The idea is to be able to switch between normal factory boost control, and manual boost control (JoeP MBC) at the flip of a switch inside the car.

I used a Grainger solenoid with two inputs and one output. Two boost signals are fed to the inputs, and the output sends one of these boost signals to the wastegate, and blocks the other. One of the input boost signals is from the factory solenoid/wastegate actuator. The other is from the MBC. The MBC receives its boost signal from a line tee'd off from the BOV. A 12V switch activates the solenoid. I've set this up before on a WRX, and it worked really well. The nice thing is that you can pretty much switch between the two settings anytime -at a stoplight, or while driving. The car doesn't complain. I have a diagram of the set-up that I've been trying to load in this post, but I don't think it's working.

Anyway, I'm pretty happy with the results, except for one thing. With the MBC on, my max PSI is different for every gear, which make setting up the MBC difficult. I'll get 3-4 psi difference in the peak boost between the 1st and 5th gear (5th gear gives the highest boost numbers).

I can set it up so that 4th gear gives a steady 19 psi, but then in 2nd gear, I'll only get something like 16 psi. But if if I set it up, so I get 19 psi in 2rd gear, I'll go over 20 psi and hit boost/fuel cut if I punch it in 5th gear with the MBC on.

Any advice on how to get more steady peak boost between the gears or how to avoid the boost/fuel cut?

 

I'm surprised to see the diagram came out. The red/orange-colored lines are what was added to the otherwise stock set-up. There are also two wires coming out of the grainger solenoid: one goes to gound and the other goes to +12V, though a rocker switch inside the car.

 

If you are really trying to change the boost per gear you may want to just get an EBC. Better yet, get something like the Xede and you can tailor the boost per the speed you are going and RPM. I am sure the Utec and AEM EMS can do the same.

 

He's not trying to change the boost per gear.

He is getting different boost levels per gear.

D

 

Boost is determined by engine load. I don't think you can force more boost aside from what the exhaust provides without using an auxillary boost provider.

 

Pretty much the nature of the beast with a manual boost controller on our cars. Set up your grainger solenoid between two manual controlers, and have the switch located on the shift lever of the transmission so that when you switch to higher gears it drops to the boost controler with the lower setting.

Keith

PS: Great idea, and great diagram!

 

So when I hear guys saying that they achieved a solid 19 psi to the redline, I guess they're only talking about a single gear.

I was worried that since the factory solenoid still sees the boost when the MBC is on, that somehow its still managing to control the boost, even though the line to the wastegate is blocked. I say this because I heard a lot of people emphasizing that those lines to the factory solenoid have to be completely blocked off, for the MBC to be effective. I can always add another solenoid to completely block off the factory solenoid when the MBC is on.

Your idea about the tranny switch is interesting.