Air mass readings...

[rysmee]

would anyone know what a decent reading for an air mass meter is on a c270 (w203) CDi ? I'm getting about 400 g/s at idle then 600 when full throttle, either of which readings I think are suspect, and the car is suffering with a real bad lack of power. Although there is no boost pressure i think it may be being caused by the dodgy air mass....
any help appreciated ta

 

[Dieselman]

Is it meant to be g/s or g/m? If the reading is only 1.5 * as much at full revs as it is at idle then the MAF is duff.

Just use a voltmeter to meter Pin5 WRT Gnd. Expect ~2v at idle rising to 4.8V at full revs and boost.

 

[RaceDiagnostics]

In the VW-Audi-Group world (my world), maf figures for petrol cars are measured in grams per second for petrol and mg per stroke for diesel, are you sure about the units for your readings. Also were they taken at idle or when driving?

Assuming the values are actually mg/stroke, they would indicate that your are only seeing half a bar of boost thus pushing only 1.5 time as much air into the cylinders, what boost level are you reading. Dont forget that these figures need to be tested under load, not at idle.

 

[rysmee]

ok i need to double check the units then... was testing under load, but no boost pressure was being recorded at all ( may have risen to 1090 hpa - just over a bar, so in other words no additional boost). cheers guys