1.8T ECU Power Swap
By: Dan Barnes

Wetterauer Chip

TAP Chip

AMS Chip

Hoppen Chip

This article appeared in the May 1998 issue of european car magazine. Reprinted with permission.

Since the advent of computer-controlled automobile engines, the possibility of plugging in a new program and instantly making vastly greater amounts of power has been the holy grail of the tuning industry. At first, significant improvements were not unheard of , because the quantum improvement in the change from a carburetor to electronic control meant OEMs didn't have to fully optimize systems for them to be good enough to market. A smart engine guy who knew how to program could often just work a little harder and get good results. Then competition and increasing regulation forced the OEMs to do better, and silicon horses become more scarce.

In recent years, the spectrum of improvements has ranged from moderate to zero. In some cases, sitting cross-legged on a little rug and meditating upon a large blue silicon crystal would have given better results. But all along, the promise of something for nothing, of stumbling upon a gusher of untapped potential somewhere in the digital jungle of the ECU's memory, has lingered on the horizon like a mirage, continually drawing tuners onward. Finally, there has come a case where the lake was still wet when the hackers got to its edge.

The Audi A4 1.8t (an engine also found in VW's Passat), with its computerized regulation of turbo boost, is El Dorado, the hidden land with streets of gold. Of the four chips we report on here, the least-improved provided a 22.2 hp increase over stock measured at the wheels. The largest improvement was 40.5 hp. These gains are from an engine rated at only 150 hp. The icing on the cake is that the A4 is a great car in every other way as well. In fact, if we had to have one car to do everything for the next ten years, the A4 would be on the list, maybe at the top. It is a nice, comfy four-door, a car for cruising with the kids and groceries.

In quattro form, it has all-weather capabilities with the idiot-proof awd handling; we can hammer the throttle in first gear around a 90-degree corner in the rain (yes, it does rain in L.A.), even with one of the chips we tested installed, and the car just hooks up and goes where it's pointed. Audi has developed a remarkably efficient drivetrain. Coast-down measurements indicated losses of only 7 hp in fwd configuration, and stock hp at the wheels was 139 on a rating of 150. That is a loss of only 8 percent, as opposed to the traditional rule of 20 percent, a significant technical achievement.

Driving the A4 with one of these chips, one gets the felling that one could go very quickly cross-country in it without attracting attention, while remaining in perfect comfort and completely relaxed. While the 1.8 cannot hide its four-cylinder identity at high rpm, a bit of noise is hardly to be complained of while pressing n; around town, it is among the most civilized fours on the road. Sliding behind the wheel the first time, on tester said, "The tach isn't at zero. That means it's running right?" the A4 is not in the traditional idiom of tuner cars, and it is certainly not an M3, but in spite of that, it may yet carve out a niche as the archetypal tunable car.

It has been said of some legendary marques that the cars did not become great in history because they were great, but because they were almost great. It was very easy for an owner to make them much better than they were stock, and far better than any of their competition. The A4 1.8t is great stock, but it too can be improved dramatically. Three or four minutes should suffice. That is how long it takes to open the waterproof box that holds the computer, exchange ECUs, and screw the cover back on.

Rumors that this was possible have circulated since the engine's introduction in Europe, and now that the car has been available in the U.S. for a time, several tuners have entered the market with chips to increase engine output. Four of them answered our call to provide and upgraded ECU for our long-term test vehicle. We tested the upgrades back-to-back both on the dynamometer at Jackson Racing (laboratory conditions) and on the street (real world). And we didn't just take measurements, we also recorded our subjective impressions of driveability.

The key to the ease with which improvements are made is Audi's electronic regulation of turbo boost. Unlike most turbocharged cars, which use some form of mechanical boost limiter-with electronic safety nets to keep the engine from self-destructing should that boost go above levels deemed acceptable-the Audi uses the engine's computer to regulate boost pressure, providing complete control of how much air enters the engine and what happens to it once it is there.

Within limits, the computer can be programmed to produce as much or a little power as is desired at any rpm. That is why the official stock peak torque can be 155 ft-lb between 1750 and 4600 rpm. Every chip we tested works by increasing turbo boost to a level that is appropriate in the judgment of the turner, and then modifying spark and fuel maps to work with the extra air. This is a dramatic improvement over the usual methods in which turbo boost is increased mechanically, and the computer then has to be fooled into going along. The chips are presented first in order of most improved to least improved on the dynamometer; the results of acceleration testing will be discussed later. On the dynamometer, the Wetterauer chip clearly outstripped the others. Peak improvements were 40.5 hp at 4100 rpm and 57.4 ft-lb of torque at 3200 rpm. However, the torque curve was even more impressive. The Wetterauer chip jumped right up to almost 200 ft-lb of torque at 2600 rpm, dropped a little, then went right back up and stayed near 200 ft-lb past 4000 rpm, where it began tapering back down to only a little above stock output at 6000 rpm. This low-rpm behavior is very important, but is not reflected at all in the peak figures.

First runner up in the chassis dyno grand prix was the TAP chip, which posted improvements of39.5 hp at 4000 rpm and 51.9 ft-lb also at 4000 rpm. The torque curve of the TAP chip, however,, was quite different. It jumped to only 175 ft-lb at 2600 rpm, then ramped up to its peak at 4000, where it tracked the Wetterauer chip's taper to near stock out-put toward redline.

In third place was AMS, which improved by 26.3 hp at 4900 rpm and 33.5 ft-lb at 4400 rpm. Its torque curve gradually ramped up to a peak at 4300 and then tapered like the others as speeds increased.

The Hoppen Motosports chip brought up the rear, producing increases of only 22.2 hp at 5200 rpm and 36.7 ft-lb at 3100 rpm. However, the wide separation of these peaks hinted at the shape of the torque curve. Like the Wetterauer chip, the Hoppen chip provided a solid bottom end, jumping to about 180 ft-lb by 2500 rpm and staying there till 3500 where it dropped slightly, ramped gradually down to 5200 rpm, and then tapered like the others at high speeds. Interestingly, the Hoppen chip's high-speed fall-off was not a s pronounced; it made more torque at 6000 rpm than any of the others, though the AMS chip was close. Comparing power outputs can be instructive, but commutes and canyons aren't paved with dynos. To get an idea of what the chips meant in the real world, we timed 0 to 60 mph and 50 to 7 mph runs, the latter in third gear. Each measurement is not the best time, but the average of multiple runs.

The stock chip managed 0-60 in 9.41 seconds, and 50-70 in 6.17 seconds. The first chip we tested on the road was from Hoppen Motorsports. If it had been the only chip we tested, we would have been happy, as just pulling out of the parking lost showed a dramatic increase in power. The torque came on strong at very low speeds for a turbo motor-only 2700 rpm. Accelerating hard, we noticed a slight, but very slight, "tink, tink" of detonation as we passed 40 mph in second gear, but it is likely that with more time on the chip, the computer would learn to prevent this.

Typically, the computer needs 40km to "learn" a program and while out test did not cover that distance, the pinging cased after a few passes. When shifting, the chip maintained boost so that upon reapplication of throttle, power was instantly available. Needless to say, acceleration was dramatically improved over stock.

The next chip tested was the TAP unit. This chip began pulling strong from between 2700 and 2900 rpm, and built poser in a smoothly progressive manner. The TAP chip did have a slight, though somewhat variable, lag in throttle response and seemed quicker to dump boost with a declining throttle opening. The latter characteristic was especially noticeable when shifting; shifts themselves were smoother, but there was a slight pause when getting back on the gas. The TAP chip never hinted at detonation. In addition, it felt faster by the seat of the pants, and in fact posted the fastest 50-70 time of the group, though beating out the Hoppen chip by only 1/20th of a second 0 to 60. The Wetterauer chip did well on the road, taking second-place honors for acceleration both 0 to 60 and 50 to 70. Despite its spectacular low-rpm performance on the dyno, on the road the Wetterauer chip seemed to hit later than the other chips, with a big rush of power around 4000 rpm. As with the Hoppen chip, our hypersensitive ears detected very slight pinging as the needle swung quickly past 4000 rpm, when it felt that boost was building rapidly. The Wetterauer chip bested the TAP chip 0 to 60, but was significantly behind in the 50 to 70 contest. One tester noted that the Wetterauer chip "seems the most impressive" by the seat of the pants. The AMS chip was a conundrum. It made the least improvement and the least torque overall of any of the chips, so we were not surprised when it was slowest in 50 to 70 testing. But when it came out quickest 0 to 60, we could only scratch our heads. It was noted as "very progressive," as one would expect from examining its torque curve, and that may be responsible for its performance off the line. Our tester described his launch technique as, "Let it sit at 3000 rpm, and gently drop the clutch." Apart from the fact that the AMS chip's mild torque curve may have favorably influenced what was meant by "gently dropping the clutch," we cannot offer any good explanation for its performance.

None of these chips is a loser. Some provide clearly better performance than others, and based solely on that, the TAP chip would probably be a good choice. However, even the Hoppen chip, slowest of the four in our limited testing, reflects admirable choices in turning. Its torque curve is widest and flattest of the four, solid on the bottom end and superior above 5500 rpm. The way it maintains boost during shifts means that through the gears, and hence around a racetrack or up a canyon, it might make up for its shortcomings on the dyno. Furthermore, we know that Hoppen Motorsports ahs been around for a lot of years and takes a long view of things. We would not be surprised to find they could have made a more powerful chip, but chose not to for what they judged to be risks of long-term unreliability. In the end, as usual, what is comes down to is, "you pays yer money and you takes yer choice."

Before concluding, there are several points we feel are important to make about tuning the A4. We begin with a recommendation for the use of synthetic engine oil and a Turbo Timer or equivalent device. These are good ideas for any turbocharged car, but especially for this Audi. Its small turbo, though water-cooled, is worked hard even in stock form, and one admittedly lead-footed tester remarked that with a chip installed, the turbo was glowing after just moderate driving around town. This and the fact that high-rpm torque was limited to near stock levels even with the chips suggest that these chips are working the turbo past its efficiency peak. If power increases much greater than those provided by these chips are desired, it would be wise to upgrade to a slightly larger turbo and put up with a more traditionally turbo-like torque curve, and perhaps slightly more lag in response. Also, a low-restriction exhaust could be helpful, since turbos like as little back pressure as possible. A distributor for the Oettinger product line claims that the Oettinger exhaust, which leaves everything from the resonator froward in pace, can add 10 hp to an engine that is already equipped with its chip. A nice side benefit of a turbo is that it significantly quiets the exhaust by itself, making exhaust noise less of a problem for those to whom it is a concern.

The Audi A4 1.8t just may be the perfect platform for tuning. Buy the smaller engine, and use some of the money you saved to buy a chip that gets back all the power you gave up, and then some. You can still get insurance, mileage and handling benefits from the smaller and lighter engine. And best of all, if you're quick with a wrench, the modification takes less time to perform than filling the gas tank. It can be undone just as quickly, and is 100-percent stealthy. Use the rest of the money you saved to buy stock in Indonesia, or buy premium unleaded and take a road trip around the country, looking for the lost city with streets of gold. If you find it, do a four-wheeled burnout that melts the road before the tires. If you don't find it , you can still say "Eureka!" because you are driving many a performance enthusiast's grail.

Copyright (c) 1999 AudiWorld