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11-06-2017, 08:09 PM
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#1
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Senior Member
Freightliner Owners Club
Join Date: Apr 2017
Posts: 237
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On-the-road Diesel Pusher Validation
When we decided to go big and get a Class A in April of this year, we picked a Diesel pusher for a wide range of reasons. We ended up with a big (40', 32,000 lb GVWR) coach and a small engine (330hp MBE 926).
After 10,000 miles and 61 nights in the coach, our family is very happy with our selection. Over the past 2 weeks, we've left the Midwest, spent a few days in the Grand Canyon, and are now outside Phoenix at Lost Dutchman State Park. As the driver, the DP choice was forever cemented after driving I-70 West out of Denver and I-40 South from Flagstaff to Phoenix.
The two-stage engine/exhaust brake made even the steepest mountain downhills a non-event and the torquey little Benz kept us moving upwards without complaint. We didn't win any races, but big mountain driving was a non-event. I've done it in gasser moving trucks a few times and know it can be done safely, but there's just no comparison in comfort or capability.
There's no one-size-fits-all, right choice in the gas vs Diesel debate, but the DP is definitely the winner for us.
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2008 Gulf Stream Yellowstone 40UL
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11-06-2017, 08:17 PM
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#2
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Senior Member
Country Coach Owners Club Solo Rvers Club iRV2 No Limits Club
Join Date: May 2011
Location: Vancouver, WA
Posts: 37,725
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Has been for us and now just me since 2000 when we ordered our first DSDP.
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2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft, HWH Active Air
Charter Good Sam Lifetime Member, FMCA,
RV'ing since 1957, NRA Benefactor Life, towing '21 Jeep JLU Rubicon Ecodiesel
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11-06-2017, 08:22 PM
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#3
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Senior Member
Join Date: Aug 2001
Location: North America somewhere
Posts: 30,897
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I agree. There is one thing about a diesel engine and exhaust brake that everyone should realize. The mfgrs of the diesel engine and Allison auto transmission designed their electronic control modules to "talk" to each other and prevent damage to either component.
The TCM-transmissiion control module will command an upshift when descending a downgrade to prevent the engine from exceeding its maximum RPM when using the exhaust brake. This means the upshift negates most of the exhaust braking effect a great deal, leaving only the service brakes to slow down until engine RPM reduces enough for the Allison TCM to command a downshift again.
When the driver keeps that in mind they can keep RPM's low enough to prevent the upshift by judicious use of service brakes.
The ECM does not do anything so dramatic, it mainly derates engine HP enough to prevent transmission damage on take-off from a dead stop; otherwise a heavy foot could destroy the transmission.
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2000 Winnebago Ultimate Freedom USQ40JD , ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG 11B5MX,Infantry retired;Good Sam Life member,FMCA. " My fellow Americans, ask not what your country can do for you, ask what you can do for your country. John F. Kennedy
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11-06-2017, 09:04 PM
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#4
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Community Moderator
Newmar Owners Club
Join Date: Feb 2011
Location: Point Pleasant Beach, NJ
Posts: 31,508
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I agree. Even though maintenance is higher on a diesel, I wouldn't trade it for a gas coach. The air ride, air brakes, engine brake and quietness makes ours a winner too. Glad to see you are happy with yours.
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Tony & Ruth........... FMCA#F416727
2016 London Aire 4519, Freightliner chassis, Cummins ISX, 2018 Jeep Wrangler Unlimited, Blue Ox Avail with AF1. TST 507 TPMS
No amount of money can buy you an extra second of time.
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11-06-2017, 09:11 PM
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#5
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Senior Member
Join Date: Dec 2009
Location: Out there, somewhere
Posts: 9,941
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VoiceNinja,
Just for a bit of clarification, you may have been on I-40 in and around Flagstaff going from east to west or, vice versa but, if you indeed went from Flagstaff to Phoenix, you took I-17. I-40 west out of Flag is a horrible section of road. You'd have remembered that. Not a biggie, just thought you'd like to know. As for your choice in coaches and, engines, great move and glad you're really happy.
Scott
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2004 ITASCA HORIZON 36GD, 2011 GMC Sierra 1500 4x4 Toad '20 Honda NC750X DCT
2018 Goldwing Tour DCT Airbag
Retired-29.5 yrs, SDFD, Ham - KI6OND
Me, Karla and the Heidi character, (mini Schnauzer)!
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11-07-2017, 01:36 AM
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#6
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Senior Member
Freightliner Owners Club
Join Date: Apr 2017
Posts: 237
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Argh! You're 100% correct, Fire Up! I-17 South, it was!
And, double argh. We did, indeed, enjoy I-40 West out of Flagstaff on the way to the Grand Canyon. My teeth are still rattling...
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2008 Gulf Stream Yellowstone 40UL
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11-07-2017, 01:53 AM
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#7
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Senior Member
Freightliner Owners Club
Join Date: Apr 2017
Posts: 237
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Quote:
Originally Posted by Ray,IN
When the driver keeps that in mind they can keep RPM's low enough to prevent the upshift by judicious use of service brakes.
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Indeed! I'm usually able to fine "the sweet spot" with RPMs about 200 below the shift point between 55 and 60 mph on a steep grade. Depending on the incline, I may be using just the compression brake (Low) or the compression and exhaust brakes (High) to hold it there.
I've had to stab the service brakes a few times on the steepest descents to keep it from the upshift, but that's been rare.
Great advice and detail, Ray. Thank you!
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2008 Gulf Stream Yellowstone 40UL
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11-07-2017, 07:52 AM
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#8
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Senior Member
Join Date: Mar 2015
Posts: 2,984
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For the last month or two, they have been repaving I-40 west of Flagstaff.
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'04 Newmar Mountain Aire 4016
400ISL/Freightliner
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11-07-2017, 09:05 AM
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#9
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Senior Member
Join Date: Dec 2013
Location: Lake Havasu City, AZ & Plover, WI
Posts: 6,403
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Too often people compare the cost of owning a DP to a Gasser and come away thinking that the diesel costs more. In my mind, the value of the air ride, quieter cabin, increased power, much higher load and towing capacity and easy handling, is worth far more than the initial cost and annual maintenance difference. So to me, the DP cost less than a Gasser. (actually it is less, as I would have to make two trips with a gasser to get all my things there)
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2006 Monaco Executive 44 Denali
2013 43 QGP Allegro Bus ( SOLD )
2013 Avalanche
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11-07-2017, 11:13 AM
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#10
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Senior Member
Join Date: Nov 2008
Location: Cosby, Tn
Posts: 6,587
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Quote:
Originally Posted by VoiceNinja
Indeed! I'm usually able to fine "the sweet spot" with RPMs about 200 below the shift point between 55 and 60 mph on a steep grade. Depending on the incline, I may be using just the compression brake (Low) or the compression and exhaust brakes (High) to hold it there.
I've had to stab the service brakes a few times on the steepest descents to keep it from the upshift, but that's been rare.
Great advice and detail, Ray. Thank you!
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What engine do you have? I’ve never heard of a 2 position brake being a combo of compression & exhaust brakes. I understand 2 position Jakes and a third position which is the VG turbo but not what you describe.
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Steve Ownby
Full time since 2007
2003 Monaco Signature
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11-07-2017, 02:12 PM
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#11
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Senior Member
Join Date: Jan 2017
Location: Titusville, FL
Posts: 5,164
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Quote:
Originally Posted by Crasher
Too often people compare the cost of owning a DP to a Gasser and come away thinking that the diesel costs more. In my mind, the value of the air ride, quieter cabin, increased power, much higher load and towing capacity and easy handling, is worth far more than the initial cost and annual maintenance difference.
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Yeah but the "value" of the "air ride, quieter cabin, increased power, much higher load and towing capacity and easy handling" are all very subjective. That "value" will vary from one individual to another and is difficult to put in your checking account. And folks don't just "think" diesels cost more, they do cost more.
The higher acquisition and maintenance costs of a diesel are very objective, real and have to come out of your checkbook.
I guess that's why they make diesels and gassers. And they all perform the same when sitting in the campground.
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When seconds count, the police are only minutes away.
2023 Grand Design 2600RB, 2022 F-350 King Ranch tow vehicle, Titusville, FL when not on the road
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11-07-2017, 02:23 PM
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#12
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Member
Join Date: Dec 2016
Posts: 38
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I think your 330 HP is plenty for your GVWR, diesel are all about torque / power not Zero to 60. My coach is only a 300 HP Cummins @ 27,900 GVWR and pulling our jeep Liberty she moves right down the road. I would rather pick a time test engine then go for the latest in HP.
Safe journeys
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Mike & Lori
2006 376DS Cross country
Cummins / Freightliner
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11-07-2017, 02:45 PM
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#13
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Senior Member
Freightliner Owners Club
Join Date: Apr 2017
Posts: 237
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Quote:
Originally Posted by Steve Ownby
What engine do you have? I’ve never heard of a 2 position brake being a combo of compression & exhaust brakes. I understand 2 position Jakes and a third position which is the VG turbo but not what you describe.
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We have a Mercedes MBE 926. It has both a true engine compression brake and an exhaust brake. Low activates the compression brake via a 12V signal that triggers an engine oil solenoid and high adds an exhaust brake via a 12V signal that activates an air solenoid. Our compression brake is single stage - it's either all 6 cylinders on or all 6 off.
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2008 Gulf Stream Yellowstone 40UL
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11-07-2017, 02:47 PM
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#14
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Senior Member
Freightliner Owners Club
Join Date: Apr 2017
Posts: 237
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Quote:
Originally Posted by MobileOneDS
I think your 330 HP is plenty for your GVWR, diesel are all about torque / power not Zero to 60. My coach is only a 300 HP Cummins @ 27,900 GVWR and pulling our jeep Liberty she moves right down the road. I would rather pick a time test engine then go for the latest in HP.
Safe journeys
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Absolutely agreed! I don't think I'd want anything bigger. We're remarkably efficient at 55 mph, which is perfect since we seek a lot of non-highway routes.
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2008 Gulf Stream Yellowstone 40UL
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