4 Port MAC vs Compressed Air Boost Control
4 Port MAC vs Compressed Air Boost Control Would like to get a wider range of boost control out of my setup and was set on compressed air until I read a 4 port MAC valve can achieve the same result.
I know compressed air is proven and I've read the 4 port can be finicky with open loop. Anyone have any insight on this? I run a stock 411 pcm and an eboost 2 so I do see how this would be a problem.
Other than that, what are the advantages/disadvantages of running compressed air on top of the gate versus the 4 port? Not much info out there on the comparison.
FWIW, I am running a T7575 on a 5.3 with a 50mm gate and a 7lb spring. Looking to ramp in boost in first gear slowly to a max of 10-12psi and run a max of 20ish in higher gears.
I know compressed air is proven and I've read the 4 port can be finicky with open loop. Anyone have any insight on this? I run a stock 411 pcm and an eboost 2 so I do see how this would be a problem.
Other than that, what are the advantages/disadvantages of running compressed air on top of the gate versus the 4 port? Not much info out there on the comparison.
FWIW, I am running a T7575 on a 5.3 with a 50mm gate and a 7lb spring. Looking to ramp in boost in first gear slowly to a max of 10-12psi and run a max of 20ish in higher gears.
9 Second Club
Joined: Nov 2003
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From: Norn Iron
There is very little a 4 port can do, that cannot be achieved with a 3 port and a 3 port responds faster.
And with whatever configuration you currently use, are you restricted with base boost level and top boost level ? 7-20 should be relatively easy to achieve.
And no....using engine boost is not quite the same as compressed air, because with CA you have the ability to use much higher air pressures for control which can make things work faster and over a wider range.
Likewise CO2...it's much higher pressure so has an ability to make changes faster and either fully open the gate or blow it shut harder if needed.
And with whatever configuration you currently use, are you restricted with base boost level and top boost level ? 7-20 should be relatively easy to achieve.
And no....using engine boost is not quite the same as compressed air, because with CA you have the ability to use much higher air pressures for control which can make things work faster and over a wider range.
Likewise CO2...it's much higher pressure so has an ability to make changes faster and either fully open the gate or blow it shut harder if needed.
I'm going to try to get this to work before making the switch. If I could ramp the 10lbs in slowly then I'd probably be fine.
Thanks for the inoput on the 4 port.
TECH Addict
Joined: Dec 2004
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From: Florida
I had a compressor and tank on my truck for a while and just ended up taking it off. it was too much hassle, space, and weight for the value.
I never got all the leaks out of the system so the tank was always empty when i got in the truck. after a while i just gave up.
i was using an ams1000 with 100psi and it worked very well, but its almost as good just feeding the ams1000 with pressure from the turbo compressor housing. It spools a tiny bit slower but my truck is 100% driver, not track car.
if i went to the track with it at all then the compressed air is much more likely to be worth it.
that said, my evo has a single 3 port and it works extremely well with ecu controlled boost. Its basically a gear x rpm x duty cycle table. boost is very repeatable and ive run anywhere from 20 to 33psi. my evo is plumbed like the second picture in the post above.
I never got all the leaks out of the system so the tank was always empty when i got in the truck. after a while i just gave up.
i was using an ams1000 with 100psi and it worked very well, but its almost as good just feeding the ams1000 with pressure from the turbo compressor housing. It spools a tiny bit slower but my truck is 100% driver, not track car.
if i went to the track with it at all then the compressed air is much more likely to be worth it.
that said, my evo has a single 3 port and it works extremely well with ecu controlled boost. Its basically a gear x rpm x duty cycle table. boost is very repeatable and ive run anywhere from 20 to 33psi. my evo is plumbed like the second picture in the post above.
9 Second Club
Joined: Nov 2003
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From: Norn Iron
Well if I run the setup with the top port of the wg vented then I am restricted to only about 14lbs. If I run the setup in the second picture then I make a minimum of 10lbs but can make as much up top as I want.
I'm going to try to get this to work before making the switch. If I could ramp the 10lbs in slowly then I'd probably be fine.
Thanks for the inoput on the 4 port.
I'm going to try to get this to work before making the switch. If I could ramp the 10lbs in slowly then I'd probably be fine.
Thanks for the inoput on the 4 port.
If you are using the method you've pictured on the right, then you will need to drill or create a small bleed hole in the top chamber or line to it.
Without this stable control can be very difficult to achieve at some duty cycles. By small I mean around 0.6-0.8mm....a bleed via a MIG tip can give this if you cannot create it any other way.
Yes you lose a small amount of boost from the top chamber by doing this but it is a small sacrifice to get easy stable control over a wide range at no cost.
Well if I run the setup with the top port of the wg vented then I am restricted to only about 14lbs. If I run the setup in the second picture then I make a minimum of 10lbs but can make as much up top as I want.
I'm going to try to get this to work before making the switch. If I could ramp the 10lbs in slowly then I'd probably be fine.
Thanks for the inoput on the 4 port.
I'm going to try to get this to work before making the switch. If I could ramp the 10lbs in slowly then I'd probably be fine.
Thanks for the inoput on the 4 port.
3-port should do that fine.
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If you can get "all the boost you want" up top and want less down low, then you need to drop the spring rate in the gate. Drop down to a spring rate that gives you your minimal desired boost with just the bottom port connected. You should be able to come close to doubling that with no reference, and tripling that with full boost to the top port.
3-port should do that fine.
3-port should do that fine.
I can hit 17-18lbs at 75% duty but then boost bleeds off at higher rpm. Usually bleeds about 3lbs, the bottom cell of the data log shows it in purple.
What can I do to fix this? I've checked all my couplers and it doesn't seem to be a boost leak.
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Verdad Gallardo I'm trying to have it consistant across the rpm range, not have it bleed off 3psi to the desired amount of boost. If I turn up they duty, the same problem is still there.
9 Second Club
Joined: Nov 2003
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From: Norn Iron
The whole point of an electronic one is to allow you to adjust anywhere, anytime to achieve what you need.
SO you're saying that even with 100% duty at the top it makes no difference ?
How big is the orifice on the welding tip? It may be bleeding off too much. I'd try .020 or smaller. (you can solder the tip closed and use a jewelers bit set to vary orifice size)
Are you running open loop for the solenoid control? My ECU runs closed loop. If it senses boost rising or falling past my target it automatically adjusts duty cycle to keep it on target.
Chances are if you are just set at "X" duty cycle and have no control you aren't going to get rock solid manifold pressure across the entire RPM range. .... It's gonna vary.
Are you running open loop for the solenoid control? My ECU runs closed loop. If it senses boost rising or falling past my target it automatically adjusts duty cycle to keep it on target.
Chances are if you are just set at "X" duty cycle and have no control you aren't going to get rock solid manifold pressure across the entire RPM range. .... It's gonna vary.
It is possible that you may be better off with a smaller gate. Typically, the problems you describe are of a much smaller scale with the right hardware. I think you may be chasing your tail on this one.
Launching!
Joined: Jan 2018
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boost most likely falling off up top as exhaust manifold pressure builds because the 75mm turbine cant flow all the combustion gas which it now hotter, and consequently a greater volume.
while it waits in line to get through the bottle neck that is the turbine pressure in the exhaust manifold builds pushing on the bottom of the gate helping it open at less "signal boost" venting manifold pressure and reducing turbo wheel speed.
single snail LS need the turbine flow. turbine housing and wheel is king for single turbo LS power
while it waits in line to get through the bottle neck that is the turbine pressure in the exhaust manifold builds pushing on the bottom of the gate helping it open at less "signal boost" venting manifold pressure and reducing turbo wheel speed.
single snail LS need the turbine flow. turbine housing and wheel is king for single turbo LS power
If you do not want a controller where you can make it do what you want, may as well just use a manual bleed valve.
The whole point of an electronic one is to allow you to adjust anywhere, anytime to achieve what you need.
SO you're saying that even with 100% duty at the top it makes no difference ?
The whole point of an electronic one is to allow you to adjust anywhere, anytime to achieve what you need.
SO you're saying that even with 100% duty at the top it makes no difference ?
How big is the orifice on the welding tip? It may be bleeding off too much. I'd try .020 or smaller. (you can solder the tip closed and use a jewelers bit set to vary orifice size)
Are you running open loop for the solenoid control? My ECU runs closed loop. If it senses boost rising or falling past my target it automatically adjusts duty cycle to keep it on target.
Chances are if you are just set at "X" duty cycle and have no control you aren't going to get rock solid manifold pressure across the entire RPM range. .... It's gonna vary.
Are you running open loop for the solenoid control? My ECU runs closed loop. If it senses boost rising or falling past my target it automatically adjusts duty cycle to keep it on target.
Chances are if you are just set at "X" duty cycle and have no control you aren't going to get rock solid manifold pressure across the entire RPM range. .... It's gonna vary.
Thanks for the insight guys.
9 Second Club
Joined: Nov 2003
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From: Norn Iron
Higher back pressure usually makes boost control easier. It’s the low back pressure setups that I’ve had trouble controlling. Your gate size likely fine, I had no issues with a 50mm on mine. I’d look into the controller settings more.
Your bleed is probably fine too. Going smaller is an easy check though. It’s just to vent the dome after the pull. I run an MS3 setup on mine.
Your bleed is probably fine too. Going smaller is an easy check though. It’s just to vent the dome after the pull. I run an MS3 setup on mine.