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Link G4+ closed loop boost control

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I have watched this course and the electronic boost control webinar a few times and still not 100% sure i've got this right.

I logged a run with 100% DC in open loop to give me a idea as to what Boost i can expect to see at a given RPM. I've used these numbers in the closed loop boost target table. I also used these figures as the Y axis in the Wastegate DC table.

Planning on only running 16 psi (212kpa) so im unsure if i only need to to set the target table to 212kpa in all cells and the Y axis of the wastegate DC table to 212kpa. Below is a screen shot of my table.

Attached Files

Closed loop looks up the boost target on the Target table for a given RPM. Unless you want the boost target to be increasing with RPM, it should be 212kpa at all RPMs.

As part of the closed loop system operation, the ecu will reference the wastegate DC table relating to the RPM and boost target. Therefore, ideally the wastegate DC table would accurately reflect the wastegate DC required to deliver the boost target on the Y axis (ie, verify this with closed loop turned off). With closed loop turned on, this accuracy assists boost targeting (which comes from the target table).

As there are various trims that can be applied to the boost target, it is worthwhile correctly tuning the wastegate DC table below your target boost. I take it from your comment below that if you plugged in 100% to the whole wastegate DC table, it wouldn't deliver more than 16psi?

Thanks Cam

I changed my table and hopefully get time for testing tomorrow. I did a run with 0% duty cycle to see if my pluming and wastegate setup was right. I also did a run using 100% duty cycle it see how fast it would build boost, that way i know what im trying to aim for when setting up closed loop. I had the MAP limit set at 16psi for safety.

Attached Files

I've mentioned this in a previous thread here, however I'll just caution you that the current closed loop boost control in the G4+ is problematic. Particularly if you're fussy, you'll find it impossible to get 100% accurate and repeatable boost. Link are aware of this and there is an update in the pipeline. Until then personally I'd use the passive closed loop setup discussed in the course.

I do remember you saying the above in the past. Do you know if Link addressed this in the just-released firmware? Or still on the "to do" list?

Thanks Andre ill set it up the way as i am fussy.

As of yesterday it's still on the 'to-do' list. I understand it's actually done and tested successfully but hasn't made it to production firmware yet. Seems I was one of the few people complaining. Fortunately I complained loudly enough and backed up my complaint with data logs showing the specific issue :)

I agree with Andre on this issue , Closed loop BC on the Link isn't very good , transition BC isn't good , your get good control on the dyno but once your on the track/road and transitioning with the throttle the BC will not be as good.

Hi Andre can you elaborate the bug a bit more. I found it quite hard too to get consistent boost on the road

Agree also with Mark thats solid on the dyno.

I would be very interessted to see your logs and whats going on with the PID controll algorithm.

What I've found is that on gear shifts or any kind of throttle transition you'll see a reasonable level of over boost occur. I've spent hours on this and never got results that I was happy with. I don't have the logs on this laptop but if I recall the issue was that the ECU was going back into Stage 1 on a throttle lift when it wasn't supposed to. This gave it a large duty cycle which was applied to the wastegate and caused the initial over boost to occur. There was also something weird going on with how the proportional element was applied. I'll see if I can give more detail when I can find the logs.

Hi André, is there anymore information when Link will release an update for the G4+ with improved boost control?

My tuning guy is desperate to switch me over to a syveccs S6 as the boost control is much better and the turbo speed can also be logged.

I asked the Engineering team about this subject today since it is not an issue I was aware of. They say there are no plans to further improve the boost control function in the G4+ range. Development time is now mostly focused on our next platform and there will only be minor updates and fixes rolled out to the G4+ when needed.

That's a shame. I tried to set up closed loop on the G4+ last night. Vehicle was a RB25, GTX3076 Gen 2, and external gate. I could not get consistent boost. I was getting exactly what Andre is describing. The only success I had was "half closed" or open loop and a table with MAP vs RPM axis.

I'm a bit disappointed - This is a major component of the ECU that needs to be sorted out even if the resources are being pointed towards the next gen ECU.

Post a log file please.

I'm using passive open loop and get a 4kpa overshoot at the point it reaches Max boost than a Max of 3kpa difference for the rest of the pull. No need for closed loop