SBC TPI manifold questions

[FIScot at aol.com]

    Subj:   SBC TPI manifold questions
    Date:   96-01-30 22:30:57 EST
    From:   jsg at coulomb.eng.ohio-state.edu (John S Gwynne)

  > Just a couple of quick question...  I don't really want to buy a
  > service manual for this car since I only have its manifold.

  > Manifold:  89 Camaro TPI 305 w/ cold start injector

   Check the year, 89 Camaro's did not use the cold start injector.

  > Q) The EGR valve has what looks like a temperature sensor built into
  >    its base.  How is that used?

    It is used in EGR testing.  It is mounted on the output side of the EGR
    valve.  If the EGR is on, it gets hot, and activates the switch, if the
    EGR gets turned off, it cools, and deactivates.  The EGR test checks
    this for proper operation.

  > Q) I've traced the idle air passages down through the base plate.  Near
  >    the cold start injector there is a hose nipple.  What attaches here?
  >    Does this tee-off to the MAP sensor which I assume is attached to
  >    the rear left nipple on the plenum?

    The first mentioned nipple is for the PCV valve.  Nothing else is
    hooked to it.  The MAP is connected to a nipple in the plenum.  The
    85-89 TPIs used a MAF sensor, so had no MAP provisions.  The 90-92 used
    MAP, and had a plenum that had a MAP sensor mount and nipple.  Just use
    a plenum nipple. (Personal opinion: MAF's are ugly.)

    Are you going to use a MAP sensor?  Do you have your VE table yet?

  > Q) How did GM originally route the radiator bypass hoses?  One through
  >    the throttle body then back to the block and a second to the heater?

    The large nipple on the front of the throttle body is for the incoming
    hot water out of the manifold.  The throttle body exit did go to a
    switch that was controlled by the HVAC system.  Normally this would go
    to the heater core, but the heater core is shut off during max A/C, and
    the the switch keeps the throttle body warm at all times.


    Scot Sealander   FIScot at aol.com

    HVAC - Heating, Ventilating, and Air conditioning
    MAF  - Mass AirFlow sensor
    MAP  - Manifold Absolute Pressure sensor
    TPI  - Tuned Port Injection
    VE   - Volumetric efficiency