throttle lift off lag

vipor

not necessarily for emissions, but the ECU holding the RPMs to make sure the fuel is burnt and such makes perfect sense.

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2009 NISMO # 0193 | QAB | Albums! | 05.04.10 (Dynojet) 291.94hp/248.28tq
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370Zsteve

Here's my take: It is the modern, electronic equivalent of the old decel controls on carbureted engines. Meant to control emissions on deceleration when throttle is fully closed.

US Patent 3957022 - Carburetor deceleration emission control



Description

This relates in general to a two-stage motor vehicle-type carburetor. More particularly, it relates to one that is provided with suitable apparatus for cracking open the secondary induction passage throttle valve during engine deceleration conditions to improveemission output.

This invention has particular use with four barrel truck-type carburetors, although it will be clear that it will apply equally as well to any carburetor having dual stage operation. In a four barrel carburetor of the type describedhereinbefore, the conventional idle provides a quite lean mixture to the engine cylinders. During closed throttle deceleration operation, therefore, the engine will be provided with a very lean mixture to the point where incomplete burning mayoccur, which may result in unburned exhaust gases and the emission of undesirable into the atmosphere. If, during this time, fuel and air is added to supplement the idle system mixture, then a more complete burning of the mixture may occur. The addition of fuel alone generally is not sufficient but both fuel and air should be added to provide the proper mixture ratio.

Accordingly, it is a primary object of this invention to provide an engine deceleration control apparatus incorporated in the carburetor that operates during deceleration conditions when the primary and secondary carburetor throttle valves areessentially closed to crack open the secondary induction passage throttle valve to supply a quantity of both fuel and air mixture to the engine to supplement that mixture emanating from the primary induction passage.

It is another object of the invention to provide a four barrel carburetor with a vacuum servo connected to the secondary induction passage throttle valve and operable during predetermined deceleration conditions to crack open thesecondary throttle valve to allow the induction of an additional air/fuel mixture into the engine.

It is a still further object of the invention to provide a four barrel carburetor construction having a servo operated secondary throttle valve system with an additional vacuum servo that is independently operable during predetermined enginedeceleration operating conditions to crack open the secondary throttle valve to allow the addition of air and fuel to the engine regardless of the position of the primary throttle valve and quantity of flow of mixture through the primary inductionpassage.

It is another object of the invention to provide a four barrel carburetor construction having primary and secondary induction passages each provided with a separate throttle valve rotatably mounted across the respective passages to control theflow of an air/fuel mixture therethrough to the engine cylinders, the secondary throttle valve being opened to provide greater air flow capacity to the engine during engine acceleration conditions by means of a vacuum servo connected to the throttlevalve and operated in response to a vacuum signal in the primary induction passage venturi at the appropriate time, an additional vacuum servo being connected to the secondary throttle valve by a lost motion connection and operable in response to theattainment of both a predetermined engine speed and vacuum level condition to crack open the secondary throttle valve to permit the induction of an air/fuel mixture through the secondary passage to supplement that flow quantity being supplied to theengine by the primary carburetor section, to render the engine air/fuel mixture burning more complete and thereby reduce the output of harmful emissions.

It is a still further object of the invention to provide a carburetor of the construction as described immediately above in which the second servo is actuated by vacuum as controlled by a solonoid actuated valve that iselectrically actuated in response to engine speed and manifold vacuum both rising above a predetermined level.

Carburetor deceleration emission control - US Patent 3957022 Description

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SOLD MY Z MARCH 2018 - another Core OG moves on - new ride 2019 Z Corvette Grand Sport - no mods necessary but already have eyes on HFC and intakes LOL IT NEVER ENDS.