For me this thread isn't about saving gas per se, but rather knowing how your car works. The more you know about how you car works, the better driver you are and the more rewarding the experience is.

 

Look at it this way, 55 mph = about 2500 rpms. The car idles at 800 rpms, so you are using about 1/3 - 1/2 the fuel while you coast but you also loose momentum and getting back up to speed you have to depress the gas peddle more thus loosing what you thought you just gained. So you can drive like grandma and squeeze 1 or 2 mpg out of your sports car or you can have fun! Isn't that why you bought it anyway?

 

what does really goes in a combustion chamber is a mixture of fuel and air, and from that u can go on about ur exhaust tip and smell the mixture burns, what drives the car is when the gear engage in a position to force the wheels to drive.

my point is, the engine still consume gas when neutral, but not as much as when on gear, even if it's really minimal, but it still consumes.

 

^Preaching to the choir. Like I said, this thread for me isn't about saving gas. I work from home and share another car with the wife. The Z only gets driven occasionally so I tend to drive it like I stole it...If anything, probably too aggressive for the street at times. I usually avg 19-21 mpg and enjoy every minute of it.

 

I'm pretty sure the Z stops faster than a bus.

 

Not when the ECU shuts off the injectors, which is what happens when you lift.

bill

 

Correct. . . but not for long. Obviously the injectors start firing again as normal.
But I will agree as I have tested this. Your injectors do cease fire when you first let off the gas.

As far as the other comments on in gear and out of gear.
Its common sense that more mechanical strain on the engine is going to use more gas then none or little.

I dont understand the debate here.
We might as well compare our tire pressures and how that affects our gas milage as well as aerodynamic changes between the years.
At least make it interesting. lol

 

I think it makes a difference in my suv. I get right above cruising speed and let it go in neutral until i get to the next light/stopsign. It works for me

 

IT WASTES GAS

fuel is being used to keep the engine at idle position

when coasting in gear no gas is used to turn the engine just the momentum of the car.

 

so according to everyone one here that supports the no fuel while in gear theory, if you raise your car so the rear is off the ground, get it up to 4000 rpms, and then let off the gas pedal, no exhaust will be emitted from the car? This simply is now true. It won't be nearly as much as if you were pushing down on the pedal but there will still be some combustion and exhaust will come out of the car.

 

Yeah i really don't know why people argue about gas being used when car is in gear over coasting, the higher the revs, the more fuel being burnt, regardless of your foot being on the gas pedal. Same with down shifting to a stop your revs go up; you save on brake pads, but burn more gas due to higher revs, i don't know why everyone treats this like its the Y2K bug.

Coasting in neutral would save you the most gas, check your MPG gauge.

 

There are so many other things that we are exposed to in our lives that can save us more money and take less of a toll in our planet than the difference between coasting in neutral or staying in gear in a sports car. I can understand the fact that some of us still want to learn how is the best way or efficient way of driving the car for the sake of the engine but I cannot understand the underlying idea of saving a minimal amount of money from choosing between these two techniques.

If you are concerned about saving money I heard that you can save a bunch of money by switching your car insurance to GEICO,

 

Fun Fun!

Just one point I hadn't seen yet. With the car in gear and the engine breaking, you are wasting precious kinetic energy! When you get to the bottom of the hill you will not have as much speed and will not continue to coast as far as you would have if you did not have any engine breaking.

So while you are not using the gas to keep the engine idling, you will need to use more gas when you get to the bottom of the hill.

As far as the environment goes. Far far better than buying a hybrid? Living nearby your work. Someone commuting a mile in their sports car is going to consume a lot less energy than the Prius commuting across town.

--
Coz

 

If you do that, the wheels are no load the engine to keep it spinning, they aren't converting the inertia of the car while moving to spin the engine, so the engine must continue to operate on its own, hence the smoke. This isn't the same situation as going down a hill in gear where the momentum of the car spins the wheels keeping the engine rotating. Nice try

 

Thats assuming no speed limit, based on your idea, why not just accelerate down the hill since its easier and use that kinetic energy, then when you get to the bottom, throw it in neutral going 100mph and see how far you get

 

Just shutting of the fuel doesn't shut off airflow. As long as the engine is turning, it continues to pull air itno the cylinders on the intake stroke, and push it put during the exhaust stroke.

Shut the key off. that disables both fuel delivery an ignition. But the engine still pumps the same volume of air in and out.

The de-cel fuel shut off only shuts of fuel flow.

bill

 

This is not true, why is this so hard to understand? And this isn't anything new either. Here is a quote for a patent for a electrically controlled fuel injection system dated 1977:

In the above-mentioned control system, it is of usual practice that the system is designed in such a manner as to cease the fuel injection for an economical purpose and reduction of harmful exhaust emission while the vehicle runs by inertia, i.e., free-wheels, that is, when the engine speed is above a predetermined value (for example, 1300 rpm) and at the same time the degree of opening of the throttle is below a predetermined value

http://www.freepatentsonline.com/4062328.html

 

True , but your going to slow down faster. On a long hill you will have to use the gas to keep from slowing down, coming up to a light you may have to hit the gas to speed up or maintain speed , both will cause more fuel use.

 

So basically what you guys who say that engine braking uses no gas are stating here, is that we can hook your Z up to a tow truck from the front, and put the car in oh, lets say second gear, and then have the tow truck drive around town.

If the engine runs without gas while engine braking, then it should allow the tires to spin and pump air through the engine, creating that whining sound that we hear when we engine brake.

If you are like me and believe that a combustion engine must use gas to run, then in this scenario the Z's rear tires will be dragged around town, ruining the tires and creating quite a commotion.

Think about this, and then tell me if you think engine braking uses no gas.

BTW. I conducted my own experiment with the Z's fuel gauge a while back when faced with this argument on another forum. Check out my results

 

How can you argue this? I have posted numerous patents stating that is the way it works.

Your experiment was flawed, the engine speed must be above about 1200 rpm before the fuel is cut off. In six gear this means you would probably need to be going about 40 mph before the fuel gets cut off. If you coast in 1st or 2nd gear, it is pretty easy to feel the fuel kick back in when your rpm drops to about 1200.