ScanGuage not accurate on HEMI MDS
 

I drove the 2006 RAM 1500 HEMI MDS towing the 6x12 Race Trailer to Clemson last weekend. I planned my trip well, stayed at 62-65mph on I-75, drafting the slower 18 wheelers when able, then exited in Macon heading up scenic backroads. Overall 13.55mpg for 900 miles. There was some good hills mixed in and about. Stayed off Cruise Control except for some boring flat sections.

The ScanGuage freaks when I go into MDS (4 cylinder mode). I'll be cruising along at 4gpm then when the truck slips into MDS, then FF almost doubles, and instantaneous mileage readout generally doubles as well. It must take avg pulse width then multiply that value to get FF.

I'm not complaining, but just wanted to advise anyone attempting ScanGuage on MDS equipment. You won't be accurate unless you run exclusively in tow/haul where MDS is obviuously disabled, or so it appears. My tow gear is light, so I tow in OverDrive mostly as long as it's not seeking lockup in 5th.

As compared to Civic, it's terrifying the gas it uses. Heck, I can average 40mph in the Civic on what it takes to idle the Hemi.

Does the MDS come with it's own FE display?

Yep, but it's useless as it reads 1.5-2mpg high for trip average of any distance as compared to fill. It doesn't to Instantaneous at all. Not until I hooked up ScanGuage could I even model "when it went to MDS." There are no other indicators, nor published condition specifications I can ever find. I hear the $125 service manual doesn't even publish specs.

It was worth the gas money.. I won my Division start to finish as did my oldest son. My youngest son went down on first downhill section, and recovered for strong 2nd. Good racing weekend in front of tons of family! Only bad side was burning 66.5 Gallons of fuel.

We just got an 2008 Aspen with the 5.7 and MDS. I noticed my torque app does the same thing you are describing, mileage is way high when in MDS. At least my Aspen says "fuel saver" on top of the average economy display when in MDS so I can tell when it's in MDS. I also found the Aspen's average economy read low when compared to a full tank fill up. It said 17.2 MPG for a long trip and I actually got 18.1 hand calculated. speedometer was right on GPS speed. That was at 60-72 MPH average and in 32-35 degree temps with two mountain passes. It seemed to go into MDS more often and longer at 72 then at 65, I don't know why, the RPM there is about 2200 so maybe it just makes more torque. Around town it seems easy to keep it in MDS mode and get 17 MPG so I don't know where the EPA 13mpg rating comes from except their stupid test.

It is sad that Scanguage and Torque can't figure out the MDS mode and correct the economy. I have a feeling the onboard MPG gauge also isn't adjusting right but hopefully not doubling MPG like the Torque app seems to when in MDS.