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Project at a Glance

Project Status: complete

Title: Temperature testing and analysis of the vacuum advance disconnect exhaust emission control

Contractor: Northrop Corporation and Olson Laboratories, Inc.

Contract Number: ARB-1086

Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels


The Vacuum Advance Disconnect (VAD) technique is an exhaust emission control method presently being applied to pre-1966 Model Year (uncontrolled) cars in California. In conjunction with other techniques VAD is also a proposed method for emission control on 1966 to 1970 (controlled) Model Year vehicles. The terms "controlled" and "uncontrolled" refer to the presence or lack of exhaust emission control systems on cars delivered in California.

The Air Resources Board (ARB) staff and the Technical Advisory Committee (TAC) have presented estimates regarding the immediate benefits if a suitable "used car" device were available, and the subject device was immediately installed on a large number of all of these vehicles. The California Legislature has passed a bill that will require all 1966 and newer vehicles to have a device by 1973, which controls oxides of nitrogen.

VAD devices have been tested from an emissions effectiveness point of view and have proven effective. However, doubts have been raised about driveability and operational problems that may be created after installation of VAD devices. The Northrop Corporation, Electra-Mechanical Division, in association with Olson Laboratories, Inc., was selected to perform the temperature testing and analysis of the vacuum advance disconnect exhaust emission control study to evaluate the temperature effect of VAD on vehicles. Standard Agreement Number ARB-1086 was consummated on May 5, 1972.

This report documents the results and analysis on the testing of one hundred (100) uncontrolled and one hundred (100) controlled vehicles.


For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893

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