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03-27-2016, 06:43 PM
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#1
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Senior Member
National RV Owners Club
Join Date: Jun 2010
Posts: 4,581
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Best RPM for economy CAT C7
The following spec recommendations are for vehicles that are 50,000 lbs. or less GVW or GCW. • For the best balance of performance and economy, spec axle ratios and tire size to obtain 2000 rpm @ 60 mph (97 km/hr).
Found that on this site: http://www.toromontcat.com/truck/pdf...EDT7014-01.pdf
Anyone agree or disagree? Or have other formulas?
__________________
Bob & Sandi, dogs Tasha a Frenchie and Tiki a Skipperkey
SW OREGON 2005 34 foot DolphinLX
If towing: a bright red 2016 Mini Cooper on a tow dolly.
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03-27-2016, 06:46 PM
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#2
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Senior Member
Newmar Owners Club
Join Date: Oct 2009
Posts: 10,308
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RPM's sound really high for 60 MPH Bob?
__________________
2012 Essex 4544 2011 Jeep JK, M&G Braking, 2014 MTI 27' Hog Hauler, Wireless brake control, 2006 Ultra & 1989 Springer, 2003 Harley-Davidson
FLHR Road King Anniversary
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03-27-2016, 07:11 PM
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#3
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Senior Member
Join Date: Nov 2009
Location: Warren, Oregon
Posts: 2,559
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Bob
My C-9 runs around 1600rpm doing 60, that does seem high.
2 stroker
__________________
2006 Country Coach Inspire 360 40ft Genoa Designer Series, Samsung 197 RR
Cat C9--STEEL & COPPER Bolt Together Radiator w/ updated rubber mounting
SilverLeaf 330 Magnum 2812 PSW 2011 Ford Edge Sport-Air Force One
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03-27-2016, 07:17 PM
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#4
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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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Usually the calculations for economy posted are for heavy trucks weighing more than RV's so they aren't necessarily true for lighter vehicles.
__________________
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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03-27-2016, 07:22 PM
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#5
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Community Moderator
Newmar Owners Club
Join Date: Feb 2011
Location: Point Pleasant Beach, NJ
Posts: 31,248
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I have a C-9 and I run 65mph at 1700 rpms. That does sound high for your case.
__________________
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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03-27-2016, 07:34 PM
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#6
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Senior Member
Monaco Owners Club
Join Date: Mar 2014
Posts: 916
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I am no expert. I have heard from people who I do consider expert that a CAT engine usually gets it's best fuel economy at 1200 RPM. For most, if not all, that is somewhere in the 50-58 MPH range. Again, that's hearsay! I have found it to be true in my case.
__________________
Jerry, "EWC (SW)" USN Retired
2003 Beaver Patriot Thunder 505 HP C-12 1550 TQ
Allison 4000MH Ram 4X4 towed
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03-27-2016, 09:42 PM
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#7
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Senior Member
Winnebago Owners Club
Join Date: Jan 2014
Location: North Central Alberta
Posts: 193
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The brochure says "for best balance of performance and economy" and pertains to gearing options for the C7 on vehicles less than 50,000 lbs.
It also pertains to all iterations of that engine from 210 hp and 520 lb-ft of torque all the way up to 360 hp and 925 lb-ft of torque.
I read it as sort of a blanket statement for a lot of different applications and wouldn't read too much into it...
__________________
2004 Winnebago Journey 36G 330Cat
2004 Grand Cherokee BlueOx towbar
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03-28-2016, 10:57 AM
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#8
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Senior Member
Join Date: Jan 2011
Location: Santa Clarita, CA
Posts: 929
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My CAT C13 makes the best torque at around 1300rpm. I usually run at around 1450 at 60-62mph. I pull my hills while cruise is set at 62 and end up at the top of the grade usually in 5th slightly lugging the engine at about 52mph for a 6% grade.
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03-29-2016, 08:47 PM
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#9
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Senior Member
Forest River Owners Club
Join Date: Apr 2014
Posts: 246
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my 3126b runs at 1750 RPM's at 62 MPH in our Sport Chassis truck
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2007 Forest River fifth wheel toy hauler 385 RLTS, 1999 Freightliner FL-60 with Western Hauler bed, new 3126B CAT motor, new Allison MD3060 transmission, air ride rear suspension, air ride cab, air ride seats
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03-30-2016, 06:45 AM
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#10
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Senior Member
National RV Owners Club
Join Date: Feb 2012
Location: Spokane Valley, Wa
Posts: 1,987
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Best performance
Best efficiency on a diesel should be at or slightly above max torque RPM.
__________________
Art
1999 Trade Winds 7371 Cat 3126B w/current upgrades
1990 D 250 Dodge Ram Cummins Turbo
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03-30-2016, 07:46 AM
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#11
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Senior Member
Join Date: Nov 2008
Location: Cosby, Tn
Posts: 6,587
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Quote:
Originally Posted by wb7auk
Best efficiency on a diesel should be at or slightly above max torque RPM.
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This is absolutely the best answer in the thread. As max torque rpm is engine size/model specific, a hard rpm number for all diesels doesn't exist.
__________________
Steve Ownby
Full time since 2007
2003 Monaco Signature
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03-30-2016, 08:42 AM
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#12
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Senior Member
Monaco Owners Club
Join Date: Oct 2014
Location: Rigby, Idaho
Posts: 3,902
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My Cat book says my c7 engine is most efficient between 1400 and 2000 rpm, or 1700+/-300 as my pee brain handles it. Take whatever safe speed that yields. The fuel efficiency differences within this range are negligible, and not worth my consideration. Of course, my family's safety is more important than anything else, so a safe speed for the road and weather conditions is WAY more important than maximizing my fuel.
__________________
Cheers,
TonyMac
2006 Monaco Safari Cheetah 40PMT
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03-30-2016, 05:33 PM
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#13
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Senior Member
Tiffin Owners Club Freightliner Owners Club
Join Date: Dec 2010
Posts: 578
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Quote:
Originally Posted by 1ciderdog
The following spec recommendations are for vehicles that are 50,000 lbs. or less GVW or GCW. • For the best balance of performance and economy, spec axle ratios and tire size to obtain 2000 rpm @ 60 mph (97 km/hr).
Found that on this site: http://www.toromontcat.com/truck/pdf...EDT7014-01.pdf
Anyone agree or disagree? Or have other formulas?
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I would be in 5th gear @ 2000 rpm's @ 60 mph. I try to keep my speed b/t 60-62 mph in 6th gear @ 1650 rpm's. That works for me.
__________________
07 Monaco Dynasty Diamond IV 42 ScanGuage D, AG Performance Module, Koni FSD, Safe T Plus, Ready Brake Elite, Ford F150 4x4 EcoBoost
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03-31-2016, 01:13 PM
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#14
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Senior Member
National RV Owners Club
Join Date: Jun 2010
Posts: 4,581
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Quote:
Originally Posted by wb7auk
Best efficiency on a diesel should be at or slightly above max torque RPM.
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According to a chart in this attachment max torque on a 330 C-7 is 1440 rpm. http://www.rvtechlibrary.com/engine/Cat_C7_Specs.pdf
So running 1500 rpm would put me in the slow lane all the time. I haven't driven for a couple of months but if I remember correctly 1800 rpm is about 60 mph - but I could be wrong, memory isn't as good as it used to be. I'll be on the road in a couple of weeks and will try to write down the RPM & mph.
__________________
Bob & Sandi, dogs Tasha a Frenchie and Tiki a Skipperkey
SW OREGON 2005 34 foot DolphinLX
If towing: a bright red 2016 Mini Cooper on a tow dolly.
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