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Boost gauge
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<p>A boost gauge is a <a href="/facts/Pressure_gauge/fJrvoTDU">pressure gauge</a> that indicates manifold air pressure or <a href="/facts/Turbocharger/xuabwHlB">turbocharger</a> or <a href="/facts/Supercharger/gvEtspvw">supercharger</a> <a href="/facts/Boost_(automotive_engineering)/xuabwHlB">boost</a> <a href="/facts/Pressure/eyc37GRG">pressure</a> in an <a href="/facts/Internal_combustion_engine/Ju4BXzj0">internal combustion engine</a>. They are commonly mounted on the dashboard, on the driver's side pillar, or in a radio slot. </p><p>Turbochargers and superchargers are both engine-driven air compressors (exhaust-driven or mechanically driven, respectively) and provide varying levels of <i>boost</i> according to engine rpm, load etc. Quite often there is a <i><a href="/facts/Power_band/nI43vrhH">power band</a></i> within a given range of available boost pressure and it is an aid to performance driving to be aware of when that power band is being approached, in the same way a driver wants to be aware of engine rpm. </p><p>A boost gauge is used to ensure excessive pressure is not being generated when boost pressure is being modified to levels higher than OEM standard on a production turbocharged car. Simple methods can be employed to increase factory boost levels, such as bleeding air off the wastegate diaphragm to 'fool' it into staying closed longer, or installing a <a href="/facts/Boost_controller/9azUr83L">boost controller</a>. To prevent the <a href="/facts/Air-fuel_ratio/l2BGvlyw">Air-fuel ratio</a> from going lean (caused by increasing the boost beyond the fuel systems capacity) care must be taken to monitor boost pressure levels, along with <a href="/facts/Oxygen/acyn6o8r">oxygen</a> levels in the exhaust gas, using an <a href="/facts/Air-fuel_ratio_meter/pFg8ywk3">air-fuel ratio meter</a> that monitors the <a href="/facts/Oxygen_sensor/Yj0rxfdo">oxygen sensor</a>. </p><p>A boost gauge will measure pressure in <a href="/facts/Pound-force_per_square_inch/RMdeTlB0">psi</a>, <a href="/facts/Bar_(unit)/wwFWTTkT">bar</a> or <a href="/facts/Pascal_(unit)/Am1To2Qm">kPa</a>; many also measure manifold <a href="/facts/Vacuum/BTk3goyV">vacuum</a> pressure in <a href="/facts/Inch_of_mercury/jRv55tBk">inches of mercury</a> (in. Hg) or <a href="/facts/Torr/Y83YBu34">mm of mercury</a> (mm Hg). </p>