[urq] Manual Boost Controller

[Rich Letsinger]

Jason,

Not a WX, but I've run a couple different MBCs on my 3B.  There's some issue
in the wiring of my frequency valve, so I've experiemented with other boost
control means.

First I ran a ball & spring type valve.  Basically, the spring holds the
ball down and plugs the hole until a certain pressure is reached.  I found
this to provide much faster spool of the turbo but to make a small spike of
overboost before coming back down to the desired pressure.  This spike was
great, I've got to admit, because it'd break the tires loose in the first 3
gears.  Wild but I cringe to think what the diffs and CVs think of that.
It'd also tend to pop my hoses off no matter how much mustard I put on the
clamps.

Now I'm running one of the Greddy Profec B deals.  It's got low and high
settings, which is nice when trying to stay cool on the street and not do
anything that'll make the cops and insurance companies pay attention.  It's
also got another dial which adjusts the "sharpness" of the boost control.
You can set that high which makes it spool the turbo really quick and do
that spike thing or set it low and it behaves more like the factory control.

The one issue with these things is it can't taper the boost like the 3B
ECU.  A normal "chip" will make 18-20 in the mid-range but gradually lower
the boost to 13-15 at redline.  An MBC can't do this and high boost at high
RPM is asking for pre-ignition trouble.

Anyway, just my experiences.

Cheers,
Rich