Turbocharging a CMFI engine

[ChrisBourk at aol.com]

In a message dated 98-09-10 23:56:49 EDT, you write:

<< 
 Hi,
 
 I'm still looking into turbocharging my CMFI engine. I received my
 service manual from Helm today (oh goody goody!)>>

What is  CMFI engine?  why isn't it like turboing any other?
 
 <<WOW!  This friggin PCM is complex compared to what I'm used
 too working with!!!   The DTCs go up to 82!  Geez!  And who's idea
 was it to implement J1930 and change all those nice terms I've
 finally learned by heart, like ALDL, ESC, and such?  Okay, enough
 griping.  :)>>

I've got a BMW 535 i want to turbo and don't know how to read the fuel and
ignition maps and how to go about "reprograming them.  It uses an e-prom but I
need to understand what it does when,  any hints?
 
 <After reading a bit, I have a few of new concerns about this engine's
 ability to take forced induction:>

I think any engine can take forced induction if you have the information you
need.
 
 <a) The fuel pressure regulator is fixed at 55 PSI.  It isn't connected
 to a manifold vacuum/pressure source like most other regulators I'm
 used to.>

Then why not connect it to vacum and make it self regulating?  a simple vacum
tube should take care of that

  <On turbocharged cars, this 1 pound of fuel pressure increase
 for every 1 pound of boost is essential.  I wonder if a vortec FMU
 would simulate this functionality well enough?>

I'm not really sure it is,  fuel presure varies with atmospheric anyway so as
long as you're above the boost by x amount you should be in the ball park.
 
< b) The system uses poppet valves fed by a central injector.  I am
 concerned the boost pressure in the manifold may force the poppet
 to open (raise the ball from it's seat).  I can't think of an easy solution
 to this occurance, should it happen.  Does anyone know how much
 outside force is required to open a poppet?>

Is the popet spring loaded?  can you shim the spring or replace it with a
heavier one?
 
 <c) The central injection unit is specialized and non-serviceable.  Is
 there any way to increase the amount of fuel the system injects at
 any given pulse width and fuel pressure?  (ie: make it act like a larger
 injector)>

Only way I can think of is by installing a larger injector or addional
injectors
 
< Are there any  aftermarket forced induction applications running on
 CMFI engines?  If there are, does anyone know how they address these
 issues?>

Again,  I don't know what a CMFI engine is...
 
 <The more I look at this, the more the idea of just tossing on an
 additional injector and controller in the up-pipe becomes appealing.>

Nothing wrong with that,  how about a whole new controler?
 
 <TIA! >>

Let me know if I can help,

Christopher