Hi

I am trying to correctly set up my ego PID. I have done some research to find a huge difference in the way people do this. I am wondering which person is correct if any from the three choices below. All of them have a different approach.

1.Tuning PID is the same general process regardless what you're trying to control. If you happen to own the boost control course then there is a complete module on this and how to tune it which is very valuable.

With closed loop fuel control I'd start by getting the main fuel table close as this means the closed loop system isn't going to be chasing huge errors - The less work any closed loop system needs to do, the better it will work.

Start by adding some proportional gain only and measure the effect. I start with a small amount and then begin doubling it until the system becomes unstable and oscillates. This let's you know the range of usable values and you need to back the P gain off again. I aim for a little oscillation/overshoot and then add some derivative gain which has the effect of slowing the system down and preventing overshoot. Too much D gain will result in slow response while too little can result in oscillation. Lastly you can add a little integral gain to correct any remaining error.

In essence I try and use the minimum gain possible. The biggest mistake I see is people trying to use closed loop fuel control to fix a poorly tuned fuel map. The results you'll get in this instance are likely to be poor.

2. PID control of anything is tuned basicly the same. You should tune Proportional control first, then add Integral control, after that add Derivative control if needed.

Proportional control is how fast the system reacts on measured unit change. Too big coefficient - you will see huge oscillations until measured unit reaches target. Too small - it will take a lot of time.

Integral control based on summing errors through past time. Too big coefficient will increase oscillations more and more until system fails.

Derivative control usually not needed. This control is an attempt to predict the unit change in near future.

Try to make engine running on steady AFR on minimum RPM you can hold steady AFR with closed loop control on and all coefficients dropped to zero. Slightly increase Proportional coefficient, change target AFR and measure delay between target change and system stabilized on that AFR using your logger, increase coefficient and repeat the procedure until you see overshooting (oscillations around new target). Step back and this should be the minimum time to reach the target hence the optimal P coefficient. Integral control tuned after Proportional, which should be on. The target is the same - to drop the delay between Target AFR change and wideband signal reaches that target. Usually that's enough.

3. Here's what I found during testing... "I" is the most important to tune and should be tuned first with P set to a low number and with D set to zero. Not enough "I" will not allow the AFR to reach it's target during steady state operation. If you notice that you are not reaching your target you need more "I". To much "I" will cause overshooting, and oscillation. I think "P" is how fast it responds when the AFR is changing, but I could never really notice P's effect during testing. D is a damper to prevent overshooting, but Ken recommends not to use it.

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Regards

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