Lugging diesels = bad or newfangled myth?

[AMP762]

Just 2 pennies from an old mechanic /forums/images/graemlins/wink.gif In the good ol days engines had a long stroke and ran at lower rpm,less stress on parts. Size and weight didnt matter. Todays engines are built as small and light as possible to save money. But I still believe they will last as long as the old engines. Cars of 40 yrs ago at 100000mi. the engines were pretty well used up now a car may see that in a couple yrs and still be going strong. Differant times /forums/images/graemlins/confused.gif

 

[rockyridgefarm]

Here is the advice in my JD Owners manual:

IMPORTANT: Avoid damage! Select the proper speed range and gear for the job:

· The machine may be operated in any gear with engine speeds at 950 - 2920 rpm. Within these limits, the engine can be placed under varying load operations.

· Never overload engine by lugging machine at low idle speeds.

· Raise engine speed to match expected loads. If a slight increase in engine rpm occurs simultaneously with moving hand throttle lever forward, the engine is not overloaded.

 

[cowboydoc]

What you quoted is exactly right Mike. Anything other than this and you are going to cause damage to your engine and shorten the life. Also you better change your oil quite a bit as you are going to have fuel in your oil too.

 

[Dargo]

Hey! The JD manual copied from what I posted earlier!! /forums/images/graemlins/laugh.gif Apparently the JD engineers agree with my long time friend and long time diesel mechanic.

 

[QueBota]

Use the glow plugs, absolutely. Get a block heater if you don't have one.

Start her up, once the idle has stabilized exercise the hydraulics and then operate conservatively until the fluid temps come up to a reasonable level.

I think the owners manual has info regarding the amount of time to wait before working the tractor based on temperature ranges.

On a cold day it could take a very long time for the thermostat to open on a diesel engine at idle.

Dave

</font><font color="blue" class="small">( So Dave,

If it's 20* out and I need to start my Bota, I use the glow plug for awhile, crank it and it fires.

Surely you don't mean for me to take off working with it at that temp. Wouldn't idle be better for a short period, rather than reving it up right away?

Curious. )</font>

 

[To20Chris]

I would not worry about it so much. I'd like a bigger displacement, low RPM motor too, but it would likely not be as efficient, and that is important to me. The only real problem with running these engines at the RPMs they are rated at is that it is annoying! With proper servicing, I have no doubt that these small diesels will last a long time. Yes, those older tractors were sturdy and well built, but one of the reasons they lasted so long is that parts were plentiful and they were fairly easy to work on. They're not magic, they wear out too! So run your engine within its operating range, and use ear protectors if it gets too annoying.

Also, remember that the HST peddle is not a throttle - with a gear tractor, it's more obvious what gear you're in, so running at lower RPM is not as much an issue. If I'm running at 1500RPM, it's unlikely that I'm going to drop it into a tall gear and try to pull a load, and if I do I can feed it some fuel with the foot throttle first. With HST you are changing the "GEAR" with your foot, which is probably one of the reasons they recommend higher RPM - that way it's harder to run it into too tall a "gear" for the RPM you are at.

 

[rockyridgefarm]

BTW, while we are bemoaning newfangled stuff, I have to say the LoadMatch is a great help. It automatically keeps the engine from lugging down or stalling. Sure, all it does is adjust the hydro by wire, but it does a fantastic job.

 

[Dargo]

Cool! Can I have one? /forums/images/graemlins/smile.gif

 

[rockyridgefarm]

Yup! I can put it on that I6....

 

[rambler]

A diesel engine has a torque curve. There is a spot about 75% of full power (throttle set at top rpm, engine lugged down to 75% of top rpm) where most diesel engines develop their top torque.

You can pretty much play in this range without problems.

You can also lug the tractor down lower than this for short periods without problem.

However, if you lug the engine down too low for too long a time, the exaust temp rises. A lot. This doesn't always show up on your temp gauge. Big farm tractors have a seperate exaust gauge. (They burn out a lot - tough environment for them!) Turbos make this worse - or I should say, an even finer line to watch.

Running for a long time in this lugged down condition will overheat the exaust valves, pistons, and so on, and drasticly shorten the life of your engine.

I have no problem at all lugging down my big or little tractors going up a hill. That's short term. No big deal.

If you are going out brush hogging for 3 hours with a hog too big for your tractor, & lug it the whole 3 hours - you are doing damage to it. Note that you do have some room to play with - that power curve where torque rises as rpms slow a little. No problem with that, but if your engine does not respond to more throttle, that means you are lugging it down too low.


The problem with running at 1/2 throttle is that you totally mess up that sweet spot, where the engine gets the power/ torque bulge. It becomes much flatter & smaller, and you have very few rpms to 'play' with any more. It is just so much easier for you to overly lug the engine in this state...

A good general test to see if you are lugging the engine too much is to increase the throttle a little. If the engine has a hard time responding to that, then you are probably overdoing it. Again, for a couple minutes out of 3 hours running time - no big deal. For the whole 3 hours - oh boy! You are cooking it.

Combine manuals from Deere talk a lot about the power bulge and how you can use it for unloading on the go, but you can't use it for constant operation; and farmers who added turbos on to non-turbo engines became real familiar with this; and diesel pickup manuals will talk about it for long hill towing & the like.

How this all applies exactly to a tiny compact diesel - well, I'm just a simple dirt farmer, but I would assume the same basic principles would be there.

--->Paul