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Boost control resolution

Boost Control

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I'm working on a race car with a PSA N18B16A engine and Motec M142 and I'm struggling to control the boost pressure.

Within the range that OEM ecu uses (let's say from 10 to 80 kPa) I have a very good control of the target pressure, but above 1 bar of boost I start to have issues with the resolution. An increment in the feed forward table of just 2/3% duty cyle brings to a jump of over 20 Kpa, resulting in a very poor control. The size of the turbo is made to reach high pressure already at 2500 rpm, so as I try to increase the target pressure, it tends to have a very rapid and hard to manage peak at low rpm. I guess that over 1 bar the geometry of the wastegate does not allow to finely control the boost. We can't use an external wastegate due to the race rules, so I'm forced to rely on stock components only.

I see two strategies to help controlling the boost. One is creating an auxiliary output table to use the electronic blow off bypass valve, but I'm not sure about what kind of resolution I could achieve. The second one is taking advantage of the dbw throttle to limit the flow to the turbo, but I find the GPR package a bit limited here, because the only table that relates the dbw to the boost allows only to limit the throttle opening when a boost warning state is active.

Do you have experience with this kind of obstacle and an advice to overcome it?

Be aware that your M1 can handle very fine resolution it it's tables. Try changing the properties (use Component->Active Item->Properties) for a table (ie, Boost Control Feed Forward Main) to show more decimal digits (say 3 instead of the default 1). You can tune the difference between 2.530 and 2.487% if you want.

I find the Gear Throttle Limit useful. It has the axes Gear and Engine Speed.

If you would like to make changes to the GPR package, consider upgrading your ECU to a development license, and implementing whatever strategies you can dream of. If you need help, I do this for several of my customers.

Thanks David. Yesterday I had good results using two more tables to manage the bypass valve and the throttle opening to control the boost. A gear boost limit will be added as soon as I'll move the car from the dyno to the road. The package I'm using is based on the gpr but it implements a specific can protocol. Anyway, I guess that upgrading the ecu with a development license would be the best option

Since you have a custom package, just work with your developer to give you the features (tables) you want. There is a small cost to update the version, but adding an axis to a table, or changing the axis is not very difficult.