What the hell is a Manual Boost Controller

Posted by Arro

I thought it would be nice to post information on manual boost controllers for those who weren't sure or wanted to learn more detailed info. Many of you of course already know what they are.

The "manual boost controller" is merely a "bleed valve" that is installed between the turbo and the wastegate.
http://www.lotuselancentral.com/images/mbc.jpg

If the pictured line was directly connected, then the boost would be fighting the spring in the wastegate's actuator can (brass vaccum canister here). Most actuator springs are rated at 5-7 PSI, after which boost begins to defeat the spring, the actuator opens the internal wastegate flap, and exhaust is leaked out and bypasses the turbine blades, creating a cyclic effect... as soon as the leak affects the turbine enough to steady the boost, the spring does not get pushed open any further, and hence the actuator does not open the internal gate any more. Thus steady boost is achieved.

With the line straight to the actuator can, it's considered to be a "mechanically-controlled" turbo. A "computer-controlled" turbo uses a three-barb solenoid to alter the line pressure to the actuator can. By doing this, boost can go higher than the psi rating of the spring in the actuator can. It basically leaves the solenoid "open", meaning the line from the turbo outlet barb is vented to atmosphere, the wastegate spring keeps the internal gate flap shut, and boost keeps steadilly rising up. At some point (ECU programmed), the solenoid CLOSES, and all that boost hits the spring, defeats, it, and thus regulates the boost... typically this "boost control solenoid" kind of "pulses", opening and shutting rapidly to regulate boost levels.

What a manual boost controller does is kind of similar. There are a couple commin types out there. Ball & Spring and Needle. Some MBCs use a combination of the two.

Ball and spring uses just that. The ball is on the boost side and the spring is on the wastegate actuator side. In order to get the boost "signal" to the actuator (and defeat the actuator's spring), it must first push the ball back to get air around it. That means it has to defeat the spring holding the ball. Usually a tensioning screw compresses the spring, making it either harder or easier to defeat.
http://home.att.net/~jason510/BoostControl.jpg

In this picture, the hose barb facing the bottom would be connected to the wastegate actuator can, and the one on the right would be from a boost source BEFORE the throttle body (on an S12, this would be on either the stock airpipe to the throttle body, on the turbo outlet, or on your intercooler piping somewhere if you custom installed an IC).

These work extremely well. You can use a solenoid on an electric switch to create a switchable Y-junction, where one MBC is set to a low boost level and the other one to a higher level.

The other type of MBC is a needle bleed. Basically a needle valve is stuck inline on the hose leading to the actuator can. Depending on how much it is opened, it will take longer to build up the necessary PSI in the vac line to the actuator can to defeat the can's spring. If it is open all the way, the spring will never be defeated and the boost will continue to rise (because the line cannot pressurize).

"I want an MBC and more boost! Where do I get one of these?"

http://www.titanmotorsports.com/dnamanboosco.html
http://www.turboxs.com/
http://www.turbosmart.com.au/
http://www.boostcontroller.com/
http://www.joepmbc.com/
http://www.twosrus.com/mbc.htm
http://home.attbi.com/~MitsubishiEclipseGS..._MBC1/MBC1.html
http://www.turboimports.com/hksmanboosco.html
http://www.mm-racing.com/mbc.htm

Wow the TurboXS one is pricey!

"These things look cheap and simple. Can I build one myself for less?"

I'm glad you asked.

http://home.att.net/~jason510/ManualController.htm
http://velocity.websitegalaxy.com/mbc.html
http://www.thedodgegarage.com/turbo_boost.html
MUST SEE:
http://www.xmission.com/%7Edempsey/perform/grainger.htm
ANOTHER MUST SEE:
http://www.geocities.com/chmwatson/FAQs/mbc.html
http://home.earthlink.net/~turbogus4/boostcontrol.html

An alternative to bleeds and ball&spring MBCs:
http://pages.cthome.net/gus/pictures.html
This one uses a method that puts more tension on the actuator can's spring (by shortening the actuator arm) thus making it harder for the spring to be defeated. Sort of. Read and see.

Happy boosting

Just remember: ALWAYS MAKE SURE YOU ARE NOT RUNNING LEAN! Raise boost one or two PSI at a time (1 is best) and check fuel mixture between each raise in boost!

"How do I check the fuel mixture?"

If you don't know how or have a way to check your fuel/air mixture, you shouldn't be tinkering with higher boost! Period! Before you put on an MBC, buy an air/fuel ratio gauge and/or an EGT gauge. Perferrably both!

[span style=\'color:red\']Posted by Arro[/span]

I thought it would be nice to post information on manual boost controllers for those who weren\'t sure or wanted to learn more detailed info. Many of you of course already know what they are.

The \"manual boost controller\" is merely a \"bleed valve\" that is installed between the turbo and the wastegate.


If the pictured line was directly connected, then the boost would be fighting the spring in the wastegate\'s actuator can (brass vaccum canister here). Most actuator springs are rated at 5-7 PSI, after which boost begins to defeat the spring, the actuator opens the internal wastegate flap, and exhaust is leaked out and bypasses the turbine blades, creating a cyclic effect... as soon as the leak affects the turbine enough to steady the boost, the spring does not get pushed open any further, and hence the actuator does not open the internal gate any more. Thus steady boost is achieved.

With the line straight to the actuator can, it\'s considered to be a \"mechanically-controlled\" turbo. A \"computer-controlled\" turbo uses a three-barb solenoid to alter the line pressure to the actuator can. By doing this, boost can go higher than the psi rating of the spring in the actuator can. It basically leaves the solenoid \"open\", meaning the line from the turbo outlet barb is vented to atmosphere, the wastegate spring keeps the internal gate flap shut, and boost keeps steadilly rising up. At some point (ECU programmed), the solenoid CLOSES, and all that boost hits the spring, defeats, it, and thus regulates the boost... typically this \"boost control solenoid\" kind of \"pulses\", opening and shutting rapidly to regulate boost levels.

What a manual boost controller does is kind of similar. There are a couple commin types out there. Ball & Spring and Needle. Some MBCs use a combination of the two.

Ball and spring uses just that. The ball is on the boost side and the spring is on the wastegate actuator side. In order to get the boost \"signal\" to the actuator (and defeat the actuator\'s spring), it must first push the ball back to get air around it. That means it has to defeat the spring holding the ball. Usually a tensioning screw compresses the spring, making it either harder or easier to defeat.


In this picture, the hose barb facing the bottom would be connected to the wastegate actuator can, and the one on the right would be from a boost source BEFORE the throttle body (on an S12, this would be on either the stock airpipe to the throttle body, on the turbo outlet, or on your intercooler piping somewhere if you custom installed an IC).

These work extremely well. You can use a solenoid on an electric switch to create a switchable Y-junction, where one MBC is set to a low boost level and the other one to a higher level.

The other type of MBC is a needle bleed. Basically a needle valve is stuck inline on the hose leading to the actuator can. Depending on how much it is opened, it will take longer to build up the necessary PSI in the vac line to the actuator can to defeat the can\'s spring. If it is open all the way, the spring will never be defeated and the boost will continue to rise (because the line cannot pressurize).

\"I want an MBC and more boost! Where do I get one of these?\"

[url]http://www.titanmotorsports.com/dnamanboosco.html[/a]
[url]http://www.turboxs.com/[/a]
[url]http://www.turbosmart.com.au/[/a]
[url]http://www.boostcontroller.com/[/a]
[url]http://www.joepmbc.com/[/a]
[url]http://www.twosrus.com/mbc.htm[/a]
[url]http://home.attbi.com/~MitsubishiEclipseGS..._MBC1/MBC1.html[/a]
[url]http://www.turboimports.com/hksmanboosco.html[/a]
[url]http://www.mm-racing.com/mbc.htm[/a]

Wow the TurboXS one is pricey!

\"These things look cheap and simple. Can I build one myself for less?\"

I\'m glad you asked.

[url]http://home.att.net/~jason510/ManualController.htm[/a]
[url]http://velocity.websitegalaxy.com/mbc.html[/a]
[url]http://www.thedodgegarage.com/turbo_boost.html[/a]
MUST SEE:
[url]http://www.xmission.com/%7Edempsey/perform/grainger.htm[/a]
ANOTHER MUST SEE:
[url]http://www.geocities.com/chmwatson/FAQs/mbc.html[/a]
[url]http://home.earthlink.net/~turbogus4/boostcontrol.html[/a]

An alternative to bleeds and ball&spring MBCs:
[url]http://pages.cthome.net/gus/pictures.html[/a]
This one uses a method that puts more tension on the actuator can\'s spring (by shortening the actuator arm) thus making it harder for the spring to be defeated. Sort of. Read and see.

Happy boosting

Just remember: ALWAYS MAKE SURE YOU ARE NOT RUNNING LEAN! Raise boost one or two PSI at a time (1 is best) and check fuel mixture between each raise in boost!

\"How do I check the fuel mixture?\"

If you don\'t know how or have a way to check your fuel/air mixture, you shouldn\'t be tinkering with higher boost! Period! Before you put on an MBC, buy an air/fuel ratio gauge and/or an EGT gauge. Perferrably both!

\"What else is there to know about MBCs?\"

Well, let\'s see. Some people tinker with hose location to try to improve response. Some tinker with hose length to try to reduce spiking (a condition where the boost overshoots the set limit, then settles to whatever it is set for). Others use a combination of ball & spring AND needle valve, using the ball & spring for coarse adjustment and the needle for fine adjustment. TurboXS has a premium MBC that does just that... it has a needle valve AND a ball & spring. I in fact used this very valve. I can tell you it was more trouble than it was worth.

Regarding hose lengths, often the shortest hose means the less delay, which would also mean less spike. As far as location goes, just remember that ICs have pressure drop, so placing it after the IC will require a bit more boost to defeat the ball & spring.

That is why most people place it so close to the turbo itself. Short lines, and more accurate boost line signal.

\"How does a manual boost controller compare to an electronic boost controller?\"

That\'s a bit tricky, as there are a few types of EBCs out there, but the biggest is the ability to control the dial from inside the car. You can do this with an MBC too, but your hoses will need to be long enough to reach to the inside of your dash.

The Greddy Profec-B is not actually an electronic controller, but more of an *electric* one, as it has a single potentiometer knob that then tells the unit to dial up or down.... the unit itself is a small box that sits underhood and basically is an electrically-actuated version of the beloved MBC.

A true *elecTRONIC* boost controller calculates a variety of factors and can usually affect its response based upon speed, RPMs, and custom settings like \"scramble boost\" that boost higher for a predetermined period of time before returning to normal settings.

All in all the only dash-controlled piece I would personally go with is the Profec-B. But for the cost, I will always run a manual boost controller instead. I\'m not too lazy to get off my ass and pop the hood, plus it gives me a chance (if I want) to check oil, pull and read sparkplugs, notice any spewing fluids, and (at night) glance at the turbo\'s exhaust housing to see how hot it is.

The more often you have to pop the hood to check things, the better. You\'re more likely to spot something early on, before it becomes more than a nuisance.

Good write up on this but I have a question.  When boost pressure forces its way past the check ball it seems to me like the pressure would get trapped behind that same ball and hold your wastegate open to long.  I built myself a mbc out of one of those grainger relief valves and I added a pressure operated dump valve between the mbc and the wastegate can.  So when boost is applied the valve is closed keeping air from escaping from the wastegate signal line and when the boost drops (when I let off the gas) it dumps pressure from between the mbc and the wastegate quickly closing the wastegate off.  I would like to know if this was necesary or if I wasted 15 bucks making this thing.  Thanks.