There are more complexities in dealing with the Bosch Motronic 7 in the S4, as there is much anti-tampering and encryption built into the code. Said Todd, "Once the encryption is broken, it's a matter of knowing your way around the file. This is a 1-megabyte chunk of code and data, and that's huge for a car. There are all kinds of maps in it, and they aren't sequential. You've got very obvious maps for boost, fuel or spark advance, but just manipulating those doesn't always achieve the desired result, because there are secondary maps that are linked to the main maps. These have to meet certain parameters to allow the main maps to do what you're asking the engine management to do. With the 500+hp S4, that pushed everything so much over the edge it made it very obvious what we had to concentrate on. So really, we knew of no other people who had gone to these kinds of power levels in these cars. But the technology translated fairly well into all the other cars."
The grueling part of reverse engineering the Motronic code is that it's basically in hexadecimal, representing data and microprocessor instructions-not exactly the kind of thing human beings process well. "Once Garrett has cracked the file, it's a lot like reading something from 'The Matrix.' He writes his own software to decrypt the files, look at the maps, and then reprogram the ECU. He used to sell that tuning suite to anybody who wanted to buy it-up until a couple years ago. We convinced him it wasn't a good idea, since it was allowing our competitors to get an edge. Prior to the drive-by-wire cars, that's what he did. But the new cars that have drive-by-wire aren't so easy to figure out. He's got a lab with about five networked computers that allow him to do the disassembly," chuckled Todd.
Todd is in awe of Lim's wizardry. "All of the software tuning companies usually boil down to one or two individuals, because it is such a specialized talent figuring out the code of the factory ECUs. Garrett is really close with the Bosch engineers, because there are only a few people in the corporation who can do what he does. These guys seek each other out, just out of mutual respect. When it comes to GIAC, there are a number of people who run the corporation, but Garrett himself is the chip-tuning talent. He federalized a Porsche 959, which no one else has been able to do yet. That demonstrates his prowess; he was able to rewrite a portion of the code to recognize O2 sensors in the loop."
How do each of the three cars relate to the big tuning picture at AWE? "The silver car with the carbon hood was a design exercise, though it does have a number of our production parts on it," said Todd. "The Silver Bullet is very much a one-off car, though we could reproduce it if someone had the money and desire to do so. In contrast, the black car is all production AWE pieces; it's our factory demo car, so to speak. The black car, the Avant wagon, has our production kit installed. What stays on that car are all the parts we offer straight to the public, but we do put some experimental parts on it from time to time for testing. It has our RSKO4 kit, which has the turbos from the European-spec RS4. Some other companies would call it a Stage IV kit. We have the complete kit, which is turbos, headers, upgraded injectors and GIAC software. We dynoed it at 418 hp at the crank, with 515 lb-ft of torque. It's a potent car but a daily driver that will run on pump gas. The Silver Bullet also has the KO4s. It was very educational for us to see exactly how far we could take those turbos to make power."
The raw carbon-hooded car with the stock KO3 turbos runs with the factory-supplied injectors, though a 5-bar fuel pressure regulator has been installed to increase the pressure at the rails. The ignition also remains factory stock, but a prototype airbox has been installed that capitalizes on space freed up by the front-mounted intercooler. AWE downpipes and cat-back exhaust were also installed.