OK, I cant post pictures right now then, but I can post some of my simulation results.
The take away from my real world fuel economy results is this- On my other cars, normal cars, like Jaguars XJRs, VW Golfs etc- stop start driving usually brings the average fuel economy down and longer distance Highway driving brings the average up.
For the Ram diesel it seems to be the opposite- I think this is because of the immense frontal area of the truck and the poor drag coefficient- that driving it at speed kills the mpg.
FWIW the simulation shows exactly the same trend. It's best not to focus on the exact numbers of the simulation but to utilize it in terms if trends and then compare it to our real world experiences;
So I have
Stock Quad Cab Dodge Ram 2500 with 48RE , 3.73 rear end and 265/70 -17 tyres
Fed Highway sim avg: 20.94 mpg
Stock QC Ram 2500 with NV5600 ,3.73 RAR and 265/70-17
Fed Highway sim avg: 18.49 mpg
My problem with this result is that the Fed Highway doesn't utlise 6th and revs the engine quite high, more so than any driver seeking fuel economy would- so I would like to modify the shift schedule if possible
QC 2500 with 48RE, 285/70-17 tyres and a 3.42 rear end
Fed Highway: 21.35 mpg
- Here you can see the effects of both the larger diameter wheels and the 3.42 rear end. I need to separate out the effects
Stock QC 2500 with 3.73 RAR and 265 tyres
running constant 75mph: 12.23 mpg
QC 2500 with NV5600 with 3.42 RAR
running constant 75mph: 13.51 mpg
QC 2500 with 3.42 RAR and 285/70 tyres
running constant 75 mph: 12.98 mpg
I know I need to separate some of these effects out.
Other notable assumptions- I used a drag coefficient of 0.56 as a guess. The SRT10 was 0.45, the stock 1500 is listed as 0.53 so I guessed at 0.56 due to the higher stance and I increased the frontal area accordingly.
I used 88% as average efficiency for the 48RE- most autos ( like the NAG1 Benz trans are low to mid nineties). Because this is derived from an old torqueflite_ assumed a low figure. This is probably a bit harsh of me but I'd rather be pessimistic.
I assumed the efficiency of the NV5600 at around 98% in direct drive top and 97% in 0.73 over drive ratio.
There's quite a lot of 'stop and go' in the Federal Cycle.
This is the cycle-
It doesn't really get up above 60 mph- which is why the figures look quite good.
The other factor is that for the BSFC map (break specific fuel consumption) for the 5.9 Cummins I used some measured data from a Semi Truck dyno data I had and some 8 mode test data I had I extrapolated the rest. Also the spec of he semi truck application of this engine isn't EXACTLY the same as the Ram pick up. In addition, when this BSFC data is derived- its steady state on an engine dyno, what a vehicle achieves when driving can be a bit different.