Vehicle manufacturers rate power and torque numbers at the flywheel. While this is great when the engine is on a stand, once it is dropped into a car those numbers represent the car’s performance. A good rule of thumb to convert flywheel horsepower to rear wheel horsepower (RWHP) is to take flywheel horsepower and subtract 15% for a car with a manual transmission and 18-20% for a car with an automatic transmission to get RWHP. This won’t always be exact, but it’ll get you in the neighborhood. Since Ford rates the Bullitt at 265HP and it’s a stick, that means the car should but down around 225HP at the rear wheels.
Oh, and did I mention they have a 1,700HP dyno? More than capable of handling the factory HP of my steed, the staff at Detroit Speedworks was more than willing to get the car on the rollers.
Once she was all strapped in and wired up, it was time to make the car scream.
A dyno run consists of running the car, full throttle in fourth gear to redline. The dyno computer measures HP and TQ at every RPM, and records these numbers. The numbers are then plotted on a graph.
As the graph shows, the car produced 229.7HP and 262.4ftlbs of TQ at their respective peaks. While this is above the expected 225H based on Ford’s rating the car is still being broken in, and I expect to see a few more ponies once it gets closer to 5K miles or so.
To see what this translates to in terms of head to head performance, the staff at Detroit Speedworks graphed the run against a 2000 Camaro SS (also stock). I was disappointed.
The light blue and red lines on the graph represent what GM offers to their customers, while the pathetic dark blue and green lines are what Ford offers as a special edition for about the same price. To get a better “apples to apples“ comparison, Detroit Speedworks also showed the Bullitt against a ’99 Cobra (with the fix).
This shows that while the Bullitt comes in about 20HP shy of the Cobra, TQ is about the same. Where the dyno results really start to shine is in comparing before and after HP and torque levels when performing a modification. The dyno graphs will show if you’re getting more power from the parts installed, how much you gained, and what RPM that power is at.
If you’re in the Detroit area and would like more information or to set-up a dyno session call Detroit Speedworks at the number below. For other areas, contact your local speed shop to see if they offer this service.