Ask Rob About Cars 1-2-10 Exhaust systems, catalytic converters and dyno tuning

Question: I need some sound but cheap is good. What will removing the converters do? Louder? more air flow? Also about how much does a dyno tune cost?
- PJ Des Plaines, IL

Answer: Thank you PJ. Replacing the mufflers is the cheapest way for good sound without a decrease in performance. Completely removing the mufflers can rob horsepower and torque in lower rpm ranges and also have an objectionably loud sound resonance in the cabin.

Removing the catalytic converters is illegal but will also give a performance gain provided the engine adapts to the additional airflow. In a modern engines error codes will occur without "cats" and this is another reason tuning with an electronic device that addresses such codes is needed. Aftermarket high-flow catalytic converters are available to bridge the challenge of emissions with less exhaust flow restriction. Be sure to know your state laws regarding emission equipment and sound level requirements.

Dyno tuning optimizes the power potential of the engine especially when modified and for most street cars costs less than $400. When the intake and exhaust is freed up significantly, it's essential not only to optimize fuel delivery but also prevent problems by running too lean. In Northern California for example, a session which includes a baseline run and multiple "pulls" for two tunes to accommodate different octane ratings (91 octane and a race gas mixture) is $380. In other words, a tune for a 91 octane daily driving and another for race gas. This may require a separate hand-held tuner. A hand-held allows the owner to modify various parameters such as cooling fan temperatures, shift points, etc and also save the tunes on your PC for back-up purposes. Examples include the Diablosport and Hypertech are just a few tested by GM High Tech Performance in this test.
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