2TonJellyBean |
10-04-2007 08:23 AM |
Okay, so what I am finding is the DFCO is often mapped as a straight line curve to the engine temperature. An example would be 2000 rpm cold and 1100 rpm when the engine is at operating temp.
If it's 1100 rpm for my vehicle and I'm at 45 mph (1400 rpm) coasting to a light, that basically explains why I'm aware of an "after shift" effect as well as the initial quick deceleration.
I get the initial drag from DFCO and then at maybe 1100 rpm DFCO is disabled and then the vehicle coasts a bit better until 1000 rpm when it does the auto downshift. This puts the revs back around 1400 rpm and then there is engine braking again down to perhaps 1100 rpm.
No wonder I like neutral coasting, it's smoother and easier to predict.
Anyway, based on what I'm describing, I'd say that effectively, the DFCO is probably active about half the time if I just let off the gas from 45 MPH. This thing uses very little fuel at idle... 1/3 gallon.
I guess the key question is, if I know of a stop way down the road, I can either stay in gear and wait a bit longer to coast and then cycle through DFCO phases as it goes down through the gears saving perhaps about half the idling gas or I can lift from cruising speed sooner and idle all the way.
I'd love to see a micro fuel measurements of a few different cars and what the net consumption is for the two techniques.
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