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Old 08-10-2004, 10:38 AM   #12
Scooby Guru
Member#: 32792
Join Date: Feb 2003
Chapter/Region: NESIC
Location: lincoln, ri
2003 GGA MBP
12.9 / 105+


Originally Posted by subiekid
I have been looking at that MBC for some time now. From the looks of it it has just like a cable and turning the knob changes boost. Can I ask where you mounted the knob? Good write up.

the system has essentially an integrated "twist cable" (for lack of a better term, it's just like a speedometer sense cable, only a bit more robust) that adjusts the MBC spring preload bolt.

i found that the cable itself is pretty flexible, but the plastic housing that is provided is fairly stiff. this is probably done purposely, since it prevents you from running too tight a radius bend and kinking the cable. obviously the friction is reduced to a minimum when you keep the bending to a minimum too.

because the twist cable is made up of a good number of solid strands it is difficult to cut. hallman recommends using a plasma cutter, which i do not have! i'm sure a dremel or other cutoff wheel would work too, but it was too much for me to take on at the time. you'd have to grind the tip down so that it does not fray. so i left the cable as long as it came from hallman, which is pretty long.

you can see where the MBC is situated underhood. the adjust cable then routes below the IC and makes a gentle arc right into the firewall hole to the outboard side of the clutch actuator.

from there, it makes a turn to the outside of the car, up under the dash, then down back towards the front of the car, then finally to the knob which i located on the driver's plastic kick pannel next to the dead pedal. it isn't the MOST convenient place to locate it, but since i didn't want to cut the twist cable i kind of had to put it where it wanted to go, to avoid tight bends and such. still, where it's located, it's out of the way, in such a place that most people would NEVER see it, and there's no way anybody but the driver could adjust it.

i find that it actually does not require much adjustment, despite weather changes, and when it does it's a quarter turn in either direction. that's enough for about a pound of manifold pressure difference. i have gotten good at reaching down while left-foot brake loading and quickly dialing in the boost i want to run. it takes literally 5 seconds.

i originally balked at the thought of spending 180 bucks on an MBC, but i have to say that this MBC is very nice and has features that you're just not going to find in any other unit. i actually went out and bought a speedo cable to see if i could make my own in this style, but the speedo cable was only really good at transmitting torque in one direction of rotation. attempting to source a cable similar to the hallman was fruitless. the ceramic ball makes a VERY good seal in the valve body and is a decent diameter (around 1/4") and the adjustment resolution, even with the "stiff" spring, is very fine.

i'll take some more pics of the install and get them up soon.

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