Holley 6500 Feedback Carburetor

With the increasing emissions standards being put into effect in the late 70s feedback system carburetors became developed for california emissions cars to meet these new standards. Feedback carburetion was the precurser to fuel injection since they were some of the first systems to use engine sensors in closed loop to monitor and adjust fuel mixture to lower engine emissions. Starting in 1978 Ford began using the holley 6500 feedback carburetor on their 2.3 Liter engines in California and extended into nation wide use in 1981. Because the Holley 6500 is largely based off of the Holley 5200 it is recommended you watch the tech video below. Tech Video: Holley 5200 Introduction Holley Feedback Carburetion So what exactly is feedback carburetion? A feedback system uses a set of sensors which provide a feedback signal to a computer which adjusts fuel mixture using in this case a solenoid attached to the power valve. The OEM carburetors used on the 86-93 Mazda B2200 and B2000 are very complex feedback carburetors with lots of sensor inputs to the computer and lots of solenoids being controlled by the same computer. The first Holley 6500s used a vacuum controlled feedback solenoid integrated with the power valve later they developed an electric controlled solenoid also on the power valve which operated at a frequency of 0-10 Hz to change fuel mixture. Manually Controlling Feedback Anyone with a little bit of electronics knowledge should be able to build a small electronic circuit to control the feedback solenoid. The type of circuit needed is a Pulse Width Modulation (PWM) circuit, these are sometimes designed to be used as electric motor controllers. Many of these have a variable speed that is adjusted with a potentiometer (sometimes called a variable resistor) tuning the circuit to adjust between 0 and 10 Hz from the dash will allow you to control fuel mixture. The higher the Hz the more fuel the engine will get. Fuel mixture can be monitored by connecting an air/fuel meter to the O2 sensor. For additional information see the Holley 5200 page. Please support MazdaTruckin.com by searching for your needs here: