Here is my dumb physics question:
I'm thinking about fuel consumption for the Transit. For some very odd reason, its hard to find track day fuel economy figures of such a car...
Anyway, my plan was this - tell me if this sounds logical or not;
I used the lap simulator 'OptimumG', plugged in the Transits values including mass, drag, torque curve, gearing etc. Using this info it simulates a run around whatever circuit you want, in this case I chose Barcelona as its my default (I believe this runs with no elevation, hoping it won't affect the results too wildly).
Using those values it calculates how much energy was needed to complete a lap, whichin turn will be used tell you the fuel consumed using the fuel energy density (diesel) and the engine thermal efficiency.
This is obviously one area where I had to guess - what is the thermal efficiency of a Transit diesel engine? I went for 40%, based on what I've read about relatively modern diesels (feel free to offer better guesses!).
I thought this was a great idea and would provide the best guess at the sort of fuel consumption I should expect in AC with the Transit.
However, the suggested fuel consumption from the Optimum Lap software is much lower than I expected for a heavy van going flat out for a whole lap (which btw was tweaked using the tyre friction values to give similar laptimes as I get in AC). Is this simply down to being too optimistic with the thermal efficiency, or is this just not a reliable way of working out fuel consumption in the first place?
The value this gives me for Barcelona is 0.67kg/lap, which using Kunos' diesel mass/litre (0.832kg/litre) is around 0.8 litres/lap.
To me this seems too little, but the process seems logical to me - is it? That'd mean it could do 100 laps on a single tank, or 17.2l/100km (13.7 US MPG, or 16.4 UK MPG) flat out.
Though when I quantify it like that in MPG it doesn't sounds quite as absurd as I first thought - maybe this is somewhere in the ballpark. So if anyone has any thoughts on this or suggestions on how it may be accurate/inaccurate or could be improved, let me know!