![]() Each cylinder can be more closely maximized for power, economy, and aggressive lean-of-peak operation greater maximum engine power is thus possible compared to rudimentary carbureted systems, and more economy is possible when leaned, too. Mixture variations are limited to intake manifold design, something the engine manufacturer can easily get close, plus you can fine-tune mixture variations by substituting different size nozzles. But the Bendix unit also meters fuel, hence its fuel servo name the EFII electronic throttle body simply throttles the air supply and reports the throttle position to the computer.Ĭlearly the big advantage is the fuel is administered individually to each cylinder rather than a single point as with carburetion. Nozzle pressure can well be under 1 psi at idle and around 7 psi at full throttle.īoth the Bendix fuel servo at left and the smaller EFII unit at right are throttle bodies. ![]() Therefore fuel pressure is much lower at the fuel nozzles than at the fuel servo. Fuel pressure is the energy operating what could be called an analog fuel computer (the fuel servo), and so fuel pressure is, by design, consumed operating the various diaphragm springs, overcoming line losses, and pushing fuel through the main jet. Fuel pressure as delivered to the fuel servo varies with demand, and is often around 20 psi, but can rise to approximately 45 psi. Note there is no pulsing of the fuel it flows in a steady stream. There fuel passes through a precision nozzle, spraying in a constant stream into the intake port, just upstream of the intake valve. Like a railroad roundhouse the flow divider parses the fuel to small lines running to each cylinder’s intake port. But unlike carburetion, the fuel is not administered to the air stream at the fuel servo instead it is routed to the flow divider. The servo senses air pressure and employs a series of diaphragms to meter the fuel flow for the mass of air passing through the throttle body portion of the servo. An engine-driven diaphragm pump supplies fuel to the fuel servo this is a throttle body and fuel metering assembly that typically mounts in the same place as a carburetor. Post-war, Bendix developed their wartime single-point pressure carburetor system into the RS multi-point fuel injection, and by the late 1950s that was detail improved into the RSA system that’s still with us, both in original form and updated by several aftermarket sources, notably Airflow Performance and Precision Airmotive.īendix’s RSA is constant-flow, mechanical fuel injection. Attempts at multi-port fuel injecting Allied airplane engines were mostly unsuccessful or not developed in time (your first clue fuel injection is not your average technical accomplishment). ![]() At the start of WW-II the Germans were ahead of everybody with Bosch direct-cylinder mechanical fuel injection (a result of diesel engine development). ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |