The Power Stroke Improver - Trailer Life's Product Evaluation

The following article, written by Jeff Johnston, appeared in the May 1998 edition of Trailer Life magazine.


Today's light truck diesel engines just keep getting better. Turbochargers, intercoolers, and sophisticated fuel-injected systems are now standard equipment from the truck manufacturers. While these engines are certainly not your "fathers' diesels," there's always room for improvement. A number of companies offer add-on equipment designed to enhance performance and throttle response; Hypermax's version is called the 350-Horsepower Kit, and it can really spike the performance of the Ford Power Stroke diesel.

Jerry Lagod, Hypermax's owner and head engineer, has taken a "modular" approach to improve the Power Stroke engine's performance. His company markets equipment designed to boost horsepower to 350 (fly-wheel horsepower, which is always higher than rear-wheel horsepower due to friction losses through the powertrain). Powertrain losses are typically 10 percent with this type of vehicle when comparing flywheel to rearwheel horsepower. The Hypermax system has been CARB-approved and is, therefore, legal for 50-state use.

The complete 350-HP setup includes a low-restriction exhaust system, an intercooler (also known as an aftercooler), a replacement electronic engine control module (ECM) and a set of modified fuel-injection nozzles. These parts are sold separately and can be assembled in various combinations, but for maximum efficiency, the full boat does the truck the most good. A rundown on the parts, all of which carry one-year warranty against defects and materials in workmanship as follows:


There are two components to the low-restriction exhaust system. The basic 4-inch diameter exhaust system ($335 suggested retail price) extends from the catalytic converter back and includes a low-restriction muffler plus aluminized-steel mandrel-bent tubing. All of the stock exhaust hanger parts are employed to mount the system.

The second part is a 3-inch diameter turbine discharge pipe ($130) that replaces the flattened-steel Ford counterpart. The stock part was flattened to gain firewall clearance, but the amount of space gained is actually more than was needed; the flattened pipe leads to exhaust restriction. The new piece of equipment allows the gases to flow more freely to the rest of the exhaust system.

Designed primarily for 1994 1/2 through '97 models, the Hypermax intercooler kit includes all necessary plumbing, cooler, clamps and brackets.

All the stock hangers are used on the 4-inch diameter after-cat exhaust system, which includes a low-restriction muffler and aluminized-steel mandrel-bent tubing.


Ford's Power Stroke electronic fuel injection is controlled by the ECM, and Hypermax offers reprogrammed modules that provide the fuel-flow characteristics necessary to crank out the extra horsepower. A new replacement 350-Horsepower Kit ECM is $750, or $650 with a service-trade-in core. This is a plug-in unit that simply replaces the the stock Ford part. (A plug-in 'Max-Chip' is now available which attaches to the factory electronic engine control module. Recent Hypermax electronic development makes the performance of the 'Max Chip' superior to the afore mentioned ECM at nearly 40 percent less cost. ($465 vs. $750))

One Hypermax gauge provides boost pressure and exhaust temperature. The ECM is the brain of the system, and it controls all fuel-flow characteristics


The new model, 1999, heavy-duty Ford trucks with the Power Stroke engines come equipped with intercoolers from the factory, but for 1994-1/2 through 1997 models, the Hypermax intercooler ($1,145) can do a lot of good. An intercooler is a large air-radiator that plumbs into the truck's air inlet system between the turbocharger compressor and the intake manifold. As high-pressure intake air is pumped from the turbocharger, its temperature is increased due to the compression. The intercooler reduces the turbocharger-discharge temperature to within about 10 degrees of the ambient air temperature.

Lower intake air temperature results in lower exhaust temperature, and that means more fuel can be burned without excessively raising the exhaust temperature. In this case, more fuel is a vital part of producing more power, and keeping the exhaust temperatures at a reasonable level while making that power is very important.

Although most of the kit parts are bolt-on replacements, the intercooler requires the installer to cut two holes in the front radiator-support brackets for passage of the 3-inch diameter air pipes, as well as drilling a few holes for the intercooler support brackets. The front grille, bumper, headlight-housing supports and related parts must be removed and the auxilliary transmission oil cooler must be temporarily moved aside during installation.

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