Federal 4A-C Emissions/Vaccum delete for USDM SR5

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Federal 4A-C Emissions/Vaccum delete for USDM SR5

Postby CloudStrife » Tue Feb 16, 2021 4:23 pm

Hey guys! Hope all is well. Im in the middle of doing complete emissions and vaccum delete on my 1987 Corolla SR5 Coupe, equipped with 4A-C. I am also deleting my cruise control components.

What items must be retained for power steering and/or AirCon (if any)? I remember the 4A-GE needed idle-up, but unsure of 4-AC.

Systems I wish to delete:

Exhaust Gas Recirculation: Removed. Should not have to do much besides obtain intake manifold block off plate (not sure if 4AC specific ones are available? And looks like the bung on the intake pipe needs to be closed with a large bolt (metal gasket?) That had housed the old EGR inlet.

Fuel Evaporative Emissions Control (EVAP) W/ Charcoal Canister: Removed. I believe I'll need to sort what to do with the purge/tank lines. Maybe an inline filter seated in the engine bay for the purge line from the tank?

High Altitude Compensator: Removed. Being at Sea Level I do not require it.

Air Suction (AS) System: Removed. Still need to remove the metal pipe that sucked the AS Filter/Reed Valve and weld the hole on the Catalytic Converter.

Air Bleed with Feedback System: Removed.

Things I'm unsure of removing for benefit:

Throttle Positioner (TP):
*To reduce Hydrocarbon and CarbonOxide emissions, the throttle positioner opens the throttle valves slightly more than at idle when decelerating. This causes the air-fuel mixtire to burn completely.

1. See no reason to remove this one. Also sounds weird in terms of driveability. Looks engrained into carb system mechanically though.

Automatic Hot Air Intake System (HAI)
*This system leads a hot air supply to the carburetor in cold weather to improve driveability and to prevent the carb from icing in extremely cold weather.

1. Also don't see this having any use in my tropical climate.

Hot Idle Compensation (HIC) System on the Air Cleaner
*This system allows the air controlled by the HIC valve to enter the intake manifold to maintain proper air-fuel mixture during high temps at idle.

Automatic Choke System
*This system temporarily supplies a rich mixture to the engine by closing the chock valve when engine is cold.

Choke Breaker (CB) System
*When the choke is closed, this system opens the choke valve slightly to prevent too rich a mixture.
Then, when the engine is warmed up, the choke valve is forcibly opened further.

Choke Opener System
*After warm up, this system forcibly holds the choke valve open to prevent an over-rich mixture and releases the fast idle to the 3rd step to lower the engine RPM.

Auxiliary Acceleration Pump (AAP) System
*The carburetor air-fuel mixture is very lean. When accelerating with a cold engine, the main acceleration pump capacity is insufficient to provide good acceleration. The AAP system compensates for this by forcing more fuel into the acceleration nozzle, to obtain better cold engine performance.

Deceleration Fuel Cut Systems (USA Only)
*This system cuts off part of the fuel flow in the slow circuit of the carburetor to prevent overheating and afterburning in the exhaust system.

1. Does not seem essential to droveability or performance.

Cold Mixture Heater (CMH) System (USA Only
To reduce cold engine emission and improve driveability, the intake manifold is heated during cold engine operation to accelerate vaporization of the liquid fuel.

***There is a heater ring that seats under the carburetor that looks essential. Would I still have to retain the huge ring even if the plug was deleted (so that the carb can seat properly and/or not leak)?

Lastly, I am considering replacing the carb with a 32/36 Weber DGV. Anything I should know before purchasing? Does it need to be electric choke?

My sr5 is a coupe, manual, with air con, power steering, sunroof and cruise ( I am also deleting cruise).
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