Hey guys I picked up a Motion Raceworks CO2 setup the other day and I'm curious if anybody here has played with CO2 and Holley EFI?? I'm mainly looking for a start point with the PID settings in the controller.

I'm running 80 psi on the regulator and my mac valves are about 5 inches away from my wastegate so lines are as short as I could get them. I have everything plumbed like you'll see in the Holley diagram, compressor to lower port, Tee from mac valves to the dome with a pressure sensor in the dome.

When I was using my compressor as the pressure source my PID settings were sitting at P: 10, I: 35, D: 0. This followed my boost curve fairly decently with only a tiny bit of overshoot. Now with the CO2 in the mix these settings are way too wild and it's got lots of overshoot. If I increase the P term to say 11.5 or 12 it's unstable and oscillates like a madman

Now if I go the other way with settings say like 8,20,0 I'm still getting massive overshoot. Should I just try and keep going lower and lower?? Until I see a smooth follow?? How low is too low?? Or is that even a thing when using high pressure CO2??

And yes I've read the Holley boost control manual a bunch of times and while I do understand the majority of it the PID stuff in that manual was written by an engineer.

Anyways I'd love some opinions on this by anyone that cares. Thanks guys have fun

 

Have to kinda test it. The manual had some instructions on how to do it. Setup a wonky boost vs time curve and trigger it with the throttle tps. Watch it work and play with it. Once you get it matching well enough in static conditions, once you run the car you may need to tweak it.

my settings are small values. I cant exactly remember off top of my head but will check later.

 

Awesome thanks I'd definitely be interested in seeing what another guy runs to see if I'm going in the right direction. Yes I've been testing things out with the key on and engine off I'm seeing crazy spikes off the hop. I was looking into it a bit deeper last night and it seems like the CO2 guys run really low PID settings like P: 1-2, I: 1-4, D: 0-0.5 with a target rate limiter at 100 psi/sec

I'll head down to the car sometime today and go try super low settings and see how that looks. I'll also bump up my dome pressure curve to like 25-30 psi instead of the slow ramp in I was using with compressor pressure

 

This was P 3, I 4.5, D 0

This was P 3.25, I 5, D 0

I feel like that's looking better than it was yesterday

 

https://documents.holley.com/techlib...r10628rev3.pdf

Did you start with a I and D of 0 and increase P til it overshoots? Then start increasing I to make everything follow closely. Also can lower the target rate limiter

your above examples i think need alot more P component and abit less I i think

 

Mine are higher than i thought. I forgot to mention my solenoids are abit farther away from the wastegates and i have a small reservoir inline that gets filled to help dampen the pressure pulses and i think it stabilizes control abit better for my setup.
my P is 20
my I is 10.5
D is 0.

target rate limit is 60 psi sec. I run 120 psi supply for my air shifter so i think i had lowered the rate when i added this

 

Got the car out after playing with PID settings a bit more. I ended up landing on P: 7, I: 14, D: 8, Target Limiter 100 psi/sec, 80 psi on the regulator. I could probably fine tune from this point as it seemed to follow my boost curve pretty well


This was a on a p little highway pull. It's following pretty good. Not bad for now anyway. I'll be able to dial things in

 

As long as it follows and does it consistently. You could go a bit more P to get the dome to get to the commanded target, as it still remains under abit but could be fine if its tracking in real time

 

Yea I noticed that too. I'll try bumping it up 1-2 on the weekend when I have a bit more time. But so far it's looking promising