Feedback carburetor
A feedback carburetor (also known as electronic or computer controlled carburetor) is a specific type of carburetor made mostly during the 1980s to improve emissions on certain vehicles in the US.
History
[edit]Before the 1970s, most vehicles didn't have many emissions systems on them, but as time went on, smog pumps, charcoal canisters, and thermal reactors were added to meet new regulations.[1] As vehicle emissions standards became more stringent due to the Clean Air Act and CAFE standards, vehicle engineers had to come up with different ways to meet this problem. Initially decreasing the engine compression and installing EGR systems and two way catalytic converters were able to solve this problem but later this became more difficult. In the 1980s, many vehicle manufacturers were required to use three-way catalytic converters and oxygen sensors to determine the air fuel ratio (AFR) of the vehicle to determine if the car is running correctly.[2][3][4]
This was paired with either an early version of fuel injection (typically through a Bosch Jetronic system for European vehicles)[5] or through a feedback carburetor, which had an increasing number of solenoids and settings to make sure the vehicle would emit less and less harmful emissions.
First results occurred in the mid to late 1970s, where Chrysler was first out with their new "Lean Burn" system in 1976 for its larger 400-cu in V8s, that would change engine timing and AFR so that it would run as lean as 18.0:1 AFR, which is much leaner than stoichiometric 14.7:1.[1]
Other brands would soon follow and would design different ways to tackle the same problem and would increase in complexity until they were replaced with electronic fuel injection (EFI) in the mid to late 1980s and early 1990s. Throttle Body Injection (TBI) was common to see as a cheap and simple way to swap to fuel injection in the 1980s from a carbureted engine design, and many early EFI cars used it until a newer engine could be designed for Multi Point Fuel Injection (MPFI).
Some of the last cars with carburetors in the US include the 1994 Isuzu Pickup, 1991 Jeep Grand Wagoneer, and the 1991 Ford Crown Victoria P72.[6]
Features and Operation
[edit]The basic operation of a feedback carburetor:
- The carburetor would take in a signal from the oxygen sensor and would determine if the mixture was correct
- If the mixture needed to be adjusted, a solenoid or stepper motor would move to adjust the AFR
- Most included electric chokes for cold starting
- Typically was a 2 barrel design where one barrel was only opened when necessary for fuel economy reasons
Examples
[edit]- Chrysler Lean Burn (1976-1989)
- Ford: Motorcraft Variable Venturi (2700 & 7200) (1977-1991) (Controlled by the Ford EEC-III and onwards)
- Ford & AMC: Motorcraft 2150
- GM: Rochestor EM4 Quadrajet (1980-1990)
- GM: Rochestor E2ME Dualjet 210
- GM: Rochestor E2SE Varajet
- Carter YFA
See also
[edit]References
[edit]- ^ a b Koch, Jeff (2024-03-26). "Chrysler's Lean-Burn System". Hemmings Motor News. Bennington, Vermont: American City Business Journals. OCLC 1245789004. Retrieved 2024-11-16.
- ^ US EPA, OAR (2016-06-27). "Timeline of Major Accomplishments in Transportation, Air Pollution, and Climate Change". www.epa.gov. Retrieved 2024-11-16.
- ^ McDonald, W. R. (1978-02-01). Feedback Carburetor Control Electronic Design for Improved System Performance (Report). Warrendale, PA: SAE Technical Paper.
- ^ "Advance Auto Parts - Down for Maintenance". shop.advanceautoparts.com. Retrieved 2024-11-16.
- ^ admin (2018-09-20). "A Song of Air and Fuel: How Fuel Injection Got into Cars". Škoda Motorsport. Retrieved 2024-11-16.
- ^ "Autotrader - page unavailable". www.autotrader.com. Retrieved 2024-11-16.