Hello
I’m probably on the edge of the forum territory 
My VW TDI had an injector failure on the highway (which caused the engine to self protect). After towing, the car restarted perfectly the day after :-D
The injector was replaced on the basis of the computer car diagnosis.
Now, I have higher fuel consumption (+1,5l/100km), but I also have a major leak on the fuel return line of the injector (the engine was completely drowned in gasoil).
My question is: do you know how the fuel consumption is calculated ?
Is it from the data sent from the injectors ?
Is it with a fuel flow meter as on our aircrafts ?
Do you think the leak on the return line can explain the excess in fuel flow ?
Bottom line: between DPF, EGR, high pressure fuel injection, fragile injector, leaking water pump… you’ll say I’m old fashioned, but I don’t fancy car engine on aircrafts
Is it with a fuel flow meter as on our aircrafts?
Continental CD155/135 and Austro Engines AE300/330 measure fuel consumption with FADEC data rather than with fuel flow meter. I guess similar mechanism is used in car diesel engines.
It isn’t a turbine flowmeter like the fuel totalisers we have. Everything in a car has to be dirt cheap. It is done indirectly e.g. if you have a piston pump topping off a carb or some other fuel reservoir, then the pump pulse rate gives you the fuel flow.
Typically it’s done on newer cars by calculation, not direct measurement, based on e.g. fuel injector pulse time, fuel pressure, engine rpm and vehicle speed. Instantaneous fuel consumption is then integrated and averaged. It’s not always that accurate given that some of the constants (individual injector flow characteristic, fuel pressure and tire radius) are not that constant between vehicles and it’s not individually tuned with a K-factor, as it can be for an aircraft. However, a change indicates something has changed in the car.
Thank you for your help and nice input.
@Emir
My bottom line was provocative :-)
Can you confirm if EGR and DPF are actually removed ? I think I remember you had a coolant leak at the beginning of your Da42 ownership. IIRC it was bad routing of the flex tube. Did anything like that happened again ?
As I’m struggling with the injector, it appears a significant value called « quantity deviation » which is the quantity of gas added or removed from the nominal value, calculated by the engine for each injector, in order to have a stable engine.
During maintenance, do you have such parameters available ? Are injectors to be replaced on timely basis considering the high pressure they work with ?
@Peter
The turbine / fuel flow meter is a good technology it seems.
Nothing stops you installing a Shadin totaliser on your VW
That’s an idea and will be unique
Will you help me determine the K-factor ? :-)
You need an accurate fill-up
However, to make it work properly you need to link it to a GPS so it can display the LFOB, so you need to install perhaps a KLN94, GNS430…
Can I do it under CS STAN or do I need EASA major mod approval ? 
