In 1936, Cliff Garrett began manufacturing turbochargers in Los Angeles, California. Originally, Garrett Corporation made turbochargers for a single client. Since then, Audi, BMW, DaimlerChrysler, Fiat, Ford, Peugeot, Renault, Saab and Volkswagen use Garret products in their vehicles. As of 2011, Honeywell collaborates with Garrett Corporation. The Garret VNT-15 turbocharger was one of many products produced for Volkswagen and Audi diesel engines. The VNT-15 was the European equivalent to the North American Garret GT-15 turbocharger. VW and Audi used these turbochargers for their 1999 to 2003 TDI engines.

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VNT Function

• VNT is an acronym for "variable nozzle turbine." The Garrett VNT turbocharger adjusts the gas throat section at the inlet of the turbocharger’s turbine wheel, as stated by Honeywell. At low speeds, the VNT system decreases the throat section for increased boost and turbine power. Essentially, channels within the turbo narrowly direct exhaust gasses, producing a higher flow rate. A higher flow rate increases how fast the turbo spools or spins. At high speeds, the VNT system increases the throat section for balanced turbo pressure. In this case, the turbo channels open and allow less energy into the turbo, decreasing the spool rate and chance of turbo failure. The VNT-15 does not use a waste gate component because of its variable geometry design. The waste gasses produced in the engine’s combustion ports pass through the turbo turbine continuously.

Applications

• From 1991 to 2003, Garrett produced 13.2 million VNT turbochargers. More specifically, the 1999 to 2003 Volkswagen Golf TDI, 1999 to 2003 Volkswagen Jetta TDI, 1998 to 2003 Volkswagen Beetle TDI and the early American ALH TDI Audi A4 used the Garrett VNT-15 turbocharger. The VNT-15 turbo worked with European Volkswagen and Audi TDI engines that produced up to 100 horsepower. Volkswagen recommends replacing the oil feed lines when installing a VNT-15 turbo. Old oil feed lines restrict oil flow when plugged, which will result in turbo failure due to a lack of oil circulation.

Technical Specifications

• The VNT-15 used a manufacturer’s part number of 7683315002S and original equipment number of 038253019C. The variable geometry turbocharger smoothly sustains 18 PSI and under maximum boost produces 20 PSI. Pricing on a new VNT-15 varies by retailer. Exalt Motorsports sells it new for $845, Kinetic Motorsports sells it for $819 and idparts.com sells it for $839. The North American equivalent, the Garrett GT-15 turbocharger, produced up to 18 PSI of boost and sustained 15 PSI boost within 90 horsepower Volkswagen and Audi diesel motors.

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