6.5L Turbo Waste Gate Movement

[HoveringHMMWV]

I have a stock 6.5L TD in my recently acquired M1151A1. I haven't driven it very much because I am still waiting on the SF97. The times that I have driven it, I have noticed very little turbo whine until reaching higher rpm levels. I was therefore, wanting to confirm that my turbo was operating properly by marking my waste gate rod so that I could more easily see it's movement while reving the engine. I increased rpm's to approximately 2200 before seeing any appreciable movement and even that was slight. Are there any parameters at which the waste gate should begin to open and/or be fully opened?

 

[Mogman]

Sounds pretty normal to me, the waste gate is so simple I doubt any have ever failed unless they fell apart.

 

[Maxjeep1]

I might be wrong but I thought waste gate purpose was to relieve pressure when you are getting on it and then let off.. you should be able to pull on that rod and release it and here the flap hit the housing. I have not driven mine yet but I don’t think they make but a few pounds of boost in stock form so no whistle is not unexpected

 

[HoveringHMMWV]

Wasn’t sure about the turbo whistle. The turbo HMMWV’s that I’ve seen in YouTube videos seem to whistle much more than mine. I was trying to confirm that my waste gate was not stuck open and also operating correctly.

 

[Mogman]

The waste gate is simply spring loaded, you can pull the rod towards the rear and it should spring back, I cannot hear mine at all except idling cold, but then again I have moderate to severe hearing loss.

 

[DaneGer21]

I might be wrong but I thought waste gate purpose was to relieve pressure when you are getting on it and then let off.. you should be able to pull on that rod and release it and here the flap hit the housing. I have not driven mine yet but I don’t think they make but a few pounds of boost in stock form so no whistle is not unexpected

A wastegate is used to limit boost pressure by relieving exhaust pressure from its turbine so it won’t spin any faster; a blow off valve is used to relive the boost pressure when you let off the throttle.

 

[Mogman]

DaneGer21 is correct, that turbo does not make anywhere near the pressure that would require a "blowoff" valve.
If it was not working correctly you would be getting a substantial amount of black smoke.
EDIT actually I don't think any diesels have blowoff valves, only makes sense if you have a throttle butterfly to cause a rapid rise in intake pressure, diesels don't have them.

 

[DaneGer21]

DaneGer21 is correct, that turbo does not make anywhere near the pressure that would require a "blowoff" valve.
If it was not working correctly you would be getting a substantial amount of black smoke.
EDIT actually I don't think any diesels have blowoff valves, only makes sense if you have a throttle butterfly to cause a rapid rise in intake pressure, diesels don't have them.

Correct for diesels. I guess I should have noted that also. I mentioned the blow off only because it was being described and didn’t want them confused. But yes, you’re correct that Diesel engines do not need a “blow off”.

Now if you want to get technical, haha, some of these new vehicle Diesel engines that have fancy electronics, are starting to include and/or make an electronic “blow off” valve. More of a solenoid valve that is connected to the ecu/sensors and so it uses sensors to open and close it vs actual boost pressure. Why you ask? Because some diesel turbos/engines still have slight boost surge which can wear on turbo bearings/washers.

 

[diesel_dave]

I have watched my waste gate rod while driving around and I couldn't see any kind of movement on it at all but as far as I can tell, the turbo does seem to be working fine. I can definitely hear it spool up and the truck is pretty peppy like its making boost. The turbo whistle isn't crazy because of the deep water fording kit, catalytic converter and the muffler, but I can hear it.

 

[badger_610889]

The waste gate just relieves the turbine side of the turbo by redirecting a part of the flow from the exhaust so it doesn't feed the turbo, and importantly drop the pressure significantly which slows down the turbo as the pressure upstream and downstream the turbine are theoretically equalized.

The blow-off valve is mostly part of the anti-lag system and relatively uncommon on diesel it seems. The idea is that when too much boost occurs (for instance because of the inertia of the turbo while shifting gear) instead of loosing turbo rpm with a wastegate which may not even respond fast enough (again because of the momentum of the turbo) the blowoff releases the pressurized intake air and as soon as it's closed, the pressure can build up again if the turbo is still spinning fast enough. That's critical for gasoline engines where rev variations are obviously much faster than on our big fat Diesel engines.
Also gasoline engines are extremely sensitive to the boost and gas/air mixture ratio that can lead to engine destruction real quick.
That's particularly true for smaller gasoline engines with a large turbo (think small 2L engines producing 350 hp or more) different beasts... we don't need it
But it always sounds fun!

 

[Mogman]

Diesels do not have a throttle valve, totally different animals.

"A key function of blowoff valves is to prevent compressor surge, a phenomenon that would otherwise occur as the THROTTLE is CLOSED in a turbocharged engine. If the turbocharger's compressor wheel is spinning at high speed when the throttle is suddenly closed (such as during a gear change), the flow reduces beyond the surge line of the compressor."

What going beyond the surge line means is the compressor would surge or "unload" and the turbo would exceed its RPM limits and destroy the bearings, again NOT an issue with a diesel.

On a diesel when you "chop the throttle" the intake dynamics do not change only the exhaust volume decreases slowing the turbine down.

 

[badger_610889]

Diesels do not have a throttle valve, totally different animals.

"A key function of blowoff valves is to prevent compressor surge, a phenomenon that would otherwise occur as the THROTTLE is CLOSED in a turbocharged engine. If the turbocharger's compressor wheel is spinning at high speed when the throttle is suddenly closed (such as during a gear change), the flow reduces beyond the surge line of the compressor."

What going beyond the surge line means is the compressor would surge or "unload" and the turbo would exceed its RPM limits and destroy the bearings, again NOT an issue with a diesel.

On a diesel when you "chop the throttle" the intake dynamics do not change only the exhaust volume decreases slowing the turbine down.

Absolutely, which is a reason why a blowoff doesn't really make sense on a diesel. You don't have that instant pressure spike when closing the throttle.

 

[DaneGer21]

Absolutely, which is a reason why a blowoff doesn't really make sense on a diesel. You don't have that instant pressure spike when closing the throttle.

Y’all should check out the new diesel line of valves then. As I mentioned before. They’re finding that a dump valve/“blow off” is helping to extend turbo life on some vehicles. Although, not an issue with what we are talking about.