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Old 02-28-2014, 08:49 PM   #15
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Hi, new member. I am researching gas vs diesel, have my eye on a 37' Holiday Rambler Endeavor with a Cummins ISB Turbo Diesel Power (275 Horse Power). I have no experience with diesel, but have owned 3 different class A gas rigs. Questions: is 275 HP enough? what MPG is normal? Its a 99 with 68k miles. Thanks, Jim.

I have a 34 ft Itasca with 330 hp / 860 ft lbs of torque. I wouldn't want any less engine if you want to have a pleasant trip. My first coach had a small diesel in it and it was a chore to drive.
My MPG runs 7.5 to 8 average measured over 90,000 miles.
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Old 02-28-2014, 09:32 PM   #16
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The veracity of that guy might be a bit questionable. The best I ever got on a 300 Cat in a 36 foot Itasca Horizon was 10 and towing a Tracker. That coach was a bit weak in the Rockies and some of steeper pulls here in the east.
Cat mileage is never as good as a Cummins. We had a 36ft Discovery with the ISB 275, not pulling we averaged 11.5 mpg, pulling our 10K lbs race trailer we were 9.1-9.3 MPG's. That's mostly Wyoming and Colorado, not flat ground. The ISB is a great Diesel engine, slightly under powered but drive it's like a tractor trailer and it works well. The ISL we have now gets 7.5 at best, but the power is nice.
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Old 02-28-2014, 10:14 PM   #17
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There are lots of discussion forums on D vs G and I'm a diesel promoter. Agree with the other guy on Arkansas, it has some really steep hills. so do WV, KY, VA and MD. CATs use more fuel than Cummins for the simple reason they put out more HP. Cummins measures from the flywheel, CAT measures from the wheels. After engine losses, horsepower at the flywheel is considered to lose about 20 to 22 percent of its value on its way to the rear wheels through the transmission, driveshaft and rear axle. CAts all have higher compression than a like rated Cummins having owned CAT and run lot's of Cummins, the cummins is still a great engine. A 550 Cummins has 1100 ft lb and a 550 CAT can produce 1850 ft lb
Specific fuel consumption tables are available and they are pretty accurate.
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Old 02-28-2014, 10:43 PM   #18
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There are lots of discussion forums on D vs G and I'm a diesel promoter. Agree with the other guy on Arkansas, it has some really steep hills. so do WV, KY, VA and MD. CATs use more fuel than Cummins for the simple reason they put out more HP. Cummins measures from the flywheel, CAT measures from the wheels. After engine losses, horsepower at the flywheel is considered to lose about 20 to 22 percent of its value on its way to the rear wheels through the transmission, driveshaft and rear axle. CAts all have higher compression than a like rated Cummins having owned CAT and run lot's of Cummins, the cummins is still a great engine. A 550 Cummins has 1100 ft lb and a 550 CAT can produce 1850 ft lb Specific fuel consumption tables are available and they are pretty accurate.
So my Cummins 400 has more torque than a 550 Cummins? Doesn't seam right , my 400 Cummins has 1250 ft lbs of torque.
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Old 02-28-2014, 11:02 PM   #19
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Jim042 - I average about 7.2-7.5 mpg on our 43,000 lb DP towing a 4 door Wrangler. My guess on the rig you mentioned is about 10 mpg. HP is not the key with a diesel torque is. I would guess you have enough torque in that motor. The key to the attraction of a diesel pusher is that they are so much nicer to drive down the highway. 1. Motor is way back where you can't hear it. 2. Suspension is usually air and you just glide down the road. But once you get where you are going a gas motorhome camps the same as a DP.

I bought a DP because I really wanted one. And I love driving ours. I will never ever go back to a gas rig with the motor right next to me. But each persons needs/wants are different and that is why they build so many types of rigs. My experience over the last 34 years of motor homing is that most people like their rigs. So different things for different people.
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Old 02-28-2014, 11:28 PM   #20
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There are lots of discussion forums on D vs G and I'm a diesel promoter. Agree with the other guy on Arkansas, it has some really steep hills. so do WV, KY, VA and MD. CATs use more fuel than Cummins for the simple reason they put out more HP. Cummins measures from the flywheel, CAT measures from the wheels. After engine losses, horsepower at the flywheel is considered to lose about 20 to 22 percent of its value on its way to the rear wheels through the transmission, driveshaft and rear axle. CAts all have higher compression than a like rated Cummins having owned CAT and run lot's of Cummins, the cummins is still a great engine. A 550 Cummins has 1100 ft lb and a 550 CAT can produce 1850 ft lb Specific fuel consumption tables are available and they are pretty accurate.
The overwhelming majority of OTR Diesel engines are sold to big truck builders and then to trucking companies. It makes no sense to me that two major manufacturers would use two different systems to measure power output. What is your source of this info. My Cummins ISM is rated at 500 hp @ 1700 rpm and 1550 lb/ft of torque at 1200 rpm. I've always assumed that is at the flywheel as it's not in a vehicle when it leaves the engine builder.
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Old 03-01-2014, 06:56 AM   #21
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my 2 cents worth

that 5.9 will serve you fine, it is not a race car on steep hills but neither is my ISL and it burns a pile more fuel I had a gas coach of similar vintage and went as fast as we could to diesel HR Ambassador, the entry level diesel at the time, it was twice the coach my bounder was, burns half the fuel the bounder did, and the wife could actually breath when trucks passed us, never mind the quiet ride, bigger tires, and quit frankly better built period, with the 5.9 the maintenance was virtually identical to a BB gas engine, the transmission you will have is likely 5 or 6 speed Allison, far superior to gas coach trannys of the time. So you will have a better ride, easier to handle, better fuel economy, more power, likely diesel generator, better tires, better brakes even if they are the air over hydraulic discs of that vintage, quieter ride, and a better built coach for a little more money, its a no brainer if you were to ask me.

Good luck

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Old 03-01-2014, 08:40 AM   #22
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WOW! I am very impressed with all the information and sharing I have received on this forum in about 24 hours of joining! What a great group of people!

I really like the idea of DP and my analysis of gas vs diesel cost on a trip we make at least twice a year looks like this:

Mode Miles MPG Gallons Price $Cost Motel Net Cost Difference

Cadillac DTS 4000 21 190 3.50 666.67 400 1,066.67 0.00
Cadillac Truck 4000 16 250 3.50 875.00 400 1,275.00 -208.33
Gas Motorhome 4000 8 500 3.50 1,750.00 1,750.00 -683.33
Diesel Motorhome 4000 10 400 4.20 1,680.00 1,680.00 -613.33

Based on that, it appear pretty much a push on the gas/diesel question if my assumptions are correct. Of course, we all know what "assumptions" are!

I would be using it mostly for travel and the ability to have my own bed when visiting kids in various parts of the country, mostly on the west coast. As a partially retired person, I could do more of that traveling, hopefully. At present, I do not see pulling anything, especially with a large car and large truck as my vehicles.

I really do like the look and the floor plan of the 37' Endeavor (DP), and I really do welcome more facts and comparisons from all of you. There is no better information that actual experiences. Thank you so much. Jim
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Old 03-01-2014, 08:58 AM   #23
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Hi, new member. I am researching gas vs diesel, have my eye on a 37' Holiday Rambler Endeavor with a Cummins ISB Turbo Diesel Power (275 Horse Power). I have no experience with diesel, but have owned 3 different class A gas rigs. Questions: is 275 HP enough? what MPG is normal? Its a 99 with 68k miles. Thanks, Jim.
I think the one simple fact of generator placement in a gas vs diesel pusher made my decision. In most class A gas chassis, since the main engine is up front, they put the generator in the rear - RIGHT UNDER OR NEAR THE BED. That way if you need the generator running to power your air conditioner while you sleep, you feel all the vibration and extra noise.

In a diesel pusher, the main engine in the rear, the generator is at the very front of the coach, and barely noticeable when all the way in the bedroom.
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Old 03-01-2014, 09:01 AM   #24
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Hi, new member. I am researching gas vs diesel, have my eye on a 37' Holiday Rambler Endeavor with a Cummins ISB Turbo Diesel Power (275 Horse Power). I have no experience with diesel, but have owned 3 different class A gas rigs.
Questions: is 275 HP enough? what MPG is normal? Its a 99 with 68k miles. Thanks, Jim.
Horsepower numbers can be misleading. First I should say that yes 1 HP is the same gas or diesel.
A good example is the big 3's 1ton pickups and their top engines.
The Diesels are 6.6L (GM) and 6.7L for the Ford and Ram. All have very close to 400HP and 800TQ.
The Gas engines are 6.2L (GM & Ford),6.4L Ram All are Very close to 410HP and 420 TQ.
The HP number get you your highway speed minus Aerodynamics loss (unless you are RPM limited Most RVs are)
The Torque is Weight and TQ gets you your acceleration/hill climbing minus weight.
Diesels Cost more to build and buy and that is passed on to consumers (less so to the 2nd consumer)
The good side is that in RVs weight/sizes where there is a choice of gas/Diesel the Diesels get better fuel efficiency getting farther down the road per gallon of fuel and tankful.
Even though the diesel fuel might cost slightly more it will translate into less money per mile since the increase in MPG(usually 35%) will outweigh the increase cost (about 20%).
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Old 03-01-2014, 09:24 AM   #25
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Thanks, I had not thought of the generator location. All of my previous MH's did have that problem. I had a 24' 71 Explorer ( in 73), a 24 'Winny Brave, and then a 31' 91 Dolphin. The dolphin had a real sloped nose, which helped the gas mileage.

I always felt tired after long driving hours in the MH vs using my car, but my wife needs the bathroom facilities, or else she just doesn't drink any liquids while traveling. So the biggest reason is for that, 2nd, the ability to have my own privacy no matter who I visit.
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Old 03-01-2014, 10:05 AM   #26
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After reading all of these post about engine size and Horsepower and what is good.
Take it for a drive to make sure that the performance is up to YOUR expectations!
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Old 03-01-2014, 10:16 AM   #27
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Jim042 - I average about 7.2-7.5 mpg on our 43,000 lb DP towing a 4 door Wrangler. My guess on the rig you mentioned is about 10 mpg. HP is not the key with a diesel torque is. I would guess you have enough torque in that motor. The key to the attraction of a diesel pusher is that they are so much nicer to drive down the highway. 1. Motor is way back where you can't hear it. 2. Suspension is usually air and you just glide down the road. But once you get where you are going a gas motorhome camps the same as a DP.

I bought a DP because I really wanted one. And I love driving ours. I will never ever go back to a gas rig with the motor right next to me. But each persons needs/wants are different and that is why they build so many types of rigs. My experience over the last 34 years of motor homing is that most people like their rigs. So different things for different people.
Ditto. When we bought ours I noticed that the more weight, the more capacities. Gas coaches = less weight and less coach. Not talking about floor plan but storage, fuel, black, grey, and fresh. Heavier coaches also get heavier amenities which gives a nicer feel. The ceramic tile floors, heavy big fridge, Corian tops are all heavy. Gas coaches also get a little worse mileage in a much light coach. DPs are heavy, real heavy..and get 8ish?? So, like B Bob, we LOVE our DP, for those reasons.

We also can sustain a whopping 45mph up 7% for miles with a JK toad. And you won't see a gasser do that!
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Old 03-01-2014, 11:40 AM   #28
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There are lots of discussion forums on D vs G and I'm a diesel promoter. Agree with the other guy on Arkansas, it has some really steep hills. so do WV, KY, VA and MD. CATs use more fuel than Cummins for the simple reason they put out more HP. Cummins measures from the flywheel, CAT measures from the wheels. After engine losses, horsepower at the flywheel is considered to lose about 20 to 22 percent of its value on its way to the rear wheels through the transmission, driveshaft and rear axle. CAts all have higher compression than a like rated Cummins having owned CAT and run lot's of Cummins, the cummins is still a great engine. A 550 Cummins has 1100 ft lb and a 550 CAT can produce 1850 ft lb
Specific fuel consumption tables are available and they are pretty accurate.
I question most of this statement. It's hard to know where to begin. I went from a 330 Cat in a 40' MH to a 380 Cummins in a heavier 40' MH. By his "Theory" I should have had the same power. However, even with 3000#s more weight I had noticeably more power and torque for climbing mountains. How can that be if I lost 20% (76 hp)?? Cat and Cummins both rate their power and torque at the flywheel. Both companies make different versions of the same hp depending on what the intended use will be. A 450hp engine for MH use will have about 1250# torque. A 450hp engine intended for an OTR truck might have close to 2000# torque. The MH engine will be a 9 liter and the truck engine could be a 12-15 liter. The larger block will have more torque, but could have the same hp as the smaller block. All diesel engines have very similar compression ratios.

Sorry to side track this thread, but I do not accept what was stated.
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