Have we been doing it wrong? High rpm's bad when not needed?

[MaineGuy1]

Hey guys,
According to this video and John Deer, we should not be using high rpm's on our tractors IF it is not needed. Supposedly people saying it is better for the emissions controls or DOC filters etc. have it backwards. Watch part or all of this video, check out what Deer says and let me know your thoughts?

 

[ericm979]

My Branson's tach has a green band from about 2000 to 2500 rpm. The manual says to keep the engine in that band for best DPF performance.

 

[TractorNoob85]

Every tractor is a bit different. I generally stay between 540e and 540 pto on the tach. That's like 1700-2600rpm on the DK4520. If I am on and off the clutch a lot, I'll keep the revs down around 1700rpm but once I'm rolling with no stopping, I'll bump it up to 2400-2600rpm. From what I read, the higher exhaust gas temps help keep the DPF clean. High exhaust temps allow for passive regen to occur. I've never run at WOT. Maybe like 75-80% throttle.

 

[CloverKnollFarms]

Bransons regen like once every 200 hours anyway.

 

[MaineGuy1]

It's basically saying that it's worse to run tractor at higher rpm's if you aren't using the HP, this dirties up filter quicker than lower rpm's.

 

[ning]

I remember reading recently in another tbn thread that even at 540 pto speeds without much of a load a diesel is still not burning hot enough to avoid soot deposition, but without pyro readings it's a matter of faith.

I guess to answer this properly we need a pyrometer in the DOC/DPF, and run the tractor at whatever RPM it takes to keep the temps in the burning - or at least slower accumulating - range.

 

[MaineGuy1]

I remember reading recently in another tbn thread that even at 540 pto speeds without much of a load a diesel is still not burning hot enough to avoid soot deposition, but without pyro readings it's a matter of faith.

I guess to answer this properly we need a pyrometer in the DOC/DPF, and run the tractor at whatever RPM it takes to keep the temps in the burning - or at least slower accumulating - range.

Yes, but this is exactly what he and Deer are kind of saying is the Myth.

 

[ericm979]

https://imgur.com/SV8D1zR

This graph shows soot production as a function of power and rpm. BMEP which is effectively torque is on the vertical axis and rpm on the horizontal axis. You can see there is a sweet spot of low soot right in the range where its putting out some power at a range of operating rpm. I don't know what engine its for or how much it changes for different engines but at least it's an idea of how it is for one engine.

You can tell that letting it idle with no load is going to generate many times more soot that working it.

 

[Wagtail]

I've learnt through use that my 4105 (Tier III) works best at just a titch above 2100rpm, unless PTO operation or 'roading'.

Anything more and I'm just wasting diesel. Every individual tractor has a 'sweet spot', rev wise, that needs to be ascertained.

Fortunately this 'regen' process is not a concern for me... and it's why Tier III tractors have such high re-sale value.

 

[RjCorazza]

I limit my idling time (at any rpm) by turning the engine off if not being used for 5-10 minutes. I agree with the John Deere video that keeping a load on the engine increases passive Regen, however, my experience has been different in operating an engine at no load and higher (1500+) rpms.

I record my regens, and my machine DEFINITELY increases soot production when there is no load and at low idle rpms. No load and 1500+ rpms results in less soot accumulation and less frequent active regens.

 

[Jstpssng]

I don't keep track of regens but perhaps should start. It seems like mine does it more often than other posters suggest.. When cutting wood my tractor sits at idle a lot. Lately I've been shutting the engine off between winches but it seems like repeatedly starting it would also create more soot.

 

[Jrasband]

I started keeping my throttle over 1500 by setting the hand throttle when I first got my Kubota as I was worried about the DPF. Now I let the RPM go down to 1000 when doing loader work sometimes, as I have so much control over the movement of the tractor if you let it throttle down when desired. For instance when picking up or setting down bales and working in high range, you want to be able to go as slow as possible at that last moment. I am more concerned about riding the clutch.

 

[JCoastie]

I seem to be in the minority and have frequent regens, clearly documented in the LS forum.
For me, I have a regen with almost every 5gal fill-up, somewhere within those 5 gallons.
If I burn through that 5 gallons fast (higher RPM) I have a regen sooner, if I burn through it slower (lower PRM) I have more time between regens, but still within 5 gallons.
Yes, something is wrong, but LS does not agree, they say that's normal.

 

[RandyT]

Something to keep in mind is people with hydrostat transmissions need to operate at a higher rpm to maintain proper oil flow to the pumps.

 

[jyoutz]

I don't keep track of regens but perhaps should start. It seems like mine does it more often than other posters suggest.. When cutting wood my tractor sits at idle a lot. Lately I've been shutting the engine off between winches but it seems like repeatedly starting it would also create more soot.

When I’m running for long periods at 540 rpms, like rotary cutting, my machine regenerates about every 75 hours. But I’ve noticed when I’m puttering around doing loader work, the frequency drops to about 50 hours.

 

[Paystar]

RPM's mean nothing. What matters is keeping in-cylinder combustion temperatures high. Which means make your engine work. Keep it under a load.

 

[Hilbilly]

My tractor soot level increases whether I am idling or running at high rpms with no load but when I run at PTO speed and work the engine, the soot level decreases. I especially note the soot level drop in the winter, when I use my inverted snow blower and run uphill. I can hear the tractor working hard. I have seen the soot level drop by as much as 5% in one pass.

When I run the gravity wood chipper at PTO speed the soot level still increases. That does not work the engine enough to burn the soot.

 

[deserteagle71]

Can't speak to John Deere. But the owner's manual for my Kubota M7060 specifically warns against idling the engine too much and I have found that to be true. As long as I keep the rpms up to at least 1800 rpm it rarely goes through a regeneration cycle. If I let it idle a lot, the regeneration cycle will occur every 10 hours or even less.

 

[ning]

https://imgur.com/SV8D1zR

This graph shows soot production as a function of power and rpm. BMEP which is effectively torque is on the vertical axis and rpm on the horizontal axis. You can see there is a sweet spot of low soot right in the range where its putting out some power at a range of operating rpm. I don't know what engine its for or how much it changes for different engines but at least it's an idea of how it is for one engine.

You can tell that letting it idle with no load is going to generate many times more soot that working it.

I (sloppily) colored the graph in as I think those are isolines? so perhaps this is more intuitive for some:

 

[steve tym]

Diesels like to be worked. When I exercise my generator, I always put a load on it.