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VW Diesel Engine Tuning and Upgrade Guide - Diesel Dynamite

Justin Fivella Looks At Tuning Options For The Existing Vw Diesel Engines.

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.

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.

Next in line is a clutch, because the factory unit is usually toast by then. At this point, most enthusiasts call it a day, happy with the output - the car remains quiet and economy is intact.

But like most of you, we'd never stop there. So next would be a bigger downpipe and exhaust, along with either a different cat or cat-delete. These mods generally max-out the turbo at 150whp and around 220 lb-ft. The open exhaust adds a muscular Mac truck-like sound as the turbo-spool becomes more apparent.

The next step is an upgraded turbo like a VNT17 or VNT20, which will take you into the region of 160-185whp and over 260 lb-ft with the aforementioned mods.

While these straightforward additions can double your power and torque, it isn't without its problems. Both Kerma and JSP stressed that the transmissions are the single biggest hurdle to modifying these cars because nothing can withstand that much low-end torque.

Most of us realize that a VRT or big-turbo 1.8T will eat its gearbox for lunch, but the diesels can exceed 300 lb-ft at around 1500rpm - a violent collision of axle-snapping, gear-grinding torque.

You've been warned; if you turn to the darkside, you'll quickly get really proficient at swapping your transmission!

Racing Diesels
In case you've been living under a rock, Audi won the 24 hours of LeMans with their diesel-equipped racecars. Proving these robust engines are every bit as competitive as gas engines has put the racing world on notice. And equally impressive are smaller diesel programs like Chili Pepper Racing (CPR) and its fleet of Jetta diesel racecars.

Although new to the sport and pioneering diesel racing in the states, CPR is gaining early success. Driver and President Jim Osborn explained that since little is known about building VW diesel race motors here, they've had to forge their own way. "If it wasn't for the help of some European tuners, we wouldn't be where we are today. They know so much about diesel tuning over there, while we know virtually nothing," Jim said.

Despite the steep learning curve and the lack of aftermarket support at their level, Jim said the indestructible nature of the diesel and its massive torque fit right in. "We're able to take an over-the-counter engine from VW with stock internals and turn it into a racecar - that's impressive when you consider most of our competitors have thousands of dollars in their engine alone," Jim said.

With a stock block, Jim also retains the stock nozzles but adds an unspecified VNT Garrett turbo, an in-house FMIC, downpipe and exhaust. They also have custom ECU tuning to extract the most from these parts.

"Because of our torque, we're able to run a higher gear through corners and save four or five shifts per lap. This translates into roughly half a second per lap; that's a lot."

Ignore them if you wish, but one day you might get spanked by a diesel. And when it happens, remember we told you so!

The Future
The future is bright for diesel, thanks to the threat of $5 gas making 40mpg from a fast car appear enticing. Both JSP and Kerma explained how new hybrid turbo technology is allowing them to exceed 200whp and 320 lb-ft in street-driven cars. These new Garrett turbos are allowing diesels to carry power at high revs like a gas engine, while still retaining the earth-turning torque.

Diesels are here to stay. Companies like Audi have shown these engines can be fierce competitors. And while it's nice to know diesels can win on the track, both Kerma and JSP expressed their excitement for the latest VW diesel technology arriving this year.

Elsewhere in this issue you can read about the turbo-diesels that are arriving over the next few months and learn about their tuning potential based on what's already happening in Europe.

Kermatdi Chili Pepper Racing
JS Performance
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