I. BACKGROUND
Those who have spent much time around a dyno shop find out rather quickly that anyone who installs an upgrade throttle body on a 4.6L 2 valve Mustang is not going to be excited with the results. Dyno testing the popular 70mm throttle body upgrade has shown that it will only add AT BEST 2 rear wheel horsepower (see dyno scan provided), and even then it isn't a consistent gain throughout the RPM range. The reason for this is because the factory throttle body is not hardly restricting flow through the factory plenum. It is the plenum itself that keeps more air from getting into the lower intake manifold and then on to the cylinder heads. The actual increase in airflow delivered to the engine through the installation of a larger throttle body on the stock plenum is a measly 20 CFM, or 4%, which means that the larger throttle body has minimal effect on the total amount of airflow that is actually allowed into the engine itself.
We started work on an all-new design intake manifold for the 2-valve Mustangs nearly 2 years ago, but we had to put the project on hold to complete new C&L Trueflow inlet pipes to cover all of the most popular Mustang applications. After hearing over the past 18 months or so that some 4.6L enthusiasts were experimenting with plenum spacers and the porting of stock intakes, we decided to develop and test a totally unique item for these vehicles. Be very wary of outlandish performance claims pertaining to other plenum options, as what we are providing has been proven in flow testing to outperform anything else available. Originally, this plenum was going to be truly "one of a kind". The concept was to cast a single manifold that included the plenum, the throttle body and an intake spacer (provided we found the optimum plenum volume). The only problem was that most people have already purchased a throttle body, and the inclusion of it would limit potential customers who didn't want to purchase another one. Not to mention the fact that it would also make the item much more expensive than the "under $200" price point that our new plenum comes in at. After a great deal of development and solid engineering, we are confident that this new plenum will be embraced by the modular Mustang community, and will allow vehicles to reach higher horsepower levels than what was previously possible with other stock plenum modifications and options. One telling factor of this is that most "bolt-on" 4.6L GT's seem to hit a wall at around 270 rear wheel horsepower in naturally aspirated form. One of the vehicles used for testing of our new plenum was able to surpass this level of performance with only external bolt-ons and stock headers! For more details on this, please read about Test Car 1. To learn all about the design of our new plenum, including flow bench test numbers, please continue on to the Product Design section.
