by Richard Rowe
Images from Thinkstock / Comstock / Getty Images
First, to clear up a common point of confusion: the TD04 and TD04L turbo is an MHI, which stands for Mitsubishi Heavy Industries. IHI is an independent turbo manufacturer that did not produce the casing for the TD04L, but did produce other similar turbos that can be used in place of the TD04L. Regardless, the TD04 is one of MHI’s most popular turbochargers, found in a number of variations on several different vehicles. The TD04L is one of those variations.
The two most common applications for the TD04L were the Dodge Stealth / Mitsubishi 3000GT and the Dodge Neon SRT-4. Subaru also used a variation of the TD04L instead of the standard TD05; the smaller TD04L didn’t produce as much high-end power as its larger counterpart, but its fast-winding nature made the TD04L-equipped Impreza WRXs drive more like a naturally aspirated car than an upgraded turbo ride.
Mitsubishi’s turbo rating system can be a bit confusing, but it’s pretty straightforward once you learn the basics. “TD04” represents only part of the full turbo designation; the full name of the turbo can be TD04-13G or TD04-15T. The first series of numbers and letters, TD04, designates the turbine casing / wheel design and diameter. The second series, 13G or 15T, represents the design and diameter of the compressor casing / wheel. In the MHI system, letters generally designate a particular design and numbers designate a size. For example, a TD04 uses the same basic design as a TD05, but is slightly smaller. A 15G compressor wheel / housing is roughly the same size as a 15T, but uses a different design.
The TD04L differs from the standard TD04 only in that its puller is approximately 0.15 inches larger in diameter. A compressor and a turbine wheel have two basic measurements of diameter, the inductor, where the air enters, and the exducer, where the air leaves. In an exhaust turbine wheel, air enters through the larger diameter part and exits through the smaller diameter part. A compressor wheel is the other way around. The TD04L uses a turbine wheel with a 1.86-inch inductor and a 1.62-inch exducer, versus the 1.57-inch exducer on the TD04.
The size and design of the exhaust housing is only half of the equation, and it plays an important role in determining how fast the turbo rolls up and maximum capacity rpm, but it has little to do with quantity. of air that the turbo can actually pump. The size and design of the compressor determines how much air the turbo can pump and ultimately how much boost it can produce. The TD04L turbo came with compressor housing / wheel trims including 09B (US-Sprec Mitsubishi 3000GT VR-4 / Dodge Stealth) 13T (Subaru WRX), 13G (Japanese specification 3000GT VR-4) 16T (Volvo), 18T ( Saab), 19T and 17G (Subaru WRX).