The 3 port MAC valve limitations with high boost

I thought I remember reading about issues with the LCDBC and MAC valve combination when it comes to high boost. Actually more so just the valve after talking with Antero. I did some research about this and was finding mentions of a 4 port MAC valve, so I did some searching on 3 port vs. 4 port. and found this forum conversation on a Supra site:

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OP: 3 port mac valve vs 4 port mac I currently use a 3 port mac valve, is there a way by changing to a 4 port mac valve I can make more than 35lbs of boost? I'd like to make 40-45 if possible.

MEMBER 1: Absolutely. I have a 12lb spring in my tial 44mm and a 4 port Mac valve and my highest boost setting is 43.5lbs. There is still room on the duty cycle for the boost controller for more boost, too.

MEMBER 2: How do you set it up...never heard of doing this before, interesting. Also, what part number is it?

MEMBER 1: http://www.mr2turbz.com/images/Supra/4port.jpg

MEMBER 2: So, does this work better than two 3 port valves? I can see its advantages but after doing some research its cheaper to buy 2 of the normal mac valves than this single 4 port.

MEMBER 3: I was making 30+psi on a 8lb spring. For high boost applications the 4 port is great. I found it difficult to control low boost situations with the 4 port because it has less resolution than a three port. However if you are going for high boost than the 4 port is great.

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I also learned that running a 4 port valve or two 3 port valves http://www.dynamotorsports.ca/tempfi...ort_Method.jpg Allows for small spring rate in the wastegate and still accomodate big boost. Am I on to anything here or just pissing into the wind?

*small spring in the wastegate. BOV is unrelated

Using both ports on the wastegates is definitely better in EVERY boost control scenario. They cost more to make and manufacturers don't want the extra cost associated with the build & all of the plumbing.

Most 3Ses are running single port wastegates...

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Originally Posted by DocWalt

*small spring in the wastegate. BOV is unrelated

Using both ports on the wastegates is definitely better in EVERY boost control scenario. They cost more to make and manufacturers don't want the extra cost associated with the build & all of the plumbing.

Most 3Ses are running single port wastegates...

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Edited my post from BOV to Wastegate

kinda related but trying to control boost on my internally gated 16g's with my lcdbc and MAC solenoid has been a PITA. i get a 4psi spike before boost finally settles down.

For example im trying to run 17psi on pump gas, but it will spike to 20+psi on the initial hit before settling to 17ish by 5000+rpms. Ive tested both of my WG's are functioing and crack open at the same psi(12ish).

I'm going to try to run a hybrid boost setup temporarily then switch to EMS controlled boost.

Well the main thing here is what is considered high boost? 20+psi, 30+psi. Supra guys are talking 40+psi which IDK of anyone pushing 40+psi on our platform. What is the limitation of the 3port? I know mine is working fine holding 18 psi and I'll be pushing it to probably around 20psi when I'm done tuning.

Like Doc mentioned most are running stock single port wastegates, So my assumption is that anyone running 30+psi is not TDO4 and Hence probably running external WG's, probably using a 4 port valve anyways.

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Originally Posted by DrGonzo

Well the main thing here is what is considered high boost? 20+psi, 30+psi. Supra guys are talking 40+psi which IDK of anyone pushing 40+psi on our platform. What is the limitation of the 3port? I know mine is working fine holding 18 psi and I'll be pushing it to probably around 20psi when I'm done tuning.

Like Doc mentioned most are running stock single port wastegates, So my assumption is that anyone running 30+psi is not TDO4 and Hence probably running external WG's, probably using a 4 port valve anyways.

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In the 3S TD04 family I would call high boost 25+ and those that have DR750's are saying if you do not plan on pushing 25+ PSI, don't bother with DR750's.

Boost spikes can come easily if you use LCDBC's turbo spoolup cheating features "PSI Start" and "PSI End". If you have them set to 1psi and 2psi, they are effectively turned off and the boost solenoid will run a steady duty cycle.