I pulled this info from K2RD's site,

"The boost sensor tells the ECU if you're in vacuum or in boost (i.e. positive pressures). The stock FC boost sensor is only good up to 2bar or 14.5psi. The boost sensor is located on the front side of the passenger strut tower under the hood. It's the black plastic "box" with a single vacuum line running to the engine - the hose is normally (stock) plugged into a fitting on the ACV cluster.

Most people don't know, but everytime you start your engine, you're doing a self-check on the boost sensor. When first keying to the "ON" position before cranking the starter over, the stock boost sensor should jump to the "0" (zero) position.

If the boost sensor fails, the ECU will fail-safe with a default boost sensor input signal of 4.5psi. This will cause the engine to run rich most of the time. "

Now, does anyone elses TII jump up to '0' when starting? I know mine doesn't...I'm just very curious as to what he means here.

 

Nope....My stock boost gauge is buggered....I am running aftermarket....

but before it was crapped it didn't....

There should be a away to test the sensor input, I know my RX-7 mechanic checked it...if anyone knows how let me know...

 

On my car this is how it does. Key out of the ignition. Boost gauge needle rests on the lower two hash marks, way below the zero. Key in ignition and turn to the on position without starting the needle rises up about the width of three needles. Not even close to the zero on the gauge. Now start the engine. The needle drops down from the three needles width above the lower hash marks to being pegged out on the bottom. Thats due to a vaccum being pulled on the gauge by the engine. So I'd say my car does its dead level best to do as you described. By the way you can check out your boost sensor, pressure sensor whatever you want to call it. Its described in the fuel section of the factory manual at http://www.iluvmyrx7.com a digital volt meter is required. You basically tap into the signal wire to the ECandU and you can see the voltage vary as the engine is reved.