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Should a Tractor always be run at PTO Speed

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crunch
Join Date: Jan 2007
Posts: 271 Niagara County, NY
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2020-08-16          199612


I am on my second tractor - first a JD4310 and now a NH workmaster25s. I typically run my tractors at what ever feels comfortable for the job. I rev it up for the brush chopper, snowblower, debris blower and other pto equipment. I moderately rev up for the backhoe to whatever gets the movement speed up and the strength I need for the job.

I have recently have been sharing attachments with some folks who are mechanical and chemical geniuses. They build their own equipment, hydraulics, rewire large dump trucks, etc. They do this just for their own use and for a challenge. They insist that diesels should always be run at full throttle, that's where they are most efficient. I know that the John Deere dealer favors higher rather than lower rpms.

I watched one of the family members operating his john deere compact tractor at full throttle loading an attachment on my trailer. It was annoyingly loud and excessively jerky when a fine touch would have been more appropriate. I reviewed my NH workmaster manual and it just states to operate the tractor between 1500 and 3000 rpms. What are your opinions? Do you operate at 3000 rpms full time?






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Should a Tractor always be run at PTO Speed

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2020-08-17          199617


Quote:
Originally Posted by crunch | view 199612
They insist that diesels should always be run at full throttle, that's where they are most efficient.What are your opinions?Do you operate at 3000 rpms full time?


No way!

First off let me correct the "efficient" aspect. From a quantity of fuel burned to horsepower generated point of view the most efficient speed is generally in the 1,300 to 1,500 rpm range, what is generally known as the "sweet spot".

In some cases however, WOT (Wide Open Throttle) is a necessity, PTO driven equipment as an example, WOT is required to achieve PTO speed on the output shaft. Another instance is heavy power draws, things like heavy Box Blade work that just plain requires the extra horsepower.

Horsepower is directly related to fuel burn rates, more power equals more fuel burned. From a common sense point of view why would you want to burn 40 hp worth of fuel when you only need 20 hp worth of work? That's not very efficient at all.


Best of luck. ....


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Should a Tractor always be run at PTO Speed

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chashm
Join Date: Oct 2013
Posts: 77 United States
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2020-08-17          199621


Interesting question. My tractor's (Cub Cadet 7305 with a Mitsubishi 3-cyl diesel) manual warns to not idle at less than 1500 RPM, although low idle is about 1000. The hints are that below 1500 proper engine temp can't be maintained.
540 RPM on the rear PTO is at 2376 engine RPM. 2000 RPM on the mid PTO is at 2632 engine RPM. Max RPM is 2980 no-load. Max HP is at 2750.

So, no real reason to run it faster than the PTO speed(s) unless you need max HP, highest ground speed or faster hydraulic actuation.
I usually run about 2000-2100 (I'm not using the PTO). I have a hydrostatic tranny so I don't need to fiddle with engine speed to change ground speed. And I'm not working the tractor for a living so time isn't money.
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As far as fuel consumption goes, the no-load consumption will be slightly higher at high RPMs, but the real fuel usage is under load. 20HP of load will have about 1/2 the fuel consumption of 40HP of load irrespective of engine speed.
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Engine wear/lifetime is largely determined by the number of revolutions, not really by 'hours'; at least my tractor's "hour" meter is really a 'revolutions' meter as it is a mechanical counter connected to the tach cable. So running the engine at higher-than-needed RPMs shortens the life of the engine, another reason to not run the engine faster than needed. ....


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Should a Tractor always be run at PTO Speed

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crunch
Join Date: Jan 2007
Posts: 271 Niagara County, NY
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2020-09-16          199695


Thanks Murf and Chashm, I'm heartened by your comments :) Makes me feel better about the way I drive my tractor!! ....


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