Possible to over-rev my diesel tractor?

[Buggs67]

This may be a dumb question but does the tractor have a rev limiter? (I'm going to try to ask Kioti but they are usually not too helpful. They repeat what's in the manual).

I was driving my tractor up a hill (on road) and advanced the throttle to rev at the PTO arrow (2600 rpm) When the hill leveled out and going got easier I looked at the Tach and I was turning almost 3,000 rpm. I throttled down and had no problems for the rest of the day. But I've noticed under load the RPM drop and I wasn't sure if the throttle stop is set to limit revs to safe levels or if there is a rev limiter like my cars have.

Also, would I have more power to the rear wheels if I operate in 2 wheel drive. On the level I can move snow and snowbanks in high range until it gets real deep. I thought if I changed to 2wd I might have more power to the rear.

Thanks in advance.

 

[kevin37b]

Yes it has a governor on the injection pump that will control the RPM . The rest of your post makes no sense whatsoever ?

 

[Gary Fowler]

This may be a dumb question but does the tractor have a rev limiter? (I'm going to try to ask Kioti but they are usually not too helpful. They repeat what's in the manual).

I was driving my tractor up a hill (on road) and advanced the throttle to rev at the PTO arrow (2600 rpm) When the hill leveled out and going got easier I looked at the Tach and I was turning almost 3,000 rpm. I throttled down and had no problems for the rest of the day. But I've noticed under load the RPM drop and I wasn't sure if the throttle stop is set to limit revs to safe levels or if there is a rev limiter like my cars have.

Also, would I have more power to the rear wheels if I operate in 2 wheel drive. On the level I can move snow and snowbanks in high range until it gets real deep. I thought if I changed to 2wd I might have more power to the rear.

Thanks in advance.

I think what you are asking is does it take some more engine power to turn 4 wheel drive vs 2 WD. The answer is yes it take a very small amount of power to engage the front wheels however you get about 60% or more in additional traction. To see how much power it takes to rotate the front wheels, just use the FEL to raise the wheels off the ground and then turn by hand. It requires very little force to turn them by hand so that is what your engine would have to contend with. It is much more efficient to use 4 WD than 2 WD when on slippery surfaces. You don't want to have 4 WD engaged when on hard surfaces like concrete, asphalt or even very hard dirt because the front wheels are designed to pull a bit faster (about 5%) than the rear so they are constantly spinning a bit which will be hard on the transfer case if they cant spin a bit freely like they can on soft dirt and grass.

 

[Gary Fowler]

As for your engine speed, check your OEM for actual no load speed. The throttle should be set so that when setting still under no load the full no load speed is achieved and no more. Yes the engine will stall down a bit from that no load speed when you put more load on it than the engine can compensate for but this is how it is supposed to work. Assuming that you have an HST transmission and you are climbing a hill and the RPM start to fall off considerably, then back off the HST till engine speed returns to approximately no load throttle speed (within 500 RPM).

With regard to your over revving, this is easy to do in a diesel engine if you are going down hill as it has very little back compression as is common with gasoline engines. This is why many over the road truckers use a JAKE BRAKE which restricts the exhaust to give them some engine braking. A diesel can over rev and damage it if allowed to run a lot over the rated speed. In your case, I don't think 400 RPM is enough to worry about, but you can use the HST to help slow down by just decreasing the pedal pressure a bit or if highly over revving, just use the brake lightly to slow the descent rate.

 

[ksbrdmkr]

The throttle position corresponds with the engine rpm only at no load conditions. The governor adds fuel attempting to maintain the no load rpm. If you add throttle on an increasing load when the load lessens the rpm will increase. Will the governor allow max fuel at half throttle gets in to a design question.

 

[KennyG]

With regard to your over revving, this is easy to do in a diesel engine if you are going down hill as it has very little back compression as is common with gasoline engines. This is why many over the road truckers use a JAKE BRAKE which restricts the exhaust to give them some engine braking.

Actually, what a jake brake does is open the exhaust valve early so the compressed gas in the cylinder is released instead of forcing the piston back down, like it ordinarily does on the power stroke. That way you get the engine braking from the compression stroke without the recovery of the power stroke. I'm really not sure that compression braking is any different with diesels and gas engines. Heavy diesel trucks just have more need of powerful braking. I think a jake brake would have similar effects on gas engine.

 

[RalphVa]

Don't think you can overrev a diesel. They have governors to restrict the speed.

Think what you need in pushing snow is traction, not power. I'd keep it in 4wd. In 2wd, you only have 2 wheel brakes, too.

Ralph

 

[Gary Fowler]

Actually, what a jake brake does is open the exhaust valve early so the compressed gas in the cylinder is released instead of forcing the piston back down, like it ordinarily does on the power stroke. That way you get the engine braking from the compression stroke without the recovery of the power stroke. I'm really not sure that compression braking is any different with diesels and gas engines. Heavy diesel trucks just have more need of powerful braking. I think a jake brake would have similar effects on gas engine.

I have never seen a Jake brake(patented name) that was hooked to any part of the engine, they are in the exhaust system and simply put back pressure on the engine. I suppose that one could build an engine with a system as you described. They are essentially a pressure relief valve that keeps back pressure on the exhaust to ****** the engine from building up RPM. Lacking a Jake brake (or equivalent design), a diesel has very little back compression. A gas engine can close the throttle body thus limiting air intake and thus able to slow a vehicle down via back compression without over revving the engine. A diesel engine wont slow down, just rev higher and higher since you cant close off the intake air it just keeps freewheeling and running more and more RPM.
Don't believe it? Just get your tractor on a steep hill and throttle back, see if you slow down any.

 

[DK35vince]

I have never seen a Jake brake(patented name) that was hooked to any part of the engine, they are in the exhaust system and simply put back pressure on the engine. I suppose that one could build an engine with a system as you described. They are essentially a pressure relief valve that keeps back pressure on the exhaust to ****** the engine from building up RPM.

You are describing an exhaust brake.
The Jake brake system bolts to the top of the engine and controls the exhaust valves.
I've run both types and the Jake brake system provides MUCH stronger engine braking than the exhaust brakes do.

Exhaust brakes work great on the Doge pickup at work, but on a heavier tri axle or tandem axle truck I've run that had the exhaust brake system on they aren't worth a dam.
Nearly all big trucks run the Jake brake type system.

 

[Looking4new]

Nearly all big trucks run the Jake brake type system.

But they are an option you must specify when you buy the truck. Personally, I wouldn't drive a truck that doesn't have a Jake®.