Trimmer engines CCs are start about 26 and go up as high as 32cc. Usually it's not the CCs of the engine, but quality of the trimmer. meaning if serviced correctly the engine usually outlasts the head, shaft, clutch, and the cable running the head. Problem with trimmers is the time they set around not in use. This can kill trimmer quicker than over use due to the fuel today has lot of alcohol mixed which retains water that rusts and plugged carb. small passages up.

You are also trying to compare ohv 4 stroke, with a 2 stroke
and real h.p. ratings can be fuzzy advertising math.
Looking at the old Briggs 10-12 h.p. engines, slap a set of
overhead valves on them, you can add 5 or more h.p. with
the same displacement. Even with that said, an Identical
engine could be rated with a h.p. varying 2-3 h.p.

I guess my question is more to similar engine to similar engine, just of different size. The Echo PAS engines and Stihl KombiSystem engines are all 2-cycle engines as I understand it. Would a Brand A 28cc engine be the same (in terms of power and whatever) as Brand B's 28cc engine?

No the Stihl unit you mentioned is a 4-stroke unit

Okay, well. How do the Echo PAS-266 and Stihl KM90R compare? The Echo is 25cc and the Stihl is 28cc. "Upper" end Echo vs "lower" end Stihl...

I'm looking more for generalities and theory. Does an Echo 25cc engine produce less power than a 28cc Stihl? Is there a straight number to number direct comparison?

I think I'd research durability and reliability more than CC's.
Mike

Wondering if you're not approaching this from the wrong direction? You seem interested in getting Max HP, but in a string trimmer the ones you mention all do pretty much what they're supposed to do-trim.

Are you planning on putting a saw blade or mini tiller on the unit? Might need more "oomph" for that, though, personally, I'm not in favor of "multi function" tools.

Questions like ease of replacing line, balance, etc. might be more appropriate. also, "generally," 4 cycle engines are easier to live with than 2 cycle. However, todays "mystery fuel" does present challenges to any small engine that isn't run a lot. There are arguments that the 2 cycle oil added to the gas helps offset the mystery fuel. Personally, I add Stabil or equivalent to every can of gas I purchase for small engine use.

Good luck,

Ev

I am in fact looking at a multi-use tool, but that's besides the point. I am simply trying to understand engines and how companies represent them. I have done research into durability and reputation and weight and whatever else. What I do not understand is how one company twp "professional" lines from different companies can have drastically different displacement for comparable prices. Are two 28cc engines the same?

cbiscuit, I "feel" for your confusion about HP ratings and things. Do a search here and you'll find way more than you ever wanted to about the topic.

FWIW, a while back, my 22HP briggs was replaced under warranty by briggs. They didn't have a 22 and shipped out a 26HP. The local Briggs/Kohler/etc. "factory certified" shop that did the work were curious. They had the two engines "side by each" and were identical. Totally and completely identical. I was there and could not see any difference, same carb, etc. etc.

I posted about it at that time and a lot of folks seemed to think that the big difference was the decals. If you get into it and research what HP means in small engines, they could well have been right.

Good luck,

Ev

I was there and could not see any difference, same carb, etc. etc.

maybe the carb. was jetted differently and the torque band was taken at different RPM?

Thanks!! This seems to answer it. It seems there is more than just horsepower when rating engines. Torque is a huge part too! Thanks Exmar!