Re: Fuel economy - coasting vs decel (spoonie)
I read this earlier and had to do a test. I am the kind of person that will occasionally put the car in neutral going downhill (with the clutch disengaged of course). Been doing it with bugs since I was 17 (I would actually turn the engine off then... ahhh the old days). There is a huge hill on the 805 on my way to school (as it crosses the 8 if you are curious) that I "neutral".
Normally, I know where the "crest" of the hill is, where I can take the clutch out at 75 and not loose any speed. After about 100 meters, I start to gain speed, and if I am drafting other vehicles, I can hit 85 at the bottom. The entire section that I am able to coast is about 1km (0.6 mile). At the end of the coast, I am back at 75.
I decided to run a test today on my way to class. Instead, this time I let her coast in gear. The net effect is I was able to coast for only 100 meters. My speed never exceeded 75. So for the other 900 meters I would normally coast, I was applying some level of throttle. Not full throttle of course.
Simple back of the napkin calculation on that scenario works like this: is it better to use no fuel for 100 meters, or use idle mixture for 1000? Sounds like a simple win for the "neutral". But it is not so simple. What about the fuel expended getting the motor spun back up? That is not negligible, as anyone who has worked on a carbureted vehicle is familiar with (comparing volume of fuel delivered by the accelerator pump versus normal jets).
So, I am not sure anymore. I will try to run a test using VAG-COM on the same hill soon.
After finals.
