ozzie tractor
Gold Member
Doc_Bob said:
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.
Wide Open Throttle
- Thread starter Hooked_on_HP
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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
Platinum Member
Doc_Bob said:
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.
Tom_Veatch said:
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
Super Member
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.
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.
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.
