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

   / Have we been doing it wrong? High rpm's bad when not needed? #1  

MaineGuy1

Silver Member
Joined
Nov 9, 2018
Messages
196
Location
MAINE
Tractor
Kubota BX 25D, Massey Ferguson 1735M hydro cab
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?
 
   / Have we been doing it wrong? High rpm's bad when not needed? #3  
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.
 
   / Have we been doing it wrong? High rpm's bad when not needed? #4  
Bransons regen like once every 200 hours anyway.
 
   / Have we been doing it wrong? High rpm's bad when not needed?
  • Thread Starter
#5  
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.
 
   / Have we been doing it wrong? High rpm's bad when not needed? #6  
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.
 
   / Have we been doing it wrong? High rpm's bad when not needed?
  • Thread Starter
#7  
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.
 
   / Have we been doing it wrong? High rpm's bad when not needed? #8  


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.
 
   / Have we been doing it wrong? High rpm's bad when not needed? #9  
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.
 
   / Have we been doing it wrong? High rpm's bad when not needed? #10  
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.
 
 
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