DRIVING in NEUTRAL: Gas
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Originally Posted by ObD' post='595859' date='Jun 4 2008, 10:22 PM
Coasting downhill is dangerous. Much better to use engine braking in gear for more control.
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From: Dallas, TX
[quote name='ukamath' date='Jun 5 2008, 08:34 AM' post='596091']
In most fuel injected cars fuel injectors are turned off when coasting in gear (at least for a manual tranny). I know this for a fact because you can see this with a scan tool. So you would use more fuel in neutral than if you were in gear, when coasting to a stop or on the hwy.
In a car with a carborator this is different story.
[/q
I'd absolutely agree if you're staying in gear for the engine braking effect - might as well shut off the fuel supply and save your brake pads. But if you're just coasting, it may be more efficient to disengage the clutch (assuming manual tranny). It would depend on which costs more (in fuel terms): >the fuel used by the idling engine while coasting in neutral, or > the car's momentum lost due to engine braking while coating in gear.
Either way, probably not worth the trouble, given the potential safety issue.
In most fuel injected cars fuel injectors are turned off when coasting in gear (at least for a manual tranny). I know this for a fact because you can see this with a scan tool. So you would use more fuel in neutral than if you were in gear, when coasting to a stop or on the hwy.
In a car with a carborator this is different story.
[/q
I'd absolutely agree if you're staying in gear for the engine braking effect - might as well shut off the fuel supply and save your brake pads. But if you're just coasting, it may be more efficient to disengage the clutch (assuming manual tranny). It would depend on which costs more (in fuel terms): >the fuel used by the idling engine while coasting in neutral, or > the car's momentum lost due to engine braking while coating in gear.
Either way, probably not worth the trouble, given the potential safety issue.
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From: northamptonshire, UK
modern cars switch off the fuel supply when coasting so you actually use no fuel as opposed to the small amount required to maintain idle.
About 20 years ago i nearly had a major accident coasting into a service station on a motorway/freeway. I left the motorway onto the slip road, put the car in neutral and entered the turn for the parking area at about 70-80 miles an hour. I hadnt realised that the engine had stalled. When I went to brake, there werent any, as the vacuum assist (this is before electronic abs) wasnt working - you really had to push hard and the car slowed very little. Then when i went to steer the wheel was virtually locked as there was no power assist. (Think tho that an E60 has electric steering assist).
So, on an E60 the above might not be a problem, but its still not a good idea and will actually cost you a thimble full of fuel. Which is likely (not!) to be significant if you are driving a 550i or similar
About 20 years ago i nearly had a major accident coasting into a service station on a motorway/freeway. I left the motorway onto the slip road, put the car in neutral and entered the turn for the parking area at about 70-80 miles an hour. I hadnt realised that the engine had stalled. When I went to brake, there werent any, as the vacuum assist (this is before electronic abs) wasnt working - you really had to push hard and the car slowed very little. Then when i went to steer the wheel was virtually locked as there was no power assist. (Think tho that an E60 has electric steering assist).
So, on an E60 the above might not be a problem, but its still not a good idea and will actually cost you a thimble full of fuel. Which is likely (not!) to be significant if you are driving a 550i or similar
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I've driven plenty of stick-shifts and I coast in them all the time.
As for safety, its better to coast idling in neutral than to risk stalling out in gear - which would really leave you "dead in the water". Besides, its cheaper to replace worn brake pads than to repair a damaged transmission.
However - I wouldn't recommend doing this procedure with an auto tranny, especially with an electronic shifter. These type of trannies are already less fuel efficient to begin with and there are many complicated parts that could wear out.
As for safety, its better to coast idling in neutral than to risk stalling out in gear - which would really leave you "dead in the water". Besides, its cheaper to replace worn brake pads than to repair a damaged transmission.
However - I wouldn't recommend doing this procedure with an auto tranny, especially with an electronic shifter. These type of trannies are already less fuel efficient to begin with and there are many complicated parts that could wear out.
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