Volkswagen's Turbocharge Direct Injection (TDI) Clean Diesel engine offers high mileage between fill ups and fuel economy more than 50% better than similarly sized gas engines. With a potential 43 highway miles per gallon, you can get up to 795 miles per tank, in a car that emits lower CO2 commissions than 93% of other vehicles. The TDI is available in new Volkswagen cars such as the Passat, the Golf, the Jetta sedan and Sport Wagon, the Beetle and Beetle Convertible, and the Toureg.
To keep your TDI running at peak performance, it's important to understand how it works and how to maintain it.
What Makes A TDI Engine Different
TDI's secret to success lies in the engineering. By replacing the indirect injection of older diesel models, the new models use a fuel injection system that sprays atomized fuel right into the main combustion chambers and not into pre-combustion chambers. This process is combined with forced induction with the turbocharger that increases the amount of air that passes into the engine cylinders and an intercooler to lower the temperature and density of charge air from the turbo.
The result to you, the buyer? More fuel is injected and combusted, so you will notice greater engine efficiency and greater power outputs, along with more torque and fewer emissions.
Fuel Requirements For TDI
The Volkswagen TDI engine operates on diesel fuel (petro diesel) or certain types of biodiesel fuels. The trade-off for the engine's technical prowess is that it is picky about the type of fuel it takes. In the US, VW recommends Number 2 diesel fuel which has a higher cetane number than Number 1 fuel and lower viscosity. Proper fuel right from the pump is common in Europe, but some US drivers must use additives or premium diesel to make sure that cetane levels are correct.
“Mis-fueling” your TDI engine with regular gas instead of diesel can be a costly mistake. Some older VW models were more tolerant, but putting the incorrect fuel into a modern TDI engine will damage the fuel pump and ruin the engine when the fuel passes through the fuel system. That system in 2013 vehicles have been redesigned with a fuel tank gate to prevent you from inserting a gasoline nozzle rather than a diesel nozzle into the tank.
The cost of accidental mis-fueling can be range from $100 or so to pump out the improper fuel and replace the filters to over $8,000 to replace the entire fuel system. Most of these repairs are not under warranty.
What Can You Diagnose Yourself?
Your local VW dealer has a great service department that can keep your TDI engine running strong. Costs for regular maintenance run about the same as professional service for a gas engine VW. However, if you're a competent backyard mechanic who enjoys doing your own car repairs, there are some situations unique to a TDI that you may be able to diagnose yourself:
- If you hear noises, are they “normal” to your TDI engine? Most drivers notice clicking in the steering column, clicking from pressure control and AGR valves, and a swishing noise from the shoulder valve when turning off the engine. These noises indicate proper performance, not a problem, but as a new TDI owner you need to learn what to disregard and what to pay attention to.
- Does the engine fail to start or is reluctant to start? While the car is in neutral, turn the ignition to the run position to see if you get a check engine warning or glow plug lights. If not, you may need a new battery as the engine is getting no power.
- Does the engine crank? If you see check engine or glow plug lights on the dashboard, but the car is noisy as it tries to start, you may have low fuel, corroded wires leading to the battery, or loose connections.
- Do you get a “relay 109” failure? If your check engine light or glow plug comes on and off, you may have a relay 109 failure that calls for replacing the relay. If that doesn't work? You might have a faulty ignition switch or security system. You might also see the glow plug light if you have a burned out brake light.
- Does your engine smoke when it's fully accelerated after a fill-up? You may have gotten a tank of low-quality fuel.
A Volkswagen TDI engine offers the best in performance and efficiency, but they are particular engines that require very specific maintenance and repairs. Always remember to replace defective parts with genuine Volkswagen replacement parts, or choose your local VW service department for professional service from certified, experienced mechanics.