Post 8: The Role of Sensors in Fuel Delivery

If you haven’t started at the beginning, then you are missing some things in your education. Please go to Post 1 and start there NOW to be sure you get a thorough understanding.

There is more computing power in the average cell phone than what was used to take the Apollo 13 mission to the moon?


The sad thing for us is when we buy these fuel consuming beasts, it actually works in the reverse. We become slaves. Slave to those that program and design the systems that drive them down the road, for they are the ones that determine how much fuel it takes to move us to our destinations.

In the past 100 years, technology has advanced to a phenomenal degree. We allegedly have the most fuel efficient vehicles than have ever been made. While I believe this is true to a certain degree, it is also true these systems enable the Slave Masters to control what can and cannot be done to improve your engines fuel ECONOMY. And economy is not to be confused with efficiency.

The industry considers the measure of the exhaust to be representative of a system’s efficiency, NOT the amount of fuel required to get the job done. But the public is programmed. Programmed to put their faith in the liars cheats and thieves that are running our world.

In the interest of taking some of our power back in one small area (how much fuel we use) we face a number of obstacles, the vast majority residing in the actions and limitations set forth in the programming of the ECU. Ignition Timing, Injector Pulse Width, Catalytic Converter Temperature, and many other aspects that affect fuel economy are pre-set and immutable.

What we’re going to do today is to talk about the role of various sensors in the computer’s calculations that determine the amount of fuel to deliver while the engine is running. ALL of these systems must be considered in your quest for 100+.

I’m going to start with the air and move with it through the engine, considering the actions of each sensor start to finish. Then, we will consider what can be done with each to further enhance the results of The Gadgetman Groove.

Now, some of these will enhance a NON-Grooved engine, but they are to be used with caution on engines that are not vaporizing the fuel completely, for it is this wasted energy is what we want to reclaim, enhancing not only Efficiency, but Economy as well. It is this waste fuel that causes most of the wear in our engines, so reducing it will also enhance engine operation and life-span.

Study this diagram for insight into MAF sensor operations.

The first sensors the air encounters is the MAF and/or the IAT. The Mass-Air Flow sensor is a device that measures several dynamics. It measures both the amount of air passing over it, the temperature and even the relative humidity as it acts on a heated element (resistor) and uses the current flow through the circuit to determine the how much fuel should be delivered according to the amount of air, thereby managing the Air-Fuel Ratio. To get more technical data on the MAF, go to the Wikipedia article.

The Intake Air Temperature sensor does essentially the same thing, in the same way (using a resistor) and is much simpler in construction as well as operation. Use the information from the Wiki article on the MAF to learn about its function.

From there, the air will be drawn through the throttle assembly. Here, the Throttle Position Sensor (TPS) has its role in the ECU’s functions. Using a variable resistor that is actuated by the throttle controls (whether cable or computer controlled throttle assemblies) the ECU can determine how much fuel should be delivered. It also uses this sensor to determine shift points in many vehicles.


The TPS is also a key component if you’re working on

fuel vaporization systems to determine vapor delivery rates.

Now, the air enters the intake manifold. Here, the air is presented to the MAP or Manifold-Absolute Pressure sensor. Again, turn to Wikipedia for good information.

This video explains in simple terms how the MAP sensor functions.

This sensor is designed to measure the difference between the pressure inside the intake Manifold and the outside or ‘Absolute’ pressure using (again) a variable resistor. Using the value presented to the ECU, the computer calculates the proper measure of fuel to deliver, once again referencing all the other sensors to confirm the proper AFR.

From here, the air enters the head, where the fuel is delivered to the air stream as it enters the combustion chamber. To determine ignition timing, the ECU utilizes both the Crankshaft or Camshaft Sensor and the Knock Sensor.

Here’s a short video on what the knock sensor does and how it does it:

There are more in-depth videos on YouTube if you want to look for them. Remember, knowledge is power. Actually, knowledge is only POTENTIAL power. If you don’t use it, it is not very powerful, now, is it?

Once the ECU has made it’s determination of proper ignition point, it will send the signal to to the ignition circuit commanding a spark be delivered.


Don’t use Motorcraft spark plugs!

Their design is defective, as is common with resistor-style plugs. When the internal resistor

burns out (they all do in time!) the anode of the resistor can fall into

the combustion chamber, necessitating engine rebuild.

This happened to us in Provo Utah. $4,000 in repairs and one week later,

We could finally continue our trip.

Ford/Motorcraft is facing class-action lawsuits because of this.

When the fuel in the combustion chamber is ignited, it is then pumped out to the exhaust manifold, where it is exposed to the Oxygen Sensor.

Here is a nice video by ADP Training on its operations. (I do so LOVE YouTube!)


The O2 Sensor compares the oxygen level in the exhaust with ambient air.

The method of measuring the external O2 content is unclear, but

it is known that grease and oil deposits on the OUTSIDE of the sensor and

sensor wires may cause erroneous readings.

This sensor is only read during ‘Closed Loop’ operations. During ‘Open Loop’ operations, fuel management is calculated based on all sensor activity, disregarding the oxygen content. This can be a pain in some systems as the engine operations in some systems drop into Open Loop whenever there is a change in engine speed.

Using the values determined by the Upstream O2 sensor, the ECU will alter the fuel trims to maintain proper AFR.

Now, the air is in the exhaust and the process should be complete, shouldn’t it? But it is most DEFINITELY NOT!

From the upstream O2 sensor, the exhaust gas passes down the pipes to the Catalytic Converter. Here is the most insidious aspect of the programming of the ECU fuel management systems. Using yet another oxygen sensor, they are able to manage catalytic converter function.

As the operating temperature of the Cat is closely controlled to maintain its catalytic function (they operate best at 900-1000 degrees F. (According to this article) In order to maintain this temperature, the ECU will either decrease or increase fuel delivery, despite what the upstream O2 indicates. They do this by using the heater circuit, which will increase in resistance as the temperature increases.

Now, we’ve covered about all the sensors I can think of. At least, I’ve covered the ones of which I’m aware! Let’s move on to how they work together and (more importantly!) what can be done to effectively regain management of your own fuel delivery needs.

Management of Sensors to Increase Fuel Economy

The management of many of your sensors will enable you to take maximum advantage of whatever methods you’re applying to enhance your fuel economy. From managing the system electronically to simply relocating your sensor points, much can be done to convince the ECU that less fuel is perfectly appropriate, even desirable.

While I’m not a big fan of adding more electronics to an already complex system as they tend to reduce or even eliminate the ECU’s Adaptive Memory circuit, which we rely on for prolonged increases in mileage with The Gadgetman Groove. While I couldn’t find a decent article of video on its role in the ECU, here’s an article from Wikipedia on what Adaptive Memory is all about. They use these principles to ensure optimum operating efficiency, adapting to various environmental and driving conditions and habits.

As all sensors respond to whatever environment they are designed to monitor, if you alter the environment to which they are exposed, you will have an effect on the ECU and its fuel management system. If you know how they operate, you can figure out how to adjust its signal to the ECU.


In altering the signal from any sensor, you MUST consider the ECU

considers the input from ALL the sensors simultaneously,

comparing the values for consistency.

Some alterations may result in error codes in other regions

as well as for the sensor with which you are experimenting.

Make your changes SMALL and INCREMENTAL or

you will be making diagnostics

VASTLY more difficult!

Mass Airflow and Intake Air Temp Sensors

Let’s start with the MAF/IAT sensors. Many developers have come out with devices that alter the signal they send. As they use resistors to manage the fuel delivery, one can simply present an obstruction that diverts some of the intake air around the sensor element to convince the ECU there is less air entering the engine.

You have to be careful reducing air flow!

If you reduce the perceived air flow too much,

you risk over-heating the resistor and potential

catastrophic failure of the MAF!

Alternatively (as in the case of an IAT) one may simply replace the IAT with an appropriate resistor. I use a 3.3 ohm resistor, and the ECU likes it just fine in most cases.

With the MAF, the wiring is a bit more complex, so if you’re planning on adjusting these, I encourage people to use the help of professionals like Mike Kehrli of They make the most reliable devices I know of, and Mike is absolutely dedicated to customer service. Check out his company’s offerings. He carries my highest recommendation.

Again my reminder to make your changes


You make your road to 100+ much more difficult

if you ignore this advice!

Throttle Position Sensor

Now, I don’t have anything to offer in the area of the TPS. The reason I don’t is because in many vehicles, the transmission shift points are controlled to a large part by its feedback. I do not recommend modifying this sensor at this time.

Manifold-Absolute Pressure Sensor

There are two different types of MAP sensors. Voltage-Based and Frequency-Based. With the voltage-based MAPs, all that is necessary it to reduce the supply voltage by a minimal amount. This can be done most effectively with a MAP adjuster, although you may insert a resistor into the circuit. The problem with the resistor approach, you are locked into one value, while if you use a ‘MAP enhancer’ you have the added ability to adjust it to your own particular driving styles. (Heavy load conditions versus low-load or cruise conditions)

For systems with Frequency-Based MAP sensors, Go to Mike Kehrli!

Using a potentiometer (concealed by a rubber plug on The MAPster) one can adjust the supply voltage to the MAP sensor, thereby altering the output voltage while maintaining normal operational parameters. You can literally starve an engine for fuel to the point it shuts down with this little thing!

That’s not to say your mileage will necessarily increase, for if you go too low, your mileage will actually DROP in some cases, so be careful with your adjustments of this device. “Make your changes small and incremental!”

Oxygen Sensors

With Upstream Oxygen sensors, due to the complexity of the signal, I recommend leaving them alone. That being said, with the advent of utilizing water as a fuel source through generating Hydrogen on Demand. (There are none better at information on HHO than GabeT123, the founder of

Again, if you decide to attempt altering this signal, it’s your party. If you do, then rely on Mike Kehrli to assist you. He’s not real good at telephone calls, but email works VERY well with him. He also has a single unit called the “Digital Quad EFIE” that will allow adjusting the values from all four O2 sensors so common in today’s engines.

Downstream Oxygen Sensor

Since my discovery of the role the heater in managing fuel delivery, I have spent years trying to get someone to make a device that manages the perceived temperature of the Catalytic Converter, only to come up with an even simpler solution.

Having many friends in the development community, Mr. Mike Holler offered to test my theory and tested many vehicles. What he discovered is the system can tolerate ½ ohm resistance without error codes. So, we are now releasing (as a test run) a resistor pair to solder into the heater circuit. This should elevate the perceived temperature of the Cat by about 200 degrees.


This is not recommended for every vehicle.

Reducing the Cat temp will reduce its ability to catalyze fuel.

You MUST ensure the engine can consume all the fuel,


Apply Wave-Form Technology BEFORE you apply this modification!

Every system is different. Every single one has its own driving history as well as its own maintenance history (or lack thereof!) that will affect your efforts at 100+.

Remember this when you approach a new modification. You should treat each one as an individual, with its own personality, and start from the beginning. Inspect the system thoroughly, and perform your modifications making each change SMALL and INCREMENTAL to guarantee the greatest chance of success with the least amount of effort.

If you would like to help us solve our energy problems,

then Join Us In Gadgetman Land!

We have taught people in more than 40 states and more than 20 nations

to apply our discoveries and we want YOU to become a part of our network

of people that can say “I’ve had ENOUGH!”

and want to help us change this planet for the better.

Join Us in Gadgetman Land!

Post 1-Basic Flows in a Gasoline Engine

Post 2-Intake Flows and Wave-Form Technology

Post 3-Improving the Vacuum System

Post 4-Flubbing the Dub

Post 5-Varnish and Vacuum

Post 6-Hidden Weaknesses

Post 7-Diagnosing Error Codes

Post 9-Adjusting Your Spark Plug for Maximum Efficiency

3 Responses to Post 8: The Role of Sensors in Fuel Delivery

  1. Pingback:Solving Your Fuel Efficiency Puzzle. | Post 7 Diagnosing Error Codes

  2. Avatar divedaddy03
    divedaddy03 says:

    This is a very good post Ron. It really does help me to wrap my mind around all of the sensors and their functions!

  3. This is by far one of the most informative articles i've seen related to the mass air flow sensor and which codes they throw. I did NOT know that reducing the air flow levels too much could kill the MAF. I wish I would have known that 6 months ago, and it would have saved me some money.