coasting
07-21-2009, 11:07 AM
#1
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Join Date: 12-20-2008
Location: durham north carolina
Posts: 835
coasting
i don't do it much , but i occasionally put the trans in neutral and coast down some hills....it does make a difference because even though i not giving it any gas , it revs more rpms when in gear...i'm sure the computer must be sending some gas......today i made what i thought was a really big and stupid move , i put it in reverse instead of neutral 
......i guess the hrr has a switch that kills the engine , for idiots like me 
.....i pulled over and stopped expecting to find that i had damaged somthing....nope , as far as i can tell , nothing....all i can say is thanks to gm.
......i guess the hrr has a switch that kills the engine , for idiots like me .....i pulled over and stopped expecting to find that i had damaged somthing....nope , as far as i can tell , nothing....all i can say is thanks to gm.
07-21-2009, 11:29 AM
#2
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Join Date: 06-19-2008
Location: Indiana
Posts: 1,454
good to know that is built in, ha.
i coast down a big hill on my way to work every single day, unless i am behind some slow person and i gotta ride the brakes. The hill is large and about a mile long, and as soon as i pop it into N, the instamatic mpg shoots up and i ride at 99 the whole way down. I sometimes forget when i get to the bottom though, and go to turn the corner and hit the gas and all i do is rev it...
i coast down a big hill on my way to work every single day, unless i am behind some slow person and i gotta ride the brakes. The hill is large and about a mile long, and as soon as i pop it into N, the instamatic mpg shoots up and i ride at 99 the whole way down. I sometimes forget when i get to the bottom though, and go to turn the corner and hit the gas and all i do is rev it...
07-21-2009, 08:03 PM
#4
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Join Date: 06-19-2008
Location: Indiana
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yeah i can see that. In my town it kills the mileage anyways. However the same hill in my last post, i can coast down it getting 80+ mpg, and when i go up it home each day i get between 18-24, usually around 22-23, not bad at all.
07-22-2009, 07:30 AM
#5
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Join Date: 10-02-2005
Location: VA
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Guys, there's a feature built into the ECM calibration called DFCO (Decelleration Fuel Cut Off). Under many conditions when off throttle, the fuel will be cut off to the injectors completely (= NO fuel).
If you just put into neutral, basically you're in an "idle" condition, where there is some (not much, though) fuel being injected.
IOW, it won't make a big difference, but you're more likely to save gas by just leaving it in gear.
If you just put into neutral, basically you're in an "idle" condition, where there is some (not much, though) fuel being injected.
IOW, it won't make a big difference, but you're more likely to save gas by just leaving it in gear.
07-22-2009, 09:58 AM
#6
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Join Date: 12-20-2008
Location: durham north carolina
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better?
Guys, there's a feature built into the ECM calibration called DFCO (Decelleration Fuel Cut Off). Under many conditions when off throttle, the fuel will be cut off to the injectors completely (= NO fuel).
If you just put into neutral, basically you're in an "idle" condition, where there is some (not much, though) fuel being injected.
IOW, it won't make a big difference, but you're more likely to save gas by just leaving it in gear.
If you just put into neutral, basically you're in an "idle" condition, where there is some (not much, though) fuel being injected.
IOW, it won't make a big difference, but you're more likely to save gas by just leaving it in gear.
07-22-2009, 11:19 AM
#7
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Join Date: 08-18-2006
Location: Hatboro, PA
Posts: 1,036
Catdaddy,
Is that on an auto trans?
Just an FYI if an auto trans ... When putting it in neutral, you only need to bump the shifter - not squeeze the trigger. It shouldn't go past neutral this way. You can just bump it back and forth between drive and neutral this way.
Joe,
Is that on the Auto or Manual? I would think that something like that would be on the manual trans. With a manual trans there is a mechanical connection between the engine and trans. If you didn't have fuel going to the engine in an auto trans, wouldn't the engine just stop? (I may be wrong on this... there may be enough residual friction to keep the engine turning at speed?)
Is that on an auto trans?
Just an FYI if an auto trans ... When putting it in neutral, you only need to bump the shifter - not squeeze the trigger. It shouldn't go past neutral this way. You can just bump it back and forth between drive and neutral this way.
Joe,
Is that on the Auto or Manual? I would think that something like that would be on the manual trans. With a manual trans there is a mechanical connection between the engine and trans. If you didn't have fuel going to the engine in an auto trans, wouldn't the engine just stop? (I may be wrong on this... there may be enough residual friction to keep the engine turning at speed?)
07-22-2009, 11:35 AM
#8
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Join Date: 12-20-2008
Location: durham north carolina
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[QUOTE=GCarp;399180]Catdaddy,
Is that on an auto trans?
yep , auto...thanks for that....so , what about the 2 other gears ? will go down past D without the lever thingy?....is this info in my owners manual ?...i've heard of a few having issues with the auto shifter , so i've always tryed to be gentle but firm with mine....i really can't believe i put it in R , but i did.
...i get a little tired/stressed on my 275 mile a day route.
Is that on an auto trans?
yep , auto...thanks for that....so , what about the 2 other gears ? will go down past D without the lever thingy?....is this info in my owners manual ?...i've heard of a few having issues with the auto shifter , so i've always tryed to be gentle but firm with mine....i really can't believe i put it in R , but i did.
...i get a little tired/stressed on my 275 mile a day route.
07-22-2009, 11:57 AM
#9
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Join Date: 06-19-2008
Location: Indiana
Posts: 1,454
mine is an auto as well, i never touch the button in, just a slight nudge between N and D. I've never tried to nudge past D since i've never really used the other 2 and would want to know what the I is for more before i did it.
in D i definitely think there is a mechanical drag. As soon as i switch over the mpg shoots up. Even if it didn't though, with Less resistance I can roll a lot farther. I have to watch the speed on mine since it is technically 25 or 35 (who knows...)
in D i definitely think there is a mechanical drag. As soon as i switch over the mpg shoots up. Even if it didn't though, with Less resistance I can roll a lot farther. I have to watch the speed on mine since it is technically 25 or 35 (who knows...)
07-22-2009, 12:10 PM
#10
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Join Date: 02-14-2007
Location: Luskville, QC, Canada
Posts: 380
I've had my scanguage show no fuel to engine (0 l/100k) in I gear on a long downhill last week. So fuel cutoff is for real; this was on my automatic. It's done it another time in D while I was coasting behind slow traffic.
The engine keeps turning and it's not any different than normal behavior on deceleration; in fact I couldn't tell if I was not seeing the scanguage reading.
What's the harm? The engine is still getting lubrication, and it's the transmission that is turning the engine, but other than a bit of an extra load on the transmission, I don't see what could go wrong.
Yves
The engine keeps turning and it's not any different than normal behavior on deceleration; in fact I couldn't tell if I was not seeing the scanguage reading.
What's the harm? The engine is still getting lubrication, and it's the transmission that is turning the engine, but other than a bit of an extra load on the transmission, I don't see what could go wrong.
Yves
