VW Diesel Engine Tuning and Upgrade Guide - Diesel Dynamite

While most would consider the VR6, 1.8T or 2.0T the go-fast engine of choice for their Volkswagen, an army of Dubheads in Europe (and even some here) march to a different beat; a sooty "clattery-clack" beat.

We're talking the other white meat, the bottom-of-the barrel sippers; we're talking diesels, baby!

With redlines in the neighborhood of 5000rpm, they may not spin like a gas engine, but stump-pulling torque makes these oil-burners a viable alternative to their gas-burning brethren. And before you join the chorus of cliches that are traditionally associated with these fossil fuel alternates, why not have your cake and eat it with nearly 200whp and over 300 lb-ft plus 40mpg, too...

Brief History
Gone are the days of the loud, sooty, slow Mk1 diesels that managed a paltry 50hp. In fact, these days you'd be hard pressed to know you were driving a diesel, such are the wonders of modern technology. And while VW has stuffed diesel motors in just about every platform after the Mk1, most of the modified diesels you'll find in the US are on the Mk4 platform. Therefore, we'll focus on that chassis for this article.

The first VW diesel to shine in the states used the '96-03 BEP TDI (Turbocharged Direct Injection) motor. However, we will discount the '96-99 AHU variant and focus on the '99.5-03 ALH motor - a true workhorse, these later 1.9 liter motors are stout, to say the least, and came with 85hp and 130 lb-ft at the wheels from the factory, according to JS Performance.

The motor remained relatively unchanged until '04, when VW decided to replace it with the short-lived Pumpe Duce (non-TDI) VEW engine. These used an in-house design similar to the latest "common-rail" technology and spray fuel at over 20,000psi into the combustion chamber for more power and lower emissions.

While the future of the newer VEW engines looks bright, the BEP motor presently dominates the market. And rightly so, with tuners like KermaTDI and JS Performance continuing to push the performance envelope.

But there are still hurdles to overcome, and modern diesels must still fight the preconception that they're slow, smoky and smelly. However, VW has strived to perfect the diesel so that smoke is virtually non-existent (except at start-up) and passing power is plentiful.

Largely overlooked in the US, it's only in recent years that tuners have realized that VW diesels can rival the potential of the 1.8T and 2.0T motors, while returning over 40mpg.

Tuning
Like the 1.8T/2.0T engines, a simple software upgrade, along with the standard bolt-ons, can net significant power and torque gains on a diesel. Where a 1.8T can expect a 30% increase in power, the BEP diesels can nearly double their outputs with similar mods.

Traditionally, people begin tuning their gas-engine cars by uncorking the intake and exhaust sides, followed by tuning the ECU. The succession then usually progresses to a bigger turbo and, eventually, a built motor.

After talking to both Kerma and JSP, we learned that relieving the intake and exhaust on a diesel, without proper tuning, can actually hurt its performance. A diesel might be an internal-combustion motor, but Kerma and JSP warn newbies against applying gas-engine logic to diesel motors.

With the parts available for the 1.9 TDI, achieving 200whp from your diesel is considered a respectable feat. And while 200hp might not seem much, remember that a diesel in that neighborhood will be making over 300 lb-ft of axle-snapping torque to the wheels.

In general, most people on the street will see 150-175whp, with 270-320 lb-ft of torque without any loss of drivability, while returning over 600 miles to a tank of fuel.

Following Kerma and JSP's proven recipes for power, we'd recommend you start with a matched nozzle and ECU upgrade. This will typically net around 130-140whp and over 200 lb-ft.