No boost on secondary

[TerryM]

Hi all - long time reader, first time poster.

I\'ve got a BG5 GTB and it feels like all boost is lost after 4500rpm. Definitely normal boost down low, just nothing when the secondary should kick in. No error codes being generated.

I got a solenoid control box from a wrecker and swapped it over. Didn\'t change a thing so have ruled that out unless it has the exact same fault...

I managed to borrow a vacuum pump and have confirmed operation of the vacuum controlled valves so happy they are not seized.

Next is to buy a boost gauge and check if any boost at all is being generated after 5000rpm.

All hoses appear to be connected and don\'t seem to be cracked or perished.

The problem was present before the head gaskets were replaced, but when the engine was out we checked the turbos. Both spun fine and had barely any shaft play so assume they are fine. However the secondary turbo had a lot of carbon on the wheel compared to primary. It also was stiffer to spin than the primary but would still spin freely enough.

From what I read the throttle position sensor has a part in the secondary turbo coming online. When I tested the sensor with a multimeter I got infinite resistance (open circuit) no matter what pins the multimeter were connected to and where the throttle position was so possibly the TPS is buggered? Would a buggered TPS be causing this?

Is there any other tips or a check guide/step by step elimination process any one has that could assist in confirming what is causing the problem? Thanks in advance for any help! Cheers

[Rosssub]

Hi Terry, welcome to Clubsub ;D

The TPS doesn\'t effect TT operation, Changeover is triggered by Engine Rev\'s.

The Primary is a Journal Bearing and the Secondary is a Ball Bearing. So the Secondary\'s Shaft should spin easier than the Primary. Also with the Carbon Build Up on the Compressor Wheel, chances are your Secondary might be naffed?

You can check the operation/condition of the Vac operated TT items by putting the ECU into D-Mode (diagnostic mode). Connect the Green and Black plugs under dash, then switch Ignition on. Car enters D-Mode, so all Vac Solenoids start pulsing/test mode. Doing this you can see the ECV Actuator/IACV etc opening and closing.

Make sure your ECV Actuator Diaphragm is ok (holds Vac/Pressure).

Double check Intake Pipe, from Secondary to TMIC, for splits/cracks/holes. This pipe is only open during TT mode.

Make sure your Secondary Relief Valve is closing/sealing properly.

All items mentioned are covered in detail here:

http://www.clubsub.org.nz/forum/index.php/topic,41358.0.html

[Marky]

Boost gauge first

A seized secondary will show as youve found, itll dump all boost out the non spinning secondary turbo back to the inlet. Can you hear it change into twin mode and back?

Tps would throw a fault code id think, but its easy to test via voltage, should be about 0.45v when closed on the middle pin and just under 5v open? Google will confirm if ive got that right anyway.

[TerryM]

Hi guys, thanks for the responses.

I have put the car into diagnostics mode and can confirm the correct operation of IACV and ECV.

I took off the intake pipe from secondary to TMIC and can confirm no cracks or splits. Even blocked one end and blew in the other to confirm no leaks.

ECV did hold a vacuum when I had the vacuum pump on it.

Secondary relief valve is sealing properly.

Last time I drove it I don\'t think I could hear it change into twin mode and back.

I have bought a boost gauge online so when that arrives I\'ll confirm if any boost is being generated on the secondary.

Even though the ECV opened during diagnostics mode, I\'m thinking about hooking up a webcam under the bonnet to watch (or not watch) the ECV open during a road test to totally eliminate it.

If the ECV is definitely opening during a road test then the only other thing that makes sense to me is a stuffed turbo.

Given the secondary could be spun freely with fingers when the engine was out, how could it be seized? Or can it somehow still spin but no produce boost?

Is there any other tests to confirm if turbo is stuffed?

Thanks for the help so far - much appreciated!! Slowly getting my head around how these twin turbos operate...

[Marky]

Ive heard of them snapping the shaft for mystery reasons so the wheel spins... on one end not the other

Simple way to know if its working is just listen, unbolt the muffler if need be. The sound change is very obvious, dont need to faff about with a webcam

If you felt like it you could try locking it in parallel, see what happens then too as it takes all the valvey nonsense out of the equation. But a bit pointless without a boost gauge to be sure whats happening

[TerryM]

Thanks Marky. Went for a drive and could not hear any sound change when the secondary should kick in. So I\'m assuming the ECV is not getting a signal to open?

[Rosssub]

 TerryM said:

Thanks Marky. Went for a drive and could not hear any sound change when the secondary should kick in. So I\'m assuming the ECV is not getting a signal to open?

If the ECV is working ok in diagnostic, mode it\'ll be fine. Unless the ECV\'s Flap Shaft has come loose. Can you hear the ECV Closing? Clapping shut.

Sounds like your Secondary is toast.

[TerryM]

Thanks Rosssub. Yep it\'s working fine in diagnostics mode. I haven\'t noticed it making a noise when closing. Should I hear a noticeable clap when it\'s closing in diagnostics mode?

I\'m still trying to figure out how the secondary is toast when it could be spun when it was off the car not long ago. As suggested above, the shaft may be broken in half which does make sense to me although I was imagine this would be very rare.

What else could be wrong with the turbo? If it can spin then it can still make boost right?

Also if for some reason the ECV is not closing properly, wouldn\'t that mean the secondary would always be making boost? So again everything is pointing towards a stuffed turbo?

[Rosssub]

You can remove the Circlip at the base of the ECV Actuator Rod, then open and close ECV by hand. D-mode closes it slow so maybe not a slap, but you should hear it close. Also see the Rod come to a definite stop.

But yes, all symptoms point to Dead Turbo. It should of spun perfectly free when you had it off.

[TerryM]

Thanks Rosssub. I agree that it\'s looking like a dead turbo. Excuse my lack of knowledge about turbos, but if it could spin freely when I had it off, how is it dead? What has gone faulty in the turbo to stop it from making boost?

[Rosssub]

Could be warn bearings, causing resistance on the Shaft. Can\'t spool up.

Could be Broken shaft or loose compressor wheel free spinning. Front or Back.

Could be damaged fins on the compressor wheel, from loose bearings/shaft.

[TerryM]

Thanks again Rosssub. Time to pull it out I guess!

From my research, my car should have a VF19 as secondary. Chassis code BG5B5CD.

Can anyone please confirm this is correct? Would like to get a replacement before taking the old one out.

[Marky]

Just.., wait till you have a boost gauge on it, and test it in parallel first

[TerryM]

Thanks Marky. Boost gauge should arrive later in the week so will play with that prior to pulling turbo.

By test it in parallel do you mean force the car into parallel mode to test? If so, how do I force the car into parallel mode? Cheers.

[Rosssub]

http://www.clubsub.org.nz/forum/index.php/topic,32984.0.html

[TerryM]

Thanks. So if I follow that guide I should be seeing 12-14psi boost at the inlet manifold at high revs? If only 7psi then that confirms secondary turbo is dead?

[Marky]

Yeah if anything at all. If its not spinning then it will be basically a massive air leak back into the inlet

[TerryM]

Thanks - I\'ll let you know how I get on. Cheers.

[TerryM]

Hi all - hooked the boost gauge up tonight.

Got about 8psi on primary, 0 through VOD, then about 3-4psi in the higher rev range.

Then I forced the car into parallel mode and got 3-4psi once the revs got up.

So looks like dead secondary turbo.

Any advice on how to spot a good condition second hand turbo? No shaft play, no damage to compressor wheel etc?

[Marky]

Follow your nose pretty much. If it looks healthy it probably is, fins should be straight, it should free spin pretty smoothly, dont want to see evidence of oil through it.

It will always have a little bit of side to side play, like a tiny bit, but it shouldnt have any end to end is the main thing. You can use any secondary up to a vf27 from a bh/be legacy as far as Im aware. I wouldnt pay more than 150 for one either, their only application is this car so not much demand

[Rosssub]

Grab Marc\'s VF27:

http://www.clubsub.org.nz/forum/index.php/topic,41934.0.html

Here\'s a write up for Secondary Removal/Replacement:

http://www.clubsub.org.nz/forum/index.php/topic,41508.0.html

[TerryM]

Thanks Rossub.

Does the VF27 bolt straight on? No modifications, same number of hoses etc?

[Rosssub]

Does your BG5 have a Secondary Waste Gate? Have you got VF18/VF19?

[TerryM]

It\'s got the black plastic \'disc\' thing. Ontop of this is a black plastic "U" pipe in a sqaure shape. 1 leg goes to the turbo, the other to the \'disc\'. Hose 22 connects to the "U" and i think hose 8 to the "disc". If that makes sense?

Can\'t seem to see the model numbers on the turbo with them in the car... But from my research I believe it should be a VF19 as its a GTB BG5B5CD

[TerryM]

The item described above is in the 3rd picture of this post http://www.clubsub.org.nz/forum/index.php/topic,32984.0.html.

Assume this has a wastegate? My set up looks the same...