Kill Switch: 2007.5 Dodge Ram 2500 Diesel

[Fat Charlie]

Excellent work. With real data, I'm looking forward to seeing your next best tank. And the one after that...

[Diesel_Dave]

Originally Posted by Fat Charlie

Excellent work. With real data, I'm looking forward to seeing your next best tank. And the one after that...

Me too! If I assume I was off my the same amount last summer when I pulled my best tank ever of 47 mpg, adding 8.5% is 51 mpg. And since then I've made a few more mods.

I can't wait for it to warm up! That record tank was with an average temp of 78 deg F. My last was at 29 deg F.

[DieselX]

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.

[Diesel_Dave]

Originally Posted by DieselX

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.

[DieselX]

I guess my question is if there is an advantage to engine off coasting vs. engine on coasting if the pcm cuts fuel when you coast. In nuetral of course.

[Diesel_Dave]

Originally Posted by DieselX

I guess my question is if there is an advantage to engine off coasting vs. engine on coasting if the pcm cuts fuel when you coast. In nuetral of course.

The computer can't cut fueling if you're coasting engine-on in neutral because there'd be nothing to keep the engine turning.

[DieselX]

Got you.. Been driving my automatic but thinking of my 6 speed haha.

[mechman600]

Diesel_Dave, your mileage astounds me. Imagine what you could do with something smaller like a VW TDI!