I can't remember who makes Towers engines, but the muffflers used to be huge...however if you're thinking of getting a Tower engine (any engine) and flying it now to put on a twin later, with a new engine..... I wouldn't...on your twin you want two of the same brand and size engines, with roughly the same run time on them......One of your new engines will be weaker than the other...don't ever try to bring the weak engine up to the stronger one..instead adjust the strong engine to the weak one..in other words the weak engine is the master