Poor fuel MPG

[Scarecrow]

Checked the Mileage when I topped off this afternoon, and  found that I got 13 MPG. Now granted it's winter, and the truck idles more, this is still pretty crappy.

The particulars are as follows: 1998.5 3500 24v, edge EZ box, DAP 100hp VCO sticks, New OE size tires (215 85 r16) 400,000 Miles 5 spd trans. I'm planning on jumping on the quadzilla train this spring, but does anyone have an idea why my mileage sucks so bad?

 

Mark

[Scarecrow]

Ok, found this after about a couple of hours looking thru threads, and may have a impact on what I've got going on right now,

Quote

Timing is based on two factors which most will not get. Cetane of the fuel and the pop pressure of your injectors. Cetane that is high requires more retard, of course low cetane require more advanced timing. Pop pressure is going to affect clean atomized spray or big droplets that are difficult to vaporize and ignite. Hence why my 7 x 0.010 injectors were popped at 320 bar not 305 bar like most get. This provide a very fine mist but the timing is late. Quadzilla allows for adapting to different pop pressures and cetane. This is where Edge screws up big time. It follows the stock timing and adds rough +2 on top. So if the IAT temp falls to 80 or lower the ECM automagically jump +4 degrees to timing screwing up the winter MPG even worse. 

 

I had my 7 x 0.009 injectors popped at 320 bar also, and with the Edge EZ adding timing, plus the whole winter thing could be what's pooching my MPG. Without going to a Quad just yet, does anyone have ideas on how to fix this, or just bite the bullet and get a Quad and tune?

 

Mark

[Tractorman]

1 hour ago, Scarecrow said:

So if the IAT temp falls to 80 or lower the ECM automagically jump +4 degrees to timing screwing up the winter MPG even worse. 

 

Have you done the IAT sensor fooler with a resistor yet?  I use a varaiable resistor that sets the IAT sensor reading at 143° all the time.  This really helps for winter performance and fuel economy.  Plus, the engine runs quieter when cold.  I use a Smarty S03 on a mild tune with stock timing - RV275 hp injectors. 

 

About a month ago, I made a trip from Baker City, Or to Crescent City, Ca (a 1,000 mile round trip) carrying about 800 lbs in the bed for traction.  I averaged just over 20 mpg with ambient temperatures ranging from 5° below zero to 40° above.  Most of the time the temperature was in the 20's.

 

- John

[Royal Squire]

@Tractorman

John - What did you run for speed on that trip?

[Tractorman]

The speed was quite variable.  On the way to Cresecent City, the roads were snowpacked for about 350 miles, so speed was about 45-50 mph with a lot of time in 4WD.  On the return trip, speeds were about 60-65 mph where the roads were clear which was most of the way.  The speeds were slower through the mountain passes (7 passes each way).

 

- John

[Scarecrow]

No, I haven't tried a IAT fooler yet, but sounds like something that would work even with a Quad.  Sounds like you made yours, but I'm not that electronically inclined.  So how/where can I get one of these?

 

Mark 

[Tractorman]

8 hours ago, Scarecrow said:

So how/where can I get one of these?

 

Mine has been on my truck for about 8 years.   I will take a photo of it tomorrow and post it here.  From what I remember, it is a 5,000 ohm 1/4 watt variable resistor.  I mounted it in the engine compartment near the driver side hood hinge.  Essentially, the IAT sensor is disconnected and sealed off.  A two-pin Deutsch  male electrical connector with a six inch lead can be purchased from Amazon and used to lengthen the wiring to the the mounted potentiometer.   It is a relatively simple process.  I can post more detail tomorrow.

 

Also, I forgot to mention that I use a homemade winter front during the winter months for faster engine warmup and improved driveability.  This also helps improve fuel economy.

 

- John

[Mopar1973Man]

I'm working on bringing my high idle kit back to market. I'll keep you all posted.

[Scarecrow]

I see that you can input different pop pressures in the Quad, what about inlet temp, or do you just do a winter/cold weather tune and adjust the timing? Trying to decide whether to:

A) get a Quad now and save some fuel, or

B) Wait until spring and get some bills paid off first 

As I see it right now, I'll need at least 3 tunes to start with, a winter tune, a milage tune, and a tow tune.

 

Any suggestions and comments are welcome and encouraged.

 

Mark

[Mopar1973Man]

Pop pressure alters timing like my setup with 7 x0.010 popped at 320 bar is about 2 degrees retarded. Then monitoring my engine oil as long as engine oil is about 30 degrees cooler than coolant then time is close to right. Lower the engine load better your timing. This is why I can run 24 to 26 degrees at 2k rpms.

Edited March 4 by Mopar1973Man

[5akman]

On 3/3/2024 at 6:54 PM, Tractorman said:

 

Mine has been on my truck for about 8 years.   I will take a photo of it tomorrow and post it here.  From what I remember, it is a 5,000 ohm 1/4 watt variable resistor.  I mounted it in the engine compartment near the driver side hood hinge.  Essentially, the IAT sensor is disconnected and sealed off.  A two-pin Deutsch  male electrical connector with a six inch lead can be purchased from Amazon and used to lengthen the wiring to the the mounted potentiometer.   It is a relatively simple process.  I can post more detail tomorrow.

 

Also, I forgot to mention that I use a homemade winter front during the winter months for faster engine warmup and improved driveability.  This also helps improve fuel economy.

 

- John

I'd like to see this set up also as I'm trying to milk a few more mpg out of my rig. 

[Tractorman]

The two photos below show my setup using a 0-5,000 ohm variable resistor (potentiometer).  I have it set to display a constant 143° when checking with my OBLink scanner.  The temperature never varies.  There are lots of resistors (fixed and variable) to choose on Amazon or other sites. 

 

 

 

Here are some excerpts from Michael Nelson (Mopar1973Man) from a few years ago.  They should be helpful for understanding how cold intake air / warm intake air affect engine performance and fuel economy.

 

- John

 

 

 

[5akman]

So, instead of a potentiometer,  a guy could just go with something like the 2.2k resistor by itself and get the same effect, correct? Now, what wiring harness branch and what color wire are we wiring this resistor into?

[Mopar1973Man]

Just info purpose... If your running a Quadzilla tuner the IAT isn't really used. You'll gain more from proper timing than chasing IAT mod that isn't really used in Quadzilla tuning. 

 

Things to be aware of...

Pop pressure your injectors are set too. 

>310 bar timing is retarded by the injectors means it's late to fire being it needs more pressure. You can add timing.

<310 bar timing is advanced by the injectors means take away some of timing being the injectors are adding it mechanically

 

Proper timing your engine oil temperature should be -30°F cooler compared to coolant. So if your engine oil temperature are high then your timing isn't set right. Just keep in mind I'm running 26° BTDC at 2,000 RPM on cruise timing pushing me into the mid 20s for MPG. The biggest thing is your boost pressure MUST BE 5 PSI OR LESS!!! Do not attempt to run high timing with more boost or head gasket failure could occur. This means you have to keep low engine load setting on your light engine load timing.

 

As your setting timing if engine load goes up then your going the wrong way. If engine load is going down then MPGs are getting better.

 

 

Trans temp is engine oil temp.

Coolant will flip to -40°F when coolant is over 204°F and I'm reaching 210°F with my 200°F thermostat. 55 MPH for me in 5th gear is near 1,600 RPM with 22° BTDC. Again proper timing nets way more.

Edited March 5 by Mopar1973Man

[5akman]

Mike, I'm running your Econ tune and I'm always up around 25 +/- on engine load and oil temp is usually 5 degrees over coolant temp while commuting on flat ground, 200' AGL, 70 mph, 2000rpm, 5-8 psi boost, timing rarely up to 17 or so. I'm seeing a steady 16 - 17 mpg. Any suggestions short of tire size reduction (it would take a lot of mpg savings to counter 1000.00 for new tires). 

[Mopar1973Man]

Final ratio is huge. I'm running 3.69:1 final ratio. Below 3.55 is hard to to tune out because you will be required to manually keep your RPMs near 2k for optimally. Too low of cruising RPM could be considered lugging because you too low in RPMs.

[5akman]

48 minutes ago, Mopar1973Man said:

Final ratio is huge. I'm running 3.69:1 final ratio. Below 3.55 is hard to to tune out because you will be required to manually keep your RPMs near 2k for optimally. Too low of cruising RPM could be considered lugging because you too low in RPMs.

I was thinking I was good on final ratio with the 32" tires and regear to 3.73's. Maybe I'm just not going to get over the 16-17 mpg with the auto transmission. 

[Mopar1973Man]

Info needed...

 

Boost at 55 and 65 MPH

Engine load for 55 and 65 MPH

Timing for 55 and 65 MPH

 

Let's see if ican get you to ride in cruise timing and alot of people don't return to get that programmed up right.

 

Double checked... addon. You matched with me.

 

So let's look at the tuning more in depth.

Edited March 6 by Mopar1973Man

[5akman]

Here you go Mike:

55mph = 1600 rpm, 2 psi, engine load 21, timing 16

65 mph = 1900 rpm, 4 psi, engine load 23, timing 19

65 mph with slight grade = 2000 rpm, 7 psi, engine load 32, timing 14

[Mopar1973Man]

So what is you max timing for 1.5k, 2.0k, 2.5k, 3.0k RPMs?

 

Light throttle load limit?

 

Then light throttle timing advance?