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Good morning gents,
I did a little digging on this subject and while I found guys running compressed air for boost control, I didn't find the performance pros and cons for each.
My current car has boost control setup in the typical manner via air from the turbo using a Cortex EBC and 3 port mac valve which seems to work well.
The car has a Viair compressor with a 1-gallon tank onboard which I got working this weekend as the previous car owner never got around to finishing the install.
My question is what is the benefit if any to using compressed air for controlling boost over using the turbo?
What modifications to the current boost control setup would be required and how would you plumb it?
It looks like the Cortex can control boost with compressed air, so I know I'm good there.
I wouldn't normally look at doing something like this but since the compressor is already in the car and working, I thought why not?
Any insight you guys can lend would be greatly appreciated.
Dual solenoid fixed source air dome control is awesome
But it really does nothing for you on the control/solenoid setup you currently have
Right so if I wanted to make the move to a compressed air control setup I'd have to do what and what would be the benefit over the current setup?
I've read a 4-port mac valve would be needed at minimum?
I also found a bunch of extra line in the car so I'd really only need a few things to do it I think.
You're using a compressed air setup to control boost aren't you?
Found this plumbing diagram on Motion Raceworks website.
For dual waste gates would I just tee them together but still use this arrangement?
Thinking the dome pressure sensor would report to the EBC?
Bringing this full circle, there are two different types of EBC, Duty Cycle and Dome Pressure controlled.
Duty Cycle uses a single control valve and Dome uses twin control valves.
The Cortex is a duty cycle controller so only one 3-port Mac Valve is needed for boost control.
Benefits from what I've read are more accurate boost control, builds boost faster and a greater range of boost settings.
The only thing that is required is replumbing my lines and testing.
So, since I'm using the Cortex and since the air compressor is already installed and wired, I'm gonna give this a try.
Will report back in the spring for anyone who is interested.
I have twins and have been running CO2.. replumbed briefly to use cold side pressure as a test.. still get well above spring with no issue. I only run about 25psi max...
So this winter I have plumbed it with a tee into the boost solenoid with a valve so I can change it to use turbo pressure or CO2 with the turn of a valve.. This way if I find out I need CO2 for some tiny bit of gain at the track I stick the bottle in, turn the valve and away I go, but still have plenty of boost on the street without using CO2... I am using the Holley High flow solenoid setup tor run 2 turbos and not had any issues with that setup..
I tried an Air Compressor but found it just too noisy for my liking, getting old I guess, or I need a louder radio...
I have twins and have been running CO2.. replumbed briefly to use cold side pressure as a test.. still get well above spring with no issue. I only run about 25psi max...
So this winter I have plumbed it with a tee into the boost solenoid with a valve so I can change it to use turbo pressure or CO2 with the turn of a valve.. This way if I find out I need CO2 for some tiny bit of gain at the track I stick the bottle in, turn the valve and away I go, but still have plenty of boost on the street without using CO2... I am using the Holley High flow solenoid setup tor run 2 turbos and not had any issues with that setup..
I tried an Air Compressor but found it just too noisy for my liking, getting old I guess, or I need a louder radio...
If this was a streetcar that I spent a significant amount of time cruising in like my last car, then I probably wouldn't have gone this route.
Technically this is mostly a racecar that I drive on the street at this point.
My compressor is pretty quiet and from the people I've talked to who run one, it shouldn't run often if the system doesn't have any substantial leaks so hopefully my experience will be the same.
I also have a 4" fender exit so noise isn't an overall concern for me lol.
Like everything, depends on the application and how much control/range you need. Again, I’m a fan of the K.I.S.S. methodology. What range of boost you require? IF you can easily hit that range without onboard air of some sort, why add another system? It’s another failure point, and extra weight.
The WG spring I run nets me 8lbs on gate and 30+ if I want it. *IF* setup properly, onboard air and 4 ports MAC valves won’t make you spool any faster than a single 3-port mac w/ manifold pressure. Figure with the gate shut 100% that’s it. That’s as quickly as it will build boost. So you setup the 3 port to run as much DC to the dome as needed to keep the valve closed 100% when building boost.
I use 1 3port to control 2 38mm gates. 100% DC diverts all the pressure to the top of the gate, none to the bottom. 0% DC routes all pressure to the bottom, none to top. All DC in between is a ratio of top/bottom and controls boost really well in my experience. For most, that’s all that’s needed. When you get into competitive racing and 1200++hp setups, I can def see wanting more resolution across the board and better control that onboard air offers. Can’t see it as being necessary for the weekend warrior at the track though. Esp. guys with smallish motors that need to leave on decent boost and ramp it in fast anyway.
Last edited by Forcefed86; Feb 1, 2023 at 09:09 AM.
Like everything, depends on the application and how much control/range you need. Again, I’m a fan of the K.I.S.S. methodology. What range of boost you require? IF you can easily hit that range without onboard air of some sort, why add another system? It’s another failure point, and extra weight.
The WG spring I run nets me 8lbs on gate and 30+ if I want it. *IF* setup properly, onboard air and 4 ports MAC valves won’t make you spool any faster than a single 3-port mac w/ manifold pressure. Figure with the gate shut 100% that’s it. That’s as quickly as it will build boost. So you setup the 3 port to run as much DC to the dome as needed to keep the valve closed 100% when building boost.
I use 1 3port to control 2 38mm gates. 100% DC diverts all the pressure to the top of the gate, none to the bottom. 0% DC routes all pressure to the bottom, none to top. All DC in between is a ratio of top/bottom and controls boost really well in my experience. For most, that’s all that’s needed. When you get into competitive racing and 1200++hp setups, I can def see wanting more resolution across the board and better control that onboard air offers. Can’t see it as being necessary for the weekend warrior at the track though. Esp. guys with smallish motors that need to leave on decent boost and ramp it in fast anyway.
You're not wrong and normally I would tend to agree with everything you said but the main factor here is the compressor was already in the car, wired and plumbed when I got it and if all I have to do is re-route my reference lines to use it then why not try it, it would be more work for me to remove it from the car lol.
Plus I can use the air to fill my tires when leaving the track for the cruise home which sounds nice.
Okay gents, this was way too easy. The previous owner ran the pressure line from the compressor all the way up to the mac valve so all I had to do was remove the reference line from the mac valve and plug the compressor line into the mac valve, so the swap is done. Now for tuning, Chris at cortex said it's really dependent on how much boost I intend on running as well as other factors like WG spring, back pressure, etc. that will determine dome pressure. He suggested starting with 20-30 psi of dome pressure as that's what most combinations require, if my duty cycle is very low but hits target boost then reduce dome pressure, if I'm at 100% duty cycle and can't hit the boost target than add dome pressure. I'll be curious to see if this eliminates my boost spike on the 1-2 and 2-3 shifts as well. Looking forward to testing this spring, will report back on how well it works.
I hope you like the compressor running or you have it configured so the noid is dead other than when you are in boost
and I don’t know what salesman you have been talking about a single 3 or 4 port giving better boost control than a single 3 or 4 port
yes I run air, but I also run dome control along with map over the top
I've got it on a switch on the dash but even when the tank is empty it only runs for about 45 seconds until it fills and turns off.
It's pretty quiet and will be under the panels in the back which should hopefully muffle it a bit more, maybe I'll add some sound deadener if it becomes annoying but I doubt it.
Not sure what you're saying here I'm assuming dual 3 or 4 port "and I don’t know what salesman you have been talking about a single 3 or 4 port giving better boost control than a single 3 or 4 port"
The salesman is Chris at Sirhc Labs (Cortex), he said the Cortex is a duty cycle-based controller and can't control dual solenoids unlike say the Holley which is a dome pressure-based controller which can run twin solenoids.
He never said one was better than the other, only what capabilities his has.
I set this up exactly as he said to so I'm not anticipating any issues......
Hi,
Did you ever end up running the onboard air with the cortex?
Regards
Gav
Yes sir I did, I was running it that way up until I installed the Haltech this winter when I went to dual 3-port Mac Valves with the compressed air.
Rotary1307cc was correct on all points in that it caused the compressor to cycle more frequently since the single 3-port would bleed off some pressure which the air compressor would have to replenish. It wasn't a constant thing but the more I was going WOT the more often the compressor would cycle. I did have a smidge bit better control since the air compressor source is a constant psi versus the turbo which is constantly varying so the Mac valve doesn't have to work as hard but I also had to change a few things with Chris's help, the sense line for the Cortex was pre-TB so the pressure spikes from closing the TB would make the EBC get a little wonky so that line was moved to the intake.
Now this setup is nowhere near as good as a dual Mac valve setup with compressed air, boost hits like a hammer and my compressor has yet to cycle again after filling up initially. A much better setup but requires and aftermarket ECU of course.
Just for comparison, I was running about 20-25 psi to the Mac valve with the Cortex which was supplied to the waste gate dome for control. With dual Mac valves I'm running about 90psi to the Mac valves, so it really slams the valve closed when applied.
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Boost Control - Compressed Air or Turbo? 
