E36 3.0 ITB Race Build

[Touring_Rob]

I wonder if the wastegate setup is helping with stability. Most of my setups i've been involved with are internally gated and running 20-30psi. Saying that the actuator will somewhat close the loop if your boost is near to wastegate pressure.

I've not thought about this much but I also wonder if the error is a percentage, so running pretty low boost you're getting a 10% error ish of 0.5psi, so the higher boost setups will see a more worrying error.

Pass - if it works it works. My personal experiences with closed loop boost have been very positive, performance has always been dependent upon the solenoid used more than anything but thats the same as with open loop.

Do you have a separate table for peak boost? I could see your target and actual in the vid and the actual was often >1psi above target without cut.

 

[f0xy]

I wonder if the wastegate setup is helping with stability. Most of my setups i've been involved with are internally gated and running 20-30psi. Saying that the actuator will somewhat close the loop if your boost is near to wastegate pressure.

I've not thought about this much but I also wonder if the error is a percentage, so running pretty low boost you're getting a 10% error ish of 0.5psi, so the higher boost setups will see a more worrying error.

Pass - if it works it works. My personal experiences with closed loop boost have been very positive, performance has always been dependent upon the solenoid used more than anything but thats the same as with open loop.

Do you have a separate table for peak boost? I could see your target and actual in the vid and the actual was often >1psi above target without cut.

It probably is - I tried to give it as much priority as possible, and wanted the biggest gate I could so I had zero possibility of creep and could control the boost well. Didn't initially realise how much surface area of the gate would affect it... so I put a 3psi spring in it... and it made zero boost on the initial tuning. Swapped to 5psi spring and made like 2psi, and so on. Obviously with more timing on ethanol its making more power, so more exhaust energy, and more force acting against that wastegate face.

My intention was to run up to half a bar, which is how it sat last year, however with the ethanol I could up that a little more, but I'll then be out of injector. We'll see what the dyno shows and what my boost limit is based on injector - I'm not changing them, there has to be a headline somewhere before you start breaking more things.

I have two boost target tables, 3psi vs 7psi.

The CAN rotary switch blends between those two:

The boost solenoid duty cycle table looks up the % DC for a given requested boost:

Which was pretty well set up on the old turbo core. The new Garrett is much more efficient, and making more boost..

However I wasn't adjusting this table at the track day, as you need it in steady state really.. I could work it out after the fact from the logs, but in reality that entire table needed dropping by n% with the new turbo, to reduce the actual boost.

This is the duty cycle correctiont able versus ethanol content:

That is all now irrelevant though, as it was on the 3 port solenoid. I've now switched to the 4 port so I don't just pin the duty cycle at 100% when running on ethanol, and can apply more boost to the top of the gate. Next week I'll set up the duty cycle on petrol, then run upto ~E50 and get the duty cycles correct across the board - I'd then expect the target vs actual to be very close most of the time, like it was before

 

[f0xy]

Should add, the peak boost (cut) is just a single setting, set at a global level - not per mode/target.