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Governed RPM

I have noticed the term, "governed RPM" speed in several recent posts.  I am not familiar with that term so I did a search of the forum to find out about it.  I also googled the term.  I came away with more questions than answers.  My basic questions are, what is the actual definition of governed RPM and its significance to me as an operator.  Also, where would I find the governed RPM for my engine. 
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2008 Roadtrek Adventurous RS Sprinter
2011 Jeep Wrangler Unlimited
Jan: NO5U, Richard:KA5RIW
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Re: Governed RPM

Reply #1 –
Quote from: Jan & Richard –
My basic questions are, what is the actual definition of governed RPM and its significance to me as an operator.

Also, where would I find the governed RPM for my engine.
Richard,

I'll have to research the first question - I think I know the answer, but want to be sure I am correct...

As to the second question, one answer is for you to register your engine at Cummins QuickServe Online (link below).  It is free, and all you need is your engine serial number.  Serial number is found on the engine data plate, which is somewhere on your engine.  On my C8.3 it is affixed to the sheet metal cover over the front of the engine, directly below the mount for the A/C compressor.

After you are registered, you will find a wealth of information about your specific engine, including such things as the "Governor Break RPM", which I think is the same as what you are asking about in question #1.  This info comes directly from the Cummins data base, and is the same as what they see in a Cummins shop when they call up your engine serial number in their computer.

Cummins QuickServe Online
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"It goes without saying..."

Re: Governed RPM

Reply #2 –
Governed RPM is the highest RPM your engine should see when WORKING (UNDER LOAD).  Down arrow to, say 2nd gear and floor it-- it should not exceed your engine's stated governed RPM.

There will be a higher RPM that is relevant to all drivers and that is the highest no-load RPM (with exhaust brake, engine compression brake or transmission retarder on-- with the throttle closed.  Reasonably, if the engine is not doing any work, a little higher RPM will not harm it.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Governed RPM

Reply #3 –
Chuck,
I had signed up for Quick Serve Online several years ago, however, I never entered the serial number of my engine before.  I will do that as soon as I am back at the coach.  Thank you. 

Brett,
Thank you for the clarification. 

I suspect that the only time while driving that I may be likely to exceed the governed engine speed is when down shifting under power while climbing a grade or down shifting with closed throttle while descending a grade.  The only other situation that I can think of is with the transmission in neutral while revving the engine. 

Since my M-11 engine is computer controlled, will the computer limit the engine speed to safe levels, or do I, as the operator, need to monitor and limit the RPM's as you say to about the governed RPM's? 




Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2008 Roadtrek Adventurous RS Sprinter
2011 Jeep Wrangler Unlimited
Jan: NO5U, Richard:KA5RIW
The selected media item is not currently available.

Re: Governed RPM

Reply #4 –
It is my understanding that we can't hurt our
M11's under a lower gear throttle down situation .
The Rev limits built into our engines computers will never allow it.
They're almost goof proof in this area, far more likely would be damage from one of us " lugging " under heavy load in too high of gear.
Tom
1998 U320 40'

Re: Governed RPM

Reply #5 –
Drive it like you stole it
George Ray 1992 U280 40'

Re: Governed RPM

Reply #6 –
The engine/transmission are idiot proof.  The transmission will not downshift until it would not overspeed the engine in the lower gear.  And, if you are on a downgrade and speed exceeds spec, it will automatically upshift, even if you have down-arrowed to try to hold it in the lower gear.

Don't know which would cut in first if you tried to overspeed in a gear-- either the engine computer would reduce fuel to not allow overspeeding or the transmission would automatically upshift even if down arrowed to the lower gear.  I have never tried to find out.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Governed RPM

Reply #7 –
Quote from: wolfe10 –
The engine/transmission are idiot proof.
Are you sure about that?
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"It goes without saying..."

Re: Governed RPM

Reply #8 –
Our Detroit is governed at 2130 RPM. This is the factory spec (max HP and fuel cutoff at 2130) and under WOT, it shifts at exactly 2130 RPM in each gear. Last week while returning from camping in the Sierras, I punched in 3rd gear on level ground and went to full throttle. It was still winding up at 2300 RPM and didn't shift. I stopped at that point. I had never tried that before. Perhaps not as idiot proof as thought.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Governed RPM

Reply #9 –
My M11 was governed at 2000 RPM.
I never got there. 1400 at 65 and 1700 (top of the HP curve) to climb hills. Up to 1800 on the down hill side. Jake Brake on at 1800 and down to 1700 then off, cycled my way down the hill. Nothing working hard. Nothing getting hot.
Unless it's a race car why push it?
I just never liked to run anything at the limit if I could control it.
John Duld
1995 U320C SE 40'

Re: Governed RPM

Reply #10 –
John,

Most of our engines are in mild tune as installed in RVs. Our 350 HP 6V-92TA routinely produces 535 HP in marine installations (or fire trucks) and maxes at 614 HP in some. The HP increase is mostly just a software change to add more fuel. To get to fishing grounds, they are frequently at high RPM for extended periods.

Using lower RPM on hills, especially up at altitude, can result in higher EGTs and less coolant circulation from the water pump. Hot summer weather compounds the problem with much higher density altitude with even higher EGTs and less effective fan/radiator cooling.

Our diesels are not like most car engines as they have been designed to operate at rated HP over long periods of time without sustaining any kind of damage as long as the engine temperature is controlled. Our U300 does get warm on hills but rather that using more throttle at lower RPMs, I keep the RPM up with less throttle. This keeps both EGTs and coolant temps down.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Governed RPM

Reply #11 –
     Here's a thought on idiot proof and computer controlled systems, though I would not recommend this to anyone. When the cruise control is set rolling down the road, what happens if the trans is shifted to neutral ?
  I do know that is caused Caterpillar exstreme consternation when my nephew crashed their multi million dollar simulator at the NTEA show in KC when their debuted the new M series with the star wars controls.
  What surprised the nephew was "even my pickup shuts down when you do that!"      Don't ask how he knew that, I didn't.
Mick
88 Grand Villa 36' ORED 3208 (throwaway)Cat.
 Build # 3150
Happiness is the maximum agreement of reality and desire.