850 Turbo...A Couple Questions

[BeachWagon]

Starting from the top, I just recently completed some extensive repairs on my 96 Volvo 850R wagon. Head gasket, all top end gaskets, cylinder head refresh, timing belt/waterpump/pulleys/tensioner, PCV system, alternator. She runs absolutely perfect, smooth as glass, engine so quiet you can hear the injectors ticking away. Doesn't leak a drop of any engine fluids. Seemed to pull healthy for an old station wagon. Overall I was quite happy with the repairs and started modding.
First was a TME stainless steel catback system. Love it! Next, I get my hands on an InMotion-tuned ECU advertised as being good for 15-17psi. Installed, no change in performance. What gives?!
A boost gauge with actual numbers indicate that it boosts up to about 5psi, flat across the board. After a little searching around the web, I tightened up the waste gate two turns. No change. Installed factory ECU. Again, no change....5psi flat. Put tuned ECU back in and disconnected the air line running from the boost control solenoid to the wastegate actuator. There it is! It snapped up to 15psi with no problem and held it. No boost leak.
Blowing considerably hard into the air line running to the wastegate actuator, I can make it move probably less than 1/8th of an inch. I know that's not the most scientific method but it kinda solidifies the idea that the wastegate actuator is probably fine. My bet is on the boost control solenoid. It looks old, probably original. My car has the large, round can-style one. I can't find a replacement locally. What aftermarket options are there? I see that I can drop in the later Pierberg style TCV but the information on "which one works" is a little iffy from what I could gather. Am I barking up the wrong tree?? l

Sorry for the long post, just trying to paint a clear picture. Thanks in advance!

[RickHaleParker]

My bet is on the boost control solenoid. It looks old, probably original. My car has the large, round can-style one. I can't find a replacement locally. What aftermarket options are there?

1. Build your own TCV, save 50%.

2. IPD Heavy Duty Turbo Control Valve Kit (HD TCV) - 850 S70 V70 C70

[BeachWagon]

Okay so I probably hit it right on the nose thinking it's a bad BCS.

[RickHaleParker]

bad BCS.

Turbo Control Valve (TCV).

Before you throw money at it.

1. Start the engine. Put you finger on the disconnected TVC port, vacuum or no vacuum?

2. Disconnect the electrical connector, vacuum or no vacuum?

3. Hook the vacuum line back up and leave the electrical connector disconnected. See if you have boost or not.

[BeachWagon]

Sorry. I've seen it referred to as a Boost Control Solenoid in other places. In fact, I got the vibe that the language was different when referring to the older large can-style that my car has on it for some reason.

Will do these tests when i get home and report results. Thanks.

[BeachWagon]

Ok so here are the test results...

1. There is no vacuum on any barb or hose.
2.Even with electrical connector disconnected...there is no vacuum on any of the three barbs or any of the hoses leading to it.
3. With electrical connector disconnected, it produces the same 5 psi. Disconnecting electrical DOES set off a CEL code for wastegate solenoid.

With electrical connected or disconnected, i can pass air freely in and out of both the top and bottom barb.

Side note: barb with yellow mark[top? of sensor] is connected to a yellow hose, and leads to wastegate actuator
barb with blue mark[middle barb] is connected to a blue hose leading to air intake, after the MAF sensor. I CANNOT push or pull air on that hose/barb.
barb with red mark[bottom? of sensor] is connected to a red hose that leads to the turbo compressor housing.

According to diagrams found on this site, it looks like the hoses are connected correctly.

[abscate]

Hoses are correct. There is no vacuum on this system at all, its all pressure.

The TCV uses the pressure from the turbo compressor housing (Red Hose) to route it to the waste gate (more pressure holds it off and raises boost) or, it dumps the pressure into the snorkel via the blue hose.

You can't test the TCV by revving the motor, it only boosts when the ECU asks for boost and cycles the valve, There has to be load to make this happen, not just revs.

[RickHaleParker]

With electrical connected or disconnected, i can pass air freely in and out of both the top and bottom barb.

That is what the test is looking for. The Valve is stuck open or is leaking. The waste gate is pushed open all the time. Replace the TCV.

Dang! A simpler test would of been disconnect the two lines and blow., oh well we got it anyway.

[BeachWagon]

Hoses are correct. There is no vacuum on this system at all, its all pressure.

The TCV uses the pressure from the turbo compressor housing (Red Hose) to route it to the waste gate (more pressure holds it off and raises boost) or, it dumps the pressure into the snorkel via the blue hose.

You can't test the TCV by revving the motor, it only boosts when the ECU asks for boost and cycles the valve, There has to be load to make this happen, not just revs.

Ok here I was thinking that the red hose pressurizes and pushes the wastegate open when boost builds.

I was in fact getting all of my boost readings from spirited drives. The 5psi I keep seeing is all the way up the revs.

That is what the test is looking for. The Valve is stuck open or is leaking. The waste gate is pushed open all the time. Replace the TCV.

My instinct wins again!

Yes, in fact I can observe the wastegate start to open as soon as pressure starts to build. I understand that it normally only takes a few PSI to get the wastegate moving?

Well anyway, I couldn't swap to a later TCV, say, from a mid-to-late 2000's T5 could I?

[Clemens]

I might have missed that. But did you ever replace the wastegate diaphragm? I get way better and more constant boost since replacing it. The hole was barely noticeable, but it leaked boost big time.