Turbo Tech
This article contains basic information about the turbochargers that were stock on the 2.2L / 2.5L turbo cars. I’ll start out by explaining the basics of how a turbo works, define some technical terms, and then get into the differences between the stock Mopar turbos. This article is written for the beginner enthusiast. If you already know it all, just enjoy the pictures!
What is a Turbocharger?
A turbocharger is a supercharger that is driven by exhaust gasses instead of belt driven off the crank, or by an electric motor, etc. Turbochargers, like regular superchargers, are designed to pressurize the intake charge of an engine to increase power output. A turbo is plumbed into both the exhaust and intake systems of an engine and is comprised of two halves - a turbine (exhaust side) and a compressor (intake side).
How does it work?
Starting on the exhaust side, the turbine housing half of the turbo is plumbed inbetween the exhaust manifold, and exhaust pipe. As the exhaust gasses exit the engine, they pass thru the turbine housing, spinning the turbine wheel, on the way into the exhaust pipe. The spinning turbine wheel is connected to a shaft that goes through a bearing housing and is connected to the compressor wheel. As the compressor wheel spins (spool up), it draws fresh air into the compressor housing inlet, and forces it out of the housing outlet and into the intake manifold. As the intake is pressurized (Boost) and flowing more cubic feet per minute (cfm) of air, more fuel is added by the computer to keep a stoichiometric air fuel ratio, and thus more power is made, based on the assumption that HorsePower is increased with the consumption of more fuel, while keeping efficiencies similar.
  A/R Ratio: Area to Radius Ratio of a turbine or compressor housing. Higher ratio equals higher flow capability.
  Inducer: The inlet side (small diameter) of the compressor wheel
  Exducer: The major (large) diameter of the compressor wheel
  Wastegate: An actuator used to proportion the amount of exhaust gasses that go through the turbine or bypass it and exit directly into the exhasut system. The OEM mopar turbo’s use the wastegate in combination with a set of solenoids, and instruction from the computer based on sensor input, as a means of controlling the upper limit of intake boost pressure.
  Throttle Body: Air metering device comprised of a housing and throttle blade used to control engine air intake, and thus engine speed
  Blow Off Vavlve (BOV): A pressure release valve between the compressor and intake, upstream of the throttle body. As the throttle blade closes, the compressed air charge is stopped, puting backpressure and stress into the compressor wheel. The BOV, which is typically vacuum actuated, opens to release this pressure. The later (‘88+)OEM mopars used BOV’s to improve durability.
  Intercooler: A heat exchanger placed between the turbo compressor and intake manifold, designed to cool the intake charge.
  Turbo Lag: The delay time before Spool up
  VNT: Variable Nozzle Turbocharger- has adjustable vanes in the turbine housing to redirect exhaust gasses to improve spool up, and reduce lag.
Next, I’ll explain what the Roman Numerals mean in order of production as opposed to numerical order
Turbo I “early” (‘84-87) Garrett T3
This is the original mopar turbo setup, and was only offered in 2.2L displacement. These early engines are different from ALL the other ones in that they used an upstream throttle body. By upstream, I mean that it is before the turbo, causing the turbo to have to suck the air through the throttle body, commonly reffered to as a “Suck thru” motor with a “log” intake. These were non-intercooled, however, Direct Connection (now Mopar Performance), Spearco, and others offered aftermarket kits. In the picture, notice how the compressor housing has flange where the inlet pipe bolts on.
Turbo II (‘87-’89) Garrett T3
The T2 is a refined version of the ‘86 Shelby GLHS Omni engine (no EGR, etc). They were offered in 2.2L displacement. The main difference with the T2 designation is that it uses an intercooler. The T2’s are also the first engines to use the downstream throttle body where the turbo forces air through the throttle body (blow thru). A “true” T2 also used bigger forged connecting rids, and a forged steel crank, and ‘87 used the Shelby 2-piece Intake manifold. The intercooled T2 numbered Whittier Shelby cars actually used T1 short blocks. In the picture notice how the compressor housing has an inlet that a hose directly connects to.
Turbo I “late” (‘88-’93) Mitsu TE04H
The late T1 is a non-intercooled version of the T2, offered in 2.2L and 2.5L displacements. These engines use the blow thru style induction system, which can easily be intercooled using T2 parts or custom installations. These were the first engines to use a factory BOV, and as the picture kinda shows in comparrison, these were the smallest turbo’s used on the turbo 2.2L/2,5L vehicles. 
Turbo IV VNT (‘89-’90) Garrett VNT 25
The T4 was intercooled like the T2, but also offered an industry first VNT turbo (see definition of VNT). The T4 was offered on 2.2L displacement engines. This cut-away shows the vanes in the turbine housing which “nozzle” the exhaust asses at the turbine wheel. The VNT turbo’s allowed for faster spool-up, with almost no lag, however, they used a smaller compressor which limits potential. Unfortunately, the vanes in the turbine housingare prone to malfunction caused by carbon build-up
Turbo III (‘91-’93) Garrett TB03
The T3 is the highest tech combination offered on a 2.2L engine. The engine uses Dual Over-Head Cams (DOHC) to actuate 16 valves (8 intake, 8 exhaust) as opposed to the T1, T2, & T4 cars that use a Single OHC (SOHC) and only 8 valves. Additionally, the The DOHC Turbo III engines used a slightly different turbo. The T3 motors had the highest factory power offered, rated at 224HP!
Turbo Comparisson
In an attempt to answer the question “ what’s the difference?,” I have put together a chart (see below) of the diffeences between the models. Keeping in mind the differences between the T1,2,3 & 4 engines, some of the turbocharger components changed accordingly. With most things, bigger is better, as that is true with turbochargers when you are looking for maximum potential. If faster spool, and low-end power is desired, then the smaller turbo’s can actually offer an advantage. Chrysler’s Turbo motors were an evolution in design, including both one of the first sucessful Multi Port Fuel Injected Turbo setups and one of the most powerful 4 cylinder engines ever sold in the USA.
Chrysler OEM Turbo Comparisson Chart
  Turbo I “early” (‘84-87) Turbo I “late” (‘88-’93) Turbo II (‘87-’89) Turbo III (‘91-’93) Turbo IV VNT (‘89-’90)
Manufacturer / Name
Garrett T03
Mitsubishi TE04H
Garrett T03
Garrett TB03
Garrett VNT25
Comp Housing A/R
Comp Wheel Inducer
36mm or 40mm
Comp Wheel Exducer
Turbine Housing A/R
Turbine Wheel Dia.
Turbine Housing Outlet Size and exhaust flange bolt spacing
2.25” Small Flange
‘88 - 2.25”
‘89-’93 - 2.5”
All Large Flange
‘87 2.25” Sm. Flange
‘88 2.25” Lrg. Flange
‘89 2.5” Lrg. Flange
2.5” Large Flange
2.5” Large Flange
Disclaimer & Credits: This information is a collaboration from Mopar manuals, Turbonetics, turbo mopar internet sites (Gary Donovan, Russ Knize, Dempsey Bowling, etc), and other sources. Unfortunately, I cannot guarantee that ALL of the information is 100% correct due to the variety of sources and few inconsistencies I found from the various sources, however, I did use the more common info if there was a discrepency. If you have documented information that contradicts what I have put together, please let me know, and e-mail the information to me. Thanks!