Why would the generator company void warranty.....
I have read a lot of yammer about back pressure. And I can imagine installations where it might actually be important (IE: Generator mounted amid-ships as mine is and exhausted out the back, that's a lot of pipe already) it is true that a elbow adds way more pressure than the same amount of straight pipe.
Plus in a heavy rain if geenrator not running,,, Well the pipe is open to the top (Tough I doube much gets in the metal pipe, more likely to run down the inside of the black pipe and drip onto the ground)
The big thing is torquing the exhaust pipe and breaking the manifold I'd suspect.
This would indicate both an improper mount of the Gen-turi and of the exhaust pipe in my opinion, but I'd guess that is their big worry.
Proper mounting, no problems.
I do stress I'm guessing why the generator companies warn about them.
Might also be a CYA thing Two ways "Any modifications may void....." is one.
The other is the occasional stories I read with like (NOTE: this version of the story is made up but there are legit stories like it) DEATH ON THE INFIELD.
Indy, date,, A group of campers in the infield campground at the Indy raceway were found dead this morning, Premlimuary reports say they were killed by exhaust from their generator which they kept on all night to run their air conditioner and aux beer cooler........
"Well, the reason we don't build them with a "Through the roof" exhaust system is the danger of damage to the generator" said a spokesman for RV's R Us.
As I said, thius is a made up story, and the last line I've never seen.. But .. Well, passing the buck is an American Passtime don't you know.