Car Data Project - Instruments to Measure Performance - WB & Logger - Dec '01

Once I started modifying the engine it became necessary to find ways to measure the results of changes.

This was especially true for ECM programming. As a result I built the DIY-WideBand Unit to measure

Air-Fuel Ratios via the exhaust; a Tach transducer to measure RPM; used a Dataq A/D converter to capture results

to my laptop; and a spreadsheet to analyze the results of timed acceleration runs on a

'secret dyno hill' road. Here are some details of the projects:

Measuring AFR while under WOT was a major concern. Fortunately the DIY WB became available toward the end of '01. I built a copy and installed it in Dec. It works as advertised and has been running happily ever since.

 The installed Radio Shack box looks like this:


 The sensor itself is a Honda part:


 Total project cost was around $300 complete and running; including the WB Unit, sensor, O2 bung, welding, logger, and tach box; excluding laptop.  Sensor was installed in the Y-pipe (below):


Once the AFR info was in hand it became obvious that Diacom ALDL logs were not of sufficient accuracy (~7 data points/sec) to permit detailed tuning & evaluation of results.

Next I built a Tach transducer, so I could log AFR and RPM info together. Tach box uses a National Semiconductor chip similar to the circuit below:



 The last piece needed was the Dataq A/D converter, which takes voltage outputs from the WB & Tach units and records them in realtime on a laptop. The combination allows test runs to be made while driving.


 The Dataq board is a complete 4-channel datalogger (priced at ~ $30), and comes with its own software.

Here is an example of an acceleration test made from a rolling start in second gear. All testing is done on the same piece of road, so results between programming changes are easy to compare. WB volts shows the AFR at each RPM band @ WOT. The slope of the RPM curve gives the power output of the test. Absolute power output can be estimated by calculating delta Kinetic Energy (1/2 mV*V) for each RPM band.


Recording data with the Dataq at 120 samples/second gives enough accuracy to evaluate changes in fuel and timing curves. 

An excellent resource to learn more about dyno results is in the Tuning and Tech Articles at PUMA Racing:

All testing is done on an empty section of private road with proper concern for safety.

ECM changes are made with the TunerCat editing package. Other ALDL data is collected/evaluated on Diacom and Datamaster software.


copyright 2003 DrJ all rights reserved