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.
