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Open vs closed loop boost control


richardpalinkas
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Running closed loop is much more time consuming to tune, as if you don't make the desires boost table match exactly what the open loop duty cycle table shows on the dyno you will end up with a horrible oscillating boost curve when you turn closed loop back on. For this reason most tuners just tune the car in open loop. 

If you want full closed loop boost control at 20psi the method is as follows.

Tune the car in open loop and log the boost against rpm and temp.

Set your desired boost table to match what is logged at that temperature and guestimate the other temperatures. Ultimately you want to do a dyno run for all conditions but this isn't possible without a temperature controlled dyno cell. 

Now reenable closed loop. 

If you have changed the turbo wastegate actuator or turbo you may need to fine tune the PID gains. This requires knowledge of tuning control systems. There are some good guides online. Even Wikipedia is quite good. 

Simple guide is if you are getting oscillation (and your desired matches what you see in open loop) decrease the proportional gain and also decrease integral. If you see that the boost never reaches target (undershot) increase the integral gain. 

The benefit of closed loop is you will get the same boost pressure on 5c and 40c weather. Same with low and high gears. Without it you will see less boost in the lower gears and if you hold it at peak torque in a tall gear you may overboost. This is especially true with the stock gt3582 turbo and actuator which is almost uncontrollable at peak torque and >18 psi. 

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  • 1 year later...
20 hours ago, sadennis1086 said:

Hi, just starting to get my head around this software, only looking through the demo at the moment and trying to make sense of it all but could someone point me in the right direction to be able to change to open loop WG only? 
 

cheers

 

 

 

 

Have a read of these two guides. 

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