The 7.3L Power Stroke Diesel is a Turbo Charged V8 that came with a fixed geometry turbo from Garrett. Older (94-97) 7.3L PSD came with a Garrett TP38 and no Inter-Cooler, in early 99 Ford added a wastegate to the TP38 and an air to air intercooler for denser air and lower exhaust temperatures, lastly, the newest (99.5-03) came with a GTP38 that had a larger wastegate and an air to air intercooler.
The 7.3L PSD used effectively the same turbo but each model had different features and slight changes as Ford made engineering improvements for power and emissions based on the current standards. Both early and late turbo models consist of the same size fixed geometry turbine and compressor wheel mounted opposite each other enclosed in separate housings. The wheels share a common shaft enclosed by the center oil cooled housing. The turbo received oil via the pedestal fed directly from feed and return ports on the top of the engine block. The turbo is powered by high velocity exhaust gas that drives the turbine wheel and turns the common shaft which ultimately turns the compressor wheel. The compressor wheel turns at speeds up to 130,000 revolutions per minute. Air entering the compressor side of the turbo is then compressed and delivered to the combustion changers which equals more engine power output, better fuel efficiency, and better performance at higher altitudes.
Here is a break out of a 2000 7.3L GTP38 PSD:
The Turbo model can be identified by locating the ID plate on the turbo itself and by counting the bolts on the compressor housing.
The TP38 fixed geometry turbo charger had a 4 bolt intake housing and a wheel designed to help control and prevent turbo surge.
TP38 specs:
- Compressor wheel inducer diameter: 59.87 mm (60 mm)
- Compressor wheel exducer diameter: 80 mm
- Compressor housing A/R: 1.10
- Turbine wheel inducer diameter: 76.2 mm
- Turbine wheel exducer diameter: 69.84 mm (70 mm)
- Turbine housing A/R: 1.15
The GTP38 added an electronically controlled waste gate. This allows the Power Control Module to control the intake manifold pressure by taking readings from the intake manifold pressure sensor and comparing it to vehicle speed and engine load then sends the appropriate signal to the solenoid control valve which alters the pressure applied to the wastegate actuator ensuring the proper boost pressure is maintained from the turbo. The GTP38 used a different intake housing with an A/R of .84 and is visibly larger than the TP38 and has 5 bolts instead of 4 on the compressor housing. The GTP38 also used a different intake wheel of the same size. The inducer and exducer diameter is also the same size as the TP38.
Garrett makes a GTP38R Powermax Turbo Upgrade for the 7.3L Ford Power Stroke part number: 739619-5004s that utilizes an exclusive ball bearing cartridge instead of a thrust bearing found in the OEM turbos for unbeatable response, efficient, and durability. This kit includes a 1.00 A/R turbine housing for free reduction in exhaust with reduced back pressure and up to 200℉ reduction in exhaust gas temperature. Both the inducer and exducer are larger on this turbo with the inducer sized at 66mm and exducer sized at 88mm. Garrett also offers a a .84 A/R housing for quicker low rpm spool-up.
Looking for more performance? There are many after market turbo replacements and stock turbo upgrades out there including different designs of compressor wheels such as the Billet Wicked Wheel 2, different sized intake housings with different A/R ratios, non-EBV pedestals, and even complete aftermarket high flow turbos such as those provided by KC Turbos.
Although turbo chargers may seem complex they are actually fairly simple devices which is good when you need to troubleshoot. Here you will find some very helpful documents when you need to troubleshoot your turbo’s operation or remove / install it for whatever reason.
View or Download a PDF of the Technician Turbocharger Guide for the Powerstroke Engine (open or save)
Riff Raff Diesel has created a great turbo removal instructional PDF you can view or download.