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to compare the air/fuel mixture readings that were recorded when the engine was on the dyno with the air/fuel mixture readcourtesy of Joe Gibbs Racing. ings now that the engine is in the vehicle. It is not uncommon to see air/fuel mixture readings quite different from what was recorded when the engine was on the dyno. The real world operating conditions that are seen after the engine is installed in the engine bay are often quite different from the ideal conditions the engine was tested at while it was in the dyno room. Additionally, most dyno testing only determine maxiThis is an air cleaner from a NASCAR race car. The cool inlet air comes from the cowl just in front of the windshield; this air cleaner package is quite different from the air inlet system that is used in the dyno room. Photo
advance can cause the engine to run too hot or lead to engine failure from detonation related problems. The additional timing from any This shot shows the cowl induction vacuum advance area where the air cleaner gets its system in most fresh air. Photo courtesy of Joe Gibbs Racing. cases should be limited to a maximum of 10 to 12 degrees of advance since todays gasoline burns somewhat faster since it no longer contains lead. Your customer should be made aware the ‘original’ timing settings may not be correct and indeed may cause damage. Once the ignition timing curves are properly tuned the next step is to check the air/fuel mixture curves the fuel system is supplying the engine with. If the customer happens to have a dyno sheet with the air/fuel mixture readings, it is always nice
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