AAN power buildup problems

[Elio]

Hi..I have a 1995 AAN URS6 with 50.000 Miles,,in have ben driving since some months but..I feel like the engine is missing some horsespower..beside the ridiculous
story given by Audi about the maximum torque at only 1900 RPM!!..pratically the engine doesn't feel as 230 hp until it reach 3800-4000 rpm..Unfortunally I don't have another AAN under my sight to compare with mine..I did a lot of tests in the engine..i checked the waste gate to assure was working..the timing belt it's new and the timing i's ok,the air pressure hoses are in good shape,the injector are checked and the fuel pressure is ok and also the quantity of gasoline in 30 seconds are in the specs..if I give full gas at 2500-3000 rpm i't like driving a 160-180 hp car..the turbo pressure it's ok,1.15 in overboost,
I have replaced the following things due of others sort of problems and because the engine was giving torque not in a clean progressive way but..it is stalling in some range of rpms..let's say..it's stalling from 2500 to 3000 rpm..from 3500 to 3800...at that range it runs nice but from 4500 to 5000 stalls again..it's like a "stairs" power generation..anyway the parts are 5 coils,the air mass sensor,2 knock sensors,spark plugs,bypass valve..(this was broken)...obviously the torque missing or stalls are not so exagerate.but who drives feels..it's like the ecu retards a lot the ignition.I also have tried to contact some friends with the Dyno..but unfortunally..in Sicily we not have the Dyno for 4wd cars..

[UrS4boy]

Could be a number of things.

Sometimes the small diameter vacuum boost hose (green plastic covered in a rubber sheath) becomes disconnected from the moisture trap between the engine and the ECU (computer) manifold air pressure (MAP) sensor. As a result, the MAP thinks you don't have any boost and tells the ECU this. The ECU in turn does not add boost via the N75 waste gate frequency valve (WGFV). As a result, you have a 160 hp 7A engine instead of the 230 hp AAN. Just re-attaching the hose (with a new clamp) will get you that missing hp. If you had a boost gauge, it would help to confirm this. Without the hose connected, you will only get wastegate spring tension-based boost (about 6 psi (0.42 Bar)).

However, you might have a boost leak, probably at the Michelin Man hose between the cross-over tube and the inlet to the intercooler. Oil sits in the grooves of that hose and rots the rubber. These cracks only tend to open up under higher boost levels, limiting the boost that gets to the engine.

Or you have a weak coil or weak Power Output Stage (POS). These can be diagnosed with a procedure like this:

http://forums.audiworld.com/showthread.php?p=18838360

Good luck.

[Elio]

..AAN turbo buildup problems..

..Thanks my friend but I have checked already all of those things..he ecu hose is ok because the pressure i read at the instrument clouster in overboost reaches 2.1 bar...regarding the Laz output ignition module..I have changed one because I was missing two cylinders..as far as i know..when the ignition module fail yoy have a missing spark..instead here the engine runs at 5 cyl..only..retard..after that i did install 5 new coils..anyway..tomorrow i'll se what to do..thanks again