NOTE: I am sorry about having no pictures.  I removed them in my last edit to do some corrections and when tried to insert them back, somehow, due to a system bug (eBay server, maybe), the pictures didn't show.  As soon as this is corrected I will put them back, as these pictures are very important for people trying certain methods described here.  Other than that, the text is accurate.

Performance Chips, IAT Mods, Performance Modules, you name it!

What are performance chips (Real EPROM or ROM Chips)?
 

Some facts:
 

Just like your PC, the car computer has a CPU, RAM memory and a boot device.

In this case, these chips are the boot device, called ROM or “Read Only Memory”, instead of a hard disk.  These ROM chips contain the car’s computer operating system and hold it even if the power is removed for any amount of time.  Once you put your car key to “ignition” or “on” position, it powers up the car computer among many other things.

Right after the car computer or ecu (Engine Control Module) is powered up, it boots from a chip (ROM chip) and reads the operating system from it, which is the program that will control the ecu itself and at the same time the car’s engine.

 

Performance:
 

When an aftermarket chip like these in our store is installed in your car’s ecu, you are changing the program or operating system of the car’s computer.  This change, affects the behavior of the ecu and its response to the different signals received from the various engine sensors in a positive way.  The result will be a change in performance, depending on the program written in the chip.

The programs we write in our chips are intended for better performance and drivability, improving the horsepower and torque produced by your car’s engine.  Among these changes, there is (1) disabling the vehicle speed limiter or governor, allowing the vehicle to reach its maximum natural speed, (2) the RPM limiter or revlimiter is slightly raised, allowing higher engine speeds for an extra punch, (3) the fuel tables and ignition tables are remapped for optimum fuel delivery and ignition firing.

 

What about the IAT resistor kit, IAT mod, etc?
 

Facts:
 

The IAT resistor or resistor kit, which is a simple 10 cents resistor and nothing else, will change or modify the computer input signal from the IAT (Intake Air Temperature) sensor.

The IAT sensor is a passive component that will simply vary its resistance depending on changes in temperature (also called a thermistor).  Since it is a negative coefficient sensor, the higher the temperature, the lower the resistance and vice versa.  When a voltage is applied through a resistive network where the IAT sensor is part of, the output voltage from that network will vary according to the temperature of the air passing through it, because of the voltage drop action of the resistive sensor.  That voltage fluctuation will be interpreted by the computer as a direct incoming air temperature variation.

So why the ecu needs to know the incoming air temperature?  Well, because of the physical fact that cold air is denser, having higher mass by volume (which means more oxygen) than hotter air.  Then a modification of the Air/Fuel Ratio (AFR) is necessary to keep combustion at optimum levels, allowing optimum engine power, preventing engine from knocking and having lower nitrous oxides (NOx) emissions.

 

The modification:
 

Some car computers (not all) will use the signal from the IAT sensor alone, to modify the ignition and / or injection to slightly compensate for the incoming air temperature variations, so making the computer “think” the incoming air is cold will make it adjust timing and /or injection.

It is accomplished by putting a fixed resistive value instead of the IAT sensor, simulating a cold intake air situation.  Remembering the facts above, “the higher the temperature, the lower the resistance”, in this case we will need to make the resistor value high enough to make the computer “think” that the temperature is low enough.

The problem with the IAT modification is that;

1. Not all cars depend only on the IAT sensors alone to make the necessary changes, so probably modifying the IAT sensor will do nothing.
2. If you successfully modify the IAT sensor and the engine make some changes, remember that the air will not be truly cold or denser, so no extra oxygen will be present ending up in a richer mixture, higher emissions and probably lower performance, unless your car is already running way too lean.
3. If you live in a cold area, you will notice no difference as the IAT sensor will already be in a better resistance value than the one you would install.
4. If you live in hot area, it will be worse than the ones in a cold area, as even less oxygen will be available.
5. If you live in high area, you will have similar or worse luck that the ones in the hot areas as oxygen and pressure progressively decrease with altitude, even if it’s cold.
6. Regardless of the all mentioned above, if you finally make the car computer do a positive modification by installing that 10 cents resistor, remember that changes will be on the factory program range limits or specifications anyway, as the chip or computer program is still in stock condition.  All changes made by sensor modifying, will stay in the factory specs unless a chip with a modified program (performance chip) is installed.

 

Don’t take my word!
 

Please, don’t just take my word about this.  You can experiment it yourself if you are a little skeptic about this or just want to try it (I would do).

 

Do it your self:

All IAT sensors average from about 4700 to 5000 ohms (4.7K-5K) when the air temperature is cold enough to make an adjustment on ignition and / or injection.  The trick is to replace the IAT sensor by a resistor with “cold temperature” equivalent values, similar to those mentioned above.

All IAT sensors have two wires, but though many of them are installed alone in the incoming air path elsewhere after the air filter, some of them are incorporated in the MAF (Mass Air Flow) sensor.  In that case, the MAF sensor connector will have 5 wires, where 2 of them will be connected to an internal IAT sensor.  You will either need to find the stand alone IAT sensor in the air path or identify the wires connecting to it on the MAF sensor connector and in the first case, disconnect the plug to put the resistor leads in the plug or in the second case, you will need to cut the two wires to some length to attach the resistor.

Remember, you will electrically replace, but not physically replace the IAT sensor, as you will connect the resistor to the cables going to the ecu, but will leave the sensor in its place.  The resistor, as the IAT sensor, has no polarity, meaning that you can connect either wire with either resistor lead.

Now, since the resistor has a fixed value and the IAT sensor is out of the circuit, resistance will no longer vary with temperature.  The car computer will permanently think that incoming air is very cold as long as the modification is in place.

After connecting the resistor, just make sure it is covered with tape or any other insulator and you can leave it hanging in a safe area on the engine bay as long as it doesn’t receive too much heat.

Now just do a test drive.  How was it?  Anything?  No?  No problem, you are not the only one. :-{

 

Extra info:

As mentioned before, the resistance values of the IAT sensor averages between 4.7k – 5k, but if you want to try the exact optimum value for your car, just take out the IAT sensor, if it is the stand alone version of course, and put it in an ice bath prepared in glass or cup.  Leave it submerged for 1 or 2 minutes and measure the resistance across the two connecting wires or terminal with an ohmmeter, preferable a digital one, in the 20K or equivalent range.

The measured resistance will be the optimal for your car.  Probably you won’t find an exact commercial value that matches the measurement, but you can get the closest one.  For example, if it measures 4633 ohms, then a 4700 ohm (4.7k) is a very common commercial value and will do the job just fine.  Color rings for a 4.7K resistor will be Yellow – Purple – Red with either a Gold or Silver fourth ring.

If your IAT sensor is the MAF type (5 wires) you can not submerge it as it will be damaged, but you may find a component cooler spray sold for electronic circuits thermal troubleshooting and spray it directly over the IAT sensor inside the MAF assembly and then measuring it with the ohmmeter before it warms back up.  The only thing is that such spray will go lower in temperature than a simple ice bath.

Make sure that the MAF sensor is completely dry before installing it back, since cold spraying it will make some condensation moisture.

Now do the test drive.

I know, probably it was the same or worse.  That is the result of 90% of the cases.  The remaining percentage?  Well, an 8% is placebo effect and the other 2% maybe people that succeed in putting fourth of an extra horsepower (1/4 hp) and are content with that.

 

What about those mysterious boxes called performance modules?

     

 

Those shiny small boxes called “performance modules” that comes for a variety of models and model years, mostly with 4 wires coming out of it or even with a power select switch or rotary power control are the same cheap resistor, boxed, given fake attributes and some of them added a fancy control (variable resistor o potentiometer) along with the fixed resistor or a switch to select from different resistor values or “power ranges”.

People no longer wanted to buy a 10 cents resistor for $15-$70, so they boxed it to make it look cool and hide it at the same time to avoid recognition, making people think that it is something way much more sophisticated than a simple, cheap and most of the times, non working resistor.  Some sellers went farther than that, making people believe that the resistor was “tuned" specifically for your car model.  There is no way of tuning a fixed part!  Others use a resistor network chip and wire two of the leads to the outside of the box.  Those chips are not semiconductors or anything alike.  They just have several internal resistors in parallel of the same resistance value to save space in circuits.  They just hook one of the internal resistors to the IAT.

The results, the same of the resistor alone… NOTHING!

 

Best Regards,

Richard Rodriguez

Auto-Motivo