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What is EECSCAN safety?
Many safeties can be programmed into the EMAS II to help protect your engine and catalyst. Two of these are preemptive safeties used to avoid overtemps before they occur. Since overtemps usually require extra fueling our safeties monitor the injector pulse widths and when we detect a problem we shutdown the test to prevent an overtemp. The two types of preemptive injector monitoring safeties are:
The Pulse width limits are self explanatory, if the engine controller demands a pulse width outside of a user defined window, the test will be shutdown. Although this method works well, there are a number of instances where the pulse widths are under the limit but wrong. Take for example the following data. |
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| The graph above is a good illustration of how EECSCAN works. The EMAS II calculates the average pulse width of the EEC and then adds a user supplied offset up and down from the average (orange lines). These lines form 3 zones labeled 1,2 and 3. The injector pulse widths are then monitored to see to it that the pulse widths to not spend too much time in any given zone. If they stay in the same zone for more than a user supplied number of engine cycles, the EMAS II will shutdown the engine.
The EECSCAN channel 208 determines the size of zone 2. For example if 208 was set to 100 then zone two would be 200 microsecond thick. 100 microseconds above the average and 100 below. A typical value we recommend in 50. The EECSCANNUMRD channel 209 determines the number of consecutive times an injector pulse width loiters in a zone. In the example above the value was set to 70. This meant that 70 injections or cycles had to take place before the EMAS II shuts down the engine. As you can see in the graph it did shutdown but not before the catalyst has damaged. A more reasonable value would be 10 to 20. This EECSCAN mode can also be enabled or disable by setting bit 2 of channel 235 to a logic 1 (enable) or to a 0 to disable the safety. |
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