geordi wrote:
Jim:
I'm not entirely sure what you mean when you refer to Turbo Bark, or if my turbo is even doing it. If it is a symptom of turbo overspeed, why would that happen when the power is released, rather than applied? I'm genuinely curious, I have no idea on that one. I know the basic theory on turbo function, my knowledge of the VM system specifically (from troubleshooting) says that when the power pedal is released, the fuel is cut almost instantly and the turbo vanes close again.
That takes a little bit, more than a couple rotations of the engine, because it might take half a second for the vanes to return to closed. At the same time, IF the boost in the system was dangerous to the turbo, I can see how logically one might think the air would push back against the turbo's compressor snail spindle. Is this what you are talking about?
If so, why wouldn't the pressure ALSO be released from the engine side, by the continuous inhalation of opening cylinders? That is a very effective way to move air through the intake system normally...
I lost a turbo on my CRD already. That caused me to lose the engine, but partly because I did not recognize what had taken place and the engine pumped itself low on oil. I also don't believe that the turbo failure was caused by overspeeding, but that is still up for debate.
geordi
No stock diesel should have this problem I don't know about the motori
I happens when you add a lot of fuel; bigger injectors, pump work, etc... and increase boost by blocking waste gate, boost fooler or otherwise
at this point you are on the ragged edge of the map range of your stock turbo... now when you unload the turbo in a hurry you cannot get the air into the engine fast enough so the pressure backs up to the turbo and goes out the fresh air intake the turbo makes a series of sharp whooping sounds accompanied by a jolt in the truck ...basically the air pressure has nowhere else to go
if it is happening you will know about it
sled pullers and drag racers run a pop off valve in their turbo housing to help with this or they would destroy even more turbos than they do now
remember we are talking about boost far north of 35lbs
this may not be an exactly correct definition but that is how I understand it and that is what it feels like...it is very hard on the turbo ...you do not get to do it very ofter without bad things happening to mister turbo
My knowledge on turbos is limited to fixed vane turbo I just don't know the variable vain type very well ...except I find them complicated, expensive and another part to break
I do not know what the boost in the motori is limited to but I would guess it is not over 25lbs
If the gde hot tune raised the boost above that he probably put it in there for safety. After talking to Keith he struck me as a very careful tuner who is trying to work within the parameters of the stock system.
you might also look on u tube for some videos of cummins sled pullers and cummins turbo bark
I hope some of this made some sense but at least you got what you paid for
jim