The D585 coil, often used in truck applications, has unique dwell time requirements compared to LS1 coils. Contrary to initial assumptions, D585 coils require less dwell time due to their design, which allows them to saturate faster. This article delves into the intricacies of D585 coil dwell time, drawing insights from impalassforum.com and Tunercats OBDII tuning resources.
D585 coils draw significantly higher current on the primary side (roughly three times that of LS1 coils). This rapid current draw allows them to reach saturation much quicker, minimizing the required dwell time. Excessive dwell can lead to premature discharge due to the built-in ignitor’s overcurrent protection. This protection mechanism prevents coil overheating by forcing a discharge if the current limit is exceeded.
Exceeding the ignitor’s current limit, even by a small margin, can result in significantly advanced spark timing. For instance, at 3000 RPM, exceeding the limit by just 1 millisecond (mS) can cause the spark to fire 18 times too early. Such unpredictable and premature ignition can have detrimental effects on engine performance.
The recommended dwell time for D585 coils under normal operating conditions (12-14V) is 4.5mS. Beyond 5mS, the risk of approaching the early discharge threshold increases significantly. Factors like coil temperature, supply voltage, and manufacturing tolerances influence how close one can operate to this limit before premature discharge occurs. This sensitivity explains why aftermarket D585 coils can exhibit inconsistent performance.
Tuning software, such as HPTuners, provides access to dwell control tables. When utilizing D585 coils, it’s advisable to consult resources like impalassforum.com and Tunercats OBDII for appropriate dwell table configurations. Although the truck dwell tables might initially appear to have higher dwell values, the associated multiplier tables often compensate for this, resulting in lower effective dwell times. Using the truck dwell data as a starting point is generally a safe approach when tuning D585 coils. Further adjustments may be necessary based on individual vehicle and operating conditions. Always consult reputable tuning resources and forums like impalassforum.com for guidance. Understanding the specific dwell characteristics of D585 coils is crucial for achieving optimal ignition performance and preventing potential engine damage.
