Practical Reflash Tuning: Boost Control
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Boost Control
03.20
| 00:00 | - If you're reflashing a factory turbocharged car, then one of the common tasks is to increase the boost pressure. |
| 00:07 | This is typically a reasonably straightforward task that can be achieved by adjusting the relevant tables inside the ECU rather than adding an additional boost control device. |
| 00:20 | The actual tables and adjustments will vary from one ECU to the other, however the process is relatively similar. |
| 00:29 | We want to start by adjusting the boost targets to match the boost we want the engine to run. |
| 00:36 | Remember that depending on what sensors the ECU uses, the boost target could be directly in units of pressure, or alternatively it may be expressed in units of engine load. |
| 00:49 | As well as the boost target, we'll need to adjust the wastegate duty cycle maps to get us to this target. |
| 00:57 | In some instances, the ECU may contain a base, or initial wastegate duty cycle table, as well as a maximum duty cycle table that limits the maximum value that can be applied. |
| 01:10 | When raising the boost, you'll need to adjust both of these tables to suit your new target. |
| 01:16 | When adjusting boost pressure, it's always advisable to make small changes, and then log the effect of these changes, rather than making wholesale changes to a number of tables simultaneously, and then not being able to tell which table achieved the result you wanted, or perhaps massively overshooting your boost target. |
| 01:38 | In OE applications, the boost control will typically be a closed loop system, and while this may work well in a stock vehicle, some platforms are notoriously hard to gain stable control of boost while using a closed loop boost control strategy. |
| 01:55 | While I'm a strong advocate for a properly turned closed loop boost control system, it is possible to create and open loop boost control system by simply setting the feedback tables that define how the ECU should respond to a boost target error to zero. |
| 02:12 | In my experience, the factory closed loop control systems normally work quite well when running a factory turbo charger without the need to modify the feedback tables. |
| 02:24 | However, if you are fitting a different turbo charger, or a different wastegate, often the feedback tables will need to be adjusted to suit the dynamics and response of the new turbo system. |
| 02:37 | Often I find that reducing the amount of control that the ECU will provide in regards to an error in boost target will improve the response and control of the closed loop boost control system. |
| 02:52 | If you're turbo charging a naturally aspirated engine, you may still have the option of employing electronic boost control through the factory ECU via a software patch. |
| 03:04 | It's quite common to repurpose the factory ECU output for something like the fuel system purge valve, and then assign this as a pulse-width modulated output that's suitable for driving a boost control valve. |
