[supremeBaleno]

Originally Posted by rippergeo

@SB- I wouldnt mind if some of the bikers around here get a little dull headache and nausea.

Ha, I think I know why you feel that way. From my experience on Kerala highway NH47, I have found the bikers there to be plain suicidal. These guys ride madly on highways, don't hesitate to attempt dangerous overtaking manouvres which even car-guys would avoid. Suffice to say that I stay clear of them.

Originally Posted by rippergeo

Switching off the engine for stops of 15secs is kind of overkill anyway.

Well, that was just for blacmagic who was looking for a specific number. This is one of those voluntary things that depends on each person and which can't be imposed. So, some switch off even for 15secs, some do at 2mins and so on. I take a decision based on either signal-timer or prior knowledge about certain signals that dont have timer etc, but usually it is 30sec or more.

But the main overriding factor is the Chennai weather and during summer (already started here), this is a no-no, unless I want to get roasted in a black-color car.

[anupmathur]

Originally Posted by Raccoon

Engine wear at start up is right... but on what basis do you say there is metal to metal contact on turning it off?? Never heard of this....

Well it's not my fault if you haven't heard of it, LOL!
The mechanism is the same as during run-up, except that the duration is smaller.
As oil pressure drops to a level that cannot maintain the hydrodynamic wedge, there is going to be a degree of metallic contact between bearing and shaft.
The duration of this at run-down is certainly smaller than at run-up.

Originally Posted by supremeBaleno

"No fuel' as in not even a drop of fuel ? I don't think so. Maybe much lesser amount, but definitely there has to be some fuel injected to keep the engine cycle running.

In modern cars (read fuel injected, ECU controlled) there is no fuel injected if vehicle is in gear and throttle input is zero. This allows for engine braking with economy.
In carburetted engines, the fuel consumption only drops to that at idling.

[Raccoon]

Originally Posted by gaurav.28ch

Your concerns about the well being of your car are absolutely justified.
As said earlier wear and tear could be equated by reduced fuel consumtion. And there shouldn't be any doubt about reduced pollution.
Sad thing is if you have made up your mind on shutting ur engine only for more than 2 mins stops,then I think probability of encountering such signals would be dismally low. And 95% of time you would be wasting oil.
Just look at the bigger picture. If each one of us could join and contribute, it could really make a difference.

Dude, there isn't even enough evidence that shutting off the engine for very short durations does any good! Some of the reasons are already covered in the last few posts. For me, its a balance between saving fuel and saving my vehicle too. And shutting down for very short durations definitely does not do any good for the vehicle.... by how much, is another issue.

And btw, the 2 min thingy isn't very rigid for me! Its not like I use a stopwatch! There are situations I encounter where the anticipated idling is longer, and I do switch off.

And yes, switching off car in summer means switching off A/c too... and that means sure suicide! Lol!!

[supremeBaleno]

Originally Posted by anupmathur

In modern cars (read fuel injected, ECU controlled) there is no fuel injected if vehicle is in gear and throttle input is zero.

Hmm. This is news to me. OK, we have the following 2 situations - 1 with petrol engine and the other with diesel engine :

1) 1.6l petrol engine, FI with ECU (Baleno) : I am in 2nd gear and foot is off A-pedal ie. zero throttle input. Car keeps moving at a constant speed and will keep moving till I brake. By your logic, the engine would not be using any fuel at all. I could drive endlessly like this and if this will happen without ANY fuel being consumed, I don't mind driving this way daily to work and back.

2) 3.0l diesel engine (Safari DICOR - suman's) : At 4th gear at 40kmph, the Safari ambles along endlessly at sub-1K rpms. Does this mean NO diesel consumed by engine ?

I don't think so.

[blacmagic]

well, not be zero, but idling fuel. which is why the vehicle keeps moving in gear @ idling RPM

[anupmathur]

Originally Posted by supremeBaleno

Hmm. This is news to me. OK, we have the following 2 situations - 1 with petrol engine and the other with diesel engine

LOL, SupremeBaleno, you can make mockery of anything that you choose to!

Of course the cars will consume fuel in both cases since they are not using engine braking but engine motive power for moving ahead!
Speed has to figure somewhere in your logic!

And please, I am not going to conduct debates and classes about this.
You want to figure, you read up.
When you can disprove what I said, please post it here!

[ImmortalZ]

Originally Posted by supremeBaleno

Hmm. This is news to me. OK, we have the following 2 situations - 1 with petrol engine and the other with diesel engine :

1) 1.6l petrol engine, FI with ECU (Baleno) : I am in 2nd gear and foot is off A-pedal ie. zero throttle input. Car keeps moving at a constant speed and will keep moving till I brake. By your logic, the engine would not be using any fuel at all. I could drive endlessly like this and if this will happen without ANY fuel being consumed, I don't mind driving this way daily to work and back.

2) 3.0l diesel engine (Safari DICOR - suman's) : At 4th gear at 40kmph, the Safari ambles along endlessly at sub-1K rpms. Does this mean NO diesel consumed by engine ?

I don't think so.

You aren't exactly engine braking in either situations. When you are slowing down in-gear, there is no fuel injected. Just connect up an OBD diag system to the car and see the instantaneous fuel consumption numbers when you are slowing down under engine braking instead of being abrasive.

[supremeBaleno]

Originally Posted by anupmathur

LOL, SupremeBaleno, you can make mockery of anything that you choose to!

That was not the intention. I just mentioned 2 examples (from the lugging thread) that matched your definition.

Originally Posted by anupmathur

You want to figure, you read up.

Any pointers/link on where to start off ?

Originally Posted by ImmortalZ

Just connect up an OBD diag system to the car and see the instantaneous fuel consumption numbers when you are slowing down under engine braking instead of being abrasive.

I don't think I was being abrasive - dont know where you got that idea. He mentioned something and I put down 2 examples which did not match. I dont have OBD or any other gear and infact do we really need to try out each and every thing, when there could be a resource available that we could instead rely on?

Agree that the 2 situations I mentioned do not qualify as engine-braking, but my understanding is that even when engine-braking happens, the engine is running and doing the intake-compression-power-exhaust cycle. If so, there is some amount of fuel being injected even in this phase. Maybe very less, but still some. That was my point.

[suman]

So, if I'm going downhill for 2 kms in (say) 1st gear at 20 kmph (Engine braking), I'm going to be consuming less fuel than (say) when I'm covering 2 kms at 50 kmph in 4th gear on a highway?

[anupmathur]

Originally Posted by suman

So, if I'm going downhill for 2 kms in (say) 1st gear at 20 kmph (Engine braking), I'm going to be consuming less fuel than (say) when I'm covering 2 kms at 50 kmph in 4th gear on a highway?

Indeed, that is how it will be.
Going downhill with engine braking, your car will consume virtually NO fuel.

[supremeBaleno]

Originally Posted by anupmathur

Going downhill with engine braking, your car will consume virtually NO fuel.

OK, I think the whole debate is about a small technicality. As I understand it, there is a difference between "no fuel" and "virtually no fuel". The latter means there still is some fuel consumed, but which is really very less.

If you in your earlier posts meant it as "virtually no fuel", then I guess we are in agreement.

But if it meant "absolutely NO fuel consumed", then I am back to googling for info, which I have to admit has confused me even more.

[anupmathur]

Originally Posted by supremeBaleno

OK, I think the whole debate is about a small technicality. As I understand it, there is a difference between "no fuel" and "virtually no fuel".

OK, SupremeBaleno, I'll make it simple for you: NO FUEL.

I said 'virtually no fuel' to Suman's query to make the point clear and to keep a tiny allowance for an occasional tap on the throttle after possible brake application to slow down at a sharp turn or a bump, since that is what I practically encounter.
If no such taps are given, even Suman's car will consume zero fuel.

[supremeBaleno]

Hmmm, call me a Doubting Thomas, but I find it tough to believe that an engine can run on ZERO fuel.

Just one query : On what do you base your claim ? An experiment done yourself using some gadget ? Or based on reading ? If it is the latter, could you point me to the link/book because googling is not throwing up anything conclusive.

[ImmortalZ]

Corolla Altis, live mileage gauge. Accelerate to 60, let go of the throttle. Gauge shows 99KM/L. It's way of showing infinite. ScanGaugeII on a friend of mine's '06 USDM Civic. Same case, except the ScanGauge does show "Inf." for mileage.

It is simple SB. The pistons turn the crankshaft and thus accelerate the car. Stop giving fuel to the engine and the momentum (kinetic energy?) of the car will force the wheels to turn, which, through the locked clutch and transmission, will turn the crankshaft and thus keep the pistons moving. However, because of the tremendous losses in an internal combustion engine, this energy will be wasted away as heat and thus slow the car down. It is still compressing air, which needs energy. Result? Engine braking.

When the car has slowed down so much that the losses are more than the power coming from the wheels, it sputters to a halt. I assume that the ECU will not let the engine go below the idle RPM without fueling. So if a car has great torque at idle RPMs, enough to keep it moving without throttle input, it will not stall and therefore, keep moving. If a car has a very high idle RPM set (like driving school cars), the same result happens.

[anupmathur]

Originally Posted by supremeBaleno

Hmmm, call me a Doubting Thomas, but I find it tough to believe that an engine can run on ZERO fuel.

Decelerate smoothly

When you have to slow down or to stop, decelerate smoothly by releasing the accelerator in time, leaving the car in gear!

Petrol and diesel cars manufactured from 1990 onwards, are generally equipped with fuel injection combined with an electronic function that cuts off the engine's fuel supply under engine braking (accelerator released and a gear engaged). The advantages of this fuel cut off function can be used by releasing the accelerator in time, for example when approaching traffic lights. This also reduces wear and tear on the brakes, reducing maintenance costs. Engine braking, not only has a positive effect on fuel consumption, but also on exhaust emissions, traffic safety, traffic flow and passenger comfort.

In case of less modern cars with a carburettor and older diesel cars (generally manufactured before 1990), it makes no difference whether you decelerate with gears engaged or disengaged, for the carburettor is a mechanical device that is not equipped with electronics to cut off fuel supply. These cars consume an equal amount of fuel under engine braking and when idling. However, releasing the accelerator in time still avoids hard braking and improves the durability of the brakes.

Please read here: ECODRIVE.org: The golden rules of ecodriving

__________________________________________________ _____________________

Q: I have a question about fuel economy. If you are driving downhill, do you save gas by putting your transmission in Neutral and coasting, instead of having your vehicle in Drive? I think that you do but my wife seems to disagree. Can you give me the correct answer, so I can tell her that I’m “Mr. Right,” as usual?

A: That depends. The engine isn’t braking the car going downhill if the transmission is in Neutral, so economy would seem to be high. But if you think the engine is still using fuel while coasting downhill in gear, you’re laboring under a misconception. Most fuel-injected cars turn the fuel delivery completely off when you lift your foot from the accelerator. They still burn fuel when idling in Neutral, so do the math. The amount of fuel burned at idle over, say, a couple of miles of coasting downhill is small, but it’s still more than zero. So if you’re driving a modern fuel-injected car, you’re wrong.

Older, carbureted cars would suck gas through the engine while coasting in gear, even if you turned off the ignition switch. In this case you’d be right.

Read here: Neutral Shift for Better Fuel Economy - Popular Mechanics