|Tell Me Everything|
| Part 2
By Tim Clark — January 2002
Immediately after you start a Cummins electronic marine diesel, the display powers on, runs a quick self-test, and then goes to a default screen, or "Basic Page." While rpm will always get the top spot in inch-high digital format on this page, you can choose five from among any of the other engine readouts to display in a smaller list below. (In addition to the Basic Page, you can configure pages of single, double, or quadruple parameters in any combinations and in digital or analog format.) Obvious choices include the standards: oil pressure, coolant temperature, system voltage. These may seem a little dull and, if you already have a set of analog gauges, redundant. But even in relation to these basics, there is already a lot more going on than meets the eye.
For every measurement it makes, the engine’s ECM is programmed with high- and low-threshold safety parameters that are much tighter than the parameters set above and below many mechanical-gauge readouts. Moreover, safety parameters for data such as oil pressure, whose "normal" level changes with engine speed, are constantly reset as rpm varies. Because of these strictly fixed yet variable values, the ECM can recognize and alert you to deviations–such as dropping oil pressure due to a loose fitting– much sooner than some mechanical gauges. As a result you are more likely to avoid serious engine damage.
Your other choices of what to display on the Basic Page might be based on more specific criteria. Some of these readouts are relatively esoteric, and you are unlikely to consult them often. For instance, Cummins engineer Daryl Wessinger pointed out that barometric pressure might be important to a truck engine in the Rockies, but not to a boat engine at sea level. Likewise, you’re not likely to look at boost pressure frequently. Although abnormally low turbo boost could indicate a need to change air cleaners, typically you won’t see much variation. According to Wessinger, boost data is there primarily for professionals to consult during engine adjustments.
But many of these recondite readouts are of direct practical use and can fine-tune your awareness of your engine’s performance. Monitoring intake-manifold temperature can give you the earliest possible warning that you left a seacock closed or your sea strainer has become blocked, allowing you to address the problem before the engine itself heats up to a potentially damaging level. Engine-oil temperature is also an engine safety readout to keep tabs on a possible overheating. Coolant and intake-manifold sensors are likely to inform you of the problem earlier, but it’s always good to have a backup.
This article originally appeared in the June 2003 issue of Power & Motoryacht magazine.