BradSt
ArboristSite Operative
When talking about expansion chamber equipped 2 strokes, this is pretty much the case, but not 0PE that just has a muffler at the exhaust port. That exhaust setup severely limits a 2 strokes output (I know you know this, and this isn't directed at you)A four stroke only fires and makes power every other rotation, therefore it takes a motor with nearly twice the displacement to produce the same power as a two-stroke
Take these 2 trimmers for example...the FS91 4 mix and the FS94 2 stroke...basically the same power output, with the edge to the FS91. The FS91 is only 10% larger in displacement. The 4 mix trimmer does weigh about 20% more though, and you will eventually have to lash the valves.
The 4 mix was developed years ago, when Stihl thought they were going to have a hard time meeting emissions requirements with their traditional 2 strokes (before they implemented strato designs). I'm pretty sure they licensed tech from Zenoah to produce some of their strato 2 strokes, and they're obviously meeting EPA requirements. IMO, they kept the 4 mix because they spent a lot on R&D, and they were working well and have been widely adopted. The 4 mix BR800 is one of the top dogs in backpack blowers. Significantly lower fuel consumption than the equivalent Echo 2 stroke. I believe that is their only new 4 mix engine in years.