ecm tune egr dpf intact
04-05-2021, (Subject: ecm tune egr dpf intact ) 
Post: #19
RE: ecm tune egr dpf intact
(04-04-2021 )Lead_sled Wrote:  I’m not trying to hijack the thread, but reading on this 1500 rpm deal. My truck runs around 68 mph at 1500 rpm in 10th gear. I’m running 11R22.5 and from online calculations, I have around 3.73 rear gears. So, anything below 68 mph, you’re saying I should downshift to 9th to preserve the engine?

I usually shift out unloaded around 1500 rpm. And usually shift out around 1700 rpm loaded.

The industry I haul for, I’m either at 36k unloaded or 78k-80k loaded. Nothing in between.


On a different note, I used to work for a large oilfield service company. All of their trucks were 350hp Cummins. Don’t know which engine. But rear gears were like 4.63. We would drive down the highway at 63 mph turn 1800-1850 rpms. Pulling 90k. Only got like 3 mpg

here is some related info..
http://rawze.com/forums/showthread.php?t...3#pid17353


User's Signature: ->: What I post is just my own thoughts and Opinions! --- I AM Full Of S__T!.
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04-05-2021, (Subject: ecm tune egr dpf intact ) 
Post: #20
RE: ecm tune egr dpf intact
(04-05-2021 )gearratio Wrote:  if you're driving for fuel mileage,you should be driving 60 mph.very few options with a 10 speed.horrible setup 13 speed only,and there's a difference between emissions trucks and what used to be on the road

I have a 10-speed tranny and 3.55's .. I do just fine.

here is some more on rpm and gear ranges..
http://rawze.com/forums/showthread.php?t...3#pid13433


User's Signature: ->: What I post is just my own thoughts and Opinions! --- I AM Full Of S__T!.
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04-05-2021, (Subject: ecm tune egr dpf intact ) 
Post: #21
RE: ecm tune egr dpf intact
(04-04-2021 )Lead_sled Wrote:  I’m not trying to hijack the thread, but reading on this 1500 rpm deal. My truck runs around 68 mph at 1500 rpm in 10th gear. I’m running 11R22.5 and from online calculations, I have around 3.73 rear gears. So, anything below 68 mph, you’re saying I should downshift to 9th to preserve the engine?

I usually shift out unloaded around 1500 rpm. And usually shift out around 1700 rpm loaded.

The industry I haul for, I’m either at 36k unloaded or 78k-80k loaded. Nothing in between.


On a different note, I used to work for a large oilfield service company. All of their trucks were 350hp Cummins. Don’t know which engine. But rear gears were like 4.63. We would drive down the highway at 63 mph turn 1800-1850 rpms. Pulling 90k. Only got like 3 mpg

If I want any sort of fuel economy, my specs are below, I run right around 58 to 62 mph in high seven, I can run up to 65 mph easily in that gear, rpm roughly 1800 - 1900, and I still have two more top gears to play with if needed ;-).

Depending on road conditions, mountains/hills, and of course wind I can do better or worse. If I am empty or there about, I can step it up if the conditions are right. My drawback is the mid roof sleeper pulling a dry van, 6 mpg is about average with this winter blend fuel. Give me a flatbed, and I can roll around 9 mpg or better...

To get any sort of decent fuel mileage and not harm the motor, I use the turbo boost gauge, try to keep it under 12 psi, and the "instant per mile" fuel usage readout on the dash. The computer in my old truck is still pretty accurate.

Now, your situation... I would be running those heavy loads at 1700 - 1800 rpm, 55 to 60 mph, and keep the rpm above 1500 at all times, or as best as you can with that 10 speed. These ISX motors can run at 2100+ rpm all day long without any issues if the motor is healthy. I believe they top out at around that 2400 or 2600 rpm value before you get into the danger zone.

Now, running below 1500 rpm you risk fretting a liner, or in layman terms, busting the cylinder liner loose from the tiny ledge in the block that holds it in place. The lower the rpm under a load, the greater the lateral thrust of the rod and piston on the cylinder liner wall. You run down there, and you are essentially beating your motor to an untimely demise, and a $30,000 in frame.

And trust me, I have played with this on more than a few occasions. My best trial and error session was running the PA TP between Pittsburg and Carlisle PA on a nightly basis this past winter, I was on that run for a number of months and had a perfect test bed to see what I could get away with for the best fuel economy. High 7 and 60 mph, 1800 - 2000 rpm, was the happy place. I averaged right at 5.8 mpg pulling a set of doubles, half the time I was right near or over that 80,000 lbs. If I ran it in a lower rpm and picked up the pace, 4 mpg was my average.

Hope this helps.

Side note, I am running all new virgin rubber on this truck too... So that will have a negative effect on mpg, along with winter blend fuel.


User's Signature: 2008 ProStar, OEM 600hp CM-871, 18spd, 3:42, in framed in Rawze's driveway. Every day is a fresh new episode of, "The Twilight Zone"... Rod Serling lives rent free in my head. I can smell the Chesterfields.
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 Thanks given by: Rawze , hookliftpete
04-05-2021, (Subject: ecm tune egr dpf intact ) 
Post: #22
RE: ecm tune egr dpf intact
thanks waterloo,i will take your driving habits into consideration driving this cummins
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