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Davis Unified Ignition - High- Voltage Power - Tech

Inside a D.U.I. Ignition

Bob Mehlhoff Sep 18, 2006

Advancements in cylinder heads, camshaft profiles, and exhaust and intake systems have provided a path to move a higher volume of air and fuel through the engine, improving the internal combustion process. Given the advancements in engine design, it's essential to have a powerful ignition system to ignite the compression stroke at the right moment for maximum power. One of the best ways to maximize ignition performance is with a good, high-energy ignition system that provides the optimal timing curve for the application.

We recently visited with the folks at Performance Distributors to learn what makes a well-designed Davis Unified Ignition (D.U.I.) high-energy distributor. We took a look at both the D.U.I. Street/Strip unit and the Chevy Tri-Power ignition unit that incorporates a smaller-diameter cap for extra firewall clearance. Besides the cool-looking products they offer with a variety of different-color caps, it's what's underneath that holds the science.

Each distributor is precision-manufactured from all brand-new parts and assembled to very close tolerances. The distributor's bottom gear is shimmed to provide between 0.025 and 0.030 inch of clearance, which helps provide a wide contact area between the distributor gear and the camshaft gear, helping ensure a strong magnetic field signal to the module.

Additionally, the module's dwell is increased about 3-6 degrees above stock, which, when combined with high-coil voltage, provides a strong and long-duration spark. With the higher available voltage, the spark-plug gaps can be increased from the traditional 0.035 inch to 0.055 inch to take full advantage of the stronger spark.

Unlike a stock HEI unit, which will often begin to misfire around 5,500 rpm, the higher-voltage D.U.I. Street/Strip units provide strong voltage supplies to 7,000 rpm. And one of the best features is that each distributor is custom-curved to match your vehicle's driving style and performance level-just provide Performance Distributors with the info. With the correctly matched distributor installed in your engine, you're ready to ignite all the power your engine can muster.

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Timing Is Critical
Establishing the correct initial timing is critical to engine tuning. To do this properly you'll need a good timing light. This Performance Distributors model (PN 380000) uses two D batteries so that you do not have to source power with an extra wire from the car's electrical system. Best of all, it generates a bright strobe that is visible during daylight.



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