Advice needed - filament that would endure vibration for a long run  

RE:

ABS/ASA would have been my first suggestion, but it looks like you already tried that.

PLA would be out of consideration due to UV and temperature.

Perhaps PC Blend or PC Carbon-fiber would be a candidate.  Nylon, maybe?

If I were designing this, I might work around the issue by increasing the thickness/reinforcement around the stress points such as the hole(s) for the bolt(s) that mount the print to the engine.

RE: Advice needed - filament that would endure vibration for a long run

That stress point pictured is where the plastic doesnt move as it has a metal bracket against it with the section next to it without the bracket support.

Either do as jsw suggests and reinforce the areas with part design to dissipate stresses in those areas (thicker sections, rounded transitions etc) or try an alternate which would be to mount using rubberised standoffs to reduce the vibration passed to the part in the first place.

RE: Advice needed - filament that would endure vibration for a long run

I´d have suggested ASA, too, but I have no experience with Prusa´s ASA, I use Spectrum ASA 275 which is the most solid and resistant stuff I know. 

Judging from the pics it looks like the housing is directly touching the screw? If so, I´d try to de-couple the housing from the screw by means of a rubber insert, taking up a lot of the vibrations. In any case I would increase the number of vertical hull lines around the screw hole to at least 4 - standard settings will probably be 2. As you are printing the housing vertically, it may further help to reduce layer height to .1mm and to leave some infill, e.g. 80%, and not to print as a solid piece; the infill gives structural support better than a 100% solid print in my experience.

Regards

Chris

RE:

In this case, probably the best option would be a nylon filament. Flexible enough to endure vibrations better than ASA or PC and resistent to high temperatures or UV.  

Which Nylon ?..  That's another question and not an easy one,  Some.nylons are filled with CF or GF fibers and tend to warp less when printed but they're also more rigid and possibly prone to cracking if stressed too much. 

RE:

TLDR: Try PCTG ... or simply PETG.

ASA can be tricky regarding layer adhesion. 

Your best bet for a material which can cope well with both outdoors conditions and vibrations would be propbably Nylon, possibly carbon fibre filled. Creeping can be an issue whith nylon however carbon fibers mititage that to some extend and if not strong forces are impacting on the printed piece contiuously, it is not a big issue. 

Second best and much easier and cheaper would be either PETG or possibly a better alternative: PCTG. I have bought the latter just now but have no experience yet. It should have superior layer adhesion and impact resistence to PETG but share its general outdoor suitability. The main downside of PETG and PCTG is the lower heat stability but unlike with PLA it should do just fine out in the sun. 

PC-Blend is not perfect if you are looking for something that copes well with UV light, even though it is otherwise super robust. It is also difficult to print. 

ABS doesn't age well out in the sun due to UV light.