Re: more boost

[Robert Houk - SMCC Bos Desktop Hardware <rdh@UrQ.East.Sun.COM>]

   Don't put a voltage divider in the output of the pressure sensor. It will
   advance the ignition and cause you problems as the boost comes up. If you

Correct, as far as it goes.

   want to do it at low cost use a 4.3v zener and a 470ohm resistor.

   There are 3 wires coming from the pressure sensor, 0v 5v and output. Use
   your meter to see which is which. The output should be about 2-2.5 v with
   the ignition on and the engine off.

   Cut the output wire and now we have 4wires. 0v,5v, output from the sensor
   and input into the board.

   Connect the 470 ohm resistor to the output from the sensor and to the input
   to the board.

   Connect the zener (stripe end) to the input to the board and the other end to 0v

   Now your computer will not retard after 12 - 13 PSI boost and all of your
   safety circuits will still work

Here I have to disagree. The Zener has essentially clamped the pressure
reading at "12-13", whether your manifold is at 20, 30, 40, ??? PSI! At
this point, a stuck wastegate (flakey/bad SchrapnelKnobben, whatever)
turns your engine into the proverbial schrapnel.

I believe the "voltage divider" is the correct solution, along with a re-
mapped ROM calibrated to the new "pressure curve", so the ECU can continue
the retard curve as your pressure continues to build, and maintain all
the safety features, such as overboost shutdown (e.g., run at 18PSI,
shutdown at 20PSI). This is the approach I am ever so slowly evolving for
my UrQ . . .

					-RDH