genuine jubilee, the audi ones are ****e imo they bend too easily.

[lune]

Update

Story so far
Disconnected MAF to turbo hose, along with a few hoses and swapped them with my mates. I included swapping the WGFV and pipework, I changed loads of clips and inspected the bottom turbo hose and clips while I had the Air Box and pipework out of the way.
Guess what, still no blo*dy joy, boost exactley the same as before! Gettin on me nerves, hoofed me car round the block, only to burn me knuckles on the hot turbo when swapping the pipes back
Next try, is pressure test and inspect hoses visually as Iain mentioned
After that

See how tommorrow goes

Ben

[S2central.net]

Yep... Get a leak test done - visual checks on the hoses often find nothing but large obvious cracks & splits.

ALso check the TBV is OK and located the right way round - also that the control hosing is all OK. That cheap braided narrow guage tubing doesn't last forever.


Paul

[lune]

Back again,
After speaking to mate again today, his S6 def ain't std. I fixed a boost leak for him the other day when changing pipes over and here he's gettin 2.4bar total boost now! Problem is it's not runnin that healthy so I reckon someones fiddled with the wastegate spring!
I'm just about coming to the conclusion that I may just be being paranoid, I think after removing all my turbo pipes and checking clips, WGFV, DV, MFTS etc. mine might be boostin slightley betta, sometimes upto 2.0bar droppin off to 1.7ish.
I'm happy with this at moment although I'll prob still do a pressure test @ weekend just to make sure.
Hopefully now I can sort out gettin it chipped when MRC pop up north

Cheers for all the help

Ben