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From a given speed, 0gph (in gear, no gas) will give you 0.0x miles of travel before you come to a stop. From that same speed, the 0.44gph will allow you to travel 0.0y miles (y>x) before coming to a stop. The difference in distance (miles) and the fuel used in neutral (gallons) will give you a miles per gallon rating that just isn't calculated in a scanguage.
I'd suggest that the braking will exert a much larger effective use of fuel than the idling in neutral.
+1 I believe coasting in N will allow you to maintain your momentum that will outweigh the coasting in gear where engine compression slows your momentum. And gas used while coasting in N is probably made up in increased rollout.
In my experience, if I'm driving at 60 mph and let off the gas and keep it in gear, give SG a moment or two to "catch up" until it gives a fairly consistent reading (the pattern of readouts is decreasing), and then I shift into N, wait for it to "catch up", the MPG reading always goes higher. Is this not valid?
Just reviewed the thread and a question popped into my head. I admit first, I'm no gearhead.
When coasting in neutral with the air conditioner on ... when/if fuel is cut to zero ... how does the A/C continue to operate, apparently with no decrease in cooling? If I shut the motor off with the A/C on (key in acc position) the cooling cuts almost immediately.
if you are coasting in N.. then the engine must power the A/C and electrical equipment... NO FUEL CUTOFF
Coasting in D.. the energy from the wheels turns the engine... fuel can be cut off, but the engine still turns, providing A/C and electrical power..
the question .... what is better...
Switch to N.. you can coast a very long distance.. but use a TINY bit of fuel running the engine....
Stay in D.. you slow down much faster, buy you MIGHT recover some energy from the cars kinetic energy to turn the engine and save a TINY bit of fuel...
Take your pick :-)
Quote:
Originally Posted by NCC1701
Just reviewed the thread and a question popped into my head. I admit first, I'm no gearhead.
When coasting in neutral with the air conditioner on ... when/if fuel is cut to zero ... how does the A/C continue to operate, apparently with no decrease in cooling? If I shut the motor off with the A/C on (key in acc position) the cooling cuts almost immediately.
Last edited by tvengineer; 07-30-2009 at 06:21 PM..
+1 I believe coasting in N will allow you to maintain your momentum that will outweigh the coasting in gear where engine compression slows your momentum. And gas used while coasting in N is probably made up in increased rollout.
I guess we need to clarify "coasting"! Level ground or downhill? Being from hill country , I was thinking coasting downhill. I coast down a 1.5 mile hill every morning in gear to save fuel. I also coast in gear on level ground to stop signs/lights and intersections, but I never really have an opportunity to coast for any distance due to curves, traffic, etc. I could see that coasting in N for a long distance in the right, safe environment might be advantageous from an efficiency standpoint.
Coasting in D.. the energy from the wheels turns the engine... fuel can be cut off, but the engine still turns, providing A/C and electrical power..
Actually, I misspoke (typed) I meant to say coasting in gear when I said coasting in neutral, as I understood that when coasting in gear the fuel is cut.
That's what I was unclear about. So, momentum or kinetic energy is powering the A/C when coasting in gear. And, gasoline is when coasting in neutral.
I guess we need to clarify "coasting"! Level ground or downhill? Being from hill country , I was thinking coasting downhill. I coast down a 1.5 mile hill every morning in gear to save fuel.
Long ago, in a previous lifetime, I lived in Colorado. There's a stretch of (as I recall) 14 miles where I'd coast, engine OFF, between Cripple Creek and Colorado Springs. That was in a 1969 Ford Custom. No question in my mind I was getting back some of the money I'd spent going the other direction.
I would think that IF the fuel is cut off when coasting in gear, then this would be the most efficient instead of coasting in N and then braking a lot. OTH, coasting in N where you will not be coming to a stop at all, but will have to increase speed at some point, I think, would be more efficient.
I have a DashDaq and I'll have to see what OBDII parameters it has that I can record, to find out if there is actually a fuel cutoff
, I was thinking coasting downhill. I coast down a 1.5 mile hill every morning in gear to save fuel. I also coast in gear on level ground to stop signs/lights and intersections, but I never really have an opportunity to coast for any distance due to curves, traffic, etc. I could see that coasting in N for a long distance in the right, safe environment might be advantageous from an efficiency standpoint.
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