I've been going back and fourth on the idea of what boost control method I want to use for a while now on my build. The options are MBC, 3 Port, MBC + 3 Port (Hybrid via Tscompusa) and 4 Port.

After talking with countless tuners and users on the forums about what they use and recommend I still do not have a factual data or solid proof as which to go with. I see good results with all the options mentioned.

Currently I have a standard 3 Port setup, but I feel I can do better than this due to now having external tial wastegates with a top and side vacuum/boost port.

I know STM recommends MBC setups via what they told me over the phone. My concern is MBC has the least control over the wastegate.

I know Tscompusa swears by Hybrid MBC to spool the turbo? the fastest but paired with EBC to aid in controlling or raising boost in the upper RPMs.

Then you have the majority of modified evo owners running a standard 3 Port and having great results.

The last option which is least mentioned is the 4 Port setup mainly because alot of evo owners are not running external wastegates needed to use this system. Also its slightly more expensive and slightly more complex. I recently saw a GTR thread where ETS Extreme Turbo Systems installed the 4 Port backwards in their GTR thread so it over boosted.

That thread got me thinking, is a 4 Port the way to go for us larger turbo guys? Can the 4 Port be controlled with the same resolution as a 3 Port? Does it install the same as a 3 Port in terms of wiring on the Evo?

 

Nothing complex about a 4-port.

I assume it's a less popular option for evo's because the benefits for a 4-port, dont necessarily benefit those with AWD.
With a 4-port, you can run an extremely light WG spring, and be able to run a ton of boost (ie; 6lb spring could be ran out to 40+). Great for a BIG hp fwd vehicle on the street or track, but not so much of a benefit for an AWD vehicle that can leave off the line with 20+ psi.

If it were me, I'd follow the K.I.S.S. method, and just do a simple, straight to the point 3-port.

 

Why would a MBC be recommended? The ECU cannot pull boost if something goes wrong. You cannot tune your boost curve to limit torque (either for traction or for parts safety). I don't see why anyone would recommend that over a 3-port controlled by the ECU. I am wondering why for a mildly tuned car, why a 3 port is needed if the OEM solenoid bleed setup can dump enough pressure? Isn't it 6 vice half dozen? Unless your gaining solenoid speed (doubt it), I don't see a reason. I am open to education though.

 

with a 4 Port you can keep the wastegate valve completely shut till peak boost because the vacuum line on the top port of the wastegate can over ride the pressure that the side port is sending. im not sure if a 3 Port can do this?

 

Ive used all the main methods of boost control (MBC, ECU 3port, Hybrid, Stock EBC with pill). Ive gone back and forth in my EVOs millions of times over the last 9 years. Right now my car is set up on ECU Boost w/ 3port.

Each has their pros and cons. Im favoring ECU w/ 3port right now because a lot of people are doing dual maps tunes and if you adjust all the temp corrections for ECU boost, it will hit your target boost all year round. But I also love a good MBC on a good setup. If your setup is not optimal, then a MBC will taper and such. Yes, this can be fixed using hybrid boost, but I live by the K.I.S.S. concept and to me, everything you can do with hybrid boost can be done with ECU boost w/ 3port and have a simpler setup. In initial testing, I witnessed MBC spooling faster then the 3port setup and favored the MBC/hybrid idea for spool (Ive even posted data people use to prove MBCs spool faster). But after more though ECU boost testing, I can get ECU boost to spool as fast as MBC or Hybrid, there for eliminating one of hybrids main pro's.

There is many many other factors when deciding which boost control method to use. One that is not brought up much is when on a weak pump gas like 91oct and when using a MBC, you will naturally boost more in 4th/5th gears. So when you optimize the timing in 3rd gear, it may knock in 4th gear, making it so you have to pull timing, which hurts all the gears it doesnt knock in ie 1-3. With ECU boost, you can make sure your boost in 4th/5th gear is the same or even less, so you dont have to pull timing and affect the other gears.

I could go on for days about boost control. The stock ECUs boost control was one of the first things I worked on in 06 when ECUFlash came out. Basically this is how I see it nowadays:

If you are doing dual maps or stock framed turbo, Id recommend ECU Boost w/ 3port. Reasons why: dual map & eliminating taper

If you have a T3/T4 setup or one fuel type, Id recommend a good MBC. Reasons why: Simple & properly setup T3/T4 wont taper

And there's a bunch of other recommendations I would make, based on a cars setup, fuel type, alt map or not, goals for car, etc.

And then there's always the recommendation of the Tuner tuning the car. Some tuners like a certain boost control and it works for them, so if you trust them to tune your car, you should trust them on their recommendation for boost control.

 

Yes, a lot of tuners, including myself use tq limiting boost control methods to limit tq and save stock blocks.

But tq limiting can easily be done with a MBC via timing adjustments. The true TQ of a motor relys on timing as much, if not more, then boost. In fact, one of the common TQ limiting method used by OEMs for traction control and stability systems is reducing timing, therefore reducing TQ. It actually can react faster then a boost adjustment.

 

I just installed a 4port, and I am still in the process of tuning. However initial impression if you have a dual port wastegate why not just go 4port. I am also running a 10psi spring in my wastegate so I can run 15-20psi at the road track, and then 40psi at the quarter mile.

Most evo guys just toss in the biggest spring they can so a 4 port really is not needed. The idea behind the 4port is that you can run a small spring, and have a super wide boost range. 10-50psi. Because a 10psi spring will crack open early you are loosing performance, and the 4port will help to keep it closed until you hit your boost target.

I am also on an AEM Infinity so the PID controller for boost control is very fast.

Anyhow I will have more results during the next week.

 

Thank you boosted tuning for the clarification on which setup SHOULD be optimal based on the parts and driving you are going to be doing. I guess each have their perks and at the end of the day the timing as well as the parts combination effect the spoolup more than anything.


Now TheBoz how do you like the 4 Port regarding the resolution? I hear 1% of wg duty cycle is like 5psi increments, is this true? I do have dual external tial 44mm MVR wastegates so I think I could benefit from a 4 Port personally being that I can keep the valve shut till target boost and not have it crack open a few psi early. Ive boost leak tested a MBC tial MVS setup on a 24lbs spring and it starts to crack open at 21psi.


I am running the stiffest spring combo in the MVR's 21psi to be exact because I was going to go Hybrid prior to this thread and its a street drag car, I do want to be dual mapped to have options but I doubt the car will ever see 91oct at this point ever again. I should be running around 30-35psi so I know a standard 3 Port can get me there with the springs I have in but I wonder if a 4 Port can get me there just a tad bit faster

 

Do you have a pic of your WG setup that you can share with us? Are you using a twin scrolled turbo mounted on a header with paired runners wherein each pair of runners is flanged for its own dedicated gate?

 

Is there any true benefits with 3 ports, etc?

 

mitsubeastlee: I am wondering how you plan to pass California's smog certification test with your non-stock looking setup?

 

LOL that is funny.



Here in the golden state we either pay for smog, or have our car registered in a different state, or put it back to stock for smog.




With my testing of the 4port, things are going pretty smooth. I am up to about 18psi now, I found the resolution to be just fine. ~15% DC to get to 18psi. I am on a 10psi spring as the base. I still have a lot of fine tuning to go, this was just a first pass over about 2 hours of street tuning. I will spend some more time this coming weekend, and once I have it all dialed in off to the dyno.

 

Hybrid boost is more taken advantage of with smaller turbos that cant hold boost to redline or turbos that are using internal wastegates with poor boost control & want mbc like spool. Hybrid is just like a 3 port, except it does spool a little sooner on the evo using the stock ecu. It varies setup to setup though. I've had customers tell me there was no difference made on multiple occasion's (usually on evo 9's), and others saying how it made a huge difference and they loved it. My personal experience favored it over just the standard 3 port by itself.

I use a mbc only in my 6466 and 2.4 setup because the wastegate keeps the boost solid to redline, so there's no need to run anything else. Not all big turbo setups are like this, but mine is.

For a stock block on a 6466 id run just the 3 port.

Never used a 4 port so I cant comment on that. I believe 4 port just uses 2 direct signals from an external gate vs 1 like a 3 port.

A 3 port (and im sure 4 port) is superior to a mbc in every way, but a mbc is very simple and if you have a built engine and your setup is holding solid boost to redline, and you are on race gas then the mbc gets the job done.

 

I have the hookup on SMOG so I don't have to worry about that.


Thanks for the further clarification of Hybrid boost Tscompusa, that explains a lot actually.

Yeah I know the MBC setup would limit my overall HP output due to the fact that I cant manipulate the torque curve as much as with a 3 Port.


So all in all I guess its pretty clear the overall options aside from the 4 Port more research needs to be done in order for me to make my decision. As of now I will stick with the 3 Port but if theBoz reports back to us with favorable results I am definitely down to give it a shot.

 

So far here is the short and skinny on the 4port.

10% DC = ~6psi
15% DC = ~8.7psi
20% DC = ~11.6psi
25% DC = ~14.5psi
30% DC = ~18.8psi
35% DC = ~23.2psi

Now, I have to taper off the DC as I near redline, to keep the boost low. At 35%DC and 6500rpm I am at 26.1psi, when at 5500rpm I am at 23.2. Now I am not running any feedback at all right now, and I am running the same DC across the RPM range. For me to see the better results, I need to adjust the pre full boost DC to 100%, which I will get to over the weekend. Just building the generic data points.

So still lots of tuning a head for me.

P.S.
My numbers in the other post were wrong, did not check my KPA to PSI chart correctly .