Re: Simple-minded turbocharger ruminations ...

[Dan Bocek <dan@di.com>]

> 	If Ned Ritchie's Stage I kit consists  of a stiffer
> 	wastegate spring and a chip only to prevent fuel-supply
> 	shutdown, it seems like a cheaper way to go would
> 	be get just the stiffer spring, and recalibrate the boost
> 	sensor electronics to increase the shut-down threshold.  I'm
> 	absolutely sure I'm missing something, because greater minds
> 	than mine have messed with this problem at length (even if one
> 	assumes that Ned's just a profiteer :-))

You are missing absoulutely nothing.  This is exactly what you'll get 
from a Hypertech or SuperChips modification (~$350!!!).  
 
> 	Looking at the Bentley quite carefully yesterday, I couldn't
> 	figure out how the engine management computer senses manifold
> 	pressure (no entry for "boost sensor", for one).  In the wiring
> 	diagram, the boost gauge has a wire going to the engine
> 	management computer, but that's about it.  So ... anyone care
> 	to enlighten me?

There's an integrated boost pressure sensor inside the engine computer.  
The modification consists simply of reducing somohow, by a fixed amount, 
the magnitude of this signal, thereby tricking the computer into thinking 
it has less boost than it actually does.  This can be done with either a 
resistor divider network, zener, or op-amp.  Note that this will also 
have the effect of advancing your timing across the board, since the 
computer uses manifold pressure as a guage of engine load, so be careful
if you try this yourself.

                                                         Dan Bocek
                                                         dan@di.com