Guys, here are pics of the Thermo King APU Tripac muffler, with part numbers. I'm telling you this muffler is super quiet. It's used for semi truck generators for running overnight in crowded truck stops while the truckers sleep. They have to meet sound requirements to be legal by DOT. I'm a Class A semi driver and I've used them, I've walked next to them while running, and I've slept with windows open in the truck while it's running. They are quiet. And the diesel engine that runs is bigger and way more loud than a little 440 clone or 670 Vtwin, guaranteed. I also am a mechanic and I've worked on these APU's, these mufflers are legit. Expensive, but legit.
You can look up and find the Stanley versions, Walker versions....not the same at all. We've used them on trucks and they are louder. The trucks would come back the next week and we'd be installing OE Thermo King mufflers at twice the cost. The drivers hated the $69 versions. The cheaper versions are made in China. The OE version is made in the US and is Stainless.
I haven't used one on a cart yet, but I will soon. The Stanley version I got from Tractor Supply is good enough for my cart. I have a decibel meter, maybe after work tonight I'll get some readings for you.
Here is the Thermo King website. Read about how much effort they put into making these quiet.
https://www.thermoking.com/na/en/roa...SAAEgKBkvD_BwE