Help sorting my underboosting S2?

[gunman]

Guy's, first off I will admit that I'm no expert what soever on the S2 engine.

I have an issue with my car where I cannot achieve boost over 1.1bar, the current map on the car should be boosting to 1.4bar. I have done a boost leak test which I couldn't pinpoint any leaks (may be me at fault here). I have done the MarkH mod with no difference and have replaced some of the vac tubes.

At the weekend I had my intercooler off and noticed a small amount of oil at the bottom, would this indicate a tired turbo? I have a spare here but not sure it's much better as there's slight play in the shaft.

Lastly, can anyone recommend anyone in N. Ireland to look over the car for me? I had been PM'ing S2central and he was going to look her over but he seems to be too busy and I haven't heard from him in ages.

[montez]

I am guessing that it has the S2 Central map then, a little bit of oil in the intercooler and pipe work is fine. How did you go about doing the boost test? How much pressure did you manage to get in there?

[gunman]

It's an MTM Map.

Cant remember quite what pressure I got but it wouldn't hold it for long. Couldn't locate where it was leaking tho.

[Christophski]

When I had a boost leak I could hear it hiss buit couldnt find it or see it and eventually swapped the wastegate??? (Big round thing on the rhs of the bay by the turbo) and it solved my issue.

[montez]

I spent a good few months chasing boost leaks I know what a nightmare it can be. If you have not done it yet I would recomend checking it on Vag-Com, the software is easily attainable and a cheap lead will often do the job off Ebay. This should narrow down whether or not the boost is being causes mechanically or electronically by being cut by the ECU.

The best way I have found to pressure test it is to go around blocking off pipes and doing a little bit at a time. I start by blocking the MAF Pipe, Turbo outlet, breather system and one half of the diverter valve to test the intercooler and inlet pipes. I then test each of the vacuum hoses indervidually.

The hard plastic lines which the vacuum pipes connect to often rub on the bulk head and produce a boot leak. I had to replace both the one to my dif lock and the ecu as they had pin hole leaks. The Diverter valve itself can often leak both the original plastic and the uprated forge ones can have problems.

There are plenty of threads with people having the same issue, I think it is one of the most talked about issues and each person has their own way of boost leak testing.

[Rusty]

Get a £5 VAG com cable & adapter and check the codes first.

Blank off the breather and boost leak test the whole system.

If that fails, also check the MFTS plug and try the engine with it unplugged to rule it out. Also check MAF plug and condition of the knock sensors as well as their bolt torque is 20 Nm.

[Greg_S]

Also if you have access to mitivac check the diaphragm on the wastegate isnt split too.

[Rusty]

And the DV.

[montez]

You can test the waste-gate diaphragm by using a bit of tube on the nipple on top of the cap. Suck on it to create vacuum and see if it holds. I am pretty sure that if the wastegate is leaking you will get over boost though.

[newsh]

Right, first off, if you have any kind of serious boost leak you'll get a "MAF cut " The ECU will not be able to correlate the amount of air going through the MAF with the Lambda reading and will cut the fuel pump. The car will lurch violently.
Secondly, if the WG diaphragm was split you would get too much boost, not too little.

I would try disconnecting the MFTS first as this will limit boost if its gone bad.

As said, you can get Vagcom and an ebay lead and read the codes or use a LED or bulb and read the "Blink Codes" using the instructions on S2Central, this is easy to do and costs practically nothing. If you can get the codes you can post them up here and we'll be able to help more effectively.

[gunman]

Cheers Guys, I have the ross-tech vagcom and have used it before with no error codes showing which is why I assumed either a boost leak or a worn turbo.

[montez]

What boost do you get on the car when you do a run in 5th gear from about 2000rpm and let it build?

[gunman]

Dont know off hand, I'll try that and post it up.

[gunman]

What boost do you get on the car when you do a run in 5th gear from about 2000rpm and let it build?

Tried this on the way to work this morning on the dual carrigway, hit 1.1 bar, as much as it ever reaches.

[Christophski]

In higher gears the cars wont reach 1.4.... they should only hit 1.4 in 1 - 4 gear so I believe????? Or is it the other way round????