Ultragauge DFCO observations

[SilverCrown9701]

So based on the above chart, would it make sense to keep track of these gauges on the UltraGauge to help increase fuel economy??


-Percent Engine Load
-Intake Manifold Absolute Pressure (MAP) PSI
-Ignition Timing Advance
-Intake Air Temperature (°F)
-Absolute Throttle Position Percentage
-Bank 1 Oxygen Sensor 2 Voltage
-Bank 1 Wide Oxygen Sensor 1 lambda Voltage
-Volumetric Efficiency
-Mass Air Flow 2, Calibrated/Calculated

[j12piprius]

The following are similar, so it's a matter of experimentation and to see which ones are most useful to you. I use % engine load or MAP for acceleration, and instantaneous mpg or (maybe) an o2 sensor for coasting. I personally didn't care for the throttle position sensor, perhaps as the pedal doesn't attenuate very well.

% engine load
MAP
absolute throttle position
o2 sensor
instantaneous mpg

Definitely calibrate the gauge to work with the various sensors in your car.

[California98Civic]

I think if you follow all those gauges while driving you're going to crash!

I find that the most useful are engine load and rpm. I follow instant FE readout too, in order to reassure myself things are going well. I started this thread to report how the UG reports DFCO.

A further observation on that point is that the O2 will sometimes need more than 2500 RPMs to go into DFCO, and sometimes not. But generally, i have determined that it will go into DFCO quickly, though often not intantly, once the engine is warm. This explains why I had erratic fuel economy variations between pump and the UG once I started using DFCO in the spring. I was relying on the instant FE reading, and it's not accurate enough. I think the O2 reading is helping me to improve my use of DFCO, which is awesome

[California98Civic]

I don't understand, what 0.600 reading? I only attempt DFCO in situations where I can coast for a substantial stretch, like 10 seconds or more. I use it for free engine cooling and battery charging. Under DFCO, I'll turn the alt on and blast the cabin fan. The O2 is helping to reveal the conditions under which the ecu will set-up DFCO more easily and quickly so that all, or nearly all, of those seconds are actually true DFCO, instead of just a very lean burn. I would guess 0.600 would be about stoich, no?

[j12piprius]

I'm not convinced the o2 sensor reading of .6 volts is indicative that Dfco is not working.

Why does instantaneous mpg show that Dfco is almost immediate?

[California98Civic]

Originally Posted by johnlvs2run

I'm not convinced the o2 sensor reading of .6 volts is indicative that Dfco is not working.

Why does instantaneous mpg show that Dfco is almost immediate?

I understand your skepticism, and I believe there is a chance it turns out correct. But it seems unlikely. The UG probably shows 999 because the UG mpg reading is not based on a specific sensor, but is rather a calculation. So when I clicked the button on the UG saying my car has DFCO the unit began showing all those nines whenever I let go of the throttle for a second while in gear. They have programmed the UG to assume that there is not fuel. I don't think they took into account the variations I'm seeing. It'snot a scientific instrument. It's really just a very good consumer toy. So I guess I'm saying my hunch is that I should believe the voltage reading from my relatively new sensor rather than the UG's calculation. Don't forget that once I started using DFCO last spring, after three years of basically accurate calibration of the UG's fuel consumption calc to the gas station pump I use, I suddenly started getting FE data showing a big difference in FE. The UG was suddenly way off. Suddenly it was always telling me I had used a lot less fuel than my regular pump was saying I had. The O2 sensor data I'm seeing is the best explanation of that experience: that the UG's instant FE calc is imprecise for DFCO scenarios and exaggerates my car's effectiveness in cutting off the fuel.

[SilverCrown9701]

I notice that in my car if I am in top gear above 45 MPH then release the accelerator, DFCO will enable and show 999.9 MPG on the UltraGauge. Once it drops into 3rd gear below 45 MPH then DFCO will disable and will read 100-150 MPG and decrease as the speed drops.

[digital rules]

Do the RPMs drop below 1100 when dropping into 3rd gear? If not, you should still be in DFCO.

You may need to fine tune the injector cutoff setting of the Ultraguage if DFCO is not registering correctly. See page 47 of the owners manual.

[California98Civic]

Originally Posted by digital rules

Do the RPMs drop below 1100 when dropping into 3rd gear? If not, you should still be in DFCO.

You may need to fine tune the injector cutoff setting of the Ultraguage if DFCO is not registering correctly. See page 47 of the owners manual.

My page 47 is blank. But on page 37, my copy makes a statement about how the value used to establish DFCO for a given vehicle only "represents a best estimate." They note that each car manufacturer "has their own algorithm for injector cutoff."

It also says that the cut off should only be seen during in gear deceleration, but I and some others--one in this thread--see it sometimes when shifting out of gear and letting the engine decelerate down to idle. Often I'll see 999.99 on the instant FE reading at such times.

I'll know better how my car use of the O2 reading to judge authentic DFCO after a couple tanks. I'll report that in my fuel log, and possibly here too if I remember.

[j12piprius]

Page 47 is in reference to injector cutoff. Page 37 refers to fuel level.
UltraGauge EM v1.2 user manual (Version 1.2, Purchased on 10/12/12 or later)
http://ultra-gauge.com/ultragauge/su...al_1_14_14.pdf

Injector Cutoff Detection ~ During deceleration, many vehicle manufacturers will turn off the fuel injectors to save fuel. UltraGauge can detect this and factor it into the fuel usage calculations. Depending on your driving conditions, this many or many not have a significant effect on mileage results. By default this feature is disabled. See the Injector Cutoff section (p47) for more information. This feature is not supported on Diesel vehicles.