BTR-Bulitpruf Twin Rotor
These are pictures of a production prototype of our twin rotor throttle body. The base plate is for the 4500 bolt pattern. The top plate is to mount a GOZA air scoop. It flows app. 3500 CFM @ 28". The 4150 design flows 2100 CFM @ 28". The Twin Rotor (Pat. Pend.) design solves some of the original barrel valve drawbacks. Its smaller and lighter. The 4150 is 7.5 pounds on the first design 7 pounds for production. The 4500 is 11 pounds. Second. the off idle air flow is much improved over a single rotor. In fact its better than a butterfly. Air is directed to the center of the manifold at all throttle positions other than WOT
The butterfly has a flaw that just can't be gotten around. It's the 5/16 diameter shaft stuck right in the largest part of the port, the center. A butterfly 2.5 in dia. has an overall area of 4.9 Sq./In. A round 5/16 shaft takes takes .78 Sq./In. from that, a slab sided shaft .5 That's more that 10% . Smaller diameters the percentage is higher because the butterfly shaft remains the same even as the bore shrinks.
The barrel valve throttle has been used in race cars for at least 90 years. Harry Miller,the father of the Offy designed a carburetor in 1917 using a throttle barrel instead of a butterfly. They were used by Cosworth at Indy in the late 90s. Honda uses it in there VTEC K20A engine intake. So its not new. What's new is with modern CNC machining and fuel injection modern racers can take advantage of this power producing technology with moderate cost. These throttles can also be designed to be bolted directly to the cylinder head ports eliminating the intake manifold. We then CNC port the throttle to replicate a continuation of the optimum intake port with no restrictions.
Bulitpruf will custom design a throttle for your exact port shape. We can set it up for EFI or mechanical injection W or W/O nitrous. From a Harley to a Sonny's 737 we have a design or two that will fit your engine.