Ford's answers to the NHTSA 6.7 Investigation
There was a request for a link to Ford's answer's to the NHTSA investigation posted on a previous thread, since closed. Here is the link: Ford's NHTSA Answers to the 6.7 investigation This PDF i...
Forum Discussion
If we can isolate the failure to the cam lobe / piston interface.
We know the Bosch boys use a form of Finite Element Analysis to run the computation and to determine the point of maximum stress.
That would lead them to be able to predict where the stresses are maximal, and concentrate their mitigation efforts accordingly.
Under what circumstances would the FEA model screw up?
If they did not coat all the parts uniformly, or if they only used the most expensive (and best) DLC at the most needed portion of the part.
A question is whether the DLC coating is sputtered on evenly on the whole thing (unlikely) or just selectively coated to cut down on the cost.
If it is selectively and narrowly done, then a consideration is whether the coating may have missed a point of high stress.
Suppose for a second that there is a "bounce" in the piston as it is pressed up by the cam.
The bounce can come from many things, from a shock wave (valve closing, common rail accumulator charging, or phase change from the charge inside (hydroshock / cavitation bubble collapsing, etc. )
The maximum stress point may be not on the lead side of the cam, but further back from the leading edge which may not be as well coated / protected against friction / pressure.
The key is we need to know the initial failure point, not the wreckage that happens as the whole thing explodes.
Microscopic examination of the early failure candidates, when it is asymptomatic, so to speak, is the key.
Another hypothesis...
We know the Bosch boys use a form of Finite Element Analysis to run the computation and to determine the point of maximum stress.
That would lead them to be able to predict where the stresses are maximal, and concentrate their mitigation efforts accordingly.
Under what circumstances would the FEA model screw up?
If they did not coat all the parts uniformly, or if they only used the most expensive (and best) DLC at the most needed portion of the part.
A question is whether the DLC coating is sputtered on evenly on the whole thing (unlikely) or just selectively coated to cut down on the cost.
If it is selectively and narrowly done, then a consideration is whether the coating may have missed a point of high stress.
Suppose for a second that there is a "bounce" in the piston as it is pressed up by the cam.
The bounce can come from many things, from a shock wave (valve closing, common rail accumulator charging, or phase change from the charge inside (hydroshock / cavitation bubble collapsing, etc. )
The maximum stress point may be not on the lead side of the cam, but further back from the leading edge which may not be as well coated / protected against friction / pressure.
The key is we need to know the initial failure point, not the wreckage that happens as the whole thing explodes.
Microscopic examination of the early failure candidates, when it is asymptomatic, so to speak, is the key.
Another hypothesis...
