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From: liu on 11 Jun 2010 19:43 I'm trying some tips mentioned by these hyper-milers. One of them is to turn off the engine while approaching the intersection with traffic light on red. Sometimes due to the distance, I lost the power to brake. So I tried using the 2nd gear to slow down the car. (Note: I only do this with enough distance between cars, or I would rather turning the engine back on.) A few times I found the power gets back up again. Initially, I was wondering if I did turn off the engine and then realized that this is the same as push-jump start a car. So how does it work? Why would the engine start up again without involving the starter? Thanks,
From: Hachiroku ハチロク on 11 Jun 2010 21:57 On Fri, 11 Jun 2010 16:43:01 -0700, liu wrote: > I'm trying some tips mentioned by these hyper-milers. One of them is to > turn off the engine while approaching the intersection with traffic light > on red. Sometimes due to the distance, I lost the power to brake. So I > tried using the 2nd gear to slow down the car. (Note: I only do this with > enough distance between cars, or I would rather turning the engine back > on.) A few times I found the power gets back up again. Initially, I was > wondering if I did turn off the engine and then realized that this is the > same as push-jump start a car. > > So how does it work? Why would the engine start up again without involving > the starter? > > Thanks, Because you're spinning the engine with the clutch instead of the starter motor. I'm finding myself asking, "Is this a trick question?" All the starter does is spin the crankshaft via the flywheel to build compression in the cylinders and getting the fuel to ignite. You're using the transmission instead of the starter motor. I am going to refrain from calling this dumb, let's just say it's dangerous. For one thing, it puts a lot of wear on the clutch, and if you're managing to do this with an automatic, I think a call to AAMCO will soon be in order. For another thing, you've already found out you've lost some braking power. God forbid a kid jumps his bike off the curb while you're trying to save a few pennies on gas. Steering goes out, as well. making the thing handle like a loaded garbage scow. Leave the car on. It's dangerous, and, in most states, illegal. Hell, in most states it's illegal to put the trans in neutral and coast. I'm praying you don't kill somone, at least other than yourself.
From: Don Stauffer on 12 Jun 2010 09:51 liu wrote: > I'm trying some tips mentioned by these hyper-milers. One of them is > to turn off the engine while approaching the intersection with traffic > light on red. Sometimes due to the distance, I lost the power to > brake. So I tried using the 2nd gear to slow down the car. (Note: I > only do this with enough distance between cars, or I would rather > turning the engine back on.) A few times I found the power gets back > up again. Initially, I was wondering if I did turn off the engine and > then realized that this is the same as push-jump start a car. > > So how does it work? Why would the engine start up again without > involving the starter? > > Thanks, If the car is in gear you are not really coasting. You need to keep on the gas a longer distance before starting your deceleration, because the car will decelerate at a higher rate when you are turning the engine over. Therefore you are not saving as much gas as when you coast with engine out of gear. BTW, some of what hypermilers say works, other things do not work. Mixed bag- depends on who says it. Coasting out of gear does work, playing lights works even better (though playing and coasting are not mutually exclusive.
From: jim beam on 12 Jun 2010 10:18 On 06/12/2010 06:51 AM, Don Stauffer wrote: > liu wrote: >> I'm trying some tips mentioned by these hyper-milers. One of them is >> to turn off the engine while approaching the intersection with traffic >> light on red. Sometimes due to the distance, I lost the power to >> brake. So I tried using the 2nd gear to slow down the car. (Note: I >> only do this with enough distance between cars, or I would rather >> turning the engine back on.) A few times I found the power gets back >> up again. Initially, I was wondering if I did turn off the engine and >> then realized that this is the same as push-jump start a car. >> >> So how does it work? Why would the engine start up again without >> involving the starter? >> >> Thanks, > > If the car is in gear you are not really coasting. You need to keep on > the gas a longer distance before starting your deceleration, because the > car will decelerate at a higher rate when you are turning the engine > over. Therefore you are not saving as much gas as when you coast with > engine out of gear. > > BTW, some of what hypermilers say works, other things do not work. Mixed > bag- depends on who says it. Coasting out of gear does work, playing > lights works even better (though playing and coasting are not mutually > exclusive. "coasting" in gear saves gas because the engine computer will cut off fuel delivery. coasting in neutral will not - the computer needs to inject to keep the engine rotating, something provided by the drive train if in gear. -- nomina rutrum rutrum
From: liu on 13 Jun 2010 11:09 > > Because you're spinning the engine with the clutch instead of the starter > motor. > > All the starter does is spin the crankshaft via the flywheel to build > compression in the cylinders and getting the fuel to ignite. You're using > the transmission instead of the starter motor. > Thanks for the response. That's the answer I'm looking for. > For another thing, you've already found out you've lost some braking > power. God forbid a kid jumps his bike off the curb while you're trying to > save a few pennies on gas. Steering goes out, as well. making the thing > handle like a loaded garbage scow. > > Leave the car on. It's dangerous, and, in most states, illegal. Hell, in > most states it's illegal to put the trans in neutral and coast. > > I'm praying you don't kill somone, at least other than yourself. Yes, it can be dangerous. I won't tell anyone I know to do that. I did that a couple of times when no car in front of me. BTW, I found the brake is fully functioning within 10 to 20 seconds after turning off the engine.
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