Boost Gauge or Boost Gage in a Nissan Skyline

Voltage, Engine Oil Temperature, and Factory boost gauge in an R32 GT-R

Now look carefully at that boost gauge.  That probably doesn't say what you think it does.  It goes from -7 to +7.  However it isn't psi.  It isn't kg/cm2. It isn't bar.  It is mmHG. Not only is it millimeters of mercury, but it is x 100. Boost -  the factory ECU does NOT have a boost sensor in an R32/R33/R34.  The OEM sensor in the engine compartment, only drives a gauge. 

Thanks to Jacob and Ryan, I learned that this range is referred to as Torr.  More information here . https://vacaero.com/information-resources/vacuum-pump-technology-education-and-training/633-understanding-vacuum-measurement-units.html?fbclid=IwAR0cPl7KeKV2Nf5AWn8nsvlwQW_hKhz9Zb_BX6YX27aTEiHxjgxxtVhU4lM

Since the gauge is divided into equal sections above and below zero we assume the hash marks are 3.5 x 100 = 350 mmHG. 

So if your boost gauge reads to that first hash mark, you are running around 6.7 psi of boost.  A factory R32 GT-R should be slightly above that mark, or about 10 psi of boost.

If your boost gauge pegs at 700 mmHG, you are running above 13.5 psi of boost.   Running too much above about 1 bar of boost, on stock ceramic turbos is not recommended.

Missing ceramic exhaust wheel

If you are modifying the car, get a real boost gauge, so you have a proper indicator of boost, because no one real, runs less than 14 psi anyway.

Look a perfectly removed ceramic exhaust wheel. 

Yellow line is where the factory boost sensor gets its source to drive the gauge

OEM boost sensor on the left. Aftermarket boost sensor on the right

Head back to the basics here.

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