Maximizing MPG while slowing down - MT

[Frink]

I can tell you for sure that my 01 Honda Civic does not shut the fuel off during engine braking, thanks to my Scangauge II.
I have a feeling that our Mazda 5 behaves the same way as well, perhaps to keep the catyltic converter up to temp at all times.
One day I'll either get another Scangauge or move mine into the wife's 5 to confirm.
Coasting to a stop or even 'pulsing and gliding' works wonders for your FE numbers.
Learn to take advantage of coasting down gentle grades and you'll find your car going faster and using less fuel than cruising along in gear.
Check out www.gassavers.org for lots of good info.
I traded in a Toyota Yaris for the 5, I was averaging about 4.8 l/100km per tank by using a few of the techniques I learned there.

 

[jlk_250]

Rev matching isnt a MUST only in that if you dont do it, your car wont die on the spot. But it is a MUST if you want to get the most life out of your clutch possible. It takes a little bit of practice, but when you downshift, clutch once to pop it into neutral, blip the throttle to raise the revs about 1-2k higher, then quickly clutch again and downshift into the next lower gear, and take your foot of the clutch before the revs have a chance to drop.

What you are describing is called double clutching. This used to be done before synchronizers were added to transmissions. You are rev matching to allow the gears to engage. The other people in the thread are talking about rev matching to minimize slipping the clutch. It's two different techniques with different purposes. I can do it all but there really is no good reason to double clutch other than for fun. You'll save on synchronizer wear but are likely to cause more gear wear by not doing it as well as the synchronizers do.

Back to the original post's subject, I have never heard that coasting in gear uses less gas than coasting in neutral but I guess it might be true. I'd guess that the difference is slight either way.

Jon

 

[Medicman]

Our injectors do cut off when engine braking (at least they do on my car so I'm guessing they wouldn't leave that out on any cars)

Unrelated question.. is that an aftermarket dash kit ? If so, where might they be gotten from ?
Thanks

 

[Kansei]

In my pic? It's all stock aside from the gauge rings.. but it's Protege5 stuff so yeah, it's different.

 

[jandree22]

Yeah you don't get a 12.8k post count by sticking to the P5 forum alone

And yeah, I like the gauges too!

 

[snax]

. . .They said that it is MORE fuel efficient to coast to a stop in gear with an engine braking load on the engine, than it is in neutral. The reasoning is that while coasting in neutral, your car is using gas to idle the engine. However when engine braking with a small load, say 2-4k revs, the rolling momentum of the car will trigger the compression to move the engine, thus causing the engine to completely stop injecting gasoline. The theory sounds plausible. . .

But planning ahead to slow less agressively saves more fuel overall by extending your rolling distance in neutral. In other words, you can get off the gas sooner and save more fuel than you would waste while idling to a stop in neutral or braking late with engine compression.

Check out this site for more ideas on fuel economy.

 

[Kid Red]

K, late to the game I guess, can someone explain rev-matching? Even tho I have an auto, I'd like to follow the thread at least.

 

[jandree22]

1) Clutch
2) Blip throttle to the estimated RPM you'll be at in the next lower gear
3) Release the clutch

...at least that's how I understand it and do it. If you don't rev match and just downshift, when the clutch engages on the next lower gear it's a sudden load on the engine causing you to kind of be lurched forward. Rev matching is smoother for the occupants and easier on the clutch, because by blipping the throttle, you're speeding up the engine so the clutch won't bear the load.

Automatics are always smooth because they don't force downshifts while braking like you can do with a MT.