Modified carburetor

Three modifications are incorporated in the carburetor. Each one influences the fuel-air mixture admitted to the cylinders, and each one is effective at a specific engine operating condition.

Choke calibration is modified so that the choke blade starts to open sooner during the warm-up cycle. This means that the fuel-mixture starts to lean out sooner, thus reducing the amount of hydrocarbons and carbon monoxide emitted with the exhaust gases.

The idle adjustment, which has a marked effect on hydrocarbon emissions at speeds up to 25 miles per hour, is set to give a leaner fuel-air mixture at engine idle. Also, throttle blade opening is slightly greater at idle. The higher percentage of air in this leaner idle mixture insures more complete burning of the hydrocarbons and lowers carbon monoxide output.

The carburetor main jets are made to operate close to the lean limit to provide a lean fuel-mixture that burns more efficiently at cruising speeds.

Altered distributor

The only alteration to the distributor consists of increasing the range of angular travel of the breaker plate so that a very substantial spark retard is obtained at idle while retaining the same maximum advance as with a conventional distributor. The reasons for this alteration appear in succeeding paragraphs.

Sensing valve

A special vacuum-operated valve is added to the engine. Installed in the vacuum circuit between the distributor and the carburetor, it is actuated only during "closed throttle" deceleration and advances distributor spark timing at this time.

During the deceleration cycle, it is desirable to allow as much time as possible for complete burning of the mixture entering the combustion chambers. This is achieved by providing the maximum spark advance at this time instead of the retarded spark normally obtained when the throttle closes.

The schematic illustration below shows the carburetor, the distributor, and the interconnecting vacuum system for controlling distributor spark timing of an engine equipped with CAP.

The essential requirement for complete combustion at idle is a late or retarded spark, and during deceleration is an early or advanced spark. How the Chrysler CAP system functions to achieve these two objectives is described below.

In the illustrations that follow, the components and elements involved in the control of distributor spark timing are shown schematically for both a conventional engine and one equipped with CAP. The principal difference in the two systems is the presence of the vacuum sensing valve in the CAP system. In addition, the CAP equipped engine has the idle spark retarded or set to occur after the piston has passed the top dead center (TDC) point of its compression stroke. To maintain normal idling speed, the retarded spark setting demands a slightly greater throttle opening than with the conventional system. This allows more air to enter the engine at both idle and "closed throttle" deceleration conditions.

At idle, the vacuum at the manifold port in the CAP system is not strong enough to overcome the spring pressure of the sensing valve. This makes the valve inactive and allows the vacuum advance to operate as it would in a conventional car engine. Because the spark advance vacuum port is partly obstructed by the throttle blade, there is little or no vacuum to advance distributor timing.

During acceleration and cruise, manifold vacuum still is not strong enough to actuate the CAP sensing valve. Thus, the CAP system operates in essentially the same manner as the conventional system. The throttle blade opens enough to permit the distributor vacuum advance to function and spark timing is advanced according to the amount of vacuum created by the pumping action of the pistons.

When decelerating, the throttle blade closes and the vacuum at the spark advance port is reduced to a negligible value. With the conventional system, this means that the distributor returns to its normal idle timing position. But with CAP, the high manifold vacuum created by the engine overcomes the spring in the CAP sensing valve and opens the alternate vacuum line to the distributor advance vacuum actuator. Distributor spark timing is thus advanced during deceleration to permit maximum burning efficiency of the mixture in the engine combustion chambers.

In general, the maintenance requirements for CAP-equipped cars are similar to the engine performance evaluation adjustments recommended in the certified care care maintenance schedules for all Chrysler Corp. cars. The only addition is that operation of the CAP sensing valve be checked. These services can be done conveniently by a Chrysler Motors Corp. authorized dealer at the 6-month intervals when he must verify that certain specified services have been performed to qualify for Chrysler Corp.'s 5-year/50,000-mile warranty.

No special care is needed in making carburetor adjustments. Although leaner idle settings are specified for CAP, the range of adjustability has been narrowed in these carburetors. Thus, adjustments of idle mixtures can be performed in the normal manner without risking the possibility of exceeding the limits set by exhaust emission standards.

No special equipment is needed to service cleaner air package components.

APPLICABILITY OF CAP

While the CAP modifications and mechanics of operation discussed above apply in principle to any automotive gasoline engine, the final adjustments for the distributor, carburetor, and sensing valve will be different for each engine model. Thus, separate packages with specially engineered components are needed for each model. Engineering work is in progress to develop cleaner

air package components for Chrysler Corp. passenger car and light truck engines. Present plans are to install CAP on all 1966 passenger cars and light trucks manufactured for sale in the State of California.

Mr. WILLIAMS. Next, Mr. Chairman, Mr. Misch, vice president, engineering and research staff, of the Ford Motor Co.

STATEMENT OF HERBERT L. MISCH, VICE PRESIDENT, ENGINEERING AND RESEARCH, FORD MOTOR CORP.

Mr. MISCH. Mr. Chairman and members of the subcommittee, I am Herbert L. Misch, vice president, engineering and research, Ford Motor Co. I appreciate this opportunity to report on the status of the Ford vehicle emission control program and to provide such facts as I can to assist the subcommittee in its deliberations on S. 306.

In discussing the Ford program, I won't retrace all the developments over the past 12 years because you will have an opportunity to see some of these when you visit the Ford Research and Engineering Center this afternoon.

I would like to mention, however, that in 1959 we had made significant progress toward the development of a catalytic muffler for the control of hydrocarbons. Hydrocarbons, as we know, are the main contributors to the California photochemical smog problem. Unfortunately, our device was obsoleted in December 1959, when the California emission standards were written to include control of carbon monoxide, although carbon monoxide does not contribute to photochemical smog.

Our major subsequent effort was devoted to the control of emissions within the engine system and led to the development of the Thermactor system. This system was described extensively in an SAE paper in March 1962. With the initial concept, we achieved emission levels well below the California standards by providing exhaust gas residence time in enlarged and insulated manifolds, but the resulting very high temperatures required an advance in materials technology before the system could become a commercial reality.

The present form of the Thermactor was evolving when the California standards were again modified in January 1964, to permit averaging of emissions within specified fleets. This modification and the later provision for exemptions on low volume vehicles eased the requirements and enabled us to undertake the current program of developing the Thermactor system for our high volume 1966 model vehicles that are produced for sale in California. The system is described in some detail in the attachment.

I will not describe it here, but you will see it this afternoon in our laboratories.

During recent months, we have completed the production design of all components of the Thermactor system of exhaust controls. The production tooling has been ordered, and the promised delivery supports the introduction of the 1966 models in California early this fall. In addition, all related vehicle components, including various brackets, braces and heat shields, have been appropriately designed to accommodate the installation of Thermactor-equipped engines in our new model vehicles.