"Low Boost Air Pressure"

[Toki]

2016 R27 Classic with the Volvo Penta D3-220. My charter customers got "Low Boost Air Pressure" on the Volvo display. Everything seems to be running fine, and they were able to clear the message off the display. What's going on?

Thanks

 

[BB marine]

Low Boost air pressure can be caused from many things.
*Air filter plugged ( should still have the issue unless cleaned)
*A fouled Turbo compressor or Turbine side. I would suspect the turbine side more. The D3 has a VGT turbo. There are adjustable vanes that move on a vane plate. The vanes are moved by a vacuum from a pump, the ECM controls how much boost pressure is needed and the vanes move to direct the properer amount of exhaust pressure to the turbine wheel spinning it up and this increases the compressor pressure or boost pressure. If the vanes are coked up they may have stuck and then freed up again. The lever that controls the guide rail’s positions can bind and stick.
* Combined Air inlet pressure and Intake manifold temperature sensor intermittently failing
* After-cooler partially plugged
* Hose between the turbo and after cooler leaking, ( I had this hose fail on my D3 220hp) you would see oil leaking near the turbo in this case. Leakage between the after cooler and the intake manifold.( you would see some evidence of oil in this case too)
*Damaged/squeezed vacuum hoses between the vacuum pump, VGT valve and vacuum capsule.
*Remove the air filter and check that the compressor wheel in the turbo turns without touching the bore of the turbo
*Faulty VGT valve.

It may have just been a quick intermittent failure that never happens again. If it does happen again I would check off the list above.

 

[Toki]

Thanks Brian,

I was finally able to get hold of the Volvo mechanic who surveyed the engine. He agreed, if it cleared and doesn't come back on it could be an intermittent blip not to be worried about. If it comes back I'll have him take a look.

 

[CAPTCRUNCH]

Regarding the moveable vanes in the VGT turbocharger, I found this in an undated boattest.com review of the D3-220:
Fail-Safe Protection. Recreational boats tend to spend a lot of time at the dock and then get worked hard for one or two days and then it’s back into shut down mode. To alleviate any concern, the vanes automatically get exercised at given intervals, while the boat is in its sedentary state.
Can that be correct? How does a mechanism that starts with a rotating exhaust camshaft periodically "exercise" while the engine is shut down?

 

[BB marine]

This goes with the theory you can't believe everything you read. There is no electrical devises attached to the Turbo. I replaced the turbo that was installed on my D3 220 Hp. I took it apart to see the the condition of the moving vanes. The vanes were in perfect condition with no sooting. The VGT Turbo and related components is a simple set up which can not operate without the engine running. The ECU or ECM monitors boost needs for proper air/fuel to maintain optimum performance. When more boost is needed the ECM sends a signal to a solenoid (vacuum regulator) the regulator is activated opening or closing an air valve. The vacuum regulator has an inlet and outlet hose on it. The inlet hose goes to a vacuum pump mounted on the aft section of the engine. This pump is driven by the cam shaft on the turbo side of the engine ( twin cam shaft engine ) The pump maintains a continuous vacuum as the engine is running. The outlet hose goes to a Vacuum capsule ( for car buffs this looks like and operates like the vacuum control module on a vacuum advance gas distributer gas engine) The Vacuum capsule has a rod attached to it that moves the turbo variable vane assembly. The vanes move based on loads and boost demands. To check the response of the VGT monitor the boost. My D3 220 would have elevated boost when I advanced the throttle and then start to back down when forward momentum would equalize. Example, I go from idle to 2250 rpm, the boost numbers would climb to 13 -15 PSI then slowly back down to 7.5 to 8 once in a while in a wave swell they would increase to 10psi. When at WOT I would see the boost stabilize right at 28 psi then if I backed down to 3200 rpm 20 to 21 psi. Once the engine rpm and exhaust flow is steady the VGT vanes just don't move much.

I could have answered your question with it can't!!! But I added a bit of an explanation of why it can't. The vane assembly operates from a vacuum produced from a pump that operates by the turning of the cam shaft. Cam shaft not turning !! No Vacuum !!! No vacuum not vane movement.