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ECU-based Boost Control Setup

Approach 1: Just disable error correction

By far, the easiest approach to dialing in the boost tables is to simply disable error correction. When you do that, you can ignore the Boost Target table entirely and just tweak the Base Duty Cycle to get about what you want. In fact, doing this is the starting point for setting up the boost target table for use with error correction.

Start by checking the Disable error correction checkbox on the Boost (WGS) tab.

Confirm that you have control

The first step is to confirm that you actually have some control over your boost.

Set the base duty cycle table to 0% across the board. You can do this by selecting all the cells in the table at once and then using the Ctrl+down arrow key combination to run all the cells down to 0%.

Go make a pull and confirm that you're getting wastegate pressure (probably around 10-15psi depending on the wastegate). You may find that you get some boost creep towards the end of the pull. That's usually fine too. You're just looking to see the minimum amount of boost you can achieve with your current setup.

Now, try increasing the base duty cycle table a bit and see that you can build more boost as the duty cycle values go up. Try setting all the cells to 50%, then 65%, then 80%, etc. You *should* see boost increase as the duty cycle increases. If it does, great…you have everything installed correctly and your system is working in a predictable manner.

Pick a point

Notes and limitations

The basic operation of ECU-based boost control in ECMLink is fairly straight forward. You dial in a base duty cycle that gets you somewhere in the range of the boost target you want and then enable error correction for fine tuning. But setting up the base duty cycle table and target boost values is a little trickier than it seems.

Each gear builds boost a little differently simply due to the fact that boost builds by “time” as much as engine speed. You need to be above some threshold in engine speed (RPM) in order to build any significant amount of boost. But you also have to remain at near full throttle above that RPM for some amount of time to build the boost you want. This amount of time changes based on engine speed too!

So it's a big ugly cycle that's not as easy to dial in as it seems. You can get real close, real fast with some quick numbers. But if you want to really dial in that last bit of consistent boost tuning, it gets more involved.

The tables provided in ECMLink are a reasonable compromise to a true model of turbo behavior. We may consider a different approach in the future that takes into account how turbos really work, but this will be less intuitive to the user (because it will involve time spans and decay values…things that are just less intuitive than duty cycle and RPM).

So for now, we'll stick with the same implementation that Mitsubishi settled on for their boost control logic. But you have to keep in mind the limitations. You will likely see some overshoot in some conditions. For example, if you dial your tables in while doing flat road pulls (our suggested procedure), then you can expect some overshoot when you are actually doing a hill climb instead (slower acceleration rate).

bcssetup.1280752896.txt.gz · Last modified: 2010/08/02 08:41 by twdorris