Boost gauge issues, revistited.
09-06-2006, 04:49 AM
#11
Whoa!... sorry guys... that was a badly written description...
Apparently I need a little more sleep!
The last 2 scentences should be in a separate paragraph.
Breakdown of how bost 'adds up' so to speak...
1 bar = 14.7 psi = 1 atmosphere of pressure at sea level
Using absolute pressure means that you measure using 1 atmosphere at sea level as the datum from which your measurements are taken. If you think about this you kind of have to do it this way.
So... your dash gauge reads 1.0 when you turn the ignition to the 'ON' position prior to starting the car. Why? Because it is measuring the atmospheric pressure only because the motor isn't running. Sometimes you will see 0.9 because one decimal place of accuracy sucks.
Start the car and it starts pumping air out the exhaust and a vac is created. Rev the engine and when the throttle plate slams shut you make a vac spike into the negative pressure range.
Drive the car and now the system is under load and the TB is opened up a little allowing more air through the motor... spinning the turbo faster and faster as more air is allowed in. Eventually the turbo manages to build enough speed to increase the air input to the motor to the point where it is essentially back to 1.0 bar on the dash. Now you are neutral with respect to the atmosphere.
Drop the pedal down and your TB is now wide open. the turbo is now allowed to spool out of control if not for the WG and the WGFV. As the turbo spins into it's highest efficiency zones the boost ramps up quickly. On a stock motor you should see 1.4 bar indicating that you are running at the maximum stock boost level of 0.4 bar of boost (about 6 psi). With a basic chip you will see 1.8 on the dash and that equates to 0.8 bar of actual boost or 12 psi. Run up to 1.99 bar and you are basically stuffing air in as if you were running the motor under another atmosphere of air pressure.
When the WGFV does not assist the WG spring you will only see about 1.2 bar in stock configuration. This is because the stock spring is very weak and the ECU uses carefully modulated boost pressure to assist the spring and accuratly release unwanted exhaust gasses and thus limiting the spin of the turbo.
Better? HTH.
The last 2 scentences should be in a separate paragraph.
Breakdown of how bost 'adds up' so to speak...
1 bar = 14.7 psi = 1 atmosphere of pressure at sea level
Using absolute pressure means that you measure using 1 atmosphere at sea level as the datum from which your measurements are taken. If you think about this you kind of have to do it this way.
So... your dash gauge reads 1.0 when you turn the ignition to the 'ON' position prior to starting the car. Why? Because it is measuring the atmospheric pressure only because the motor isn't running. Sometimes you will see 0.9 because one decimal place of accuracy sucks.
Start the car and it starts pumping air out the exhaust and a vac is created. Rev the engine and when the throttle plate slams shut you make a vac spike into the negative pressure range.
Drive the car and now the system is under load and the TB is opened up a little allowing more air through the motor... spinning the turbo faster and faster as more air is allowed in. Eventually the turbo manages to build enough speed to increase the air input to the motor to the point where it is essentially back to 1.0 bar on the dash. Now you are neutral with respect to the atmosphere.
Drop the pedal down and your TB is now wide open. the turbo is now allowed to spool out of control if not for the WG and the WGFV. As the turbo spins into it's highest efficiency zones the boost ramps up quickly. On a stock motor you should see 1.4 bar indicating that you are running at the maximum stock boost level of 0.4 bar of boost (about 6 psi). With a basic chip you will see 1.8 on the dash and that equates to 0.8 bar of actual boost or 12 psi. Run up to 1.99 bar and you are basically stuffing air in as if you were running the motor under another atmosphere of air pressure.
When the WGFV does not assist the WG spring you will only see about 1.2 bar in stock configuration. This is because the stock spring is very weak and the ECU uses carefully modulated boost pressure to assist the spring and accuratly release unwanted exhaust gasses and thus limiting the spin of the turbo.
Better? HTH.
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