Neutral at speed
01-27-2013, 07:19 PM
#1
Neutral at speed
In my ending quest to get the best mileage possible, I've dropped the tranny into neutral a few times going downhill and noticed that the engine RPMs are hovering around 1500, I would have thought it would drop to idle rpms.
Wondering if dropping in neutral actually aids in trying to improve mpg or just leave it in gear.
Wondering if dropping in neutral actually aids in trying to improve mpg or just leave it in gear.
01-27-2013, 07:33 PM
#2
Senior Member
If you leave it in gear and get all the way off the gas, the engine goes into DFCO mode (Deceleration Fuel Cut Off). Basically, it turns the injectors off completely as long as it knows the transmission will keep the engine above running speeds. Cars have been doing this for at least 20 years.
Putting it in neutral forces the computer to keep the engine running on its own, thereby using more fuel.
In Europe, some of the small cars actually kill the engine completely when coasting or at a dead stop. We rented a Mercedes B Class (not available in the US) with a standard transmission. It would kill the motor every time you put the stick in neutral and let off the clutch, and automatically restart it as soon as you push in the clutch to put it in gear. And yes, I tested it to see if I was faster than it could react and I wasn't.
As for the idle speed, it's like the rev limiter. It has different settings based on a myriad of inputs. Put your truck in neutral and floor it. You'll find that the rev limiter is much lower than it is in gear. Same thing with the idle speed.
To maximize mileage, concentrate on coasting as much as possible and it'll net some gains.
Putting it in neutral forces the computer to keep the engine running on its own, thereby using more fuel.
In Europe, some of the small cars actually kill the engine completely when coasting or at a dead stop. We rented a Mercedes B Class (not available in the US) with a standard transmission. It would kill the motor every time you put the stick in neutral and let off the clutch, and automatically restart it as soon as you push in the clutch to put it in gear. And yes, I tested it to see if I was faster than it could react and I wasn't.
As for the idle speed, it's like the rev limiter. It has different settings based on a myriad of inputs. Put your truck in neutral and floor it. You'll find that the rev limiter is much lower than it is in gear. Same thing with the idle speed.
To maximize mileage, concentrate on coasting as much as possible and it'll net some gains.
01-27-2013, 11:09 PM
#3
Senior Member
Is not the 3.5gdi engine in fact a lean burn engine, where at off throttle there is more air and less fuel involved when coasting?
I have been doing some searching on this topic. As with my torque app i have noticed the afr readings pretty high when off throttle coasting.
Someone with some knowledge chime in
I have been doing some searching on this topic. As with my torque app i have noticed the afr readings pretty high when off throttle coasting.
Someone with some knowledge chime in
01-27-2013, 11:13 PM
#4
Not necessarily, it depends on the situation. I put mine in neutral on downhills where it can maintain speed. If I leave it in gear, the engine drags the speed down and I have to stay in the throttle to maintain a safe speed.
01-27-2013, 11:50 PM
#5
Senior Member
Is not the 3.5gdi engine in fact a lean burn engine, where at off throttle there is more air and less fuel involved when coasting?
I have been doing some searching on this topic. As with my torque app i have noticed the afr readings pretty high when off throttle coasting.
Someone with some knowledge chime in
I have been doing some searching on this topic. As with my torque app i have noticed the afr readings pretty high when off throttle coasting.
Someone with some knowledge chime in
01-28-2013, 12:20 AM
#7
Inebriated 4 ur safety
Trending Topics
01-28-2013, 06:44 AM
#8
Senior Member
- Coasting in neutral: injectors on and burning fuel.
- Coasting in gear: injectors off and not burning fuel.
- Coasting in gear but applying some throttle: injectors on and burning fuel.
Simple as that.
01-28-2013, 08:37 AM
#9
Mark
iTrader: (1)
If you leave it in gear and get all the way off the gas, the engine goes into DFCO mode (Deceleration Fuel Cut Off). Basically, it turns the injectors off completely as long as it knows the transmission will keep the engine above running speeds. Cars have been doing this for at least 20 years.
Putting it in neutral forces the computer to keep the engine running on its own, thereby using more fuel.
In Europe, some of the small cars actually kill the engine completely when coasting or at a dead stop. We rented a Mercedes B Class (not available in the US) with a standard transmission. It would kill the motor every time you put the stick in neutral and let off the clutch, and automatically restart it as soon as you push in the clutch to put it in gear. And yes, I tested it to see if I was faster than it could react and I wasn't.
As for the idle speed, it's like the rev limiter. It has different settings based on a myriad of inputs. Put your truck in neutral and floor it. You'll find that the rev limiter is much lower than it is in gear. Same thing with the idle speed.
To maximize mileage, concentrate on coasting as much as possible and it'll net some gains.
Putting it in neutral forces the computer to keep the engine running on its own, thereby using more fuel.
In Europe, some of the small cars actually kill the engine completely when coasting or at a dead stop. We rented a Mercedes B Class (not available in the US) with a standard transmission. It would kill the motor every time you put the stick in neutral and let off the clutch, and automatically restart it as soon as you push in the clutch to put it in gear. And yes, I tested it to see if I was faster than it could react and I wasn't.
As for the idle speed, it's like the rev limiter. It has different settings based on a myriad of inputs. Put your truck in neutral and floor it. You'll find that the rev limiter is much lower than it is in gear. Same thing with the idle speed.
To maximize mileage, concentrate on coasting as much as possible and it'll net some gains.
no gas...no fire
