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
Hypothesis #1
Pump failure originates at the point of maximum friction / contact pressure between the cam, roller, and piston.
Failure is at the coating first, then become catastrophic.
If I were the Chief Engineer, I would consider the following design changes in the interim while we figure out what is going on:
Increase the diameter of the roller by a small amount.
That would reduce friction and also contact pressure.
Additional is to lower the aggressiveness of the cam.
Score a fine spiral trench on the piston for the roller so as to "sweep" the roller and offer abrasive particles a way out, and also to allow lubrication to flow.
That would have to be done before any coatings are applied.
The cost factor for doing this will be one machine step extra, though the fine polish, beveling will be not straightforward --- need to be very carefully done, with severe QC implications for doing it out of spec.
Without knowing Bosch's machining cost structure, I am going to guess that the extra step can be done for .1 Euros --- about .12 cents US.
That will be my interim solution.
Pump failure originates at the point of maximum friction / contact pressure between the cam, roller, and piston.
Failure is at the coating first, then become catastrophic.
If I were the Chief Engineer, I would consider the following design changes in the interim while we figure out what is going on:
Increase the diameter of the roller by a small amount.
That would reduce friction and also contact pressure.
Additional is to lower the aggressiveness of the cam.
Score a fine spiral trench on the piston for the roller so as to "sweep" the roller and offer abrasive particles a way out, and also to allow lubrication to flow.
That would have to be done before any coatings are applied.
The cost factor for doing this will be one machine step extra, though the fine polish, beveling will be not straightforward --- need to be very carefully done, with severe QC implications for doing it out of spec.
Without knowing Bosch's machining cost structure, I am going to guess that the extra step can be done for .1 Euros --- about .12 cents US.
That will be my interim solution.
