Ever since I have owned my VRS it has had a fluctuating Boost level. When on WOT in 2nd and 3rd you can feel it boost up and then back off and then boost up again. Last night I thought Id have a go at finding the problem. Firstly I fitted a new N75 valve. This didnt change anything. Secondly I tried disconnecting the MAF sensor and running it. Again no change. I now have the ASR light on also. Whats next to try? And do I need VAG COM to put the light out?

Cheers, Dan

Is the engine/map standard? Do you have a boost gauge on it?

No boost gauge and AFAIK its not remapped, although it seems pretty quick for 180bhp...

Do you mean the ASR light (as in traction control) or the engine management light?

If it's the engine management light then there will be a fault code (or codes) stored.

If it's the traction control light then sometimes it can be a faulty MAF (no idea why the MAF can put the TC light on but this has happened to several members on here in the past), and sometimes it can be a major boost leak. My traction control light came on when the large hose from the turbo to the intercooler popped off, but you generally notice this kind of leak as it makes a hell of a noise and the car goes into limp mode instantly.

As Bodge said if you can fit a boost gauge or get someone to do a boost log in VAG-COM that will tell you if it's been remapped (anything over about 10-11psi) and if it's a dodgy remap that could be the cause of your problem. If it's a standard car then it's more likely to be a failing hose or valve somewhere.

I think I might get a boost gauge as I have thought about purchasing one before and it would be helpful to see what boost Im running. Any suggestions? By ASR light I did indeed mean the Traction Control light. It came on when I started the car with no MAF connected. Im guessing I'll need to use VAGCOM to switch it off. If its dodgy remap then is it just a case of getting another remap?

Edited 29 July, 201015 yr by octydan

It should go away if you reconnect the MAF and re-start the car in that case. I accidentally left my MAF unplugged once when I fitted a new panel filter and once I'd plugged it back in and re-started the car the light went away. just indicates that you unplugged the MAF, not that there is a problem related to the ASR.

I'd recommend a simple mechanical boost gauge, can't go wrong with one of those.

If it's a remap I'd be on the phone to the previous owner to find out who did the remap and try and get in touch with them to have a look at it. And don't forget to inform the insurance company!

Edited 29 July, 201015 yr by chicken_eyebrow

Cheers Chicken Eyebrows, apparently the light has now gone out so the other half tells me. As for boost gauges is this a decent price?

http://www.awesome-gti.co.uk/product.php?xProd=10060&xSec=296

how easy are they to fit and do I need one of these?

http://www.awesome-gti.co.uk/product.php?xProd=6778

With regards to the remap I'll try to contact previous owner.

Cheers all.

That boost gauge looks ok, you can get mechanical ones a bit cheaper on ebay but that one sounds like it comes with all the kit you need to fit it. Might be worth phoning Awesome before you buy to see whether they recommend the no-buzz t-piece or whether that comes with the kit. They know their products pretty well so should be able to put you right.

Rob did a guide to fitting a boost gauge if you find the Awesome one doesn't have clear instructions.

http://www.pimpmyskoda.co.uk/Gauges.htm

Although this recommends running the hose off of the fuel pressure regulator whereas a few people on here are now saying it's better to run it off the inlet manifold instead.

my vrs will every now and again open the dump valve on its own when i'm accelerating. quite annoying. going for a new n75 valve j type under warranty.

Edited 29 July, 201015 yr by Clarkyzs

my vrs will every now and again open the dump valve on its own when i'm accelerating. quite annoying. going for a new n75 valve j type under warranty.

If you're sure the DV is opening (i.e. you can hear it releasing boost) rather than that the turbo is just slowing down then either the spring (if aftermarket) or diaphragm (if the original bosch valve) in the DV is knackered, or your N249 system is playing up, the N249 is the valve which creates a vacuum in the little hose going in the top of the DV to help it open. It can do this even while your accelerating if the ECU thinks the car is overboosting and it needs to do something quick to vent off the boost.

The standard N75 valve is an F so careful what they are putting on there.

Edited 29 July, 201015 yr by chicken_eyebrow

 (no idea why the MAF can put the TC light on but this has happened to several members on here in the past)

I was told a while back that it's because the Motronic system needs accurate data from the MAF (among other things) to work out  the overall load on the engine so it can do its torque availability calculations, and accurate traction control depends on a lot of that data.

That'll explain why the torque figures on my Liquid Gauge went up the creek when I unplugged the MAF

If you're sure the DV is opening (i.e. you can hear it releasing boost) rather than that the turbo is just slowing down then either the spring (if aftermarket) or diaphragm (if the original bosch valve) in the DV is knackered, or your N249 system is playing up, the N249 is the valve which creates a vacuum in the little hose going in the top of the DV to help it open. It can do this even while your accelerating if the ECU thinks the car is overboosting and it needs to do something quick to vent off the boost.

The standard N75 valve is an F so careful what they are putting on there.

Won't the N75J valve provide a different power profile i.e loads of low down power but not much up top? (a bit like my hair line)

The N75J just works more slowly than the original N75F (I believe it is a much older design, from early 90s Audis). So the wastegate doesn't open as quickly meaning you can get higher peak boost levels and the peak boost remains for a bit longer than it normally would before dropping down to the hold boost level. Similar I suppose to fitting a manual boost controller tap between the N75 and the wastegate actuator.

If the boost fluctuation the OP is experiencing is down to the wastegate opening and closing when it shoudln't be then the N75 is a likely candidate but it sounds from what he's saying that boost is being vented through the DV in which case I reckon its the DV or N249 at fault.

Edited 29 July, 201015 yr by chicken_eyebrow

I had generic remap on my car and everything was OK until I installed Milltek decat non resonated exhaust. Before overboost was 1bar and slowly fell to 0.8bar, after the install overboost was around 1.3-1.4Bar, then fell to 1bar,then up again. It was pumping boost all over the place when the gas pedal was pushed all the way.

After stage 2 generic remap it was even worse,peak was 1.7bar!!, so I am back on stock map and now I have no problem.

I will try with OCT stage 2, maybe it will be OK... - O.CT Tuning

Thats very strange. Sounds similar to my car. I really need to get a boost guage to see what its producing boost wise.

If you're sure the DV is opening (i.e. you can hear it releasing boost) rather than that the turbo is just slowing down then either the spring (if aftermarket) or diaphragm (if the original bosch valve) in the DV is knackered, or your N249 system is playing up, the N249 is the valve which creates a vacuum in the little hose going in the top of the DV to help it open. It can do this even while your accelerating if the ECU thinks the car is overboosting and it needs to do something quick to vent off the boost.

The standard N75 valve is an F so careful what they are putting on there.

i'll get a new DV fitted too then. just one standard one across all 1.8t's or is there a better one i need to get?

Bosch one, not sure on part no. but I have my old one in the shed so will check tonight. Suitable for VAG 1.8Ts and 2.7 bi-turbos.

Brake comp are doing DV on ebay for £44.50 delivered, just got mine today, looks very well made and it feels smoother aswell

the VAG part number for the Bosch one is 06A 145 710 N

If you can get a decent aftermarket DV for less than the Bosch one then buy it as the Bosch one is made of plastic with a sprung diaphragm instead of a piston.

Edited 29 July, 201015 yr by chicken_eyebrow

Update on the Boost problems. I tried another N75 and it made no difference whatsoever. Not sure what to try next. Previous owner not contactable anymore (to ask about whether it was remapped) it would seem. Boost Guage on order to see what boost levels are. So far I have done the following:

Changed Plugs

N75

N249 bypass

Checked for split hoses (cant see anything obvious)

Cleaned Throttle Body + new gasket

What would the next step be? Could it be a coil pack breaking down? Fuel Filter? Lamda sensor?

Dan

Update on the Boost problems. I tried another N75 and it made no difference whatsoever. Not sure what to try next. Previous owner not contactable anymore (to ask about whether it was remapped) it would seem. Boost Guage on order to see what boost levels are. So far I have done the following:

Changed Plugs

N75

N249 bypass

Checked for split hoses (cant see anything obvious)

Cleaned Throttle Body + new gasket

What would the next step be? Could it be a coil pack breaking down? Fuel Filter? Lamda sensor?

Dan

Did you ever get to the bottom of this? I have the exact same problem. Mine pulls 19 psi, then it will fall down to 8-10psi then come back on strong again?

Split hose probably

The large pipe that sits at the back of engine that comes from turbo to the metal pancake pipe has a very poor connection clip on the early cars and that can get loose and thus cause a boost leak.

Also the "S" shaped pipe on the inlet manifold(under metal bracket) and manifold is common.

can gets some pics of the area if needed.

cheers. they are the only places that I havent looked at, the hardest places

Did you ever get to the bottom of this? I have the exact same problem. Mine pulls 19 psi, then it will fall down to 8-10psi then come back on strong again?

Kind of . Took car to get a remap and turned out it was already remapped! Tuner ran diagnostics when he took my car out to roadtest it and said all was OK. The fluctuation was an overboost caused by the remap.