dmbrichie

I have a 2012 crewcab eco 3.73 gearing...ALSO I have 24" wheels, however 10,000 miles on the truck and my overall average on the trucks computer is 12.1... I have NEVER seen it above more than 16 for more than a few minutes immediately after resetting the avg mpg

TX Hoon

I only want to say that tire pressure and air filters need to be checked regularly. I just checked mine and my tires were 2-3 lbs low and the filter was the dirtiest I have even seen after only 30k miles.

Both of these will kill mileage quickly.

Bender

I have a 2012 screw eco with 3.73, and one thing to watch is find out if it really is going into sixth gear. Mine will not go until 65-70 or I hit the tow haul button. Had to the dealer and the tried a reflash of the PCM. That did not work so ordered a new one. Of course backorder. After watching this closer, I picked up a few mpg's.

Tatunka

Good luck with the tests, I have a truck that is getting 16.3 at 65mph. So I am very interested in what you find out. Thanks!

goodburbon

Here are some inital results. MAX AC, 99* ambient.

Good truck.
0-60 avg time starting from 1900 rpm : 6.97 sec

70-55 avg coast time 16.17 sec

bad truck.
0-60 avg time starting from 1900 rpm : 7.97 sec

70-55 avg coast time 13.65 sec
__________________________________________________ __
Truck off good truck:
Manifold press:14.6 PSIA

Idle good truck
Absolute throttle A 15%
Absolute throttle B 18%
Manifold Press 4.9-5.8 PSIA (AC cycling)
Ambient temp sensor 80.6*
Spark advance 12-14*
Fuel press 175-200 psig

WOT in neutral good truck
Absolute throttle A 20%
Absolute throttle B 29%
Manifold press 4.2 PSIA
Spark advance 35-39*
Fuel press 330-340 psig
-----------------------------------------------------------------------------

Truck off bad truck:
Manifold press:14.6 PSIA

Idle bad truck
Absolute throttle A 15%
Absolute throttle B 18%
Manifold Press 4.2-5.4 PSIA (AC cycling)
Ambient temp sensor 59.0*
Spark advance 13-15*
Fuel press 275-300 psig

WOT in neutral bad truck
Absolute throttle A 20%
Absolute throttle B 29%
Manifold press 5.1 PSIA
Spark advance 35-38*
Fuel press 330-340 psig

The only differences in the two trucks is
Good has stock 275/65-18 tires
Bad has BFG AT KO 275/70-18 tires

It's unfortunate that I don't have the facilities present to quickly change the tires back to show that the issue persists, as it was there before the tires were installed.

EBinMT

Is this a type o or the real deal? Could the temp sensor be faulty causing it to be on rich circuit all the time?

goodburbon

not a typo.

engineermike

Great data, goodbourbon!

I have read that the DI engine doesn't regulate pulsewidth, but rather control fuel flow with the pressure.

Beyond that, the IAT's stick out as a glaring difference. It shouldn't be too difficult to swap out the IAT sensors between the trucks. With 99 deg ambients, they both seem low. Mine always reads at or above ambient. 59 definitely seems erroneous, though.

The deceleration times are somewhat different too. Lower gears could cause some of that. Are they geared the same?

CoreyMS

Swap or replace temp sensor before you continue. This will definitely cause different injector fueling amounts.
For instance last summer I had a excavator pooring black smoke form the exaust and bogging, using excessive fuel. Temp sensor was showing 0 degrees F, while an extreme example still proves a point. Operator had no idea as the coolant temp was fine bc CAT uses seperate senders for the guages and sensor for ecm.

I think there's more to it but you need to start here.

goodburbon

they are geared the same. Those weren't IAT sensor readings , those were whatever superchips reports as "ambient" both trucks read the same IAT which I didn't write down for spome reason. Probably because they were both the same (which was around 104 IIRC) The non driving tests were done yesterday and the ambient temp was 94.

I was actually planning to swap the MAP sensors , since the program seems to shoot for about the same MAP, if one is mis calibrated it could easily lead to rich/overfueling conditions, and the readings are coming from a single sensor.

I tried to keep an eye on pressure under full load, both trucks spiked around 30 (psia) but I couldnt get exact because they bounced around quite a bit.