Shutting engine off at traffic lights with an automatic transmission - Page 2 - Fuel Economy, Hypermiling, EcoModding News and Forum

jkp1187 · 10-13-2009, 05:38 PM

Quote:

Originally Posted by Christ

I don't like to go further than a few hundred feet, but I have no evidence that supports damage for short distance coasting, either.

I know much has been made on whether or not the car is 'flat-towable' or not. If it's flat-towable, supposedly you can EOC to your heart's content. If it's not flat-towable, that generally means that the transmissions parts don't get lubricated when the engine is off, and so there is usually some distance/speed limitation on coasting listed in the owner's manual. Even so, the occasional coast to a redlight is probably no big deal. After experimenting a little with it, I didn't see any significant fuel economy increase for my vehicles -- mostly, I think, because there were really only a couple of places in my usual commute where I felt comfortable doing it. (Besides, I like having power to the brakes and steering.)

Regarding the break-even point for fuel consumption, according to the BMW owner's manual, that point is reached after four seconds of idling. Now, that doesn't take into account additional wear and tear on the car for each additional startup, so take that with a grain of salt. My own rule of thumb is basically I'll let it idle for 20-30 seconds, but I will shut down if I know the wait will be longer AND if the engine is already at operating temperature AND if I haven't shut down within the last 5 minutes or so. (AND if Mrs. JKP1187 isn't in the car, too, because she'll no doubt want me to keep the HVAC running.

)

drewwitlin@hotmail.com · 10-13-2009, 10:01 PM

I posted a thread a couple of months ago, Time Spent at traffic lights Engine off. I stop watched the amount of time that I had the engine off throughout the day. *Note - I drive an automatic, but do not EOC, I coast engine on, and I drive 150+ miles a day, different routes and roads. After 2 days of timekeeping and traffic light counting, with some math involved, I was engine off for about 20mins a day, about .25 of a Gal. 4 days = 1 Gal. of gas.

Try timing the amount your engine off drive is, and count the number of traffic lights you engined off for.

Christ · 10-13-2009, 10:11 PM

Oh hell, I can't do all that. I just turn the van off at random times when going down slight rolling hills and stuff, or when I can make a long coast to a stop sign...

(People hate me for the stop sign thing, by the way. Most everyone is used to slamming on the brakes as they approach the sign, I coast up to it gently, and I usually only have to brake from about 20 MPH by the time I get to the sign. I don't even re-start the van until I see a clear spot to pull out.)

Funny thing, too. I've had someone get mad enough at me to actually pull around in front of me while at a stop sign, shut their vehicle off, and come to me screaming their head off. This happened just a few weeks ago, actually.

So the guy comes up to Cara, and I always have a head-on attitude, so I unbuckle and get out before he gets there. I'm not an intimidating guy, so I rely on intelligence in most cases. This guy is yelling and screaming, and by the time I find a spot in his incessant rambling to actually say something, I calmly announce to him: "You're late."

"I'm late?! What the FSCK are you talking about?"

"I'm sure you were in a hurry to get somewhere, and my slow driving obviously upset you because you were in said hurry... and now, because you've stopped just to ramble on at me pointlessly, you're late."

All of a sudden, his face lightened up.. the scowl was gone, and he stopped yelling. He gave me a look of enlightenment, got back in his car, and left. I started Cara back up and drove up to the local Mickey Dick's to get some coffee.

newhavenpatriot · 10-13-2009, 10:27 PM

Wow, calmness and intelligence FTW.

I would've just gone into reverse and gone around him. Lol.

Christ · 10-13-2009, 10:28 PM

I'm not that easy going. I've been known to scrap once and again.

Seraph · 10-18-2009, 08:13 AM

That story is epic love it!

Well i guess i know what to say now if that ever happens to me =)

orange4boy · 10-18-2009, 03:52 PM

Christ, you are a god. That's hilarious and the perfect approach for the crazed lunatics who drive like there's fire in the back seat.

Lucky for me, people are so busy staring, pointing, taking pictures and laughing at my van, they don't even realize that I'm slowing them down.

Ever since I started driving with efficiency in mind, I am so much more relaxed behind the wheel. I love the silence of a still engine at a stop light.

Christ · 10-18-2009, 09:19 PM

Quote:

Originally Posted by orange4boy

Christ, you are a god. That's hilarious and the perfect approach for the crazed lunatics who drive like there's fire in the back seat.

Lucky for me, people are so busy staring, pointing, taking pictures and laughing at my van, they don't even realize that I'm slowing them down.

Ever since I started driving with efficiency in mind, I am so much more relaxed behind the wheel. I love the silence of a still engine at a stop light.

Please, modesty... :P