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Why does TWM make throttle bodies?
TWM is a manufacturer of intake manifolds, for competition style carburetors,
such as the Weber DCOE Series. When a number of programmable, fuel injection
electronic control units (ECUs) became available in the performance aftermarket,
it was obvious that many enthusiasts would want to convert from carburetors
to injection. TWM throttle bodies permit the conversion of
virtually any engine equipped with a suitable manifold to fuel injection. These individual
runner systems are the best way to convert a competition engine to EFI.
What carburetors will TWM's throttle bodies replace?The DCO and DCOE Series Webers, the PHH Series Mikunis, the ADDHE Series Solex, the SK Racing sidedraft, the IDA (2 and 3 bbl) IDF and DCNF Series Webers, and DRLA Dellortos.Does TWM make other throttle bodies not intended for carburetor replacement?Yes, TWM manufactures several dedicated injection manifolds to convert engines to individual runner EFI for racing purposes. We also make the 2000 Series throttle bodies which are dedicated injection manifolds for Honda, Ford, VW, and others. TWM also produces some large bore single barrel units which have many applications and several throttle bodies for upgrading original equipment EFI systems including the “Big Throat” throttle bodies for Datsun Z cars.When using the 2000 Series throttles, can I retain the stock ECU?Generally speaking, no. All these systems are designed for aftermarket ECUs, such as those manufactured by SDS, MoTeC, Electromotive, Link USA, Haltech, DFI, or Felpro. With some OE systems it is possible to use the V-Tec/fuel controllers from Split Second or Field (Field products are available through Group A Autosports).Why don't TWM throttle bodies have venturis like carburetors?Carburetors rely on the pressure differential created by a venturi to draw fuel from the float bowl via the various jets and circuits. By their very nature these components cause a restriction to air flow, and contribute to pumping losses. The inevitable disadvantage of this system is that, while a venturi of a certain size may be necessary to provide low speed driveability it then acts as a restriction at high RPM. Because the fuel in an EFI system is injected under high pressure there is no need for any venturi. That is the reason throttle bodies flow so much more air than a carburetor of the same size (see page 21 for flow data) and the reason that EFI systems can use larger throttles than the equivalent carburetors.Why are the injectors positioned in the TWM throttle bodies and not in the manifolds, like original equipment EFI systems?Original equipment EFI systems are configured to meet very stringent emission regulations and to provide "soft" driveability characteristics. Positioning the injector as close to the inlet valve is beneficial in this respect. Maximum power however, is usually obtained by moving the injector away from the inlet valve, some racing engine manufacturers going as far as to mount the injector high in the velocity stack and others installing two injectors, designed to operate at different RPM. When TWM designed the throttle bodies our engineers were not in favor of having high pressure fuel on the atmosphere side of the throttle plate, although this could have resulted in some power increase. We compromised by mounting the injector as far from the cylinder head as possible while still maintaining the safety afforded by keeping the fuel downstream of the butterfly.What do I need to install an EFI system on my car?You will need a suitable manifold, throttle bodies to suit your application, a fuel rail kit, a high pressure fuel pump, a filter and a regulator, appropriately sized injectors, a return line to the fuel tank or fuel cell and an aftermarket ECU. Most EFI kits are supplied with wiring harness, sensors and throttle position sensor.More explanations: What is Fuel Injection? |
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