There was a time when the average guy looking for real power gains could upgrade his intake and exhaust for decent results. To push for more, an aggressive cam went in. Intake and exhaust are still necessary steps on the path to more horsepower, but most tuners have lost interest in cams. Now they call in a geek with a laptop.

To illustrate the value of chip tuning in this guide, we dyno-tested three cars, at three different price points, representing some of the finest tuneable engines. We used our own long-term VW Jetta for the entry-level; it's equipped with possibly the best turbocharged four-cylinder currently available, the 2.0T. We tested it with the aforementioned intake and exhaust to give realistic numbers of what your average enthusiast is likely to see.

Next is a relative newcomer. We've already extolled the virtues of the BMW 335i-the term 'M3 Killer' comes up in every conversation about this car. And it's clear BMW left a bit on the table with this engine. At the time of writing, only a few options exist for software tuning. But by the time you read this there will probably be several more, and we will be testing them.

The third car is the Porsche 997 Turbo. Out of the box, it's far from sluggish. But, as with the BMW, we were stunned by how much Porsche left untapped. The real secret is running top-grade fuel. On factory programming with no mods, this car really struggles on the 91-octane gas in California. We've tested more than one car on 91, observing detonation and pinging which, quite frankly, scares us. This is a high-performance machine that deserves more than standard pump swill. Let's face it, if you're dropping the cash to buy this car, a few more bucks to mix in a little race gas with the 91 is hardly going to affect your lifestyle.

To replicate the most realistic scenario, we tested it on race gas with an aftermarket exhaust. Tuners who deal with these cars tell us that owners who are willing to modify their 911 will rarely start with just a flash. They'll generally start with the exhaust, then get the flash.

The Jetta and Porsche were both tested at GIAC's facility in Irvine, California, using its Mustang four-wheel dynamometer. Mustangs are know to be a little more pessimistic than other dynos, and since we did baseline and flashed runs, the increase is what is relevant, not the final numbers. The BMW was tested at South Coast German Cars in Costa Mesa, California.

GIAC flashed its latest switching software on the Jetta, which includes stock, 91-octane, 100-octane and valet programs. The graph shows a fairly impressive power gain at its peak, but the real story is down low. Instead of just looking at peak gains, driveability improvement is best shown by the area under the curve. There are huge torque gains in a wide rev range that makes this thing pull like a V8 at the low end.

On the freeway, you seldom need a downshift to pass. Just put your foot down, the boost is there. GIAC does not claim the biggest numbers, but power is everywhere, in a safe, reliable package. The optional 100-octane and valet modes are a nice addition. We tested the valet mode on the dyno, just to see. On zero boost, the car still makes almost 150 hp at the wheels. It would still be quick, but not with the kind of power that would allow someone to kill your clutch.

With the BMW, we went outside the box, or rather outside the ECU. We tested a brand-new product from Split Second called Turbo Tuner. We were skeptical. We tested Vishnu's PROcede last month (The Clash, ec June '07), with good results. But this thing is half the price and appears even more straightforward. The Turbo Tuner is a two-minute install: unplug the TMAP sensor and plug the unit in line with it.

To be fair, we saw more performance from the PROcede, but at just under $600, and considering the ease of install and the ability to transfer it from one car to another, this thing is quite a buy.

The Porsche was the biggest surprise of all. As stated above, we tested this car with a full exhaust and 100-octane fuel. We also tested the stock, 91-octane and 100-octane programs. Predictably, big gains were everywhere-and the great thing is that driveability is better than stock.

Types Of Software
Also referred to as an 'intercept' system, this is a computer which is physically separate from the car's brain. It is connected in-line between the electronics and ECU, and intercepts signals coming from various sensors before they reach the ECU, adjusting them as necessary to trick the computer into seeing factory parameters. It also intercepts the signals coming from the ECU and modifies them to electronically controlled components, thereby optimizing operating parameters and improving performance. A piggyback system can usually be installed or removed in minutes. Many will convince the computer it's operating within factory parameters, so in the event of a catastrophic failure, the owner can pull the computer out. When the ECU is scanned by the dealer, no evidence of tampering will be visible. This feature is especially useful for vehicles still under warranty.

Most ECUs in cars equipped with OBD-II are accessible straight through the connection port, generally found in the car's dash. This makes software tuning more convenient for the average person. It's basically downloading a new program into the ECU. This is the most common method of software tuning on modern cars. Many tuners in this guide offer software switchers that allow the owner to select which particular program to run at any given time.

Flashing has really made software tuning what it is today. Any technician with a laptop can flash a car, and no parts need to be stocked. If an updated version becomes available, the program can be updated easily. Even end users can now use their own laptop to make changes.

This is the original method of software tuning. The ECU is removed from the vehicle and the ECU's chip, or EPROM, is physically replaced. This is generally used on older fuel-injected vehicles built prior to OBD-II implementation. The downside of chipping a vehicle is that distributors had to stock different chips for each application, and when updates became available, a newer chip had to be installed.

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