After a few weeks of searching for performance upgrades for diesel engines to review and feature, one thing has become clear: the American aftermarket has for the most part ignored clean diesel engines. A major contributing factor behind any car's enthusiast popularity is the ability to personalize and tune it. The VW Jetta TDI has been the one exception mainly due to the huge aftermarket parts catalog already available for the gas-powered Jetta. Other manufacturers, like BMW and Mercedes, have yet to see a growth in the amount of tuning upgrades available-but as diesel becomes more popular in the U.S., we expect things to change.
Because diesel cars have joined the alternative vehicle bandwagon, and to prevent diesel engines from being more than just a passing green fancy, a larger market for aftermarket parts needs to become available. Through its TDI Cup series, Volkswagen has demonstrated how diesel doesn't have to be all about the environment, but can also integrate all of the customization and tuneability that we've come to enjoy with gas motors. It has been over a year since clean diesel vehicles landed here, and the following is a list of upgrades currently available.
Drop-In Air Filter
A dirty air filter can reduce horsepower and decrease overall mileage, so it's critical to keep it clean. The 2010 Jetta TDI does come with a no-charge three-year/36,000-mile Carefree Maintenance program, so we're sure the air filter is on the list of covered items. But even if they do replace the filter under the program, it would most likely be at the end of the filter's life cycle. Depending on where you live, your filter should be replaced every 5,000-10,000 miles to maintain peak airflow, and doing this with a stock paper filter will get expensive. The most economical solution is a reusable, high-flow, drop-in air filter like one from K&N. It can be cleaned as often as needed and you will have made your money back after just a few cleanings. Drop-in filters are also available for Audi, BMW, and Mercedes diesel models.
High flow drop-in air filters do have the added benefit of increase airflow, but the problem is they are still restricted by the stock airbox. To address this issue, AFE has developed a Stage 2 cold-air intake system for the '09-'10 Jetta TDI that flows 56 percent better that the stock airbox assembly. Benefits from increased airflow to the turbocharger include increased throttle response, as well as a slight increase in horsepower and torque. Unfortunately, the TDI does not benefit from an improvement in the induction sound normally associated with open-air intakes. $292.95
Neuspeed's software flash for the VW/Audi 2.0 TDI is installed through the vehicle's OBD-II port, leaving no physical trace of its installation, and is completely reversible. The software is 100 percent compatible with all diagnostic equipment and offers free lifetime upgrades. Power gains are accomplished by a small increase in boost pressure and optimized fuel injection timing and duration without altering any of the factory safety protocols.
The Neuspeed slip-joint back exhaust system for the Jetta TDI is designed to reduce backpressure and exhaust gas temperatures by eliminating restrictions found in the stock system. The T-304 stainless steel system features 70mm mandrel bent piping to optimize flow and a low restriction muffler to reduce back pressure. The exhaust is also lighter than the stock system and gives the TDI a unique sound while increasing performance.
The Diesel Power tuning box for the latest VW/Audi diesel engines is a two-channel system designed to intercept signals from the injection rail pressure sensor and the turbo boost pressure sensor to raise fuel pressure and increase boost. The unit's harness features OEM style plug housings, requiring no cutting to install and making the unit easily removable. The Diesel Power tuning box does not alter engine rpm, vehicle speed limiter, or any of the engine control unit safety parameters. Diesel Power units are also available for BMW and Mercedes diesel vehicles.
DSG Transmission Flash
The Jetta TDI equipped with a Direct Shift Gearbox (DSG) transmission lacks a gear indicator located in the instrument cluster center display when the transmission is in Drive or Sport mode. The GIAC performance flash for the DSG, in addition to adding a gear indicator feature, helps increase shift speeds, as well as making downshift revs more closely matched. In Sport mode, the GIAC flash engages gear much quicker and allows the transmission to stay in gear at lower speeds by preventing it from upshifting.
The BMW 335d uses an electronic throttle control system to provide the its ECU the parameters it needs properly open the engine's throttle body. There's a sensor located on the fuel pedal that converts the position of the pedal into a digital signal, which is then sent to the ECU. Installed at the pedal, Sprint Booster circuitry intercepts and alters the original signals to increase pedal sensitivity, increasing throttle response and eliminating throttle delays.
The ultimate enemy of any engine is heat, which reduces horsepower and robs the engine of economy and longevity. This is especially on true on turbocharged engines. Intercoolers do help but they also often become heat soaked, which reduces their efficiency. Snow performance offers its Booster Cooler-a system designed to inject a 50/50 mix of methanol and water directly into the boost stream to lower air intake temperatures. The system can be calibrated to deliver the mixture based on engine demands or environment. Since the system is universal, it can be used on any diesel engine, you just have to choose the one that best suits your needs. From $502.75