I thought one of the virtues of the Series 60 was the "lugability"?
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I thought one of the virtues of the Series 60 was the "lugability"?
Just curious, what kind of EGT are you guys maintaining while you're in the race to the top of those mountains?
Orren, On our 97 the pyro was eliminated.
I miss the pyro gauge so it is only the 8V92 guys that can address that now. On our other coach the max I would see at 2150 RPM and full boost which on my 87 was around 21 or 25 (I can't remember) was around 1100. Depending on how level we were running and if we had headwinds, highway cruise speeds was around 600 to 700.
Rereading Larrys post he says that the DD manual says "to select a gear that will PULL the hill then choose a speed that works". Pull means being able to accelerate in that gear.
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A gear that you can get the RPM's to go UP if you try.
Diminishing and or low RPM is fine but not with your foot on the floor. I am regularly low in the RPM with my straight-6, there is a great amount of torque in a diesel there, but I do not operate at those ranges hammer down unless it will "pull" out.
As I start a climb and loose speed and the trans downshifts I'll then test that lower gear with full throttle for a bit and if the RPM's are just holding or still going down I again back out a little. At that point it will either drop off and hold somewhere or downshift again at which time I will again test with full throttle. When it gets to a gear that "will PULL the hill" it will be in one that I can accelerate in if I so choose. Then for the 8-V it's 1800 to the top, whatever gear that might be.
That is exactly my method Joe, you just explained it better. Can't break truckin habits that have served well over all these years.
Your pappy must be proud!;)
Tom and Joe...I think there are differences that you are not recognizing.
First, manual transmissions are driven differently than automatics. You are the "brains" for the manual, and the automatic has its own "brains", less so on Joe's coach, but more so on later coaches with ATEC.
When you select a hill climbing gear, you can move the pedal up and down until you sense where your speed starts letting off. You do not have to hold your foot to the floor because anything past that point where your speed diminishes is not going to change your speed or acceleration. That is a throwback to mechanical injectors however.
With our DDEC and ATEC controlled engines and transmissions your throttle position is controlled regardless of where you put the pedal. The DDEC will not open the injectors beyond the point necessary to optimize the power. You can call for more power, but you will only get what the engine can deliver whether it is your foot on the pedal, or the cruise control handling the pedal (figuratively speaking).
Prior to the DDEC type engine controls, and what has prompted truckers to claim it is best to keep the pedal at or below the point where the speed dropped off was what would happen if you pushed your foot to the floor climbing a hill on which you could not maintain speed or accelerate. With mechanical injectors, holding your foot into the pedal more than the engine could handle resulted in lots of black smoke. Your pedal was the determining factor in fuel delivery so it made perfect sense for you as a driver to not use so much throttle the engine could not efficiently burn the fuel.
Except for very early coaches, that will not happen any more. Is the old way of doing things valid? It will not hurt, but the way the coaches are set up no matter how much you push the pedal the coach will deliver the maximum performance if that is what you ask of it, and there is not a downside to pedal to the metal.
Once again Jon has said it very well.
My coach happens to be the first 45 foot Series 60 that Marathon converted, and it came equipped with a pyrometer.
On the flat, cruising at say 65 mph, it reads around 300-400 degrees.
Climbing a big hill, pedal floored, I have never seen more than 900 degrees.
The computer controls it all automatically.
In my airplanes I have pyrometers in all of them and am used to monitoring them closely. They run around 1200 degrees when running rich in climb, and up to 1500 degrees normal lean cruise. But the metallurgy is different and i am not suggesting anyone run a bus at those temps.
When DD suggests or someone says says a gear that you can pull that hill the definition is clear. It does not mean anything accept you have the ability to accelerate up it.
Why wouldn't the DD manual say: Put your foot on the floor and the computer will automatically do the rest?
When anti-lock brake computers came along all the manufacturers were clear to specify the new technique, to brake people of the old habits of pumping. Seems to me that the computer controlled engines would have included similar instructions.
Jon I remember having this discussion with you the first time we met and at the time I felt I did not know you well enough to pursue the disagreement. I kinda knew this topic would eventually come up. I feel it is a very healthy discussion and now that we know each other a little more will be glad to continue to make it. Looks like some are siding up for it and I have DD in my corner;)
I will agree that under certain circumstances the computer will restrict an excessive amount of fuel to be delivered to the engine under full throttle where the manual fuel pump will not.
Another example:
My straight-6 is a 1950 RPM motor. If I am climbing and in gear-X and can get it all the way up to 1850 and holding at full throttle I will not leave it there. I will back it off to 1750 or 1800 and give it a little breathing room. This technique applies to all engines computer or not.
Tuga what do you think about all this? Gonna change your driving habits or not:eek:
Joe,
You and I are talking about apples and oranges.
Your practice is to select a gear for hill climbing in which you can actually accelerate up the hill, at least until you max out the rpms in that gear. So basically if I understand your comments it is you preference to just back off of maximum throttle and climb the hill at some speed that is less than your maximum. That's fine and what you are doing is using less than the available HP.
What I am saying is that on mechanical engines you had to do that because it you tried to get more power by using the maximum throttle, all you would do would be to convert fuel into noise and black smoke.
On DDEC and ATEC engines, apart from giving the coach a little premature assistance by dropping down a gear, and going to performance mode, gaining a little speed to help hold the revs up, you can drive with your foot to the floor or let the cruise control hold its foot to the floor. Either way the computers and transmission shifting map are going to take you up the hill at max performance and you will not be experiencing the conditions that used to prevail when there were mechanical injectors.
I can do the same thing you suggest, and that is to climb the hill using less than maximum power. I presume it may impose less stress on the engine, but I view our engines as more than capable of being asked to deliver maximum performance so I choose to attack a hill with all my coach can deliver.
Joe, you say: '"a gear that you can pull that hill the definition is clear. It does not mean anything accept you have the ability to accelerate up it."
I do not agree with your statement at all. to "pull a hill" is a totally ambiguous group of words. First off, many roads on hills do not have constant grade angles. There are steeper parts and shallower parts. So your speed and horsepower required will vary.
Second, one could easily interpret "pull a hill" to mean continue making forward progress at whatever speed, increasing or decreasing over time. As long as you are not rolling backward, you are "pulling the hill".
Question, do you accelerate from a red light at full throttle, say on a road with a 55 mph speed limit? Do you think if you do you will break some kind of DD part?
Third, if Jon and I drive like we say we do, what do you think is going to happen back there, what is going to break or wear out prematurely? How do you equate driving an empty coach verses a loaded one pulling a 20,000 pound stacker trailer? With one of those I bet your foot would be all the way down much of the time. How about driving into a 40 mph headwind on a flat road, are you unwilling to go flat out then too?
Also, I would really like to see the Detroit Diesel page where this "pull the hill" stuff is printed. I can easily believe a trucker would say it while fueling, but I have a hard time believing a bunch of engineers and marketing types would actually print it for customers.
And Joe, I think you are right about one thing, the POG group is a perfectly OK place to air one's opinions, and I really hope we all buy into the idea that we are here to learn from each other and not be too worried about offending each other. What we all want is the unvarnished technical truth. I hope.