IAT Resistor Mods vs Performance Modules vs Real Chips
What are those infamous IAT resistor mods and performance modules and how do they compare with real EPROM racing or performance chips? Need a guide to try it out by your self? Find out here…
Modern cars no longer use carburetors. Instead, they use a system called electronic fuel injection (efi) and it is controlled by an onboard computer called the ECM or Engine Control Module. The efi, replaces the carburetor job entirely. It does it by sensing environment variables such as atmospheric pressure, temperature, altitude, air density and many other variables for precise metering and injecting the needed fuel, according to its calculations. The ECM is able to do such a gigantic job by executing a software program created for that purpose, which is called and executed every time the engine is started.
The EFI software (program) has parameters written on it, like injection and ignition tables, speed limiters and many more things. Such parameters are the ones modified when using an EPROM chip, looking for more power output from the engine, like a more aggressive ignition table to take advantage of higher octane gas, or for accommodating hardware upgrades, like correcting the speedometer when using larger rims.
In some older models (up to 1995), the memory used to accommodate things like fuel and ignition tables in a removable EPROM chip. This EPROM chip is the part which is often replaced by another EPROM chip, already containing a modified copy of the ECM program. Vy the way, people modifying these programs, since it deals with the engine management system, they must know what they are doing or otherwise, the engine can be severely damaged by the modification done.
Changes made in a EPROM performance chip are done with a software for that exact purpose.
IAT Modification scams
IAT Sensor = “Intake Air Temperature” sensor. Some guys out there are selling fake “performance chips”, where they use obscure and not proven methods for “fooling” the engine ECM into “thinking” that incoming air is cold enough, as to make the ECM to increase the amount of fuel being injected to the engine in an attempt to compensate for such a “temperature change”. Since they are only using a simple resistor in their fooling attempt, they are disguising it inside a fancy box with fancy labels with two to four cables coming out of it. Not only they are fooling people into making them think it is some sophisticated chip or module, but are also claiming huge power gains which are simply impossible. Have you seen the famous +20HP? Tje “+20hp” was one of the most famous terms several years back according to Google searches. Now they changed to +30HP, +50HP, +90HP and so on. I need to say, without the intention to offend, that anyone buying a “module” with four wires for around $50.00 because it was advertised as a +50HP or more, I wouldn’t blame the seller. I would blame the buyer for biting such a foolish bait.
More and more people that have bought those IAT modifications are claiming that it does nothing. It is probably attributed to the fact that not all cars depend only on the IAT sensors alone to make the predicted changes. So it is very probable that modifying the IAT sensor of your car will do nothing, or at least nothing that you could notice.
Why trying to foolish the ECM into thinking that incoming air is cold? Because cold air is denser, which means, more oxygen. More oxygen will allow more fuel to be burned at the same time, making more power. Ever wonder why your car moves better at nights or in cold weather? Exactly, more oxygen! (unless you live in a high altitude area) But guess what? If you fool your ECM like that, it may inject more fuel, but there will not really be more oxygen. The mixture will end up being more rich, more harmful emissions will be present, but not necessarily more power.
You may also replace the IAT with a variable setup if you wish to adjust values on the fly:
Still more, if you live in a cold area, you will notice no difference as the original IAT sensor installed in your car will already be in a better resistance value than the one you would insert. On the other hand, if you live in a hot or high altitude area even less oxygen will be available for combustion.
Example of the garbage being sold online as “chips” or as “modules”
What can you expect from a real EPROM chip correctly modified?
When an aftermarket EPROM chip is installed in your car’s ECU, if it was correctly modified, you should experience a boost in engine power and torque, more driveability at all and of course, it should accommodate the changes in hardware you wanted it for. If it is done right, you simply will not want to drive your car without it ever again.
What can you expect from an IAT “performance Module”?
This is simple. Other than feeling robbed or foolish for trashing money, you may expect nothing.
Want to try yourself the IAT “modification” without spending in those $30.00-$70.00 modules?
Sure. We can help on that to. Just follow this guide:
First of all, the IAT sensor is the Intake Air Temperature sensor, so as the name implies, it senses temperature. I does it by using a variable resistor which is sensitive to temperature and it has a negative coefficient in relationship with temperature and resistance. That is, the higher the temperature, the lower the resistance. So, if we want to decrease the temperature value read by the ECM, we will need to increase the resistance value. How we do that? Simple, we put a resistor of certain value in series with the IAT sensor. Since resistance in series will add up, the total resistance value will still vary with temperature, but the lowest values will be higher than the resistor value we will insert. This will ensure a specific minimum value. In other words, it will not allow the value to fall under the level we want. That way, it will not hit the low resistance levels that the ECM interprets as hot air. As you can see, a resistance in series with the IAT will not disable it, but modify its operating range.
A typical resistance value widely used is 4.7k (4700 ohms), but if you wish to be near to the exact value for your car model, you will need to take out the IAT sensor from your car, put it in a glass with ice, wait for a couple of minutes and then with an ohmmeter, measure the resistance given by the sensor at that freezing temperature and write down the value. Now you will need to find a resistor with the closest value to the resistance you measured from the sensor while cold. Just match to the closest value available commercially. For example; 1K, 1.2K, 1.5K, 1.8K, 2.2K, 2.7K, 3.3K, 3.9K and many more.
Below is an example of a 4700 ohm resistor. Color bands must be YELLOW-VIOLET-RED. The fourth ring can be GOLD for 5% tolerance.
If you can not put your IAT sensor in a glass of water because the sensor’s design does not allow it, like for example, if it is embedded in the MAF or flowmeter, then you may use a spray which is normally used to cool down electronic components when troubleshooting a heat problem. It is commercially available under different names. Examples are below:
If the IAT is embedded in the MAF sensor, take out the MAF sensor and identify which component of the assembly is the IAT. Then spray it directly to cool it down to freezing temperatures, then take the measurement.