Project VW Fox: Making Power For Daytona’s High Banks

We were facing quite a challenge: The TireRack.com ChampCar Endurance Series would be coming to our home track–Daytona International Speedway–on July 5, and we were determined to run our low-buck VW Fox endurance racer.

Before we hit the high banks, though, we had a big goal: We’d effectively neutered our Fox by replacing our broken five-speed transmission with a four-speed box of unknown health, so we wanted add some more power. Don’t worry–we’re certainly not going to win anything no matter what we do–but we figured with just a bit more horsepower at our disposal, we’d be less likely to get run over.

How do you make more power in a Fox? An engine swap was off the table–our ’92 Jetta drivetrain was reliable and sorted–but that didn’t mean there wasn’t some low-hanging fruit. How’d we know this? Simple: a phone call with Techtonics Tuning, the U.S.’s premier Fox experts. (They also support all the good cars Volkswagen has made over the years.)

What was Techtonics’ answer? “No problem!” they said. “With a cam, chip, and exhaust system, you could pick up as much as 25 horsepower!”

Color us intrigued! We didn’t know exactly how much power our Fox was making (we’d never dyno tested the car), but had estimated it right around 100 horsepower at the crank. Adding 25 would mean a 25% increase, and seriously help our lap times. We ordered those parts from Techtonics Tuning and also bought a used Audi 80 exhaust manifold and downpipe via eBay Motors.

Sure, we could have simply installed the parts and hoped for faster lap times, but then there wouldn't be any story to tell! Instead, our first stop was to BSI Racing, a top-shelf Spec Miata prep shop that happens to be located just around the corner from our office. They were nice enough to let our steaming pile of Fox onto their dyno, where we tested the car in as-raced-at-Barber condition. 

The verdict? Actually, shockingly good! The Fox put down 90 horsepower and 98 lb.-ft. of torque at the wheels, which surprised all of us. Maybe we'd be able to make something out of this car after all. 

We pulled the car off the dyno, dragged it back home, and went to work. In a first for this project, everything that happened next went exactly as planned. We waved bye-bye to the old camshaft and said hello to the new one ($160). We also slapped the Techtonics chip ($135) into our Digifant ECU before calling it a night. 

The next day, we marched back to the garage for what we knew would be a grueling exhaust installation. Why? Because we'd be installing well-used junkyard Audi parts on a well-used, junkyard-worthy Fox, and Techtonics had already warned us that their exhaust system, a beautiful mandrel-bent setup ($270), wouldn't exactly bolt-up to the salvaged Audi 80 manifold and downpipe. Our worries here turned out to be premature as well, as the Audi parts bolted up to our Fox with no issues, and only required two welds to mate with the Techtonics exhaust system.

Just like that, we'd transformed our pedestrian Jetta drivetrain into a 7000 rpm race-winning machine. Or, at least we hoped we had. As we loaded the car back onto the trailer for a retest at BSI Racing, we smiled like idiots as the car idled lumpily–sort of like a baby Chevelle with a hot cam.

Finally, the car was strapped onto the dyno, and it was time for the moment of truth: Had we really made 25 horsepower? 

Uh, no. In fact, our first pull showed we'd lost more than 30. What had gone so terribly wrong? To find out, we dove under the hood, confirming that our cam timing was correct (it was), and then asking each other who had set the ignition timing after installing the new chip…. 

Oops. Despite it clearly being the last paragraph in the Techtonics instructions, we'd never set the ignition timing after giving the car its mechanical makeover. We set it to Techtonics' spec (10 degrees BTDC), then did another pull. 

SUCCESS! No, it wasn't 25 horsepower, but our little Fox did pick up 6 horsepower and 5 lb.-ft. That's not the story here, though. The real story is the drastically improved power curve, which is much higher everywhere, but also much longer. Before our car ran out of steam at about 5500 rpm, which amplified our gearing shortcomings. Now, though, the Fox makes strong power all the way past 6250 rpm, which should be a big help. 

Just to be safe, we tried adding even more timing advance to the car, picking up one additional ft.-lb. of torque while losing one horsepower at 12 degrees of timing advance. We'll run the car at 10 degrees of advance at Daytona in order to quell any potential overheating problems. 

We'd added power, but would it be enough to overcome our Achilles heel transmission? We'll find out on track this weekend, when we race with ChampCar at the Daytona Beach Independence Day 14-Hour.

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