Experiences with 4-port boost control valve
 

I've typically had problems with traction in 1st and 2nd so needed to limit the boost to 6-8 PSI for lower gears, but want the option to turn up to 20+ PSI in the future. As such, I put in a 4-port valve to control boost because you can get a very wide range of boost pressures. Now that I have everything running well, though, I've found the duty cycle needed varies wildly depending on ambient temperature. What works at 80 ambient causes it to spike 40 kPa over when its 50. When I lower it for that temperature it takes forever to get to the proper boost when its warmer.

My question is this: does anyone else run a 4-port valve and if so what are your experiences? I haven't found a ton of info on people running them, but I have seen a couple people mention something similar. I'm about ready to throw in a 12 lb spring and a 3-port valve and call it a day.

Relevant setup: S4 half-bridge, 3 in exhaust, MS3X, BW S366, divided SS greddy manifold, 46mm wastegate. Target boost is 220 kPa.

Thanks

You need to be running closed loop with a 4 port.

Sorry, I didn't specify on that. I am running close loop, but the duty cycle needed varies so greatly based on ambient temps that I'm getting so big spikes before the pid controls can fix it when it's cooler.

I'm still tweaking it, but definitely interested in hearing from anyone else who has used one. I've got it set at 20 hz, which allows for a greater operating range, but I'm going to bump up the frequency and see how that helps.

Just found this :https://www.rx7club.com/haltech-foru...y-day-1114272/

Looks like the answer is that I need to give up on the 4-port. Going to order a 3-port ,or in the 12 lb spring, and call it a day.

Actually, Stickman's answer was the filter/muffler being clogged on his 4 port MAC. Once removed, it functioned perfectly.

Well damn, how did I miss that? Thanks for the tip!

I've spoken w/ stickman regularly throughout his tuning and with his boost issues and there's more to it than just his post on removing the filter. Before he ended up tearing the car back down, he reported that the boost would continue to fluctuate off target for no explainable reason, day to day.

I had the same issue on my setup using a 4 port on a single turbo. Car was running a 7psi spring, targeting 14psi. Sometimes the car would hit 14psi, othertimes 16+, and many times it would fall under target. It seemed to depend on how aggressively I applied load, and which gear the load was applied. It was too hard to narrow down exactly what variable(s) caused the fluctuation from the target. The only way to keep it anyway repeatable was to run the boost controller in closed loop, which then had wild oscillations and results, despite changing the PID functions. At one point, doing dyno run, I thought I had it tuned, then go out on the street and it responds great in closed loop. Come back a week later, totally different, hitting boost cut.

I ultimately decided to ditch the 4 port and run 3 port. While I did have to run a heavier spring to reach my target effectively, the car was 100% predictable and results were always consistent with the initial boost curve in tuning.

From my experience, I can conclude that the tolerance/error is too large for anyone running low boost on a 4 port controller. If you are looking for +/-1 psi target accuracy, a 4 port is not going to cut it. However, if you are looking for +/-4psi accuracy, a 4 port will do the job.

Consider that +/- 4psi target error isn't too bad on a car running racegas/methanol etc, and 40psi, coming off the line with boost by gear. What is a 4 psi swing at that level?

But on an application where 1psi makes a big difference in performance, risk, and drivability, stick with a 3 port, hands down. Stickman switched back as well.

Good luck!

David, did you stick to just ONE 3port MAC or use two of them for your application?

I sold my application, I'll be using 1, 3 port on a 60mm on next design, but the last setup was 1x 3 port t'd off to 2 gates, worked great. Very predictable and repeatable

I have always setup the 4 port in open loop. It doesn't work in closed loop.
Its very sensitive and its also very slow due to the vent port.

We have come up with a different solution to achieve what the 4 port does that is much faster.

So cryptic... I'm assuming this is dual 3 Port MACs? Mind explaining?

?? I have a 4-port that I wanted to use sooo how do you set it up open loop?

You set it up on the ECU, Open loop setup works just like a mechanical boost controller, closed loop setup works like an electronic boost controller (like the Apexi AVC-R, Greddy Profec, etc). The MAC solenoid does not knows the difference between open/close loop, its all in the ECU.

I've run a 4 port for years- works great on my Renesis setup ... Very consistent. Just runs on a set duty cycle EBC - nothing fancy.
I like that I can run a 5psi spring in it (16psi set pressure) and use the WG as a safety with my wideband failsafe and also use it as a soft boost cut before the rev limiter activates .

you don't need to be told lol. you already know the solution ...

what if we don't know and would like to learn?