Engine speed vs. engine life?

[JDgreen227]

The last two new self propelled push mowers I have purchased, one is powered by the Chinese Kohler 173cc and the other is a Briggs with 6.75 torque rating, both were too slow for me. I speeded up both engines to gain about 1/2 mph additional ground speed by bending the tabs that springs were connected to by the carbs. Fuel consumption doesn't seem to be affected and with the engines speeded up both mowers cut better and are better suited to my walking pace.

Do they rate push mower engines by hp and torque as delivered to the consumer, or are the ratings created by running the engines at maximum rpm which would certainly shorten engine life? I do wonder if the two engines I noted about were running anywhere near the maximum rpm as delivered.

 

[art]

chances are they just used a horsepower formula of boreXstroke to get the horsepower.

 

[JDgreen227]

chances are they just used a horsepower formula of boreXstroke to get the horsepower.

A few years ago there was a huge class action suit filed against mower companies who were claimed to have misrepresented hp and torque figures for engines.

My step mom just purchased a new Sears mower that has the same 190cc Briggs my Brute mower uses, hers is 7.25 torque vs. the 6.75 torque mine has. If B&S used the formula you note, why would hers be rated higher? Bore and stroke are identical.

 

[art]

A few years ago there was a huge class action suit filed against mower companies who were claimed to have misrepresented hp and torque figures for engines.

My step mom just purchased a new Sears mower that has the same 190cc Briggs my Brute mower uses, hers is 7.25 torque vs. the 6.75 torque mine has. If B&S used the formula you note, why would hers be rated higher? Bore and stroke are identical.

That's a good question and I don't have an answer for you! Many of the manufactuer's are just giving us the cc's of engines used on small mowers, snow blowers as well as tillers. I think this way they might be getting away from stating horsepower and torque.

Back to the original question, I have seen many state here metal is metal. This is just mot the case as many engines are better built and anyone that has worked with engines will find the same. Better metal allows higher RPM wih longer life. The design will also dictate the potential life. Crude castings even at low RPM limits the life!!!!

 

[Mickey_Fx]

chances are they just used a horsepower formula of boreXstroke to get the horsepower.

????? You are kidding aren't you? No such thing. There is no relationship between power and engine displacement. Maybe you're thinking the calc for HP consisting of torque and speed.

Going back in time:

* Rumley made a 2 cyl tractor engine, 1,800 CI displacement with about 75 HP. That's 24 CI/HP.

* Model T had a 177 CI engine with 20 HP. 8.85 CI/HP Followed by

* Model A had a 200 ci engine with 40 HP. 5 CI/HP Followed by

* Later Ford flathead V8 was 239 CI if I recall and rated 100 HP. 2.39 CI/HP

Today, almost any 4-banger auto engine rated > 1HP/CI

Yes, small engine mfgrs have changed what they report about engines. Now most likely to see displacement being reported. The suit from several yrs back got too costly for mfgrs to report HP rating especially when they were most likely inflated. If auto mfgrs ever get hit with a suit like the small engine mfgrs, likely outcome will be no advertised HP rating.

Personally, never did pay any attention to advertised HP ratings.