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Old 11-19-2007, 09:52 AM   #1
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I've been F-T for 16 yrs in a gasser, and now looking at going to a DP. What I don't know about diesels is...just about everything. I've got my eye on an '02 40ft w/tag model that has a 500hp Cummins. Most of the other coaches I've had an interest in have ranged from 330 to a high of 400. In gasser terms, 500 would be a real gas-hog. In diesel terms, dunno. Would it get maybe even better mpgs because it would work less hard? Would it be more costly to maintain? Is there something unpleasant I should know about this engine?

Thanx for your input,

Gary
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Old 11-19-2007, 09:52 AM   #2
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I've been F-T for 16 yrs in a gasser, and now looking at going to a DP. What I don't know about diesels is...just about everything. I've got my eye on an '02 40ft w/tag model that has a 500hp Cummins. Most of the other coaches I've had an interest in have ranged from 330 to a high of 400. In gasser terms, 500 would be a real gas-hog. In diesel terms, dunno. Would it get maybe even better mpgs because it would work less hard? Would it be more costly to maintain? Is there something unpleasant I should know about this engine?

Thanx for your input,

Gary
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Old 11-19-2007, 12:46 PM   #3
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Gary, I'll start with a few comments. First, you generally do not see 40 footers with tags. Most of thw time this is 41 foot and above.

This must be a heavy coach. I have an '04 40 footer with a 370 Cummins w/o a tag and it provides all the power I need including pulling a 9,000# enclosed trailer. With or without the trailer I run about 6 and 1/2 mpg and rarely go over 62-63 mph. I can't imagine a heavier coach with a 500 hp doing any better than that

As to maintenance cost, my coach takes 27 quarts of oil with each oil and filter change. However, by the manual it only needs to be changed every 15,000 miles. I generally change out 11,000 to 12,000 miles.

Positive of DP vs. gas: bigger tires, air suspension, heavvier duty frame, air brakes and probably an engine brake, all of which gives a much smoother ride. The engine heat and noise are 40 feet behind you instead of right under your feet. Actually with a gasser I should probably say next to your feet considering the dog house whichgoes away with a DP.

Cummins or Cat give very long warranties in that 150-200,000 miles is longer than most of us will every run a coach. Gas warranty? Right now diesel is taking a hit at the pump--will that change--use your oiwja board as mine is on the fritz.

Good luck however you elect to proceed, Ken, '04 DSDP...
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Old 11-19-2007, 02:20 PM   #4
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Hi Gary,
From one Gary to another, the move to a diesel can be an experience (overall good, but different). Unless you tavel a lot of miles each year, the MPG means little. The 500 horses will need to be fed, even if you are cruising at 60-62 MPH. In addition, accessories like hydro hot or equivalent and the generator will take diesel. My signature coach is my first diesel. I've had it 2 + years and am happy. Like previously posted, fluids for a diesel are measured in gallons, not quarts. The chassis usually has more zerk fittings than I can ever remember greasing. Frequency of engine and tranny maintenance is usually once a year unless you drive over 15K a year. Chassis maintenance is between 5K miles (drive shaft) and 7.5K miles (other zerk grease fittings).

Lastly the engine brake is a must feature. Diesels have no compression braking, like a gas engine. Going down hill, the engine brake is the best way to keep to an appropriate speed. One can also down shift the tranny.

If the maintenance records are correct for the mileage and a diesel mechanic checks the engine, tranny and chassis with a clean bill of health, go for it.
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Old 11-19-2007, 03:18 PM   #5
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Ken -- just an FYI, CC 40' almost all have tags
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Old 11-19-2007, 04:09 PM   #6
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Techie, thanks I did not realize this, Ken...
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Old 11-20-2007, 04:52 AM   #7
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Gary and Eloise,
I can't respond to the 500 hp diesel, but we just went from a 2000 34 ft. National Sea View to a 2001 39 ft. Tradewinds LTC with a 330 CAT. We have anticipated trading to a diesel for the past two years, consequently had time to do some research as to what we wanted.

We're not quite full-timers, but for the past five years have spent four months in Old Mexico during the winter and about the same in the northern states during the summer.

Our Sea View had a bedroom slide and a living/dining slide. Early on we ruled out a kitchen slide as the living/dining slide provides you with a larger living area. The kitchen slides are only 18 inches deep where ours is 33. The Sea View had lots of storage space inside and it was hard to find a diesel that provided as much, also kitchen counter space. The Tradewinds has even more storage in spite of having a washer/dryer combo.

We just took a 800-mile round trip from Dallas to Corpus Christi, and although we haven't encountered any mountains yet, we are very pleased with the 330 CAT.

Good luck on your hunt.

Larry
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Old 11-20-2007, 05:10 AM   #8
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I've seen that on the Tiffins, the Zephyr gets equial mileage to the Allegro Bus. The Bus has a 400 ISL Cummins while the Zephyr has the 500 HP ISM. The 500 HP has that much more torque and the gearing is lower so that you are turning less RPMs than the Bus at the same given speed. Less RPMs means less fuel. The ISM is a larger displacement engine but the lower revs pretty much evens things out.
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Old 11-20-2007, 11:55 AM   #9
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Gary,
Go for it if the floor plan meets your needs, and you like the coach. As far as the 500 hp diesel goes, not a problem. I've got a 2007 Dynasty with the 400 Cumming and I've talked to people who have the Signature with the 600 Cumming and they are getting about the same mileage as my 400 is. You will love the 500 with the extra power for climbing hills. I find that the 400 Cummings is a little lacking in this dept. I went out west on a trip and some of the hills would really slow you down. That's one of the reason I just ordered a new 2008 Signature with the 600 Cummings. Always remember bigger is always better!
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Old 11-20-2007, 12:52 PM   #10
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The 500 horses will need to be fed, even if you are cruising at 60-62 MPH. </div></BLOCKQUOTE>
Actually, assuming equal coefficients of drag, frontal areas and rolling friction, the same amount of horsepower is required to move a 400 BHP rig along the straight and level at, let's say, 60 MPH as a 500 BHP rig. If the road horsepower requirement is 200 BHP, then the difference in fuel consumption will depend on which engine has a better brake specific fuel consumption when producing that 200 BHP. IOW, the 500 BHP engine could do better or worse than the 400 BHP engine depending on its brake specific fuel consumption curve.

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Old 11-20-2007, 04:25 PM   #11
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Rusty,

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">...what I don't know about diesels...everything </div></BLOCKQUOTE>

Um, about the "brake specific fuel consumption curve" thingie. Huh?
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Old 11-20-2007, 06:54 PM   #12
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Here is my first trip story. I am at the half way mark, New York, down the east coast to Ft Lauderdale, to the west coast of Florida, Cape Coral. I have a 500hp Cummins. My weight is over 20 tons. I generally drive at 65mph. I have averaged 7mph up to this point.
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Old 11-23-2007, 05:39 AM   #13
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elgarc
Lots of good info here so I'll give my non scientific evaluation. We travel quite often with a friend who has an 02, 43' Monaco Executive with the ISM500 and tows a Trailblazer. We drive a 2000 Monaco Windsor, 40', ISC350 and tow a Grand Cherokee. Both coaches have the same rear axle ratio. When traveling at 65mph we both get around 7.5mpg. We will stop for fuel at the same place and then when we need fuel again in lets say 500mi. we both take on the same amount +- a gallon.
Hope this is some help.
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Old 11-23-2007, 06:18 AM   #14
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by elgarc:
Rusty,

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">...what I don't know about diesels...everything </div></BLOCKQUOTE>

Um, about the "brake specific fuel consumption curve" thingie. Huh? </div></BLOCKQUOTE>
One measure of brake specific fuel consumption is pounds of fuel used per brake horsepower hour produced. As others have noted, it's quite possible for a 500 BHP engine to use no more fuel than a 300 BHP engine when only 200 BHP is required if both engines have the same brake specific fuel consumption (i.e., use the same amount of fuel) to produce 200 BHP which may be all that's required to cruise down the road at 60 MPH.

Rusty
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