Air Cooled Engine Life

[kotzy]

I have a sears garden tractor with a ten horsepower Tecumseh engine, the machine is 35 years years old. The engine was apart for rings at 17 years of age, and it may be due for rings in a year or two. When i pulled it apart I was amazed at the lack of wear and general condition of the engine, in spite of the fact that except for a change of oil at 50 hours it ran that time on only make up oil addition. It was not rebored the crank pin and rod was not scratched. We will see what it looks like next time. By the way it plows the garden cut the grass blows snow and I run it up against the govenor.

 

[1sttruck]

"Well, this much I do think I know. Even those who used straight 30 in the air cooled generators had shorter engine lives, or outright failures. Those who used thicker synthetics had fewer problems."

HERESAY ! EVERYONE AT BITOG KNOWS THAT THINNER OIL IS ALWAYS BETTER :^) Acutually it makes sense considering the use and possibly the head temperatures. You may need liquid cooled units, or at least ones with better heat dissipation. Running a fan to blow air across the engines, checking with a thermometer, and in extreme situations using a water mist for cooling, might help.

"My local repair shop is still full of used gensets with worn out engines. In my case 2 days between oil changes with red cap was the answer."

48 hours of use roughly correlates to 3k miles at highway speeds, which seems reasonable, rather, HERESAY, EVERYONE AT BITOG KNOWS THAT SYNYTHETIC OIL IS GOOD FOR OVER 20K MILES :^)

 

[Bill Kapaun]

A genset/pump working under full load is MUCH harder on engine/oil than a car cruising down the highway!
Apples & oranges.

 

[1sttruck]

"A genset/pump working under full load is MUCH harder on engine/oil than a car cruising down the highway!
Apples & oranges."

Top speed on my old Suzuki 1100 was about 140 mph, and I recall crusing extended distances at 110mph, and hitting at least 120 mph weekly. In the early 70s as a wide eyed kid a Porsche dealer use to tolerate me looking at the cars and taking brochures. The 911 cars wwere always interesting as the maximum crusing speed was always the top speed. In Spain the 750 BMW bike that I was driving was topped out at about 125mph, and I still needed to move over for the fast traffic.

I agree though that for cars in the US, it's apples and oranges.

 

[Lazy JW]

Quote:

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I think a lot of the problem is that people purchase the bare minimum genset that's designed for occasional use and try to use it in a "heavy commercial" manner. Their intentions were good, thinking they might only use it a few hours at a time on rare occasion. The unit ends up being used for days and just isn't "up to snuff".

Briggs for example, doesn't recommend their engines be used over 85% of their rated power.
http://www.tewinc.com/pdf/201400.pdf
Add the inefficiencies of the alternator and a lot of units are simply "working their guts out" when producing at maximum rates.

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Agreed. An 8 hp Briggs developing full power at 3600 rpm has a BMEP of just over 94 PSI. I have a copy of "The Nebraska Tractor Tests from 1920". A bit of research there shows the vast majority developing BMEP just under 100 psi at full power. Tractors are classed as "heavy duty" engines and are expected to be able to develop 85% of full power for long periods of time. They were subjected to a 10 hour drawbar run at this power level during testing. Keep in mind that nearly all of those tractors were water-cooled. Put an air-cooled Briggs engine through that level of power generation and it just may have issues (probably). From what I can gather it seems that much over 100 psi continuous BMEP requires a lot of cooling capacity and a well designed lubrication system. Neither of which is to be found in an 8 hp Briggs.
Joe