1993 Volkswagen Fox
"TeraFox"
Jonathan Pack
Columbus, OH

    I bought my second VW Fox in 1998 after crashing my first, a 1990 two door, a few months earlier.  I had always wanted to modify my 1990, but never had the money or opportunity.  Upon finding the 93, I immediately began to make plans for its modification.  My first step was to replace the factory exhaust with a Leistritz Sport Tuned exhaust.  I installed the Leistritz exhaust and a hollowed catalytic converter, convinced this would fulfill my need for performance.  It definitely did not.  I could hardly discern a difference from the stock configuration.  I decided, before I made any more improvements under the hood, to install a set of Neuspeed springs and Sachs Super Gas struts front and rear.  The suspension worked wonders.  The handling was far more responsive, eliminating the Fox's predilection toward pitching and rolling in turns.  After the suspension work, my next step was to install a performance cam from Autotech.  Again, I felt no difference.  The car was definitely a bit faster, but it lacked the "seat-of-the-pants" feel I was seeking.  After learning a bit about engines, I realized that the power I sought could only be realized through port work to the cylinder head.  So, I sent the head to a performance tuner in Tiffin, OH for a port rework, polish and stainless competition valve install.  When re-installing the head after the port work, I opted for the Techtonics Tuning dual downpipe and a VW Dasher 4-into-2 exhaust manifold with the ports slightly worked to match the new shape of the head's exhaust ports.  This modification was very satisfactory.  The power band was not narrowed significantly, but peak power was significantly higher, producing a very satisfying thrust on full acceleration.  Of course, the effect of the newfound acceleration soon was not as impressive as it had been and I was on the search for more power.  To satiate my increasing appetite for power, I decided to increase displacement.  I had the 92.8mm crank and 82.5mm pistons from an Audi 3A 2.0L engine installed in a bored 1.8L VW Fox cylinder block.  This process requires the distributor driveshaft (the engine's "intermediate shaft") gear to be cut down by about 50%.  The end result is a bit scary, but still durable.  The more advisable way to have a 2L engine is to buy an ABA (VW tall 2L) or Audi 3A (Audi 80 FWD 2L).  I also replaced the Leistritz exhaust with a custom 2.25" exhaust made at a local custom exhaust shop.  The work was very high quality.  The displacement increase broadened the power band and increased the acceleration a bit more.  Again, I was satisfied, but the satisfaction again wore off.  I decided to take a larger leap in order to anticipate my future "need" for more power.  This is when I decided to commit to a more serious project, which a friend nicknamed "TeraFox."  The name stuck.

The first goal in project TeraFox was to eliminate excess weight.  I removed the HVAC, stereo, dashboard "knee bumper" pad, rear seat, rear interior panels, front and rear bumpers, etc.  This adds "racecar cool" to the look of the car, but the reduced weight is probably not worth the sacrifices in creature comfort.  I would not recommend the removal of weight except for those who intend to use their cars for racing, in which every little bit could be a leg-up on the competition.

After stripping the interior, I turned my attention to the engine.  I decided I wanted to use a late model 8-valve cross flow head.  The cross flow head flows better than the conventional VW "wedge" style head.  Of course, the head was not sufficient on its own.  I sent the head to the same machinist in Tiffin, OH for more of the same work my original head received.  This time, the head was to receive a more substantial camshaft, cam grind #253, from WEB cams.  This is a solid lifter cam, so I had the head converted to use solid lifters.  Solid lifters are superior to the stock hydraulic lifters because they are lighter, and not reliant on oil pressure for proper operation.  That solid lifters are lighter means they will allow the engine to rev higher.  That they are not dependent on oil pressure for operation means they will not "float," or stick open after receiving an overload of oil commensurate with RPM over 7000.  Pictured at right is the highly ported Dasher manifold and Techtonics pipe, both of which remain a perfect fit for the crossflow head.

The 1993 Fox's Digifant fuel injection, a variant of Bosch's L-Jetronic, would not suffice for the demands this new engine.  Digifant injection is integral with the ignition system (grr!).  For the ignition, I chose to convert to Bosch's later style vacuum advance ignition, such as that from a 1987-90 Fox, 1984-on Rabbit, Scirocco 8V, A1Jetta.  Injection would be SDS electronic.  Pictured is the handheld programmer unit and mixture meter from Simple Digital Systems.
 

The cross flow head is a tight fit under the hood of the VW Fox, so a few parts had to move or be replaced with custom parts.  The design of the intake plenum was all wrong for a longitudinally mounted engine, so I had to design a custom intake.  Note the proximity of the intake plenum and the alternator.  The fit was so tight that I had to find the shortest possible alternator belt.  The belt had to be so short that it had to be fit around all pulleys before the alternator pivot bolt could be installed.  Once I fitted the alternator, I found that the belt was so short that it caused the alternator's fan blades to catch on the water pump housing.  I had to remove the alternator fan and shave down each blade of the fan.  Tight fit!  The alternator tensioner is also a homemade piece because the stock tensioner would not allow the number one spark plug boot to install over the spark plug.  Tight!

The custom intake required that I have a custom front mount radiator, shown here.
 
 
 

The custom rad required the installation of hood pins, because the hood latch device would have punched a hole in the new rad.  This is one of the expectable unexpected obstacles associated with a project this large.
 
 

In addition to the engine and SDS injection, custom rad, etc. under the hood, I had to match the Fox's handling to its new power.  To improve handling, I relocated the battery immediately behind the passenger seat.  Note: this requires the purchase of an Optima gel cell battery.  I did NOT want a liquid acid battery riding with me inside the car, especially in the event of an accident!
 
 

I also installed a rear sway bar from o-bars.  This is an excellent item!  The handling was markedly improved.  The rear sway bar finally gave the car balance, all but eliminating the understeer that plagues all FWD VWs.  Note in this picture the stainless steel brake hoses and the fitment of the exhaust.
 

Another part of project TeraFox was to improve the brakes.  I modified the front brake caliper carriers to accept vented rotors.  I shaved a set of metal master front pads until they were thin enough to fit over the thicker vented rotors.  A vented rotor conversion is far more easily accomplished with Scirocco front calipers and carriers.  I also installed stainless steel brake hoses.  These hoses, from Autotech, did not provide the radical difference of which many had told me, but they did make the brakes more responsive.  The rear brakes remained stock, and were completely adequate.

The transmission was the stock PSA code 5-speed.  In defiance against popular opinion, the Fox's 5-speed withstood the brutal lashing I handed it through the 2L engine.  The gears are dramatically better than the Fox's 4-speed transmission.  However, better transmissions are available.
 

I performed all modifications after the first paragraph all at once, starting October 2000 and finishing in May 2001.  From the time I stripped the interior and removed the old ported head, I did not drive the car until it was finished.  The difference in acceleration was amazing--the power I was always seeking.  The handling was very crisp and responsive.  The brakes worked very well.  I enjoyed the car to the fullest measure until August 2001, when I crashed TeraFox.  The crash was my fault: I was pushing the car too hard without respecting its limitations.  I went into an oversteer spin and never regained control.  Before I crashed TeraFox, I had time to make the following observations:

1) Acceleration was amazing!  The SDS injection provided instant throttle response.  The WEB cam was a perfect choice, providing excellent power and a broad powerband, with excellent power from 3000 to 7500 RPM.

2) The lightening effort was probably not worth it.  Further experience with a VW Scirocco has proven that a recent weight drop of 50 lbs. provided zero improvement in 1/4 mile time.  As I said earlier, putting your car on a diet is only fruitful when you need every possible advantage--as in racing events.

3) Economy was decent.  On a cruise to Canada, I got 25 MPG on the freeway.  MPG decreased to around 15-20 MPG under "spirited" driving.  Considering what the car was capable of doing, the small sacrifice in economy was acceptable.

4) The crossflow head conversion was probably not worth the extra effort.  The crossflow's intake was a bad fit for the Fox hood.  The custom intake necessitated the custom alternator mounts, home made rad hoses, custom rad, hoodpins, etc.  The conventional head would probably be nearly as good, and would have allowed all the stock Fox support equipment to stay, saving large money.

5) The drive from Columbus, OH to Mississauga, ON, Canada is VERY long without a stereo.  A stereo weighs less than 10 lbs.

6) A Limited Slip Differential (LSD) would have been very nice, but is not available.  Inside wheelspin occurs under acceleration during and exiting turns.  It's an unhappy detraction to front wheel drive cars in general, and one that we Fox owners can do nothing to prevent.  Wheelspin is not unbearable, and is probably not as noticeable as that of my Scirocco in stock condition when put to the same test.  Note: the Scirocco comes with a mild LSD from the factory.

7) TeraFox was tremendous fun.  It surprised many people, even, and sometimes especially, VW people.

8) After the crash, I can say it is definitely worth doing again.  I have another VW Fox in the dreamworks right now.  It should be ready for next summer.

If, after reading this thoroughly, you have any pertinent questions, please feel free to contact me.