air mass

leoncupra

Active member
Joined
Apr 20, 2007
Location
AUSTRIA
TDI
leon cupra 150hp
according to ross tech measuring blocks - general engine data, there are vehicle with air mass sensor and vehicle with boost pressure.
But I am sure that also tdi ang gasoline turbos have air mass, or how would ECU then know the air mass?
 

Sebastian

Vendor
Joined
Aug 6, 2004
Location
Magdeburg, Germany
These are not boost pressure sensors, but these are intake manifold pressure sensors. Based on that and the temperature the ECU calculates the mass air flow.
 

leoncupra

Active member
Joined
Apr 20, 2007
Location
AUSTRIA
TDI
leon cupra 150hp
yes now I know that there are different methods to measure air mass, with hot vire sensor (electrical resistance measurment) and intake temp and once that calculate air flow, temp and pressure and thus calculating density and mass.
 

GoFaster

Moderator at Large
Joined
Jun 16, 1999
Location
Brampton, Ontario, Canada
TDI
2006 Jetta TDI
Most vehicles nowadays, including TDI, measure BOTH the air mass flow rate and the temperature/pressure of the intake air. In the case of the TDI, the information is not redundant, because the difference between the two is the amount of EGR (exhaust gas recirculation) that is being used, since the EGR quantity cannot be directly measured.
 

leoncupra

Active member
Joined
Apr 20, 2007
Location
AUSTRIA
TDI
leon cupra 150hp
GoFaster said:
Most vehicles nowadays, including TDI, measure BOTH the air mass flow rate and the temperature/pressure of the intake air. In the case of the TDI, the information is not redundant, because the difference between the two is the amount of EGR (exhaust gas recirculation) that is being used, since the EGR quantity cannot be directly measured.
air mass sensor consist of temp sensor and hot wire that change its electrical resistance with temp. So for ECU to calculate air mass flow it needs temp data and wire resistance data. But yes engines have also pressure sensor, because TDIs have turbo and have to monitor boost pressue.

EGR valve is controled on the base of O2 readings.
EGR in diesel is because diesel engines have no throttle valve and thus operate on too "lean" mixture. With some exhaust gas recirculation (up to 60%) the engine lowers NOx emissions.
 
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