This article is the second in a series of articles which will chronicle the progress of TOV's Project Civic Si. In Part 1, we took a detailed look at the AEM V2 intake. An intake is usually one of the first things that an enthusiast will add to the car. It is a simple modification which requires very little mechnical skill. The exhaust and header usually follow shortly after. Further down the line, the upgrade bug takes a chomp out of your wallet by way of more aggressive cams, headwork, and ECU mods. These modifications usually occur later on in the modification cycle because they not only yield more benefit after the basic bolt-on modifications that increase the airflow (intake/header/exhaust - abbreviated as I/H/E), but because they are more permanent modifications. However, with the '02-'04 RSX and the 2002 Civic Si, Honda has gifted enthusiasts with a flash programmable ECU. This is a little bit out of character for Honda, as the majority of their past ECUs have utilized fixed ROMs. Besides opening up possibilities for tuners, the programmable ECU gives Honda more options if ever there are emissions or performance issues identified later.
What do we mean when we say that the ECU is flash programmable and what exactly is being programmed? If you have a digital camera or a USB memory key, you already know what it means to flash program something. The "flash" part refers to the type of memory used to store information. Your computer's hard drive is a type of memory, so is the system RAM. Flash memory is much like a hard drive, in that data that is written to it is persistent, even when the flash memory is powered down. Also like a hard drive, flash memory can be erased and rewritten many times. But unlike a hard drive, flash memory has no physical moving parts, and in theory should be a much more robust storage medium. In this way it is similar to RAM, but generally RAM memory is much faster and is volatile, meaning once you pull the plug on the RAM chip's power, everything is reset to binary zeroes, and you lose all the data that was stored. The operation of flash memory is well beyond the scope of this article. All that you need to know is that you can write new data (in this case, fuel/ignition maps, rev limiter, etc...) to the flash memory if you have the right equipment. Prior to flash programmable ECUs, the only way to change the "program" in the ECU was to remove the original memory chip on the ECU and replace it with a reprogrammed one. Needless to say, this task required some skill and knowledge of electronics.
The second question requires a little more background. The ECU is a computer. It reads various sensor data and a program adjusts several variables so that the sensor data falls within a specified operating range. There are several main variables that we are concerned with when making modifications to our Hondas and Acuras: fuel, VTEC engagement point, ignition timing, and rev limiter. The program tells the computer how to control these variables. For instance, if you add an intake, you are increasing the air going into the engine. More air requires more fuel to prevent detonation. When the computer reads the sensor data and sees that there is more air coming into the engine, it adjusts the fuel delivery to compensate for it. However, a program can only adjust the variable so far. When the modifications change the characteristics of the engine significantly, the original ECU program may not be able to compensate or fully take advantage of the improved characteristic. When this situation arises, reprogramming the ECU so may be required to adjust those variables so that the power delivery is smooth and safe for the health of the motor.
Honda enthusiasts are lucky because Hondata has been decoding and reprogramming Honda ECUs for years. Their K20A3 (2002-2004 Civic Si) program was a blessing to all Si owners. One of the major complaints from Si owners was the seemingly artificially low rev limiter (6800 RPMs). After decoding the ECU, Hondata set out to fix this problem and subsequently released a program where the rev limiter was raised to 7700 RPMs. The process for getting your ECU reprogrammed (this procedure applies to RSX owners too) is straightforward. You go to your local Hondata dealer, purchase the flash upgrade, and hand them your ECU. The dealer then sends the ECU and your key to Hondata to reprogram. Hondata sends the ECU back to you and you are set. The reason you need to send your ECU and key to Hondata is so that your immobolizer will function properly after the upgrade. Hondata has a special machine where they plug in your key and ECU. This machine uploads the new program and allows your immobolizer to work with your keys.
Since I was in Los Angeles performing the AEM V2 test, Shawn and I decided to stop by Hondata to have them reprogram the ECU. We need to thank Doug and Derek at Hondata for providing us with the ECU upgrade and Matt for taking us on a tour of their new office.