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Write ups and tutorials for maintenance and modifications.
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[How to] Install a manual boost controller (MBC)

Wed Oct 10, 2007 1:08 pm

Here are what you need to know about installing a manual boost controller (MBC) on your alltrac.

1. Stock boost controller
In every turbo system, a wastegate is used to control amount of maximum boost. CT26 turbo on or cars has internal gate system.
That means the gate is located inside the turbine housing. The system consists of wastegate actuator, rod, and flapper (gate).
The actuator is connected to compressor housing. There is a vacuum hose that sends the pressure signal to the actuator.
Once the boost reaches a certain setting (6-7 psi on ST165 and ST185), the actuator pushes the rod and causes
the flapper to open and allows exhaust gas to bypass the turbine blade.

On an alltrac, there is an addition controoler system called Turbo Vacuum Switching Valve (T-VSV).
This system consists of a hose that connects the actuator to a vacuum switching valve. The valve is activated by the ECU.
Once activated, the VSV bleeds air out of the actuator and allows the turbo to achieve higher boost.
On a normal system, your stock boost could reach 10-11 psi in 3rd,4th, and 5th gear on ST165 and ST185.

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2. How does it work?
A boost controller allows you to achieve higher boost especially in lower gear.
It mechanically manipulates the pressure signal that is sent to the wastegate actuator.
In order for the MBC to work properly, you will need to disconnected the T-VSV.
The most common method is to disconnect and cap the second vacuum hose on the wastegate actuator.
Installed location
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3. Manual boost controller types
There are couple different types of manual boost controller.
The most common ones are "bleed valve" type and "ball and spring" type.
Both are pretty cheap. You can even make one in your garage.
Many people have good experience with "ball and spring" MBC.
Here is how to make your own ball and spring boost controller by Craig Watson
http://www.geocities.com/chmwatson/FAQs/mbc.html
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4. How much boost?
How much boost you can run safely is up to your supporting mods and what turbo you are using.
On "stock" ST165 and ST185, many people are happy with 12-14 psi.
Be aware that you may reach fuel cut at that level.
Adjust boost at your own risk.

5. Important stuff!
- Never play with boost setting without an aftermarket boost gauge.
- Make sure your car and your engine are healthy.
- Fuel cut is there for a reason, to protect your engine from overboosting.
- Wideband O2 gauge is always a good idea.
- Always try to keep the charged air cool.
- More boost = more stress on the engine and turbo.
- Adjust boost at your own risk.



How to disable the T-VSV by Robert Pina
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Last edited by Gary on Mon Dec 03, 2007 12:53 pm, edited 1 time in total.
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