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
The crux of the problem in the design defect IMHO.
I've stated all along that IMHO, this has been a defective design problem with the roller, cam and follower interface. This engineer has captured the crux of the design failure, when run at 2000 bar pressures with expensive to replace when they fail piezo injectors.
I do not think the plunger running in an aluminum bore is the main issue. The big problem in my view is that the interface between the cam and the follower has a roller with line contact against the cam and the force distribution around that roller doesn't give much assurance that the roller will rotate rather than slide. (Friction from roller to cam acting in the direction of the roller spinning; friction from roller to follower acts in the direction of holding it still and there is no mechanical advantage for it to roll rather than slide against the cam.)
The CP3 does not have this situation.
One of the sub-forums has a thread concerning dissection of the CP4.1 HPFP and its various shortcomings.
__________________
Brian P.
2006 Jetta TDI 5-sp, Spice Red, Unitronics stage 1, 0.681 5th gear, and a roadrace bike on the trailer
That design element right there, is the definition of "fragile" Far too critical a condition based on fuel, and more so, operating this HPFP at near limit design fuel pressures, regardless of lubricity of the fuel. Run these pumps hard, near their operating limits with heavy or full throttle applications, and the pump will die in relatively short order.
I've stated all along that IMHO, this has been a defective design problem with the roller, cam and follower interface. This engineer has captured the crux of the design failure, when run at 2000 bar pressures with expensive to replace when they fail piezo injectors.
I do not think the plunger running in an aluminum bore is the main issue. The big problem in my view is that the interface between the cam and the follower has a roller with line contact against the cam and the force distribution around that roller doesn't give much assurance that the roller will rotate rather than slide. (Friction from roller to cam acting in the direction of the roller spinning; friction from roller to follower acts in the direction of holding it still and there is no mechanical advantage for it to roll rather than slide against the cam.)
The CP3 does not have this situation.
One of the sub-forums has a thread concerning dissection of the CP4.1 HPFP and its various shortcomings.
__________________
Brian P.
2006 Jetta TDI 5-sp, Spice Red, Unitronics stage 1, 0.681 5th gear, and a roadrace bike on the trailer
That design element right there, is the definition of "fragile" Far too critical a condition based on fuel, and more so, operating this HPFP at near limit design fuel pressures, regardless of lubricity of the fuel. Run these pumps hard, near their operating limits with heavy or full throttle applications, and the pump will die in relatively short order.
