Re: Stupid "free energy" idea

Aww a little dipshit who can't venture outside the little webverse that he created! How unoriginal.

Watcha done with your discovered wisdom puppy?

Throw you in the kill file with the rest of the shit of course, corny rubbernecky.

*plonk*

Yeah, figured as much. Go back to your little webverse, you coward.

You're dismissed.

-Mike K.

On modern cars, its LESS than idling. They typically shut fuel flow OFF on deceleration until the engine speed drops down to idle speed. So going downhill (in gear) uses zero fuel. Going downhill in neutral requires the engine to idle, so that would in fact use MORE fuel than coasting in gear.

Depends on the car. An old carbureted car will burn the same amount, within a percent or two. A modern car will burn ZERO fuel if you keep it in gear, but will burn a constant small amount in neutral to keep the engine spinning.

For an old carbureted car, you're right. For everything built since, oh,

1990, you're wrong.

Sigh. Some hills are insufficient to overcome engine compression, especially at high speeds. Gravitic acceleration < drag deceleration

• engine compression deceleration.

JFC, do you guys even OWN cars?

Dude, please just shut the f*ck up. Go find a minor decline and drive down it in gear versus not. Find one where being in gear slows you down and being in neutral doesn't. This should not be hard to find at ALL.

Trav

Your stupidity doesn't QUIT, does it?

What if gravity is insufficient to overcome compression losses?

In THAT CASE, you are better off shifting to neutral and letting the engine consume at idle.

The engine speed will NOT DROP TO IDLE SPEED, you freakin moron, because the engine is DIRECTLY coupled to the driveline via either the clutch in a manual or the converter lockup (another clutch) in an automatic.

Try THIS.

Put your car in automanual mode. Put it in FIRST GEAR. Evaluate the decleration rate on a LEVEL road from any given speed versus first or second if you do NOT understand engine braking! You will find that RPMs typical of highway speeds in top gear involve actually fairly HIGH levels of engine braking.

You should immediately notice DECREASED compression braking when you put the car into 2nd versus 1st. This is WHY you downshift to slow down.

GD, I do this thing every fking day I drive the kids to school. I put the VW into 3rd on a particular decline and let it engine brake to max at

It will still have contributed something to keep the engine ticking over, thereby requiring the less use of fuel. Or was it a trick question? That was too easy. Another one! Try to make the next one an actual challenge.

How can it be directly coupled when in neutral?

Speed affects wind drag, not the effect of the hill. Here's $.05, go buy a clue.

Yep. Restored a few from the ground up over the years as a hobby. Got a couple of engineering degrees for my "day job," too.

You have an "end user" cursory understanding of how the machine works, not a clue as to what's going on inside the "black box." Classic 'I turn the key and it goes' mentality.

Yes, keeping the car in gear applies a certain amount of drag- specifically the amount of energy required to keep the engine rotating. Guess what? If you take it OUT of gear, SOMETHING still has to keep the engine rotating (in a conventional car, not a hybrid). That "something" is gasoline being burned to keep the engine idling. For modern cars (most of those made since around 1990) there are a number of built-in factors that make it more efficient to leave them in gear going downhill rather than snicking them into neutral:

1) The final drive ratios are very low (numerically) in high gear, so that the engine speed is quite low when coasting. 1a) On those cars equipped with automatic transmissions, the torque convertor reverse-coupling coefficient is low, so that the engine speed on deceleration is even lower, causing less parasitic drag on the car. 2) Idle-fuel-cut-off algorithms in the engine controller shut the fuel flow off COMPLETELY, so long as there is enough road speed to keep the engine turning above idle speed. Yes, there's still that slight drag, BUT if you eliminate that drag by fuelling the engine, its at best a break-even trade. Its MORE efficient to steal back a little kinetic energy to spin the engine while burning less fuel than it is to burn fuel idling the engine while coasting.

The car manufacturers have arrived at this system through thousands of hours of testing, and YOU are going to presume to tell THEM what is more efficient? I don't think so. Remember, they fight for every last bit of mileage to meet CAFE requirements. Saving a milligram of fuel per mile adds up fleet-wide.

Now, I humbly stand by for your next profanity-laced tirade of non-technical nonsense.

Name me ONE vehicle on the market which leaves the torque-convertor lockup clutch engaged upon deceleration.

What part of the principle of conservation of energy do you not understand? The energy required to keep the engine rotating HAS to come from somewhere. It can either come from a slight drag on the car, or from burning fuel directly. There's no magic savings which you presume exists.

Now if you switch to neutral and shut the engine OFF, you will save (a miniscule amount) of fuel, but its illegal in most areas to do so because you now have less control of the vehicle.

Watch this space:

Then it wouldn't be much of a hill and you wouldn't be coasting. The discusion was about coasting down hill.

If the transmission is in neutral it is NOT coupled to the driveline and WILL be at idle speed.

Correct. But as soon as you step on the accelerator the ECM turns the injectors on and fuel usage resumes. So you use more fuel COASTING IN GEAR with your foot off the accelerator.

And you miss the point once again ! The question was "what uses more fuel , coasting downhill in neutral or in gear". And the answer is coasting in gear uses NO FUEL as the injectors are SHUT OFF in that situation.

Now you're just being silly. What about molehills? You've not considered molehills. Please try to frame the discussion within a sensible context!

*Sound of pencil scratching on paper*

Now you're just complicating the issue.

Ah! I see you've met Trav, then.

You people are utterly hopeless.

Thank god the engineers who worked on the Prius weren't this stupid.

Again, you cannot read. I was addressing the mfer's contention about an engine dropping to idle speed while coasting.

Trav

You'll have to bear with us; we're still having difficulty figuring out the directions to Cloud Coockoo Land.

I read 'neutral.' What did you read?

Which happens. What are you confused about?

Apart from the mechanical linkage between the road wheels and the engine by virtue of the gearbox ;-)

Certainly this is the case with a manual gearbox and I'm fairly sure that in an automatic the engine speed may fall a bit but will not drop to idling speed.

Or are you being nit-picky and saying that for a manual gearbox it is possible for the car to remain in gear but for the engine to be disengaged if you press the clutch? I'd count that as a special case of being in neutral.

If the car slows enough, eventually the engine wi;; slow to idle.

Do automatics not rest at idle in gear, with no gas applied?

No, I wasn't going in that direction.

If you don't understand idle fuel cutoff during coast-in-gear conditions, then I can't help you. Its been explained on this thread AT LEAST twice. Would it help if someone at Delphi showed you the lines of software that control it?

Then you wouldn't be coasting, you would be decelerating ! You have asked this question two or three times now, what part of it doen't YOU understand ? The conversation was about fuel usage during coasting down hill. One must assume all the criteria are met to allow the car to coast down hill. Nobody is questioning the steepness of the hill, whether or not the car will coast, what gear the car is in, and which direction it is traveling. You keep coming up with so much bullshit that doesn't even pertain to the question being asked !

The question was: What uses more fuel, coasting down a hill in gear or coasting down a hill in neutral ?

The awnswer was (and still is) : Coasting in gear uses less fuel because the ECM is programmed to SHUT OFF THE FUEL INJECTORS in that situation. IF you are coasting IN NEUTRAL the FUEL INJECTORS ARE ON, suppling fuel to the engine. Now it should be EASY, even for you, to be able to figure out which one uses more fuel !

Now the irrelevant information you keep rattling on about is, well, irrelevant ! It doesn't matter how steep the hill is as long as the car is able to coast. It doesn't matter whether the car has an automatic transmission or a standard trans. It doesn't matter that one car is using Sunoco gas and the other is using Shell. DO you get it yet ????? It doesn't matter if the torque converter stays locked or is unlocked. It doesn't matter if they are travelling north or south, they just have to be travelling DOWN HILL. It's a simple question which also has a simple answer.