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Old 04-03-2016, 09:16 AM   #1
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Engine Braking and Coasting...

I have a 2014 Corolla LE. It has one of those new automatic transmissions. It's called a CVT? It has two drives (gears?) for engine braking. One is heavier braking. They say it's a 7 speed?
I admit. I haven't read cover to cover of the owners manual yet. I have searched it. Doesn't say much.

I'm asking for experience on two things.

One... The engine brake. Should I use it as much as I can. Instead of the regular brakes. Not versus coasting. Not versus saving my brakes. Just for mileage. This is when I need to stop. Don't have the luxury of coasting. This is in the context of mileage.

Two.... Coasting. I'm coasting now, in drive. With this transmission. I'm hesitant to put it in neutral. My first impression is that it will work as good in gear as neutral for mileage. I also think maybe this transmission is designed with this in mind for coasting in drive? Injectors, etc. everything works best for coasting while in drive?

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Old 04-03-2016, 10:45 AM   #2
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With EFI, lifting off the accelerator at any time will instantly shut the fuel off to the engine. In neutral, the engine will use fuel to idle. I've tried both techniques when going downhill, results can vary, on longer less steep hills the car will travel further in neutral as the engine is not braking and slowing you down. On steeper hills, the car will still pick up speed even in gear, but use no fuel in doing so.

I can't help as regards to the CVT as I will never own a car with an automatic gearbox.


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Old 04-04-2016, 11:47 AM   #3
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"With EFI, lifting off the accelerator at any time will instantly shut the fuel off to the engine."
Perhaps with a manual transmission, but that instant varies between automatic transmissions. My old 2006 HHR had to be downshifted in order for the DFCO(deceleration fuel cut off) would kick in. Increasing fuel economy standards means that newer cars are more aggressive with it though.

The basics of coasting in gear vs. in neutral is that if you are approaching a stop or want to slow down, stay in gear. If not, then coasting in neutral is better since the DFCO fuel savings could be lost upon accelerating back up to speed.

But this all depends on the car. With a good overdrive ratio, a car may not lose much speed to engine braking.

My experience with CVTs is limited to the, not an actual mechanical CVT, eCVT of the Prius. So I really can't say much about them besides that it is sad that car makers have to make them behave like a step transmission with virtual speeds to sell them in the US.
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Old 04-04-2016, 04:34 PM   #4
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We have a 2012 Subaru Outback with the CVT, and I have to admit I like it. Once I got over the fact that the engine speed seems to bear little relation to the actual road speed, that is. Ours has the manual shift emulator, simulating six gear ratios. I have fooled with it, and usually end up ignoring it. It can be useful for long downgrades for some engine braking, but there is a useful quirk to it. In Drive, one can use the steering wheel mounted paddle shifter to force one or more downshifts, and at the bottom of the hill when the accelerator is depressed the transmission goes back to automatic operation. Nice trick. Its other quirk - I had it in manual, in 6th, on Cruise Control. On a long upgrade, it automatically downshifted to 5th when the cruise could not maintain speed in 6th. I didn't notice, at the time. On the other side of the hill, it did not automatically upshift, but stayed in 5th. I happened to glance at the indicator, saw "5" instead of "6", figured out what happened, and put it back in D.

Despite the reservations of the Manual Transmission uber alles people, I am convinced that automatic transmissions - even the old and now archaic three-speed units - can do a better job than most drivers most of the time. That's why they are usually outlawed on race tracks.
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