sack1
Kent, WA
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nlh1250,
So true. Keep in mind too that any engine develops max power only when the pedal is to the metal for a given rpm. If all else were the same two identical rigs, one gas, one diesel, will be developing the same power to keep those rigs at a constant speed.
I tow all day long in OD and only kick out of it on steeper grades, no doubt sooner than if I had a diesel. But i'm not constantly hunting between gears either. The Allison does a great job of matching power requirements and engine rpm. It would bother me also if our rig was screaming at the top of its voice to get the whole thing down the road but it doesn't.
Myself, I would have considered a diesel more if:
I had an even heavier combined weight
I travelled into the high country a lot
I put on BIG miles every year
As it is we tow just fine, nice and quiet and smooth. Fuel mileage isn't as good as the diesels but while towing the same load I'm down only a couple of mpg and I didn't have to pony up for the extra cost of a diesel. It's a personal matter for sure.
'03 Chevy 2500HD 4x4, LT, Ext. cab, LB
8.1/Allison, 4.10
'03 32' 2955 Montana 5er
XM Radio/OnStar
Valley Hitch
Honda EU1000i
1984 VF700F Interceptor
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JIMNLIN
Oklahoma
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my Cummins turbo diesel does not need pedel to the metal for max power. Thats where boost from the turbo, 20-30 psi,plays in gettin' much bigger percent of power at lower rpm's than gas engines which need WOT to put out the power and my towing MPG's is more than just a couple better than any 8.1, loaded or empty, that we R/V with.......JIM
"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers
'03 2500 QC Dodge/Cummins HO 3.73 6 speed manual Jacobs Westach
'97 Park Avanue 28' 5er 11200 two slides
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BertP
Edmonton, Alberta, Canada
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Quote:my Cummins turbo diesel does not need pedel to the metal for max power. Thats where boost from the turbo, 20-30 psi,plays in gettin' much bigger percent of power at lower rpm's than gas engines which need WOT to put out the power and my towing MPG's is more than just a couple better than any 8.1, loaded or empty, that we R/V with.......JIM
Thst's not true, Jim. Max power of your CTD is calculated at max rated boost and WOT. Regardless of what type of engine you are talking about, max torque and max HP are always at WOT. If they weren't, they wouldn't be max.
You are correct about the boost getting you more power at low rpm than a normally aspirated gasser can get. Without boost, no engine can reach 100% volumetric efficiency (ie the cylinders will never fill to their max capacity). With boost, the sky, as they say, is the limit so you can get far more air (or fuel/air mixture in a gasser) in the cylinder so that the engine behaves as if it was far larger than it is.
Bert
* This post was
edited 08/19/04 07:19pm by BertP *
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JIMNLIN
Oklahoma
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Bert
your using the word calculated for max power which is ok for advertizing.
My statement is from the actual world operation such as using them as in towing and watching stock turbo diesel trucks run on a chassis dyno and watching at what percent throttle, at how much boost, rpm's and where the max power curve meets. Its all printed out in black and white.
You need to go to a dyno days for diesels in your area and forget about calculations and see the actual numbers to get actual max power....JIM
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BertP
Edmonton, Alberta, Canada
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Jim,
Sorry, "calculated" was a bad choice of words. You are right in saying that dyno runs can be done at various throttle settings, but that is usually to determine how the engine behaves at those settings either during design or after major modification to the engine. The torque/HP curves we see are max. That means that for a given rpm, the engine is not capable of generating any more torque or HP than is shown on the graph in a stock configuration. Those runs are always at WOT. As a matter of fact, before the computer controlled dyno was available, an engine would be reved up to what ever rpm point was to be measured and the load was increased until the engine was WOT and it could not hold the rpm anymore because the load was getting too great. Back off a little and you had max power setting. Now, they just leave it up to the computer, but basically the same thing happens. I know with my DMax, if I don't have my foot on the floor, I will not get max power.
Bert
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sack1
Kent, WA
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JIMNLIN,
I'm not trying to be funny when asking this but tell me, what happens when you do put your foot to the metal while cruising down the road? Do you speed up? If you do then while cruising you do not produce max power. Another way to visualize it. Cruise down the road at a consistant speed while approaching a steep hill. Do not change pedal position while going up hill. To maintain or increase speed do you then need to step into it more?
Max power is most always developed at WOT. In our truck with throttle-by-wire when I step into it I am actually telling the engine computer that I want more power. It then regulates engine timing, throttle position and injector functions, etc. to give me what I want. In a modern turbo-diesel you have the same except for no ignition and throttle but with the addition of regulating boost by various means. But cruising down the road you are at a steady state that does not require max. boost or max fuel injected into the cylinders.
As reghards to fuel mileage I can only speak from my own experience. In fact I travel with two PSD owners, one with a 5er almost the same weight and size as ours. He averages 11.5 while I can hit a bit over 9 on average for most trips. If you truly get the mileage you say you do then there are more than a few other diesel owners who'd like to get what you say. That is with the weight and size of 5er you say you have.
Hey, enjoy your truck. We do ours.
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Texas Kid
Friendswood, Texas 77546
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Joined: 06/14/2004
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The computer reads 22.1 @ 55MPH and 19.6 @ 70MPH without the 11K pound trailer. With the trailer I get 12.6 @60MPH and that is as fast as I pull it. I'm paying $1.67 for diesel in Houston.
Texas Kid
Wifey Too
Hobby - Spoiling All 4 Grandsons
2004 F250 CC, 6.0L, 3.73
2004 Wilderness Advantage 305RLDS
Reese 15K Pro Series w/ Husky Slider
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JIMNLIN
Oklahoma
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Bert
max power for towing ain't about WOT or pedal to the metal to get max HP. In a turbo diesel its all about max torque.
Sack
as regards to fuel milage I can speak from my own experience. I travel with two 8.1 owners , 2 wheel drives, both towing about the same size 5er as ours. They average 7-7.5 and I'll average 12-12.5 on same trips .
If you truly get the milage you say you do then there are more than a few other 8.1 ownerswho'd like to get what you say. That is with the same size 5er you say you have.
Hope you boys can get to a diesel dyno meet somewhere, maybe you can learn something new. Have a good'n.......
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PSDExcursion
Millstone NJ
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Quote:Bert
max power for towing ain't about WOT or pedal to the metal to get max HP. In a turbo diesel its all about max torque.
I agree 100% but some people are dead set on not agreeing with that statement. They are the same people that will say the Hemi will tow 23,000 lb GCWR up a hill faster then the Dodge Cummins 600. And when you tell them they are wrong they say you don't know anything about HP or Torque.
2002 Chevy Express 3500 8.1 155" WB passenger van
41 Ft 2003 Thor Citation 41-ZBSR TT w/ Hensley Arrow
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BertP
Edmonton, Alberta, Canada
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Quote:Bert
max power for towing ain't about WOT or pedal to the metal to get max HP. In a turbo diesel its all about max torque.
I know it isn't, and I didn't say it was. I only said that to get either max torque or max HP at any rpm (basically the same thing in this case), you must be at WOT. I didn't say that you should tow at WOT, just that you will not realize max torque unless you do. I don't let my DMax get to those power levels (OK, maybe once or twice ![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/smile.gif "smile") ) but that is my decision, not a restriction of the engine. Like Sack said, if you are getting max torque at a partial throttle setting, what happens when you put your foot to the floor? If you speed up, then you were not developing max torque at the partial throttle setting.
Bert
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