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Old 03-20-2013, 10:21 PM   #14 (permalink)
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Join Date: May 2011
Location: Indiana
Posts: 1,194

White Whale - '07 Dodge Ram 2500 ST Quad Cab 2wd, short bed
Team Cummins
90 day: 37.68 mpg (US)
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Originally Posted by DieselX View Post
Hey Dave, on my diesel fords when you coast the pcm cuts fuel to the injectors. Do you see a big gain from cutting off the engine? My excursion is auto but my f250 is a 6sp. So I could try it on that.

I just wondered if the Dodge's cut fuel on coasting. You are obviously doing something right haha.
It depends on what you mean by "coasting."

There's basically 3 options (in order of best fuel economy):
A) Coasting in neutral with engine off
B) Coasting in neutral with engine on (idling)
C) Coasting in gear with engine on

I do A. Virtually all computers will turn off fueling for C, but not B. One might be temped to think that C is better for fuel economy than B because C uses no fuel. The issue is that C robs energy from the vehicle because the wheels are being forced to motor the engine, overcoming all the friction and pumping losses at an engine speed significantly over idle speed. That's why it's also called "engine braking". Option B does use some fuel, but only enough to overcome pumping & friction at idle speed--and it doesn't brake the vehicle.
Diesel Dave

My version of energy storage is called "momentum".
My version of regenerative braking is called "bump starting".

1 Year Avg (Every Mile Traveled) = 47.8 mpg

BEST TANK: 2,009.6 mi on 35 gal (57.42 mpg):

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