MAF sensor tuning units. There are many devices available on the market that will claim to tune your car by altering the MAF signal that goes to your factory ECU.
Examples of these MAF tuning devices include:
Greddy E-Manage Ultimate
Apexi AFC Neo
Generic devices which alter resistance
All these devices excluding the AEM FIC have one fatal flaw and that is that they do not alter the Lambda signal that the ECU gets.
While these devices may have a short-term effect on how the engine is tuned, the standard ECU will learn to adapt to the altered signal from the MAF sensor and retune the engine map back to stock settings.
The only one of these devices that deal with the lambda issue is the AEM FIC. With the AEM FIC you can alter the Lambda signal that the ECU sees. This ensures that the stock ECU will not de tune your engine.
So how in principle do these MAF tuning devices work?
First of all we need to understand how a MAF sensor works.
A MAF sensor is a device which tells the ECU exactly how much air is entering the engine. It does this by passing an electric current through a wire which is exposed to the air entering the engine.
The resistance of the this wire changes according to how much it is cooled by the incoming air.
The standard ECU calculates the resistance of the wire by working out how much voltage needs to be passed through the wire to maintain a steady resistance.
These MAF tuning devices work by altering the signal the ECU sees from the MAF sensor. By telling the engine that the engine is receiving more air than it actually is the ECU will add more fuel.
In the stock ECU there is a map which says at X MAF voltage and Y throttle position we want to inject Z amount of fuel.
Because MAF sensors are so sensitive they can automatically tune the engine to work with a performance air filter or performance exhaust system.
The issue arises if the stock map itself is not suitable, for example some car manufacturers make their engines extremely rich at wide open throttle.
As I mentioned at the start, MAF maps are tied into the Lambda sensor signals. So for example at T MAF voltage, and at X throttle position the Lambda sensor should read A.
If the Lambda sensor reading does not match what the engine expects the stock ECU can alter the engine MAP so it sees the voltage it wants when the MAF is at T volts.
This learning function in factory ECUs not only keeps the engine working within factory tolerances no matter what the temperature or fuel quality it also allows the ECU to compensate for sensors and engine parts as they wear out.
The next time you are looking at a device that claims to trick the ECU into adding more fuel remember that modern fuel injected cars use the signals from a number of sensors to determine how much fuel to add.
Altering the signal from one sensor may work temporarily but the stock ECU will probably tune the engine back to the values it thinks it should see in its fuel and ignition maps.
There are 3 main ways to tune a modern fuel injected car in a way which the stock ECU will not detune the engine.
1. Manipulate all the relevant signals that the ECU receives from the engine, so you can compensate for the ECUs compensation. An AEM FIC is an example of such a device.
2. Alter the stock ECU maps directly. This can be done with varies methods, on newer cars it is quite straight forward with OBD tuning – Cobb Access port for example
3. Fit a stand alone engine management system. DTA, Motec are examples of stand alone engine management systems.
If you want to see if it is worth retuning your engine speak to a company who specialises in tuning your make or model of car and see what their experience is. Many of today’s performance chip manufacturers publish dyno graphs before and after so you can see the difference.
Bear in mind that if your engine has been tuned, for example with a performance manifold, intake cams and so on, you should really be looking for a custom remap of your ECU. The rolling road companies and tuners listed on StrikeEngine offer these types of services.