Audi S2 ABY overboost Motronic recovery

[UrS4boy]

Hello, sorry, where can I find a complete map of the S2 ABY sensors? I means a map like pictures. Thanks a lot! Bye Alessio

Until somebody posts something for an ABY (or ADU), you can investigate using this AAN map that I did (note the hyperlinks underneath the diagram)

http://forums.audiworld.com/s4s6/msgs/222453.phtml

Hope this helps.

[Audi-Porsche Avant RS2]

Hello friends, I have again the Motronic recovery problem. Today I have again check the boost pressure and it's about 0,8 bar and more (0,9-1,0-1,1) but I have the Motronic recovery problem when I completely push the gas pedal, and the pressure is also about 0.4 bar. I have also change the N75 with a new one and the pop off valve with a old one, because the old N75 and pop off are broken. If I have a leak in the high or low pressure pipe it is possible that the boost pressure is correct? Please, help me
Thanks!
Bye

Alessio

[QuattroFever]

check for leaks. Not just pressure side of turbo also between maf and turbo inlet.

if no joy on the big pipe work, Replace all the small vacum hoses behind the throttle body by the bulkhead these are usually troublesome and are ignored. relatively cheap to do and just needs patients more than money.

if no leaks then maf??

[Audi-Porsche Avant RS2]

Hello, I will try to change the MAF with an other one, because I have already change the old one with an other one and I had not resolved the problem. I think that it's possible that the problem is in the pipe between the MAF and the turbo inlet.
Thanks a lot!
Bye

Alessio

[Audi-Porsche Avant RS2]

Hello, I have try to disconnect the N75 and the boost pressure is between 0,3 and 0,4 bar, is this normal? I have try also to change the air temperature sensor but I haven't resolved the problem. Tomorrow I try to change for the second time the MAF with the MAF of my RS2. Today I have the confirm that I have the problem only when the overboost must turn on, I have the problem if I completely push the gas pedal and also when the boost pressure is between 0,8-0,9 bar and the overboost must turn on, if I completely push the gas pedal I have the problem also if the boost pressure is about 0,4 bar with about 2000 rpm of the engine, so I have this problem only with the overboost.

[UrS4boy]

Hello, I have try to disconnect the N75 and the boost pressure is between 0,3 and 0,4 bar, is this normal?

Yes, should be about 0.4 bar (6 psi) because, with the N75 Waste gate frequency valve (Charge pressure control actuating valve) disconnecte, the waste gate (charge pressure control valve) is only controlled by the waste gate spring. Stock springs hold about 0.4 bar and then release. There are aftermarket valves that will hold higher. See below for an Audispeak explanation:

http://forums.audiworld.com/s4s6/msgs/150219.phtml

[UrS4boy]

Today I have the confirm that I have the problem only when the overboost must turn on, I have the problem if I completely push the gas pedal and also when the boost pressure is between 0,8-0,9 bar and the overboost must turn on, if I completely push the gas pedal I have the problem also if the boost pressure is about 0,4 bar with about 2000 rpm of the engine, so I have this problem only with the overboost.

Ignoring "overboost" for a moment, the maximum boost that the stock ECU (J220 ECM) will permit/deliver is a function of RPM and atmospheric pressure (at higher altitudes, in the mountains, boost is limited relative to sea level). As RPMs rise, the ECU drops the boost pressure. See these graphs from SJM Autotechnik for UrS4/S6 examples (like ABY S2):

http://www.sjmautotechnik.com/trouble_shooting/graphbst.html

Back to overboost. Overboost is only provided a certain throttle plate angle (i.e. how far your foot is down on the throttle) and the speed at which the throttle is opened, i.e. you are passing somebody on a 2 lane road and you need the extra power NOW!!

When the ECU detects the correct conditions to provide overboost, on a stock ECU, it raises the maximum charge pressure from 1.82 bar (absolute) to the "over-boost" pressure of 2.15 bar (absolute). A time limit of 15 seconds was set for this overboost to ensure drive train durability. (Reference: Aug. 82 issue of European Car, presumably based on Audi info)

So if you just add throttle gently, you might never get overboost. However, if you are in say 3rd gear and something like 2500 RPM, and you put the throttle down to the floor quickly, you should get an overboost response. If you don't, you either have a boost leak, or your N75 is dead or you have a tear in the wastegate diaphram.

Good luck /buona fortuna

Dave F.

[Audi-Porsche Avant RS2]

Hello, if I put the throttle down lower the boost pressure arrived also about 0,8 - 0,9 bar, and then the ECU go in protection, I think when I have reach the moment for the overboost, if I put the throttle down to the floor quickly I have no overboost response but only ECU protection in 3rd gear and about 2000 rpm with a boost pressure on the gauge of 0,4 bar. I have already change the N75 with a new one and also the pop off valve, because the old N75 and pop off was broken. It is possible that a small pressure leak on the intercooler connection cause this problem? If I have the wastegate spring not correct or diaphram broken is possible that the pressure with the N75 disconnect is about 0,3-0,4 bar?
Thanks a lot!
Alessio

[UrS4boy]

Here is my suggestion: You have too many possible solutions to your problem. You need to eliminate some of them. The first one is the possibility of a boost leak. Therefore, you need to pressure test your intake system from the turbo outlet (cold side) to the throttle body. Pressure test to 0.8 bar (relative) and see if the pressure holds. If not, look for the leak by spraying the hose to metal joints and boost hoses with water from a spray bottle with a few drops of some dish-washing soap in it. Once you have done that, then come back with the results.

Dave F.

[Audi-Porsche Avant RS2]

Hello, can I make the pressure test after or before the MAF? Or it is not correct?
Thanks a lot!
Bye

[UrS4boy]

Hello, can I make the pressure test after or before the MAF? Or it is not correct? Thanks a lot! Bye

Definitely after the MAF. Stay around 0.8 bar (relative) so you don't hurt the turbo seals.

There must be a test procedure in this forum somewhere.

Dave F.

[Audi-Porsche Avant RS2]

Hello, I try to find the pressure test procedure in the forum. Do you know where can I buy a pressure test kit for S2/RS2?
Thanks a lot!
Bye

Alessio

[UrS4boy]

Hello, I try to find the pressure test procedure in the forum. Do you know where can I buy a pressure test kit for S2/RS2? Thanks a lot!
Bye Alessio

Lee used to sell kits but you can make your own if you go to a plumbing store to buy some 75 mm diameter plastic plugs and use a bolt-in tire nipple/valve stem like this:


to provide a connection for your air pump. Follow the general procedure outlined here:

http://www.s2power.com/druktest-en.html However, I suggest that you also plug the throttle body hose (similar plastic plumbing cap) and the idle stabilization valve hose (wine cork and clamp).

[Audi-Porsche Avant RS2]

Hello, I have read the procedure, but I must disconnect and close the black aluminium pipe before the throttle for make the pressure test? Because if I disconnect the black aluminium pipe before the throttle how can I check for a leak in the pipe that are connected on the intake manifold? Thanks a lot!
Bye

Alessio

[UrS4boy]

Hello, I have read the procedure, but I must disconnect and close the black aluminium pipe before the throttle for make the pressure test? Because if I disconnect the black aluminium pipe before the throttle how can I check for a leak in the pipe that are connected on the intake manifold? Thanks a lot!
Bye Alessio

You really need to figure this out on your own or have somebody local in Italy help you. You have been given more than enough hints as to how to pressure test properly. Draw a diagram. You need to isolate the intake hose (and pipe) system from the turbo outlet to the throttle body and plug ALL inlets and outlets to connected devices including the by-pass valve and the idle stablization valve and anything else. When you have done that, then you pressurize to about 0.8 to 1.0 bar and check for leaks as previously described.

There are no more questions. Go out to your car and just do it.