I'm new to manual transmissions, and just came from the poll about whether you come to a stop by shifting to neutral, or keeping it in gear as long as possible before clutching in.

Shifting to neutral and clutching out leaves the throttle idling and uses fuel. Keeping it in gear, OTOH, slows you down faster and gives you less distance (though keeping it in higher gear doesn't make this too noticeable).

The third coasting option I find myself doing sometimes is leaving the clutch in, but leaving the shifter in gear (i.e. not neutral). I'm given to understand this is bad for the clutch, but how else is this different from shifting to neutral for coasting, technically speaking? Is the throttle still open in this state, as if it were in neutral/idle?

 

It has been PROVEN that leaving your car in gear, clutch ENGAGED (pedal out), with the engine above 1500RPM (in a MT car), fuel is CUT while you decelerate with no throttle input.

The other two situations you describe are basically identical, and will result in the engine idling - thus burning gas.

Not burning gas > burning gas.

Leave it in gear as you decelerate until at or just below 1500RPM. Get a ScanGauge and you can see when fuel is cut.

 

or you can FAS.

 

The third option you listed would be harder on parts of the clutch and I would avoid. Just toss it in neutral and let the clutch up. The parts are the throw out bearing and pressure plate springs and to a small amour the disk.

Here's 4th better option.
If you have a long coast kill the eng and put in neutral and go a long way with zero fuel. If you are lucky as you arrive near the traffic, you can place it in the correct gear, ease off the clutch and she will will fire back up.

When coasting be sure to leave the ign switch in II "ON" so the power steering works. Also be mindful of the vac for the brakes power assist is limited to 6 or so stops. After that they work just require way more force. Doing this at night is not too great because of the drain on the battery IMHO.

hope this helps

 

THAT will probably cause the most wear of all the options. You're making your clutch start the engine from a complete stop (0RPM).

 

I agree but what's the goal Eco or clutch?

 

Saving $. Burning out your clutch prematurely has to calculate into your 'TCO' (total cost of ownership). If you save $400 on gas but have to spend $500 to replace your clutch before you should, you are experiencing a net loss.

I'd estimate that the fuel you'd save yearly by coasting with the engine off, and pop-starting it would only be a few gallons (single digit). Your savings over a few years would not be greater than the cost of replacing a clutch.

 

OK than it's a minor tweak on the concept. Use the ele starter. I'm guessing you will say the ele starter extra use negates that...???

 

Negates the wear on your clutch? Yeah. Popping the clutch is usually an emergency start trick. I'd only recommend using it as such.

 

I would think coasting in neutral should save your more fuel as you get further. This is only useful if you actually CAN coast that far. When coming to a stop or changing light (or slower car!), I leave it in gear and coast that way. I haven't tried FAS yet...get's dark too soon here and don't want to drive with dimmed lights.

I've started coasting down some long hills on my daily commute, but when I want to pop it back into gear, I've misshifted to fourth twice! This is the first car I've had that is so easy to mis-shift to reverse...

 

i agree that the distance of the coast should be taken into consideration when deciding to leave it in gear or coast in neutral,
if im coasting for more than 10 sec, in in neutral, but i have this anal conception that by staying in neutral a lot, i am "saving" revolutions on the engine that will make it last longer, which is not really true at all, (unless your one of those people that refuse to use the brakes and downshift every gear to stop the car)
especially with new technology engine and syn oil, ..but i pretend

 

Why is this true? Wouldnt it depend on the idle mechanism? I thought that the idle was created by some mechanically-limited minimum throttle.
Coasting in gear causes more revolutions in the engine. More revolutions means that more air is being pulled through the carburetors, evaporating more fuel. If the minimum throttle is the same in the two circumstances, woulnt you then want to cut the RPM as low as possible to save gas?
Alex

 

The way I understand it is that your car isn't actually idling anymore when coasting in gear above 1500rpm...guys with scan guages have seen that the fuel is cut off and the momentum of the car is actually causing the engine to keep turning via the input from the tyres, gearbox, etc.

A lot more friction yes so more slowing down while "coasting", but no fuel being used vs a little bit of fuel being used while coasting in neutral but going further...

 

come on... you guys are driving a fit. you already have great mpg. the amount of gas saved is minimal. i would either put it in neutral with the clutch out or leave it in gear to decel. unless youre down shifting its not going to make that much difference. i think you can live without ac. that will solve everyones problem.

 

+1

I agree - I'm going to settle on doing coasting in neutral on the few long hills I have on my commute, leaving it in gear to coast to a stop (where convenient), leave the AC off if comfy and just try not to drive to fast.

The savings in fuel with the Jazz is already great and these few extra things don't cost me too much effort or time so why the hell not!

 

Alex, The Fit has Fuel Injection. No carbs.

Trust me I have data. When you lift the fuel stops flowing no matter what RPM.

A few of are close to 50mpg every tank.
Go look at both the MPG sticky polls above and tell me the mean or avg for both MT and AT Fit's and how minimal our hypermilling efforts really are. lol

 

im sorry but fuel never stops flowing. your car has to remain running. ya its very little fuel but there is no way it completely shuts off.

 

hibrids... totally different. when you push the brake your fuel stops.

 

Sorry, you're incorrect. When you lift off the throttle and coast in gear above ~1500RPM, this is what happens:

Your momentum keeps the car rolling. This keeps the wheels turning. The wheels turning keeps the transmission turning. The gears and clutch being engaged keeps the engine turning.

You follow?

Fuel to the injectors is cut in this situation. Momentum is turning the engine. No need to put fuel into the mix.

In a carbureted car, you would be correct, the intake air would still suck fuel in, and it would have to get burned, or it would be dumped into the exhaust. In a fuel injected car, you simply turn off the injectors and don't fire the spark plugs.

 

My buddy is a former Honda mechanic with his own place. He was explaining the Fuel Cut Decel to me when we were out running around one day. This has also been discussed in one of the mileage forums.

In neutral, whether coasting with the clutch in, or at a stop, the engine is turning over about 800 RPM. I think I recall someone with a Scan Gauge mentioning that this was something like .14 gallons per hour.

When you coast IN GEAR, Fuel Cut Decel cuts the fuel flow to the injectors. The engine is turning over, oil is going round and round, air is going in and out, but there is ZERO fuel consumption . . . until the RPM drops below around 800-1000. Then it will kick the injectors back in. You can feel this if you coast in gear and let the RPM drop to around 800; you will be coasting, slowly decelerating (depending on the gear) and then the engine will surge when the fuel kicks back on.

My driving has found that a mix of the two works best for me. For example, I can coast in neutral the 1/10 of a mile down the road in front of my house to the county road; can't coast the gentle incline in any gear. On city streets, if I plan ahead, I can coast to a stop, in whatever gear works out (usually 5th, 4th or 3rd) and am about ready to hit the brakes and kick the clutch in when I normally would for a stop - before RPM drops below 1000.

I've been getting close to 33 MPG with city and a little highway; just got 42 MPG on a straight highway trip. Even did 80 for about 20 minutes and ran the A/C.

John