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Old 01-08-2016, 08:44 AM   #29
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Higher hp will give better MPG than lower hp until the amount is excessive.

Many moons ago the company bought service vans with the 302 because smaller engine better mpg but way under powered so engine worked in higher load.

Convinced them to try the 351 and mpg was way better and it got to the hilltops better with cooler engine.

Same goes for everything else.

If underpowered the engine will be working at high end of power curve and may not be near happy place for fuel where a proper sized engine will be cruising along.

Excessive size working less but more overhead.
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Old 01-08-2016, 03:58 PM   #30
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Quote:
Originally Posted by TQ60 View Post
Higher hp will give better MPG than lower hp until the amount is excessive.

Many moons ago the company bought service vans with the 302 because smaller engine better mpg but way under powered so engine worked in higher load.

Convinced them to try the 351 and mpg was way better and it got to the hilltops better with cooler engine.

Same goes for everything else.

If underpowered the engine will be working at high end of power curve and may not be near happy place for fuel where a proper sized engine will be cruising along.

Excessive size working less but more overhead.
Yep my last coach had a C12 455 HP 1550 Torque and lifetime ave was 8.7 mpg. Current coach has less power and so far is at 7.1 mpg. I am hoping it still has some breaking in to do but I'll live with it either way.
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Old 01-08-2016, 04:13 PM   #31
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Yep my last coach had a C12 455 HP 1550 Torque and lifetime ave was 8.7 mpg. Current coach has less power and so far is at 7.1 mpg. I am hoping it still has some breaking in to do but I'll live with it either way.
Cat vs Cummins, Yellow or Red, tell me with a straight face the Cummins Performs better....
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Old 01-08-2016, 04:35 PM   #32
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To put this in the simplest of terms,
"If you want the Horses, you gotta feed em "
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Old 01-08-2016, 09:25 PM   #33
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Horsepower vs mileage

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Originally Posted by rdelcamp View Post
I sold HD diesel trucks for many years. Customer Joe would come in and say that customer Bills truck is just like mine and he says he gets 9MPG.
and I only get 7MP. How can I get 9MPG. My answer was ,do what Bill does, Lie.
Ron D.

LOL!

There is absolutely no way a diesel motor home is going to AVERAGE 10 mpg. Those who say they are getting into double-digit mpg numbers are either exaggerating or they just don't know any better. Yes, you might average 10+ mpg over a hundred miles or so with a howling tail wind, but you will never achieve a long-term average that high.
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Old 01-08-2016, 09:48 PM   #34
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I'm right at 40K pounds with the Maxxforce 10 non DEF engine with 19K miles. So far I'm getting anywhere from 7.5 to 10.4 MPG depending on the trip. As a side note I don't like to focus on HP. Torque moves these things up the hills. Torque and cubic inch are key to moving these things. If I focused on HP I'd have a small block blown 327 with 700 HP developed at around 7000 RPM's at 1/4 the weight of these big bore diesels. If HP was the answer all your over the road carriers wold have turbo driven gas engines.
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Old 01-08-2016, 09:54 PM   #35
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Torque gets you going and climbing, HP keeps you there. When choosing a coach you can sometimes choose among power plants. If so look at the torque curve and see which combination has the widest and highest torque ratings for a given rpm. Many times your cruising rpm is in the 1500 to 1700 rpm. If the torque is the same or at the greatest in that range you will climb hills without a noticeable reduction in mph. Higher hp does not do you any good if the higher torque is only when you are at 2500 or greater rpm. The big Cat and Cummins engines have over 1200 ft lbs of torque but it is useless unless it is where you generally cruise. On a test drive take it to a significant hill and see how it goes while you have the cruise control engaged. Comparing two coaches or engine and transmission combinations will tell which is going to perform better for your travels. Unfortunately you will find most manufacturers have their coaches at or near full GVWR and the upper limit of their engine and transmission choices. With a lot of research you can compute what engine and transmission will be optimal, but only Newell and Prevost go that far in building optimal coaches and they don't see 8 mpg on their best days.
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Old 01-08-2016, 09:59 PM   #36
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Horsepower vs mileage

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Originally Posted by Rich-n-Linda View Post
LOL!

There is absolutely no way a diesel motor home is going to AVERAGE 10 mpg. Those who say they are getting into double-digit mpg numbers are either exaggerating or they just don't know any better. Yes, you might average 10+ mpg over a hundred miles or so with a howling tail wind, but you will never achieve a long-term average that high.

Diesels come in different packages.
I had a 32 Thor Serrano FRED that got 11 @ 22,500 and 240hp. It was advertised to get 16. Meh!
Yep, the power to weight thing!
Now, a 42 w/tag w/425hp that gets 7.5 @ 42K lbs And I don't care! Yep, the power to weight thing!
My toad puts on 60K when my MH puts on 30K.
So, per simple math, MPG does not matter. The Journey does!
I truly love to hear the fairy tales of actual plus 2 or 3, but the bottom line is that it just doesn't matter.
Happy Trails
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Old 01-08-2016, 10:02 PM   #37
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Torque gets you going and climbing, HP keeps you there. When choosing a coach you can sometimes choose among power plants. If so look at the torque curve and see which combination has the widest and highest torque ratings for a given rpm. Many times your cruising rpm is in the 1500 to 1700 rpm. If the torque is the same or at the greatest in that range you will climb hills without a noticeable reduction in mph. Higher hp does not do you any good if the higher torque is only when you are at 2500 or greater rpm. The big Cat and Cummins engines have over 1200 ft lbs of torque but it is useless unless it is where you generally cruise. On a test drive take it to a significant hill and see how it goes while you have the cruise control engaged. Comparing two coaches or engine and transmission combinations will tell which is going to perform better for your travels. Unfortunately you will find most manufacturers have their coaches at or near full GVWR and the upper limit of their engine and transmission choices. With a lot of research you can compute what engine and transmission will be optimal, but only Newell and Prevost go that far in building optimal coaches and they don't see 8 mpg on their best days.
I'm at the rated torque (1250 ft lbs) at 1300 RPM's. With the Allison in 6th gear I'm going about 65MPH. That's the sweet spot for this combination.

Here's a good link explaining power and torque.

http://www.epi-eng.com/piston_engine...and_torque.htm
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Old 01-08-2016, 10:48 PM   #38
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Our 40' FR Berkshire has a 330hp Mercedes diesel and we CONSISTENTLY get 10 - 14 mpg even when pulling our toad...

This past summer we traveled over 4K miles thru Colorado, Wyoming, SD, MN, IL, TN and all the mts they offered and climbed numerous 7% grades with never a problem... We never dropped below 45mph climbing grades by downshifting when needed...

In my situation 500hp would be total overkill.... Don't want the extra weight or additional fuel costs....
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Old 01-08-2016, 10:51 PM   #39
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Forgot to mention - I have 1,000 lbs of torque which totally allows me to make those 7% grades that coaches with 675 lbs of torque slow down for....
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Old 01-08-2016, 11:22 PM   #40
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MH or Prius

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Originally Posted by luckyd View Post
Let's see. 8MPG and boondock for the night........OR
drive a car ....30MPG and $150/night for food and motel.

Guess my MPG just went sky high.

Relax, and enjoy.
10.8 mpg and when i boon dock it is in a luxury 1 bdr suite with all the amenities and luxuries , not on maybe changed sheets and definitely clean floors and furnishings , not ones that a 100 people sat on this year and what happens when Motel 6 does not have any more room at the inn , traveling to yellowstone or grand canyon taught me about staying in hotels along the way.
We enjoy our company together and the ease the motor home gives us in our travels . But the people that travel and stay in hotels have to adapt to that lifestyle . We do travel to far off places and stay in Hotels when we can not get in to one of our timeshares , damn hard to drive the MH to Hawaii

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Old 01-08-2016, 11:33 PM   #41
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330

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Originally Posted by FIRE UP View Post
"and the 330 avg about 10 mpg"

Well Sir,
If you've experienced that kind of AVERAGE with a 330, I must have gotten the bottom end of the production C-7 330 units. I drive, and have always driven very mildly and keep that big beast at or around 62 mph while out on the open road. Even when we're not towing anything, which is seriously rare, I'm really, really lucky if we get at or close to 8. I've got some buddies that also have the 330 and each and every one get almost exactly what I do. Hmmmm.
Scott
10.8 mpg @ 55 and 10.4 @ 60 but I have a 330 Cummins

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Old 01-08-2016, 11:41 PM   #42
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Forgot to mention - I have 1,000 lbs of torque which totally allows me to make those 7% grades that coaches with 675 lbs of torque slow down for....
And our ISX has 1950 lbs ft from 1100 to 1600 rpm. At 60 mph it's turning 1350, right in the middle of it's torque "band". That makes for a very responsive drive.
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