Wide Open Throttle

[sandman2234]

My statement was made considering the use of full horsepower from an engine, and if you need just a little more horsepower, will it help to run WOT.
If your already running at max torque/horsepower, by the plotted curve, and you merely increase rpm, it doesn't help anything. However if your running an item that is rpm sensitive, such as a pump, an increase of rpm might help, provided the peak output of the pump hasn't been achieved. Since a loader is rpm sensitive due to the pump output, it doesn't apply to what I was thinking, wether or not I explained it that way.

Bottom line, the faster you throw heavy metal objects up and down, the harder it is on the bearings that absorb that force and the faster metal fatigue will affect it.
Probably won't make a difference to any of you WOT people, but that is my thoughts, and I'm sticking to running at less than WOT.
David from jax

 

[KICK]

Unless you run an HST.
Bob

WTF is a HST?

is there a glossary of Tractorby Net terminologies that I can aquaint myself with before posting?


there is a term used in Engineering called BMEP, or Brake Mean Effective Pressure. generally you will find that any engine produces the most power with the least amount of fuel used at that certain RPM point.

that point where the most efficient BMEP occurs just happens to coincide with peak torque RPM.

go figure?

 

[KICK]

in other words, at peak torque RPM, you get the most with the least

 

[Doc_Bob]

WTF is a HST?

Hydrostatic transmission = HST.
Bob

 

[Soundguy]

WTF is a HST?
is there a glossary of Tractorby Net terminologies that I can aquaint myself with before posting?

While there may be a few TBN specific phrases and such, HST falls outside of this site, and rather into 'general' tractor terminology.. etc.

Doc_bob gave you the working definition.. etc.

Soundguy

 

[KICK]

While there may be a few TBN specific phrases and such, HST falls outside of this site, and rather into 'general' tractor terminology.. etc.

Doc_bob gave you the working definition.. etc.

Soundguy

makes sense. thanks

 

[ozzie tractor]

the reason an engine gets its best fuel economy at peak torque is because thats where it is most efficient. as the efficiency goes up on a motor the only thing it will do is create more torque.
bear in mind torque is a twisting force. 1 of only 2 things an engine can do.this is the amount of twist it can create at the crank. simply it is how hard a engine can pull. the other thing an engine does is rotate the crank at speed.
Horse power is a RATE of work, that is how much work is done in a set time, it is a mathematical equation which includes the amount of torque a motor produces and also the rpm of the motor.
diesels are unique in the fact if you are using 40hp they will use 40hp worth of fuel. if the efficiency of a 50hp and a 80hp motor are the same, at 40hp they will use the same fuel. just remember efficiency drops as rpm increases past peak torque. so if you have to rev the 50hp motor hard to make the hp required then its efficiency and thus fuel economy will suffer

 

[KICK]

the reason an engine gets its best fuel economy at peak torque is because thats where it is most efficient.

isn't that saying the same thing twice?

doesn't explain why its most efficient at that point, just says that it is.

 

[Doc_Bob]

the reason an engine gets its best fuel economy at peak torque is because thats where it is most efficient. as the efficiency goes up on a motor the only thing it will do is create more torque.
bear in mind torque is a twisting force.

I run at 1200-1400 or less, since my peak torque is at 1400 rpm and my peak HP is at 2200. I can do this with a manual transmission. One of a number of advantages of this setup.
Bob

 

[ozzie tractor]

isn't that saying the same thing twice?

doesn't explain why its most efficient at that point, just says that it is.

there are litraly thousands of things which affect the efficiency of a engine, to sit down and work out why it is efficient at that point would be a huge waste of time. the peak torque is not the reason for the efficiency it is the proof of it.

 

[ozzie tractor]

I run at 1200-1400 or less, since my peak torque is at 1400 rpm and my peak HP is at 2200. I can do this with a manual transmission. One of a number of advantages of this setup.
Bob

im with you on this one, thats the reason why my 125 has an economy PTO. why do i need to rev the daylights out of my tractor when its got more than enough HP at 1500RPM.

 

[Tom_Veatch]

I run at 1200-1400 or less, since my peak torque is at 1400 rpm and my peak HP is at 2200. I can do this with a manual transmission. One of a number of advantages of this setup.
Bob

If you're running at or below peak torque rpm that means if rpm decreases under load, torque also decreases. But if you are running above peak torque rpm, then if rpm decreases under load, the torque increases. Of course the amount of increase or decrease would depend on the shape of the torque vs rpm curve for the engine. But, it seems like there'd be less tendency to lug the engine down if you run a little above peak torque.

By the way, what is the typical shape of the torque/rpm and power/rpm curves for a diesel? Are they fairly flat with broad peaks or do they have sharp peaks? If sharp, I'd think running on the fast side of the peak would be advantageous. If flat and broad, it probably doesn't make much difference.

 

[Doc_Bob]

If you're running at or below peak torque rpm that means if rpm decreases under load, torque also decreases. But if you are running above peak torque rpm, then if rpm decreases under load, the torque increases. But, it seems like there'd be less tendency to lug the engine down if you run a little above peak torque.

I run at peak torque but not when I am doing anything that requires high rpm and the risk of lugging, like using my rotary cutter. 1300 RPM is very nice for humming along in 6th gear when traveling over a long distance. Or moving a bucket full of composted wood chips. No need to run at 2200 rpm. And with light loads, and high toque, I have more than enough power to get the job done. I don't have the need to run at high RPM since my TN70A has excess HP and torque for light duty applications.
Bob

 

[Farmwithjunk]

Keep in mind that we AREN'T talking about doing the same exact thing, over and over again. Tractors (and their engine) get used for a wide variety of uses. Not JUST the ones YOU use your tractor for. There is no constant to the "full throttle all the time". No 2 models of tractors are all the same. What seems carved in stone for one engine is vague at best with another.

Bottom line for me anyway, you need not use any more "motor" than what the task at hand requires. 2 tractors I own have 35 and 27 years of fairly hard use behind them. I've always maintained them as well as I possibly can. They've been unusually good tractors, both of them. Still, they've been farm tractors their entire life. Most 35 year old farm tractors have had an engine overhaul or two. This pair is ready for another 35 and 27 years. All the time I've had them, they've never been abused, motor wise. No lugging to speak of. But I also NEVER over-rev them. No wide open, hammer down throttle unless it NEEDED to be hammer down.

When I'm doing something that requires a lot of throttle up/throttle down cycling of the motor, I'll find a happy medium about 1/2 way as "low throttle". I avoid cycling a motor from idle to full throttle and back again repeatedly. (A foot throttle, and learning to use it SMOOTHLY is a big help on this one)

In short, fairly constant throttle, and no more than it needs. Just because it will probably take a hammerin', you don't ALWAYS need to hammer away.

Works for me, your results may vary.

 

[cp1969]

By the way, what is the typical shape of the torque/rpm and power/rpm curves for a diesel? Are they fairly flat with broad peaks or do they have sharp peaks? If sharp, I'd think running on the fast side of the peak would be advantageous. If flat and broad, it probably doesn't make much difference.

You see both kinds. Engines that are fuel-limited (such as a de-rated engine) have flat-top torque curves because the engine management system cuts off fuel to make sure the engine doesn't develop more torque than a specified number. There can be a number of reasons for this but it is usually because some drive train component is torque-limited.

Other (air limited) engines can have marked peaks. Cat & Mack truck engines have steep slopes, which is known as "torque rise". In fact, some of their engines make more horsepower at reduced rpm than they do at rated rpm because the increase in torque more than makes up for the loss in rpm.