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Old 02-07-2013, 06:03 AM   #29
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I never heard anyone complain they had to much power but I have often heard not enough power.
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Old 02-07-2013, 07:16 AM   #30
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Quote:
Originally Posted by Eaglesview View Post

Do you find in a long climb that you use an rpm higher than 1400 +/- 50?

At a higher rpm the torque would drop off and does that mean you would slow down?
The +/- 50 is on flat roads with slight grades. It gets up to 2200 on big climbs, 6-8% but still does not grunt, but may get down to 45-50 mph. Would I like more hp and torque? Hey, I am a guy!
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Old 02-08-2013, 08:18 AM   #31
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I never heard anyone complain they had to much power but I have often heard not enough power.
People don't complain about too much power but some do complain about using too much fuel ... odds are, if you have more power, you'll use more fuel.
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Old 02-08-2013, 08:27 AM   #32
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People don't complain about too much power but some do complain about using too much fuel ... odds are, if you have more power, you'll use more fuel.
That's a generalization that is not necessarily true. I have 425HP and 1550 ft-lbs of torque and my SilverLeaf computer says it gets a pretty consistent 8-8.5 mpg under a wide range of conditions running at about 63 mph. Sure, I could get less if I used wide open throttle all the time, but that's not a smart way to drive any vehicle.
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Old 02-08-2013, 08:34 AM   #33
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Quote:
Originally Posted by michelb

People don't complain about too much power but some do complain about using too much fuel ... odds are, if you have more power, you'll use more fuel.
Not necessarily true. If the engine is sized correctly for the weight of the vehicle and the normal load on the engine then the statement is correct. If the engine is somewhat under sized for the conditions then the fuel consumption will go up. The often quoted ratio of 1 hp per 100 pounds of weight may be the approximate tipping point. If the ratio gets much higher fuel consumption will suffer.

I had a Cat 3126 rated at 275 hp with a coach/toad combo of about 30k. My mpg averaged just over 7. My current Cummins ISM rated at 500 hp with a coach/toad combo of about 44k averages just over 8. That being said, I have to admit, the Cummins ISB seems to be the fuel economy champ no matter what the load.
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Old 02-08-2013, 08:44 AM   #34
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Talking Thrust-Weight Ratio

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Now considering Diesel pusher-1990-2000 year range. Note most are 34 to 40 feet long. HP starts at 230HP on up to 300hp in the later models...
Just like with the airplane, everything comes down to thrust-weight ratio.

Of course, in diesels, consider the amount of torque to the weight of the rig...

We just got done two years of ownership of a Fleetwood Excursion powered by a 350hp C7 Caterpillar. Now, it's a Beaver Patriot Thunder with a 525hp C13.

Here's where it gets sticky: past discussions have suggested acceleration depends on torque.

My perception is, the Beaver is sluggish, compared to the Fleetwood.

However, the torque to weight ratio of the Beaver is better, by 10%.

But, horsepower is a different story: the Fleetwood beats the Beaver by 10% here, and that corresponds to what I sense as a driver.

[You fighter guys always run around with your pants on fire, I'd opt for the most power with the least weight, just like you did in the old days... ]
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Old 02-08-2013, 11:19 AM   #35
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Originally Posted by RVNeophytes2

Just like with the airplane, everything comes down to thrust-weight ratio.

Of course, in diesels, consider the amount of torque to the weight of the rig...

We just got done two years of ownership of a Fleetwood Excursion powered by a 350hp C7 Caterpillar. Now, it's a Beaver Patriot Thunder with a 525hp C13.

Here's where it gets sticky: past discussions have suggested acceleration depends on torque.

My perception is, the Beaver is sluggish, compared to the Fleetwood.

However, the torque to weight ratio of the Beaver is better, by 10%.

But, horsepower is a different story: the Fleetwood beats the Beaver by 10% here, and that corresponds to what I sense as a driver.

[You fighter guys always run around with your pants on fire, I'd opt for the most power with the least weight, just like you did in the old days... ]
The perception of sluggish acceleration may be due to final drive gear ratio. The big Cat most likely has a 4.3/1 rear end and the the C7 was most likely a good bit greater than that. Since the smaller engine's "sweet spot" is higher up the rpm band and the higher ratio will mean cruising at a higher rpm. It does put the big C13 at a disadvantage getting that weight rolling until the turbo can spool up.
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Old 02-08-2013, 11:41 AM   #36
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Diesel HP

Back in the RAG, they told you that altitude above you and runway behind you are worthless. It's the same with HP and torque, there will be a time when you'd like to have it, but if you didn't buy it, it is worthless. Keep the smash up!
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Old 02-08-2013, 02:33 PM   #37
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RVN-----2 Yours is an interesting analysis and Steve's thoughts may be part of the answer. Grzly03 sounds as if you have been there and done that. And RVN--2 at 80 years old I don't run around with my pants on fire anymore but I do like to run. Unfortunately many of the older models that fit our budget had pretty low HP diesels in them, but with all of your posts helping me out I see what I can do. Thanks again. FP
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Old 02-11-2013, 10:57 PM   #38
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I have a 92 32' class a with 5.9 mechanical B engine (Cummins). It is rated at only 190 HP and I have the "dreaded" 4 spd allison trans that I have zero complaints about. I pull 7,000 enclosed trailer and can average 60-65 no sweat on flat ground. Hills are obviously another story but its all about expectations. My neighbors newer DP has 400 hp and we both cruise at 62 I just get a little better mileage. My next coach will have at least 275 just for when Im in the mountains. I thought my opinion may help being on the very bottom of DP power levels.
Good luck
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Old 02-11-2013, 11:17 PM   #39
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I never heard anyone complain they had to much power but I have often heard not enough power.
One of the reasons I put a Banks kit on our ISC 350! Next rig will have at least a 450 HP ISL!
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Old 02-12-2013, 12:16 AM   #40
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Diesel HP

I have a 2000 National Tradewinds 37 with a Cat 300. In the mountains you can tell it is a little short on power but we are learning to use the transmission better and it works just fine for us. 350 HP would be nice
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Old 02-12-2013, 12:48 AM   #41
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I have a 36' Alpine Coach with the 330 Hp Cummins ISC. The Alpine has a CGVW of 32,000 lbs but I'm at around 30,000 going down the road with my toad.

I live in California's Sierra Nevada Mountains. I start out on a trip in the hills. The 330 Hp is enough to keep a decent speed in the lower foothills and I can maintain 55 mph on most grades. But I sure wish I had more power to merge onto the freeways and highways. Also, when on the highway and I'm in the slow lane it would be handy to have a bit more power to pull ahead of those folks that can't decide how they are going to merge onto the highway--the ones that pace alongside you and force you to slow down because you can't pull out ahead of them and the next lane over isn't clear.

Now on the other hand, I also have a 2008 Corvette. At 7 1/2 pounds per horse power there are no hill or merging problems with that baby. Manual transmission and with the stability control off--any time, any gear--as we used to say.
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Old 02-12-2013, 12:55 AM   #42
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Horsepower is a number, torque is what does the work. Another thing to consider is size of engine. I would rather have a big engine with 1250 FT of torque than a small engine tuned to the max turning the same. Liters is a big factor in the engine to power ratio. Some are strained to the limit so the MH factorys can put bigger numbers on the spec sheet. These will generate more heat and ware than a bigger displacement engine doing the same work. You can turn up a 5.9 Cummins to 500hp but it won't last.
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