A friend and I are both planning cheap turbo swaps for our cars, and we'd like to build cheap boost controllers for them. I did a search here, and found a link for DIY MBC plans. That looked good, except that it looks like it would require alot of experimentation to get the correct spring for it.

 

The idea I've come up with is an electrical solution. I figure I could just use one of these 4-15psi adjustable pressure switches in the normally closed position:

http://dkc3.digikey.com/PDF/T042/1307.pdf

and a normally open solenoid valve. (yet to be sourced) Then all I'd have to do is adjust the switch to open at the boost level I want so it would release the solenoid valve at that point and allow the wastegate to open. This design should be safe since switch or valve failure would revert the system back to factory boost. I figure I can find a suitable solenoid valve at a junkyard, so total cost would be around $30. Can anyone forsee any problems with this design? Or have any other designs to share?

may i suggest a saab apc unit fromt he junkyard.. for boost control?

you can "adjust " how much boost it will let occur i personally use it in stock form on my suby and it hits 10-10.5 psi and it never lets it go higher

plus it has a knock sensor so if you get knocks it will taper downt eh boost till it goes away

from things like bad gas just random knock ect

also after 4500 rpm it tapers the boost down a few psi also since at higher rpm you do not need as much boost

all these adjust ments and such can be changed by turning the right potentiometer

 

but like i said i run one on mine at the stock unmolested settings and am exceptionall happy with it and its pretty much wire it up connect the right vac/boost line to the pressure sensor it has and away you boost

 

there is 3 main parts to it

one is the controller box

two is the pressure sensor

and 3 is the duty solenoid that regulates how much boost pressure reaches the wastegate thing

i mean if you want to go with a mechanical means that can not compensate for things then by all means go with it many people use them and like the results

me however.. i will stick with the apc after all saab turbo's use this system with i think 9.5:1 compression and the motors usually outlast the rest of the car and drive train... well usually

yeah especialy with the screwey way they deliver power to the tranny from the engine via a gearbox like oddcomp pointed out when I noticed the clutch was in the front of the motor instead of the back

actually

in that model of saab that i showed you

the motor is mounted backwards in the 900 series

and sideways in the whale looking 9000 series

the 900's have the weak tranny parts

 

but the 900's and the 9000's and the maserati bi turbo's all have the apc units

its a popular addon to the volvo hotrodder crowd

 

this site explians the hows and why far better than i can

all i can say is i have one and i like it

http://web.inter.nl.net/users/turbo-team-europe/apc.htm