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Old 08-02-2008, 10:28 AM   #11
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Quote:
Originally Posted by Jay2TheRescue View Post
Neutral coasting to the light is better than race to the light and slam on the brakes, but wouldn't DFCO be better if your vehicle is capable?
Most of the time, yes, in my experience. If you could neutral coast to the light and not have to brake at all then it would be better than DFCO, but that requires you to be really good at predicting when the light will turn.
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Old 08-02-2008, 06:49 PM   #12
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Originally Posted by collegekid01 View Post
lol and it's like a strange safety measure too because it's a pain to do while your on the phone, I end up cutting my driving calls short cuz of it
your talking on the phone while you are driving??
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Originally Posted by Project84 View Post
In my saturn, at a red light IN GEAR the gallons per hour is reading .45

when I slip it into neutral that drops to .32

So basically, in gear at a red light, I could sit there 2 hours and burn one gallon of fuel.

In neutral it would take 3 hours.
so if one spends an hour total a week(10min a day on weekdays plus 5min a day on weekends) idling at traffic lights, assuming $4/gal, thats almost$2 in gas if you have it in gear and $1.33 if its in neutral, a savings of less than $.70.

keep in mind your average traffic light is between 1 and 3 minutes and since one often doesnt spend the full time at the traffic light, for my calculation i did 1 minute per light.

now a lot does depend on ones commute, but if one fills up once a month and drives in traffic like i do, thats $2.80 in savings for each fillup, which is .7 gallons. i know i drive a manual, but hypothetically if i were to have an auto and it would behave like your saturn and all else was equal and i left it in gear, i would be getting approximately 2 less mpg, assuming i fill up at 300miles and currently average 30mpg making the fill up 10gallons. wow that is one massive run on sentence that i dont feel like fixing.

going from 30 to 28mpg would suck!
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...but that requires you to be really good at predicting when the light will turn.
if there is not a left hand turning lane for opposing traffic, then it is 3 seconds after when the traffic light before yours turns from yellow to red. of course you have to know the intersection, but if you do screw up and put the car in gear, bfd, you still havent gone anywhere because your foot could still be on the brake.
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Old 08-02-2008, 06:52 PM   #13
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Old 08-03-2008, 04:55 AM   #14
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Originally Posted by thisisntjared View Post
if there is not a left hand turning lane for opposing traffic, then it is 3 seconds after when the traffic light before yours turns from yellow to red. of course you have to know the intersection, but if you do screw up and put the car in gear, bfd, you still havent gone anywhere because your foot could still be on the brake.
I was talking about approaching stale red lights in neutral or in gear so you won't have to stop at all; and the issue is that you can't see the other lights.
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Old 08-03-2008, 08:10 AM   #15
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FWIW it might depend on the vehicle/tranny. I tried it with my jeep and get the exact same GPH reading on the scangague wheather I am in N or D at the stoplight. No difference.

So, my driving boils down to ......If I want fun, I drive the jeep. If I want gas mileage, I drive the car.

The thing is, when I "turn on" the jeep, it returns the favor.......the car - not so much.

Just my experience.
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Old 08-03-2008, 02:33 PM   #16
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Originally Posted by theholycow View Post
I was talking about approaching stale red lights in neutral or in gear so you won't have to stop at all; and the issue is that you can't see the other lights.
oh right! haha my bad for taking it out of context
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Old 08-03-2008, 06:39 PM   #17
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Depending on the car, you may be able to adjust the idle off spec. I have a vw fox and I've unplugged the idle boost valve so it won't try to keep the idle at 900rpm. Then I've adjusted the idle speed screw and air fuel mixture screw. Now my idle is around 500-800. It's not consistent though which is strange since I don't have the boost valve anymore.

That said, not all cars can maintain a low idle without being incredibly lumpy or stalling out. A problem I also have with my car is that if the idle is set low, initial throttle response is absolutely poor, and it hesitates for a second before revving up. There's an ecu piggyback for my car that addresses this, and I'll probably get that, although it's completely irrelevant to your case. (Sorry to post junk!)

Perhaps if you were able to lower the idle lots, it'd help a bit more, although again the differences would still be slight and you probably wouldn't see more than 0.1mpg if that. Unless of course you're driving in bumper to bumper nyc traffic
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Old 08-04-2008, 09:31 AM   #18
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My odyssey V6 reads 0.5 gph idling in Drive, and 0.45 gph in Neutral. Small but repeatable improvement.
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