under boosting RS2....

[DamoM]

Had my RS2 on the track at castle Combe for a few laps when suddenly noticed from the boost gauge that the car was under boosting.

My car has been mapped by Mihnea and produced 20 psi upto 4000 rpm with boost then increasing to 25 psi thereafter to redline. It now will not boost past 10 psi.

Have had the codes taken from the ECU and there was some minor stuff. Anyway, checked all sensors and reset the ECU but the result is the same. No more codes are appearing on the ECU.

Have checked all hoses (10 times!) and pressure tested the intake system. It holds pressure well so no big leaks.

Only thing not yet changed or tested is the WGFV (I have a spare one to try on it) and the wastegate diaphagm which I know can split.

Other than that, has anyone got any ideas as I am running out of inspiration!!!

[BRY]

WGFV sounds like a the best suspect. Easy to change too!

[Jamo]

Check the fuse to WGFV as well also check the boost hose too the ecu isn't kinked or holed.

[Chris M]

My car was loosing boost on the track a while back, was a worn Diverter valve, only had it on the car 3 months. Check WGFV and if no joy try that.

Chris

[DamoM]

My car was loosing boost on the track a while back, was a worn Diverter valve, only had it on the car 3 months. Check WGFV and if no joy try that.

Chris

I had this too. The diverters kept failing. I have tried running it without it connected though and it is the same!

Many thanks for the responses guys. Gonna try them all.......

[AAH!]

You can do an output test, which amongst other things test the WGFV.

See here:

http://www.sjmautotechnik.com/trouble_shooting/ecuf20v.html

[Doug_RS2]

Do that output test.

What pressure did you test it to?

[DamoM]

Do that output test.

What pressure did you test it to?

Did the output test and all came up fine. The system pressure tested at about 1.2 bar according to the boost gauge and very slowly dropped off?

Tried running the car with the WGFV disconnected. With it disconnected the boost is only about 7 psi so I guess the ECU is controlling the boost to some extent. The fact that it is not controlling it to limp home values, that there are no codes and the ecu has been reset (the diaphragm is fine and the MAF connections have been cleaned) kind of points me to tubo failure? Have inspected the vanes on the inlet side but it all looks ok so not too sure how else to check it without removing it? There was some oil around the inlet housing and the car did burn some oil on startup at the trackday at Castle Combe - but only the once. Also, on changing gear at full chat there was some oil blow back through the filter (that's when I noticed boost was low and came in!) although this again has not recurred?

Any ideas?

[4WheelDrifter]

I had this too. The diverters kept failing. I have tried running it without it connected though and it is the same!

How did you disconnect the DV? Did you remove it and bung the hoses?

[DamoM]

How did you disconnect the DV? Did you remove it and bung the hoses?

Yes.

[AAH!]

Multi Function Temperature Switch ? (MFTS)

IIRC to check it all you have to do to is unplug it and go for a drive and see if your boost returns. If malfunctioning it can put the car into low boost mode.

http://www.sjmautotechnik.com/troub...g/20vmfsns.html

[DamoM]

Multi Function Temperature Switch ? (MFTS)

IIRC to check it all you have to do to is unplug it and go for a drive and see if your boost returns. If malfunctioning it can put the car into low boost mode.

http://www.sjmautotechnik.com/troub...g/20vmfsns.html

Have run that test. Boost is the same. Thanks though.

[porkkis]

You seem to have done all the necessary tests to start assuming the turbo is not working as it should. Remove the intake side hose and test how it rotates and how much play can you feel.
Was the DV really off the car and hoses bunged?

MTFS overheat signal affects only 3B engines.

A really long shot would be to suspect the MAP sensor faulty so that it gives higher signal than it should. Haven't head of such but theoretically possible. Same applies to knock sensors...

[DamoM]

You seem to have done all the necessary tests to start assuming the turbo is not working as it should. Remove the intake side hose and test how it rotates and how much play can you feel.
Was the DV really off the car and hoses bunged?

MTFS overheat signal affects only 3B engines.

A really long shot would be to suspect the MAP sensor faulty so that it gives higher signal than it should. Haven't head of such but theoretically possible. Same applies to knock sensors...

Took turbo off the car completely yesterday. The vanes on impellor and compressor are complete, rotation is fine and play minimal. I was convinced that it was gonna be f**ked. I have a new GT3071 turbo on my UR quattro which needs to come off because I have a tubular manifold coming from 034EFI so considering trying that on the RS2 instead.

DV is still off the car and hoses bunged....

I could try the motronic ECU from the UR (it has a 3 bar map sensor as per RS2). That is mapped to 1.8 bar by Mihnea so a quick run would tell if the ECU has a problem I suppose.

[porkkis]

If your ur is not converted to direct ignition, do not try its ecu as the pin order is different!
I assume here your urq is original 20v RR.

Knock sensor fault is way more probable than MAP fault IMO.