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
A way to test the cavitation hypothesis
At this point, it is time to turn to experimental science rather than paper and simulations.
Simulations used during the design up until the 2010 model year pumps were design / manufacturing process frozen have probably failed the engineers as they were suppose to test and simulate for cavitation using a variety of fuels and contaminants during the design / engineering / validation phase.
A way to test the cavitation hypothesis will be to set up a number of benches with reference fuel, with samples arrayed as follows:
A) Reference fuel / reference operating conditions
B) Reference fuel w/ contamination known to be sufficient to cause cavitation / failure
C) (B) with a pump ahead of CP 4 to raise the pressure so that it should be handily below the cavitation threshold.
D) (B) with pump operated at higher rpm / volume believed to be sufficient to cause visible cavitation damage after (x) hours.
That kind of a bench would very quickly identify whether cavitation is a rat hole, so to speak --- after sufficient hours are run on the bench, the pumps can be taken apart and the surfaces inspected to see what damage is done.
Further thoughts:
Cavitation is detectable acoustically.
Need to fit accoustic, plus temperature and other sensors to test rig.
Normally you can hear cavitation --- so that might be a good way to use ONE pump, vary the rpms etc. and listen for the telltale bubble collapse sound of cavitation --- to precisely detect the point long before any damage is done.
Side note:
Can insufficient fuel pressure from tank / feed / volume also cause cavitation?
It would certainly raise the load on the pump...
At this point, it is time to turn to experimental science rather than paper and simulations.
Simulations used during the design up until the 2010 model year pumps were design / manufacturing process frozen have probably failed the engineers as they were suppose to test and simulate for cavitation using a variety of fuels and contaminants during the design / engineering / validation phase.
A way to test the cavitation hypothesis will be to set up a number of benches with reference fuel, with samples arrayed as follows:
A) Reference fuel / reference operating conditions
B) Reference fuel w/ contamination known to be sufficient to cause cavitation / failure
C) (B) with a pump ahead of CP 4 to raise the pressure so that it should be handily below the cavitation threshold.
D) (B) with pump operated at higher rpm / volume believed to be sufficient to cause visible cavitation damage after (x) hours.
That kind of a bench would very quickly identify whether cavitation is a rat hole, so to speak --- after sufficient hours are run on the bench, the pumps can be taken apart and the surfaces inspected to see what damage is done.
Further thoughts:
Cavitation is detectable acoustically.
Need to fit accoustic, plus temperature and other sensors to test rig.
Normally you can hear cavitation --- so that might be a good way to use ONE pump, vary the rpms etc. and listen for the telltale bubble collapse sound of cavitation --- to precisely detect the point long before any damage is done.
Side note:
Can insufficient fuel pressure from tank / feed / volume also cause cavitation?
It would certainly raise the load on the pump...
