boost pressure problems

[nielsl]

Hello !

I'm Niels, living in Belgium and the proud owner of a audi S2 3B coupe '92 . After a bit of work (new timingbelt + water pump, boost hoses, breather hoses, thermostat, knock sensors, porsche 996 front brake upgrade, ...) I put an aftermarket chip set (from a dutchman who have chiped more than 100 audi 5cylinders) + 250kpa sensor in the ECU and the car was going pretty fast (1,5bar boost pressure).

After several km's the boost pressure suddently was 1,1bar, but I had a warning on the dash that the coolant temperature was to high (even when engine cold) so i put a new (after market) MFTS and that problem was solved again.

Then I drove for 1000km without problems (and what a pleasure) but now the boost pressure is 1,25bar. The turbo spools good and he's doesn't make strange noises but he's a bit slower now.

Could it be again a sensor because it's just like the ECU limit the boost pressure, just like it was with the broken MFTS? But now the pressure is 1,25bar , in stead of 1,1bar. The boost and most of the vacuum hoses are new and they still look good. The DV (original audi) is also new for 1000km, and you still here him blow off. And the intercooler has the mark H mod.

I have read that the MAF or lambda sensor could go broken, should that give the same symptoms?

Thank you!!
Here's a picture of my car

[blux]

MAF measures the air that get's put into the engine. So If this is off I will result in a wrong amount of Fuel going into the engine. Also a leak behind the MAF can result in less air going in compared to what MAF registered. Lambda is you fueling quality control and will check O2 level in your exhaust and report back to the ECU for some adjustment. Lambda sensor and MAF don't last forever.
As you have pressures changing maybe do a pressure test on the boost system.

[piotr]

Try to check if any faults are stored?

[nielsl]

Try to check if any faults are stored?

how can you do this?

[nielsl]

I broke my wrist several weeks ago so it took a while before I could solve this problem

First I checked the ECU for fault codes, but it was the 4444 so there where no faults. Then I did a leak test and the diverter valve was leaking a lot.
It is only a new one for 1000km (original audi 06A 145 710P) ... I replaced it for an old (but good one) and now I have 1,5bar boost again .
What kind of DV is a good replacement for a chipped 3B? And can I use a DV that also works like a BOV? Or is this also not good?

[nielsl]

I have bought an second hand Forge DV007 and it works fine ! Hopefully now longer without problems than 1000km

[rs200]

what can limit boost on 0.9bar ? on stock ECU (AAN)

[newsh]

what can limit boost on 0.9bar ? on stock ECU (AAN)

Is your DV in good condition?

[rs200]

Is your DV in good condition?

in perfect condition.. new one few months old !

well the problem is that I fix maybe 20 of this cars (2.2 20vt) with strange problems and have a lot of experiance with it.. but this one will blow my mind..
Iv done compresion test and it is not perfect.. (from 1-5 10 , 8 , 10, 11, 10 bar ) can "bad" compresion have efect on that ?

[newsh]

Bad fuel or bad knock sensors can pull timing and reduce boost.