Still thinking about putting this on top of a tunnel ram? As far as the hat is concerned, it is simply just a butterfly valve to meter the airflow into the engine. If the 4-hole style is what you like, by all means, get what you like. There are some considerations in which throttle body is best for a specific application, for example, Enderle makes several different styles of the 3-hole hat; Bug Catcher, Bird Catcher, Buzzard Catcher, and The Big & Ugly. There are others in the Enderle lineup as well as different iterations, but you get the idea. Basically the difference between them is the area of the throttle valve opening. Think of it, to some extent, like sizing a carburetor to an engine. Too big of an injector and a lot more fuel needs to be pumped into the engine to compensate for the momentary lean condition when the throttle plates flop open. There is no accelerator pump, so enrichment has to be accomplished with fuel flow control.
Assuming the tune is right, throttle sizing plays a roll in engine mannerism. A larger throttle means less throttle angularity for the same area of opening. That means, what would be the equivalent of half-throttle with a carb would only be a small fraction of throttle opening with a large throttle body. The slightest little opening and you are hauling @$$ somewhere quick.
A large injector can complicate drivability in that it becomes difficult to modulate low speeds with a large injector. As you roll on the throttle, the opening is so great and flows so much, the RPM shoot up. On mine, I played with the geometry of the throttle arm/cable so that the first half throttle requires more pedal movement than the second half of the throttle opening.
The other thing, it takes a hell of an engine to flow a big injector. If you don’t have the ponies, the heads, cam, parasitic losses etc. become the limiting factor long before full-throttle is reached. In true poser fashion, BDS blocks off the inside of an Enderle Birdcatcher so that the engine only breathes on the center butterfly. This gives the “race” look without the drivability issues.
The 4-hole Hilborn hat that you show, I believe has 2.375 inch throttle bores. That is an area of 17.72 square inches of throttle area (minus the throttle shaft and plates). The actual Hilborn Shotgun injector has two 5.250 bores with an area of 43.30 square inches of throttle area (minus the throttle shaft and plates). The Enderle Bug, Bird, and Buzzard Catchers have three throttle bore diameters of 3.69, 4.38, and 5.00 inches respectively. This gives areas of 32.08, 45.20, and 58.90 square inches (minus the throttle shaft and plates) respectively.
Bottom line, if the 4-hole is what you like, it can be made to work. I have even seen old carburetors converted into EFI throttle bodies, just for the looks.
Cheers,
Joe
