Finding MPG?

mike71800b · **Joined:** Wed Jul 25, 2012 11:14 pm **Posts:** 23

Trying to find some mpg in my 2006 with 125k miles on it... I do mostly 85%city driving and often turn up 17 mpg hand calculated... best combined mpg 22 twice in the last 5 or 6k miles.
Stock ecm with egr delete, f37 tcm, mbrp stainless exhaust, new map sensor and filters... air and fuel both under 5k miles run 40psi in stock size street tires and no dragging brakes verified with ir thermometer.
Currently running stock 808 tune with egr and fcv delete... Boost hits 22 and holds at 20 during hard acceleration so i think the egr is closed and not leaking... i see 4 or 5 psi cruising around 60 mph... maf reads 18.5 g/s at idle.
I wish torque could stay connected for longer... when running 55 to 65 I can see torques calculated average between 28 and 32 with slight variation in road grade... I had played with substituting a 222 ohm resistor and a 200 ohm resistor in place of the temp sensor, the 200 ohm was registering 215 deg through torque display and was registering hot enough that boost cut had come into play with the ecm... the 222ohm was registering at 205 deg and I had full boost... both values you could watch the instant fuel use values not drop as low into the teens on hills as with the ecm's temp sensor functioning at 176F with working thermostat... above 1850RPM or so fuel consumption ramped up also... Any additional power tunes cause converter chatter... i suspect it has a stock hemi converter <receipt was in glove box> it has a strong pull if left in gear while not moving. I didn't find very much change in mpg with the viscous heater disabled except when it was in the 20's and 30's and I didn't mind one bit then leaving it hooked up.
Well thats the background and i see what others are claiming as their mpg and i feel on the low end of the bracket...

Does torque calculate mpg the same way the evic lie o meter does? I dont have one by the way...
I can see good numbers when i go stretch it out on a cruise but I dont often leave town so....too many short trips killing my hopes here?
Has anyone been exactly here where i am and went to miracle mpg with GDE tune?
I suspect if there is a hemi tc the pump upgrades weren't done so i cant really see if yeti stage 2 or 4 can get any gains since bad chatter is happening before 1500 rpm...
Well thats where im at with 4k $ in a good low miles solid crd and eyeballing whether trying GDE tcm program alone might satisfy with stock ecm code + deletes or GDE ecm+tcm will do, or ecm+tcm+pump upgrade is where i need to be? I'd like to get decent <25 mixed mpg?> with a mild lift on 245's for some light off roading but i dont want to get way upside down on $$$ chasing mpg that might show up.
Whats been your experience climbing out of the low mpg hole?
Hope this wasnt too long and thanks for replies !

TKB4 · **Posted:** Sat Jun 15, 2019 6:02 am

I am not sure what diameter tires you have now but original tires were about 29 inches. I would try a larger diameter tire first but not worth doing until you need tires and most increase is to about 30.5 to 31 inch without lift and max with lift of 32.1 inches with flattening pinch welds I would expect a maximum increase of between 1-2 mpg . . The only other thing you can do that may eventually over say another 60,000 miles pay for itself is the GDE tune expect another 1-2 mpg (not knowledgeable about economy with the Yetti tunes) and the TCM tune . The TCM tune may be worth doing first since you do mostly city driving if you have a lot of stretches of around 40 mph where converter would be locked. The temp you already tried. I am sure you could work with some front air dams etc but probably wouldn't help much except at highway speeds. Make sure there is no head gasket leak and no air in fuel but it doesn't sound like thats a problem. My experience is that in city driving long idling times like sitting still at lights or doing carpool waiting on kids etc seem to affect mileage more than other vehicles. One last thing if you haven't tried it do the ORM (unplug the MAF sensor) and see if there is a change.

Good Luck with your endeavors.

WolverineFW · **Posted:** Sat Jun 15, 2019 2:02 pm

Sorry but larger tires will increase the rotational mass of the wheels and equate to lower MPG, not higher MPG.

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TKB4 · **Posted:** Sat Jun 15, 2019 3:49 pm

taller tires have proven to increase mpg on the four different CRDs I have installed them on. I presume by having same effect as lowering differential gear. I would presume if you put lots wider heaver tires that are also taller it may not. If have one lifted 2inches and 32.1 inch tires that still had about .5 mpg increase in mileage. I speak from real world experience and have 6 CRDs 2 are my sons now.

WolverineFW · **Posted:** Sat Jun 15, 2019 6:53 pm

So did you have the ECM reprogrammed for the change in revolutions per mile?

How much did the new tires weigh compared to the old tires?

Did you change to different rims?

There are numerous factors that can affect mpg after changing tires. You experience is the opposite of what tire industry states about changing tires sizes.

Don't you think that if larger tires improved fuel economy that every auto manufacturer would be mounting larger tires so they could advertise better fuel economy and greater offroad capability?

mike71800b · **Joined:** Wed Jul 25, 2012 11:14 pm **Posts:** 23

Wasn't looking for this to turn into a tire argument but do see how larger can raise the *corrected* mpg by keeping rpm lower for a given speed...since that appears to be where the engine is most efficient even if the load increases.
On my troopers for example 31" tire is 10% greater in circumference than stock... so i can either add 10% to the indicated miles traveled or divide indicated miles/gallons and add 10% to that number ... same/same.
:juggle:

Im running stock wheels and tire size and indicate within 2mph of what roadside radar signs flash back at 45mph.

TKB4 · **Posted:** Sat Jun 15, 2019 9:17 pm

I stated why I believed it made the difference related to gearing. Doesn't matter what revs per mile or what EVIC says if matched with GPS MPH readings to correct speedometer/odometer and hand calculations over thousands of miles . I am sure the opposite is true of many other vehicles and conditions . Another byproduct is the tires generally last more miles. I am also sure there are lots of other variables but its still true of all 4 I have done. I think most of my tire wheel sizes are in my signature.

Others are free to give their experiences that may be contrary to mine.

mike71800b · **Joined:** Wed Jul 25, 2012 11:14 pm **Posts:** 23

To be clear i think you are correct the same way a lower numerical diff ratio could be helpful for stock tires.

***EDIT*** Adding I have not tried running with the MAF disconnected as my understanding was its primary purpose was a simple way to disable the egr activation.

Back to the MPG hunt

TKB4 · **Posted:** Tue Jun 18, 2019 6:46 pm

I believe there is also a way to make an electrical switch to manually lock up the torque converter but I have not done this .

minisub · **Posted:** Tue Jun 18, 2019 7:11 pm

The biggest bang for the buck I got for mileage was replacing all four brake calipers. The GDE tune helped when measured over a good number of miles and time. The brake job had an immediate and discernable impact.

timothyd · **Joined:** Wed Feb 20, 2019 2:58 am **Posts:** 90

I'm chasing the same numbers right now, most recently I installed an EGR blockoff plate which was significant as well as an in tank pump (I was indeed having a large amount of air coming in somewhere) and I am now averaging 24MPG doing probably 50/50. I will be going on a longer trip next week and will see what it comes out too then. I have a GDE hot tune waiting but I am ordering the TC and other parts in the next month and will see just how much that helps as well.

mike71800b · **Joined:** Wed Jul 25, 2012 11:14 pm **Posts:** 23

Think ill stay away from trying to manage lockup by myself,
viewtopic.php?p=852132&sid=d12ca77ce45aef9807b3374f2cf2a76f#p852132

Brakes on all 4 corners test under 100 deg f after stopping from 65mph at the gas station... I have found dragging brakes before and typically will find a hot corner 30 deg or more above the rest.

How much did the GDE tune get you and whats your driving like minisub?

Yeah timothyd i have seen air in fuel will kill mpg, had the typical heater plug start leaking air and horrible mpg that tank.
Plan on making an egr plate when i have a little wrench time, i may be loosing a little there but not terrible since i hit 22lbs boost on a 0-60 run.

I have a little different driving routine this week with a 20 mile round trip in the mornings and fewer traffic lights so ill post up some numbers this weekend.
Thanks guys

GordnadoCRD · **Posted:** Tue Jun 18, 2019 10:11 pm

TKB4 wrote:

I believe there is also a way to make an electrical switch to manually lock up the torque converter but I have not done this .

The Torque Converter clutch solenoid in this application is not a strictly on/off 12v. It is another famous PWM signal solenoid, electric over hydraulic.

I've been told that this solenoid never fully locks, in fact, if it's activated more than 50% modulation, it will burn out.

That's only hearsay, though. Keith @ GDE would be one that could confirm or deny.

mike71800b · **Joined:** Wed Jul 25, 2012 11:14 pm **Posts:** 23

Got some new results 250 miles with a/c mostly... 10.75 gallons = 23.25mpg
Beginning to think its capable of good mpg just not suited well for city driving.
20 mile round trips are still relatively short drives when it takes about 5 miles to get up to temp.

TKB4 · **Posted:** Sat Jun 22, 2019 9:37 am

Thats actually not bad for city driving . The transmission tune from GDE may still benefit you. However, even if it got you one extra MPG and it costs $250 . Assuming $3.00 per gallon diesel and current 23 mpg it would take about 46,000 miles but I would fudge and say at least 60,000 miles. then you also lose whatever you could have made on the $250 over whatever time it takes you to drive that distance. Of course my math could be wrong.

Finding MPG?

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