The VW and Audi TDI diesel vehicles are probably the most economical cars on the road, getting about the same or better economy than the new hybrids. They are the best way to go when looking to save money on fuel. The VW TDi’s especially are growing in popularity in the U.S.. There are some complaints though. Like not having the power needed to pass someone on the road. This has all changed in recent years. There are several upgrades that can be made to the TDi’s to improve power, and to actually improve fuel economy even more. I will touch on these subjects briefly.
The first TDi Performance mod that comes to mind is an upgraded chip or tuning box. Both of these items change how the fuel is delivered to the engine. For a chip to be installed, the TDi’s computer must be removed and sent to someone who can solder in the new chip with the new program. A tuning box will simply be connected under the hood where it can intercept the signals going to the engines ecu and alter them. Most people will say that the upgraded chip will do the most for you, but the tuning box is the more common upgrade just because it is so much easier to work with. Also the tuning boxes are well liked because they can be removed and have no trace of ever being there so that warranty work can be done.
The TDi Performance upgrade that comes to most people’s minds first is the cold air intake. An upgraded cold air intake in a VW TDi will add approximately and additional 5-10% increase in power and economy. It is able to accomplish this by 1) Flowing more air which helps the fuel to combust more completely, and 2) TDI cold air intake are sealed away from the hot engine air. Cold air takes up less space, so in turn more air is able to occupy the same area because it is cold and not hot. That is a pretty good jump and the cost for the upgraded air intake is minimal. One of the drawbacks is that upgraded air intakes are not available for all of the TDi models or year groups. There are also performance drop-in filters for most of the TDi’s that will increase airflow slightly, and add a little power and economy.
The next thing that comes to peoples minds is an upgraded exhaust system for their TDi. The only problem with that is the lack of mods for the TDI exhaust. There are currently no major companies that manufacture full TDi exhaust systems to my knowledge. A custom system can be made, but often cost in excess of $750. So most people do either 1) A mufflerectomy where the muffler and resonator are removed and straight pipes are put in their place to reduce restrictions on exhaust air flow. This doesn’t really give a measurable power or economy increase, but does give a throatier sound that some are looking for and the reduced back pressure will add to engine longevity. Or 2) People will replace the muffler with a new muffler that is able to vacuum the exhaust out the tail pipe. These mufflers will add a little performance and economy, although still not very noticeable, but they will greatly reduce back pressure to add to the longevity of the engine and will also add a deeper tone that some are looking for.
Another common upgrade for the VW TDi is upgraded injector nozzles. Upgraded injectors or injector nozzles and an improved spray pattern than the stock injectors and when required are able to flow more fuel. They greatly add to performance and add a little economy too. They are also an inexpensive upgrade, and high on the bang for your buck scale.
There are also other things such as Water Methanol Injection that will add power and economy and are quickly becoming accepted and appreciated mods for the TDi’s. Also with any modifications, a set of gauges should be added to monitor the VW TDi’s engine parameters and to make sure that things are functioning properly.
As with building up any vehicle for power, VW TDI performance starts with the basic modifications first. The vw tdi will get its biggest two gains out of a tdi chip or module and out of tdi injectors. Your average chip or module upgrade will give about a 20% power increase. A tdi injector upgrade usually yields about a 20% gain as well. If the right combination of tdi chip/module and injectors are used even more will be gained. i.e. (Van Aaken Smartbox & Van Aaken Smart Power Nozzles) Those are the most basic vw tdi performance upgrades.
Another basic vw tdi performance modification is the tdi exhaust. If you are going to increase fueling you will in turn increase EGT’s (exhaust gas temperatures). So to keep temperatures lower and to help increase performance of the vw tdi even more, one of two things can be done. One a mufflerectomy can be performed in which the muffler and resonator are removed and a straight pipe is put in their place. This opens things up a little and removes the baffling of the muffler so that the exhaust can flow more freely. The second tdi exhaust option is the aero turbine muffler. The inner design of the muffler works the same as a jet engine to increase the flow of exhaust even more than what a mufflerectomy does. The inner design splits the air via an air foil. The faster air moves through the center and the slower air moves around the outside of the air foil, the slower moving air then re-enters the main air stream through inlets that go down the sides of the mufflers inner cylinder. This recombining creates a vortex that lowers the tone of the exhaust and dramatically reduces back pressure by increasing the flow of all the exhaust that moves through it.
Increasing air flow into the engine will help more of the fuel to be combusted and to help extract more power out of each molecule of fuel. Most cold air intakes have a large cone air filter that is able to move up to 300% more air than the stock air intake system. This makes the cold air intake an important part of any vw tdi performance package, sadly though cold air intakes are not currently made for all the vw tdi models. Another modification that helps with air intake and exhaust is water methanol injection. Water methanol injection is also known as chemical intercooling. It has a three fold effect on the diesel engine. It cools the intake charge which provides for more available air intake and the benefits of a higher positive pressure ratio (more power giving fuel can be utilized safely without high combustion temperatures). Two, the combustion of water also adds power and three; methanol is also a high octane fuel that adds more power. Water methanol injection typically lowers EGT’s by about 200 to 250 degrees on bigger diesels and is slightly under that for the vw tdi.
So in conclusion, to be able to build a real beast the modifications must be made from the ground up. After these mods are made then a bigger turbo and intercooler could be added as well as upgrading the clutch and other components to help hold the added power.