Rpm's and long downhill runs

[Rockbadchild]

Have owned a tractor for serval years now, and forgive me IF I am wrong, but I have fallen unconsciously into using RPM and HST according to conditions of use (need) .... If I need more RPM I throttle up, if I need less RPM I throttle down, if I need more HST engagement I press pedal harder, if I need less engagement I use less pedal pressure..... With the cost of fuel getting stupid it would seem to using less RPM (power) there might be more savings in fuel than cost of rebuilding tractor is some far distant future maybe for the beneficiaries of my trust...

ya pointed out earlier on, the only thing with running your tractor at low rpm is it will increase the carbon deposit in the exhaust ... I don't know if they are all like that but my Massey Ferguson dealer worn me very clearly that it happen frequently that people who run excessively they MF tractor at low rpm their exhaust plug right up.

 

[finn1]

Valve train separation design point is generally at 150% of rated speed and power. Another words, if the manufacturer rates the engine at 2600 rpm, you’re safe running the engine downhill at least to 3900 rpm, if not more, almost indefinitely.

Friction and pumping work increase rapidly above rated speed, so you get best engine braking at rated speed or above.

An exhaust brake is commonly used on premium engines, and some pickup truck type engines use either an exhaust butterfly or a turbocharger wastegate as a poor man’s exhaust brake. All these devices work best at higher engine speeds, wher airflow is greatest.

 

[Bavarian]

Valve train separation design point is generally at 150% of rated speed and power. Another words, if the manufacturer rates the engine at 2600 rpm, you’re safe running the engine downhill at least to 3900 rpm, if not more, almost indefinitely.

Friction and pumping work increase rapidly above rated speed, so you get best engine braking at rated speed or above.

An exhaust brake is commonly used on premium engines, and some pickup truck type engines use either an exhaust butterfly or a turbocharger wastegate as a poor man’s exhaust brake. All these devices work best at higher engine speeds, wher airflow is greatest.

Your theory works only on gear driven machinery. Not on hydrostats.

 

[crazyal]

I don't run my diesel truck at 2500 rpm all the time so why would I run my Kubota at that speed all the time? In fact I often run it between 1800 and 2000 rpm. That seems to be the sweet spot for the engine.

 

[Bill Guenthner]

Have owned a tractor for serval years now, and forgive me IF I am wrong, but I have fallen unconsciously into using RPM and HST according to conditions of use (need) .... If I need more RPM I throttle up, if I need less RPM I throttle down, if I need more HST engagement I press pedal harder, if I need less engagement I use less pedal pressure..... With the cost of fuel getting stupid it would seem to using less RPM (power) there might be more savings in fuel than cost of rebuilding tractor is some far distant future maybe for the beneficiaries of my trust...

You will not burn much more fuel at 2500 RPM than you will at 1500 RPM given the same load. At low RPMs you’re starving your hydraulic pump and putting excess strain on the entire system. You control tractor speed with the L/M/H range selector and the pedals, not with engine speed.

 

[LouNY]

Valve train separation design point is generally at 150% of rated speed and power. Another words, if the manufacturer rates the engine at 2600 rpm, you’re safe running the engine downhill at least to 3900 rpm, if not more, almost indefinitely.

Friction and pumping work increase rapidly above rated speed, so you get best engine braking at rated speed or above.

An exhaust brake is commonly used on premium engines, and some pickup truck type engines use either an exhaust butterfly or a turbocharger wastegate as a poor man’s exhaust brake. All these devices work best at higher engine speeds, wher airflow is greatest.

You will not burn much more fuel at 2500 RPM than you will at 1500 RPM given the same load. At low RPMs you’re starving your hydraulic pump and putting excess strain on the entire system. You control tractor speed with the L/M/H range selector and the pedals, not with engine speed.

I wouldn't let either of you run my lawnmower much less my tractors.
If anyone ran my equipment that way they would be fired on the spot and left to walk.

 

[MossRoad]

I wouldn't let either of you run my lawnmower much less my tractors.
If anyone ran my equipment that way they would be fired on the spot and left to walk.

Are any of your tractors HST?

 

[WranglerX]

You will not burn much more fuel at 2500 RPM than you will at 1500 RPM given the same load. At low RPMs you’re starving your hydraulic pump and putting excess strain on the entire system. You control tractor speed with the L/M/H range selector and the pedals, not with engine speed.

Yes... BUT tractor tells me when its unhappy with power applied for job I'm trying to do....

 

[Bill Guenthner]

Yes... BUT tractor tells me when its unhappy with power applied for job I'm trying to do....

How does it “tell” you? The hydro starts to whine? The engine bogs down? I know what my tractor can do and I don’t try to do more than that.

 

[WranglerX]

How does it “tell” you? The hydro starts to whine? The engine bogs down? I know what my tractor can do and I don’t try to do more than that.

Like you I know what my tractor can do..