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Diesel Engine Modifications

MVH1
Explorer
Explorer
I recently borrowed my buddies 03 Ram DRW 3500 5.9L cummins for a trip where I drove a little over 300 miles and averaged 17 mpg on the way there and 16.2 mpg coming home. I drove between 60-65 mph towing 6500-7000 lbs. I reset the mpg computer before I left the house. The average was 20.9 when I reset it. My buddy occasionaly tows his boat 1 mile to the boat ramp and drives it approximately 2 miles to work. The only mod the truck has is a programmer. I'm not sure what brand. Although this is fabulous fuel mileage, I am worried that it might be too good to be true and harming the engine. Thanks in advance for your input.
12 REPLIES 12

AH64ID
Explorer
Explorer
rtmcavoy wrote:
I recently borrowed my buddies 03 Ram DRW 3500 5.9L cummins for a trip where I drove a little over 300 miles and averaged 17 mpg on the way there and 16.2 mpg coming home. I drove between 60-65 mph towing 6500-7000 lbs. I reset the mpg computer before I left the house. The average was 20.9 when I reset it. My buddy occasionaly tows his boat 1 mile to the boat ramp and drives it approximately 2 miles to work. The only mod the truck has is a programmer. I'm not sure what brand. Although this is fabulous fuel mileage, I am worried that it might be too good to be true and harming the engine. Thanks in advance for your input.


As others have stated don't trust the overhead on a 3rd gen (2nd and 4th seem to work). The calibration tables for the injectors aren't 100%, and that is how the computer figures fuel burn.

I would suspect you where in the 13-15 range depending on trailer type.

Many programers can do harm, and many can do good.... I have no doubt my motor runs cleaner and cooler than it did in stock form and I have +150hp at they flywheel, 415 to the ground.

Bionic Man wrote:
I had a Smarty JR for the last 2 years I had my 03. Loved the change in power. The overhead reading wasn't right when it was stock, and it was WAY off with the Smarty. That said, there was very little change in MPG vs stock.


The Smarty Jr doesn't change the duration tables, it just allows the full table to be used on SW3 and more than stock on SW2. The tables are all 100% stock. The mileage on the overhead should not be effected by the SJR.

My 05 was accurate the first 10K miles, then it slowly shifted it's average error to around 17% by 25K miles. Sometimes it was accurate and sometimes it was 30%+ off. It all depended on what part of the fueling table you where operating in.

A tuner that changes the duration table will have an effect on the overhead, such as SW5 and higher on a S-06. Any module (aka Edge) that plugs into the wiring harness will throw the mileage off. Injectors will also throw it off.

2500 Grunt wrote:
Most harmful thing (in addition to just beating it all the time)is to add rail pressure b/c it's hard on injectors. I believe the Smarty JR does not add rail pressure? Only timing and duration (which adds cylinder pressure) in SW 1, 2 or 3.


Correct, stock rail pressure on the JR. It's good and bad, peak pressure is fine but Cummins did some funky tuning on rail pressure to meet the emissions on the MY04.5-07 5.9.

SW1 runs stock fueling with added timing, SW2 runs added fuel and timing, SW3 adds more fuel and timing. As I mentioned all the fueling on the SJR is off 100% stock duration tables. The tables go beyond what was required to get 325/610, max usage is around 94% "load", SW2 is around 97% "load" and SW3 goes to 100%.

I have spent a lot of time with Smarty tuning, and tuners. I have strings of emails from the main tuner and have done Beta testing on the SJR and UDC with them since 2008 and 2012 respectively.

Last but not least.. they say is picture is worth 1000 words.

-John

2018 Ram 3500-SRW-4x4-Laramie-CCLB-Aisin-Auto Level-5th Wheel Prep-Titan 55 gal tank-B&W RVK3600

2011 Outdoors RV Wind River 275SBS-some minor mods

Slated4Greatnes
Explorer
Explorer
To accurately calculate the MPG's fill the tank all the way up until you can see the fuel after it is done foaming. Then drive the truck x miles and fill it back to the same spot. Take the total miles driven (Your odometer needs to be checked for accuracey also. I use the stopwatch and mile markers on the freeway method.) and divide by the number of gallons put in the truck to get it back to visually full. This is the way I check mine and it is within .2 to .4 MPG of my Lie-O-Meter..

From what I have heard from my inline buddies the Smarty Jr. is what you want.
2004 WW SLC3505
Truma tankless WH, 6V's, LEDs inside/out, Flipped axles Michelin LTX's.

2006 F350 Tow Boss W/Training wheels
(Bulletproofed) ARP's, Decked blk/heads, BPD Remote OC, EGR & WP, Snow H20, 4.30:1, SCT W/GH, FS bags, 6" Aus Stax, Train Horns.

larry_kruzan
Explorer
Explorer
This is one issue 4th gens don't have with the H&S mini max, been right in every check.
Larry and Debbie Kruzan

We never turn a corner without wondering in amazement at God's creation!

JIMNLIN
Explorer
Explorer
I have the same '03 Dodge/Cummins in a 2500 that I bought new. This was the first year 3rd gen HPCR engines.

Edge finally came out with a programmer in '03.5 for towing for the HPCR engine. I installed it at that time and saw no difference in mpgs before or after.

However the Edge really woke the Cummins up for towing in the 1700-2000 rpm range. I believe it was 40-50 hp and 80-100 lb torque program.

My trucks DIC mpgs actually runs less than pencil figures. The truck has the '03/'04 350/555 HO and is one of the better mpg engines from Cummins.

The truck has just over 235k miles and no issues with the Cummins o r Edge other than I changed out the 175 dollar lift pump at around 150k miles.
"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers

'03 2500 QC Dodge/Cummins HO 3.73 6 speed manual Jacobs Westach
'97 Park Avanue 28' 5er 11200 two slides

fj12ryder
Explorer III
Explorer III
path1 wrote:
My (2001 5.9) overhead computer is always 1 or 1 1/2 miles off from doing the math long hand, usually to the plus side.
My '01 is the same.
Howard and Peggy

"Don't Panic"

boogie_4wheel
Explorer
Explorer
+1 on the 3rd Gen Cummins being a lie-o-meter. Mine reads ~4mpg higher than my actual economy (thanks to the Edge programmer I'm using). Without the Edge, it still lies.


path1 wrote:
My (2001 5.9) overhead computer is always 1 or 1 1/2 miles off from doing the math long hand, usually to the plus side.


The 2nd Gen Cummins is a whole lot closer. My dad's is usually within .5mpg.
2005 2500 Cummins/48RE/3.73, QCLB, 4wd, BigHorn, Edge Juice w/ CTS + Turbo Timer,Transgo Shift Kit ISSPro Oil and LP pressure gauges, GDP 20/2 filters, Custom Diesel Steering Box Brace
'10 Forest River Shockwave Toy Hauler 21'
Honda EU3000I Genny

2500_Grunt
Explorer
Explorer
rtmcavoy wrote:
I recently borrowed my buddies 03 Ram DRW 3500 5.9L cummins for a trip where I drove a little over 300 miles and averaged 17 mpg on the way there and 16.2 mpg coming home. I drove between 60-65 mph towing 6500-7000 lbs. I reset the mpg computer before I left the house. The average was 20.9 when I reset it. My buddy occasionaly tows his boat 1 mile to the boat ramp and drives it approximately 2 miles to work. The only mod the truck has is a programmer. I'm not sure what brand. Although this is fabulous fuel mileage, I am worried that it might be too good to be true and harming the engine. Thanks in advance for your input.


Most harmful thing (in addition to just beating it all the time)is to add rail pressure b/c it's hard on injectors. I believe the Smarty JR does not add rail pressure? Only timing and duration (which adds cylinder pressure) in SW 1, 2 or 3.
2005 Dodge 2500 5.9 SRW long bed
2014 FS28 Evergreen Amped TH Blue Ox 2000# WDH
2300CC VW turbo 4 seat sandrail, Yz450f, 350 Raptor quad

path1
Explorer
Explorer
My (2001 5.9) overhead computer is always 1 or 1 1/2 miles off from doing the math long hand, usually to the plus side.
2003 Majestic 23P... Northwest travel machine
2013 Arctic Fox 25W... Wife "doll house" for longer snowbird trips
2001 "The Mighty Dodge"... tow vehicle for "doll house"

Bionic_Man
Explorer
Explorer
I had a Smarty JR for the last 2 years I had my 03. Loved the change in power. The overhead reading wasn't right when it was stock, and it was WAY off with the Smarty. That said, there was very little change in MPG vs stock.
2012 RAM 3500 Laramie Longhorn DRW CC 4x4 Max Tow, Cummins HO, 60 gallon RDS aux fuel tank, Reese 18k Elite hitch
2003 Dodge Ram 3500 QC SB 4x4 Cummins HO NV5600 with Smarty JR, Jacobs EB (sold)
2002 Gulf Stream Sea Hawk 29FRB with Honda EV6010

ScottG
Nomad
Nomad
Ya, the programmer causes you to use less throttle and it can really throw the MPG indicator (also referred to as a lie-o-meter).
I pull the same amount of weight and get 11~12 hand calculated but the overhead shows 14+.

FireGuard
Explorer II
Explorer II
The Smarty programmer works well on the 3rd gen Cummiins.
The overhead mpg isnt accurate with a programmer.
The 03 is very good for mileage. I can get around 17-18 empty with my 4x4 DRW if I keep the speed below 70. Drops to around 11-12 towing or carrying my Lance camper.
13Jeep Wrangler
07 Ragen 21FB
12 Yamaha Super Tenere
14 Suzuki DR 650

ib516
Explorer II
Explorer II
Its common for a side effect of the power programming to throw the in cab mpg out for the better. It will tell you you're getting that mileage, but its lying to you because the engine is running an aftermarket tune. Mine did the same. Mine was out by +30%.

A good tuner in the proper setting does no harm to the engine. Sure you can break things if you set the tuning on high and tow a big heavy load when it says not to tow over xxx lbs in setting xx. But, the right product used properly won't cause any problems.

Tuners come in all shapes and sizes from mild to wild. I've had both. The hypertech I used was mild and safe, and the diablosport predator was wild and smokey - but made the truck FAST! Depends what you're after. I preferred the hypertech.
Prev: 2010 Cougar 322QBS (junk)
02 Dodge 2500 4x4 5.9L CTD 3.55
07 Dodge 3500 4x4 SRW Mega 5.9L CTD 3.73
14 Ram 2500 4x4 Crew 6.4L Hemi 4.10
06 Chevy 1500 4x4 E-Cab 3.73 5.3L
07 Dodge 1500 5.7L Hemi 3.55 / 2010 Jayco 17z
All above are sold, no longer own an RV