Boost Control: Open Loop vs Closed loop
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Open Loop vs Closed loop
02.04
| 00:00 | - When we're using an ECU to control a specific parameter on the engine, we have the option of using open loop or closed loop control. |
| 00:09 | I briefly mention the term, closed loop, in the PID module, but now I will discuss what the terms open loop and closed loop mean. |
| 00:18 | Open loop is the simplest system to configure and tune so we'll deal with this first. |
| 00:24 | In an open loop control system, the ECU will operate an output, such as the boost control solenoid at a set duty cycle. |
| 00:34 | In this sort of system, there is no feedback to tell the ECU whether the boost pressure is higher or lower than our target. |
| 00:41 | An irrespective of the actual boost pressure, the ECU will keep providing the same duty cycle to the solenoid. |
| 00:49 | The result is that we may see the boost pressure very slightly from our target, based on engine load or atmospheric conditions. |
| 00:58 | This defeats some of the advantages that electronic boost control can offer, but to see these advantages, we need to use closed loop control. |
| 01:08 | Closed loop control will look at the current boost pressure as well as our desired boost target. |
| 01:15 | Any time the measured boost pressure doesn't match the target, there will be an error and the ECU will use a PID controlled algorithm to actively alter the duty cycle being supplied to the waste gate solenoid, in order to reduce the error to zero. |
| 01:31 | Closed loop control has the ability to provide more stable and consistent boost levels, as atmospheric conditions change or engine load and exhaust temperature change. |
| 01:43 | This can give superior results but also requires more work from the tuner in order to optimise the PID control settings and achieve stable boost. |
| 01:55 | This course will show you how to use open loop and closed loop techniques to control boost. |
