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Old 11-06-2016, 10:43 PM   #57
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What mileage are you getting? When you say it didn't change much, which way, better or worse?
Thanks for your response.
On average a 1/2 MPG less. I'm getting around 8 MPG. Was getting an average of 8.5 with the 350.
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Old 06-03-2018, 12:36 PM   #58
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l have the 340/2500 combination and wish I had the 360/3000. The torque is higher and you get up to 10,000lbs towing, versus 5,000lbs with the 340.
I chose to go with the 360 HP/ 3000 Allison, and I'm glad I did, albeit, if my wife wasn't helping make the decision, I would have gone newer and went with the 425 HP engine. Even with the 360 HP engine, on the steepest of grades while towing, 40 - 45 is the best I can do. Unfortunately (and I do understand why) Cummins has no choice but to underpower these diesel engines, as it wouldn't take too many owners to burn up an engine if they didn't! In my pickup truck, which has over 500 HP (deleted) I drive by my pyrometer & transmission temps) but fully loaded with a 10' Arctic Fox with slide, and 18' trailer behind loaded with toys, there's not many hills where I can't do whatever speed I wish! In saying this, my programmer quickly tells me (chimes) if I am overachieving on hills via the pyrometer. Why they don't put a pyrometer on these coaches is baffling, but for the most part folks are doing freeway speeds, but it would be useful on long steep grades in the mountains here in the west!
So, the capability of these engines is MUCH more, than what we're given, but are de-tuned to a given amount, because of safety of the engine (no pyrometer) and depending on the year....emissions!

I heard prior to buying our first motorhome (took 2 years of researching online) that the 3000 Allison was the way to go, so rather than looking only at the price, it had to have the 3000 or I would pass the ad by. We stuck to our budget, and eventually found our current unit thankfully, an '08 Tiffin Phaeton with the 360 HP diesel pusher. So far we're pleased, and now I'm doing my research on what it takes for ME to do my own service on it, albeit, some I'll leave to the Professionals! I now need to figure out all the part #'s of the brands of parts I will use (quality only), all the zerk grease fittings on these coaches, and the services I'll do, and not do...but I'm new into this, so I'll take my time at gathering all the info needed, as I know the savings are HUGE if you can do them yourself!
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Old 06-03-2018, 10:21 PM   #59
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Our 2016 Winnebago Forza 36G is around 38 ft. We tow a 2wd Chevy tracker 2 Dr.
Forza has 340/2500 combo. No complaints. Fair amount of mountain driving. Get 10-10.5 mpg with toad. Drive max 65 mph.
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Old 06-04-2018, 08:32 AM   #60
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Not to hi-jack the tread..... But it's interesting to see the HP ratings and no torque ratings.... Saying that though, our Class A is a gasser and has HP ratings of 345/370 (depending on who is writing the specs). I have done a Star5 tune so it puts out a closer 370 HP/410 TQ. It all comes down to (IMHO) power vs weight ratio. I live in areas with 6 to 7% grades and towing a car on a dolly (combined weight of 4400 lbs) and can do speeds of 60+ up thesis grades. My point is.... why would one spend so much more for a DP when they can (just from my observation) barely get up these grades. And if you all say they outlast in mileage, I will disagree with you on that. Seen many gassers go 250,000 miles +. Maintenance is so much cheaper too for the gasser......
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Old 06-04-2018, 06:19 PM   #61
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Not to hi-jack the tread..... But it's interesting to see the HP ratings and no torque ratings...

Perhaps thatís because, contrary to popular opinion, torque means nothing when it comes to the speed you can climb a grade. It is horsepower that gets you up the grade at speed. Torque means nothing here.
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Old 06-05-2018, 08:45 PM   #62
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Perhaps thatís because, contrary to popular opinion, torque means nothing when it comes to the speed you can climb a grade. It is horsepower that gets you up the grade at speed. Torque means nothing here.
So then why buy a diesel engine RV?
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Old 06-05-2018, 11:24 PM   #63
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So then why buy a diesel engine RV?
Well, to answer your question. The answer is not because we like to spend way more money. Does that help?
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Old 06-06-2018, 04:50 AM   #64
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Perhaps thatís because, contrary to popular opinion, torque means nothing when it comes to the speed you can climb a grade. It is horsepower that gets you up the grade at speed. Torque means nothing here.
LOL! For decades I have known better. HP sells the truck, torque hauls the freight.
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Old 06-06-2018, 09:05 AM   #65
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Perhaps thatís because, contrary to popular opinion, torque means nothing when it comes to the speed you can climb a grade. It is horsepower that gets you up the grade at speed. Torque means nothing here.
I would suggest you discuss this with your engineering instructor.
When was the last time you used "horsepower" to tighten your lug nuts?

Torque and horsepower are interrelated. Torque is an actual measured force to distance. Horsepower is a mathmatical number derived with a formula using torque times rpm devided by a constant. If the torque was zero, the horsepower would also be zero.
In the early days of steam and gasoline engines, they needed a way to compare these engines to horses.
HP = Torque x RPM ų 5252

Now the big question. If you have two engines with the same horsepower rating, but one has a higher torque rating, which one will pull the hill better?

I hope this helps.
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Old 06-06-2018, 11:42 PM   #66
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With the same horsepower, both engines will pull up the hill at the same speed. Horsepower is the rate of doing work. The work is the change in potential energy from a lower elevation to a higher elevation.

The difference will be that the higher torque engine will run at a lower RPM to make the same horsepower. Of course the transmission gearing will have to be higher on the higher torque/ lower RPM engine to pull the same speed up the hill.
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Old 06-07-2018, 07:34 AM   #67
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To answer the questions around HP, Torque, and why persons buy Diesel and why they pull better without starting a flame war is difficult.

As stated, HP is a calculation. Two engines with same HP will accelerate as same speed given same gearing and weight. This is where the similarity ends.

The Diesel engine is used in RV's (as well as heavy trucks) for a reason. The Diesel puts out a higher torque (lower RPM hence the lower HP calculation).( the Cummins 6.7 has over 800# torque versus 400# in gasser) Torque moves the load. If you look at the weight of the RV's with Diesel vs Gas you will see the Diesel driven RV's weigh much more. Luxury accomodations and quality materials generally weigh more. Not trying to start a flame war over quality of gas rigs here - just saying that higher end materials have a higher weight. That is why you see all high end RV motorhomes utilize a diesel engine.

With that said, look at available transmissions. Most have about 6 speeds nowadays. The gas engine to make that HP number is running at ~4500+ RPM. The Diesel engine to make that HP is running at ~1300+ RPM. So - in order to maintain efficiency the Gasser has to have a higher ratio gearing in order to drop the RPM's to a reasonable level for cruising. The Diesel does not suffer the same disadvantage. The gearing can be close ratio due to the engine RPM range. Also the Diesel will reach Peak HP and Torque very quickly thereby moving the load more easily. A gas RV would need many more gears to be able to move the same weight efficiently.

As for longevity - most Diesel engines in these RV's are rated for 500k+ miles. As stated some gas engines will go 250K. Not really an issue for an RV which most of the time will not see the miles.

As for the 350 vs 360 - The 3000 transmission is rated for much more torque than the 2500. The 2500 is rated for 575# while the 3000 is rated for 1250#. Huge difference. That is why the same engine is derated for the 2500 tranny.

Bottom line - Luxury means weight. Diesels move weights more efficiently.

FWIW
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