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!
Chili Pepper Racing's VEW-powered...
Chili Pepper Racing's VEW-powered Jetta diesel is on of the few competitive diesel racecars in the US
Racing DieselsIn 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.
Kerma suggests a downpipe...
Kerma suggests a downpipe with software can produce good gains
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!
After your typical bolt-ons,...
After your typical bolt-ons, a larger turbo will get you near 200whp
The FutureThe 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.