daytonaer wrote:
andrave wrote:
Rusty_Rabbit84 wrote:
i put mine in neutral and coast down hills... does that count?
According to hypermiling articles I have read, many modern cars (especially those with e throttle) shut off injectors when coasting downhill, essentially shooting mpg through the roof... while in neutral, the ECU switches to its idle program, which obviously cycles the injectors. So in vehicles like this, coasting in neutral actually hurts mileage compared to leaving it in gear. Something to think about (and one of the reasons some all too hyper hypermilers just shut off their cars entirely).
From what I have seen while modifying code for pre-obdII computers (that's new right??) the "fuel cut on decel" doesn't happen below 3000 rpm.
If I'm spinning higher than 3000 rpm, the engine friction/compression is going to slow me down. I have actually noticed real time mpg improvements idling (Neutral) down hills that would normally see less than 2k rpm if left in gear. My theory is fuel is injected at decel at "lower" rpm's to keep stuff from getting too hot and spewing NOX's. Less pollution at idle than decel also gives me worse mpg at decel than neutral.
My PR MPG is 48mpg. I thought I had a blown head gasket. The car would over heat instantly on any incline or any hint of acceleration. Being 400+ miles beyond AAA's first free 100, I babied it home. I could not believe it when I calculated the mileage next fill up.
My friend put it best when he summed up my "cheapness" (not really enviro green motivated). Driving home 55mph with the cruise on he told me he would be willing to pay me an extra $5 for gas to get there 5 minutes quicker. I would GLADLY pay $20 extra for gas to avoid that terrible trip blasting the heater on a 90^ day, feathering the throttle and riding the shoulder even though it netted my best recorded mileage.
So holy crap. Again, I've been using the "coast in neutral every chance you get" method and getting 32-33 MPG.
On the last tank, I didn't use this technique at all, but did sort of do the "pulse & glide" thing downhill. i.e., cruising at 70mph, when I crest a hill, gently bump it up to 75, let it drop to 65, repeat as neccesary downhill, but never putting the car in neutral, or shutting it off.
I got a record tank of 33.7 mpg when I filled up this morning (woohoo!) This was without paying as much attention to creeping up on/avoiding red lights, etc.
As an added bonus, the car has mysteriously begun stalling once it's warmed up if the revs dip down around 1,000 rpm. I was planning on chasing this problem down this weekend, but I'm thinkng I might just let it fly for a tank, and let the car shut down while approaching lights, then bump start to get'er rolling again. I'd really like to hit 35 mpg.
