WWEEELLLL
As for the pictures of smoke and flames posted on several forums of GEs, the blown seal explanation is a bunch of crap! What you are seeing doesn't happen continuously.
What is happening on the GE's is that the turbo doesn't do much thru the 4th notch. There is not enough heat in the exhaust.
Once the throttle goes to number five things start to happen. The more fuel goes in, engine revs higher, there is more heat and the turbo starts to add boost (more air) to make more HP. All of this is supposed to be controled by the engine management system.
Now if the turbo just happens to lag behind so there is not enough air going in, the mixture will be too rich, which equals black smoke. If the injectors happen to dump too much fuel in, this compounds the problem.
So what you are seeing is a real bad case of an OVERLY RICH mixture that first produces great gobs of black smoke, then it gets hot enough to ignite and there is a huge fire out of the stack. Look very closely and you will see that this fire looks very much like you poured fuel on a camp fire. There is no velocity to it like you would find at a much higher notch.
Once the turbo catches up, the mixture returns to normal, the excess fuel burns off and everything is back to normal. As I have said before, this is a rare abnormal occurance that happens on the change from the 4th to the 5th notch. Dash-8s are the worst culprits and I have seen a Dash-9 or two do it, but the Dash-9 event is rarer still.
Big Jim
