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Project at a Glance

Project Status: complete

Title: On-vehicle emissions testing system.

Principal Investigator / Author(s): May, David F.

Contractor: Analytical Engineering, Inc.

Contract Number: 00-329

Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels, Stationary Sources


Work done under this contract focused on two key improvements needed for the Simple Portable On-Vehicle Testing (SPOT) system. First, the probe geometry was to be significantly smaller such that it could be used with exhaust pipes smaller than 3 inches (7.62 cm). Secondly, enhancements were sought that may improve accuracy and signal to noise ratios. Several design iterations were investigated and two primary designs were built and tested. An optimized design based on a machined venturi with a Ĺ-inch (1.27 cm) aspiration tube was built and tested. This led to the construction of several 2 inch exhaust probes for the SPOT program. The new design offers several advantages including ease of use with exhaust pipe diameters from 2 to 8 inches, compatibility with complex exhaust pipe geometries (such as teardrop exits, pipes with rain caps etc.), accuracy and precision comparable with the best laboratory grade engine test cell mass air flow measurement systems. The results of this work culminated with the assembly of a new 2-inch probe that was supplied under another contract to CARB with a SPOT unit.


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

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