Dynojet Power Commander

Anyone who has even a passing interest in cars knows how much power the engine in their own car has, or more precisely, the factory power rating of the engine. And those who are really into cars-such as all us late-model Mustang lovers-always know exactly how much power the factory rates the engine. For example, we'd wager that anyone who owns an '87-'92 Fox-body 5.0 or a '96-'98 Cobra knows the engines were rated at 225 and 305 horsepower, respectively.

But how much power the engine makes and how much actually gets to the wheels is always a different number. And furthermore, that number is always lower because of parasitic losses in the drivetrain. In other words, the transmission, driveshaft, and rear differential on any car take some of the power from the engine and usually about 15-20 percent less power gets to the wheels compared to the factory power rating.

Our purpose here is to show you the difference using the three Mustangs we've had tested on a Dynojet chassis dynamometer. For those of you who may not be familiar, we'll give you a quick summary of what we're talking about. A dynamometer (or dyno for short) is a device used to measure how much power an engine is making at the drive wheels. Think of it as a treadmill for cars. Different types of dynos can also be used for other purposes, such as emissions testing and other kinds of research where part-throttle situations are desired. Those types of dynos are very sophisticated, expensive, and usually found in government labs and in OEM applications.

In the aftermarket, the Dynojet is popular because it measures maximum power output under full-throttle conditions. It measures the effect of installing and tuning aftermarket parts to see if a benefit is realized. This before-and-after testing scenario has become a great way to erase any doubt as to whether something works or not when installed on a vehicle.

Here, we measured the output of three late-model Mustangs (a 347-powered Fox and two SN-95s) to compare how much power their engines put to the wheels versus the engines' rating. We'll supply you with factory horsepower (engine dyno results for the 347) and torque ratings as well as the results from each car's dyno test.

The three cars we tested were a '90 LX sedan with a 347 stroker, a '99 Cobra-that was bone-stock and had yet to have the "fix" installed that consisted of a reprogrammed EEC-V processor, an Extrude-Honed intake, and different exhaust-and a totally stock '01 Bullitt with 8,100 miles on the clock. All three cars had manual transmissions, so testing them was quite easy as the pulls are made in the gear (Fourth) that's 1:1.

Testing is only slightly more difficult for those of you with automatic-equipped Mustangs, because when full-throttle is applied, some transmissions might downshift to Second gear if you begin the pull at too slow a speed. Although the general rule of thumb is about a 15-20 percent power loss for a given vehicle, those with automatic transmissions usually have a greater loss in power to the wheels than the same vehicle with a manual.

We have two different setups to illustrate what we did with the 347-powered Fox and the '99 Cobra. First, we ran the 347 on an engine dyno and then installed the engine in the car and ran it on a chassis dyno. We then had the chance to run it on the dragstrip with a set of slicks bolted up, where the car ran mid 12s (12.65 at 108 mph, to be exact) after getting 20 mpg on the highway. We have the full specs on this engine as well as other pertinent info.

We baselined the Cobra bone stock and tested it in two steps with a number of BBK pieces outlined later in the article. Finally, just for fun, we ran Mustang Monthly's staff Bullitt Mustang on the rollers, owned by yours truly, just to see what it'd do. So, without further rambling, let's get to it!