O2 Experiment 06 Xa Scion
 

Here is an update on my quest to understand how the O2 sensor operates and the possibilities for increasing fuel mileage.
I drive a stock 2006, Scion, Xa, automatic.
I ordered a manual from [URL="www.eagle-research.com"] E.F.I.E. (Electronic Fuel Injection Enhancer) and followed the instructions. They were accurate but careful attention is required.
The unit is installed and is adding 250~300 mV to the O2 sensor output.
I have just topped of the tank and will post a report in a week or two.

Briefly, the circuit I have installed adds to the voltage signal from the O2 sensor. (An Offset) This control loop uses the O2 sensor to continuously adjust the fuel injectors for the proper fuel/air ratio. This optimum fuel/air ratio is a calibration point of 500 mV. The added voltage changes the O2 sensor output to a value the computer (ECU) knows is rich. The ECU reduces the (on) time to the injectors until 500 mV is achieved. This new value is leaner because of the offset voltage. The automotive designers must use values that work for all drivers in all conditions. It is this area of (safety margin) that I believe some additional fuel savings may exist.

Is the 250-300 mV a fixed range or can you make adjustments to the offset?

Are you using your factory stock ECU?

I visited the site but had to search around to find the manual and unit. Found it here:
https://www.eagle-research.com/products/pfuels.html

Will be watching for your reports. Thanks.

Very interesting. What you say makes perfect sense, you can control the exact fuel AFR when the car is in closed loop by showing the ECU particular readings.

I'm assuming this is just wired inline with the O2 sensor and doesn't get adjusted much? So that a particular reading of 14.7 from the O2 sensor will now actually be 15 or 16:1 instead? This seems, just watch for any knocking. Reduced AFR means more chance for preignition. Most new cars ECUs will protect the engine by retarding the advance, but you'll lose power this way. You may find even with knocking (ie. retarded ignition timing and less power) that you'll still use less fuel and this may be perfect for you.

I'm not sure how you would calibrate it to be an exact AFR though (like 15.5:1 or whatever). I'd think an adjustable offset hooked to a wideband O2 sensor would be much more useful. You could ask an engine tuning shop if they'd tune your AFR for you, typcially dyno and engine tuning shops have their own wide band sensors they'll hook to your car for just the little while you're there and that'd definately be a cheaper option then buying a $200-300 wideband sensor.

I'm anxious for your results.

So this thing basically puts the car in a permanent closed loop? That actually sounds quite promising. I'll be interested to see the results of this.

EFIE Results from another user
 

Just to post some data points.

I've been using a eagle-research built unit since early 2003 and can report about 10% improvement in the Mazda (Ford) 2.3L dual plug motor. About 5% or less in a Nissan KA24E single plug. I can run much leaner with the dual plug motor as seen by using a cheap air/fuel ratio gauge. Still haven't measured added voltage by the EFIE.

This thing just steps up the voltage from the O2 sensor so the ECU thinks it's running richer and compensates by leaning it out. The changed O2 sensor signal still fluctuates as usual, and the engine runs like stock, just a little leaner.

itjstagame -

I have the same EFIE, but I haven't installed it yet because I wanted to finish my digital A/F ratio gauge (a kit you solder). With the gauge I am able to "see" what the EFIE is doing in real A/F ratio numbers, not just flashing lights. Right now I am breaking the A/F gauge in and I can see a dominant 14.7 ratio over time. Once I attach the EFIE, I will shoot for a 15.5 ratio and see what happens.

So many projects, so little time ...

CarloSW2

will this running lean destroy the factory cat? I've seen rich melt cats but not really sure on lean conditions.

ffvben -

In addition to worse emissions (more NOx), that's my worry also. That is why I am getting the A/F gauge online. It will put me in a position to "nudge" the EFIE into the lean without (hopefully) damaging the emissions system, or the engine. All of this scary stuff (i.e. You'll shoot your eye out!!!!) is less of an issue with GasSavers gentle driving style, but I am just repeating what I have read. I intend to have a switch to turn the EFIE on and off. From what I know, the EFIE is designed to have an on/off switch. That is to say, if it gets no power, it passes the unmodified voltage from the 02 sensor straight through to the ECU/PCM.

As a test, I attached the EFIE maybe a month or two ago but I didn't like their instructions. They basically said "lean it out until the car starts to stall" and then un-lean it back. In that scenario, I have no idea what the actual A/F ratio is.

But I don't think you need an A/F gauge to tune it. You only need a multimeter. Idle the car in your driveway with the multimeter patched into the 02 sensor. Whatever "dominant" voltage you observe is what the car considers to be 14.7. That will be the baseline setting for your EFIE.

This is the order that I think you have to obey when doing the test ...

Normal car :
engine -> exhaust 02 sensor -> car ECU/PCM

Monitor normal A/F ratio :
engine -> exhaust 02 sensor -> multimeter -> car ECU/PCM

Monitor how EFIE is effecting A/F ratio :
engine -> exhaust 02 sensor -> multimeter -> EFIE -> car ECU/PCM

The range is 0-1 volt for narrow-band and 0-5 volts for wideband 02 sensors.

CarloSW2

Running lean should not affect the cat in any way. Whereas running rich destroys it because of unburnt fuel increasing the temperature inside the cat running lean will mean less unburnt fuel and less of a chance to damage the cat. The increase in NOx emissions caused by this lean-burn will just mean the cat is less effective and is letting more slightly more pollution through. However, with how miserly us gassavers are with fuel, what is "more NOx emissions" to our cars is still less than "normal NOx emissions" for the leadfoot drivers of the world :D .

do you know this site: https://better-mileage.com/memberadx.html ?
It describe an alternative metod for change the o2 sensor signal.

I bought the electronics components, and the next month I will construct the device described at the Internet link

ciao

fabrio