Turning off engine at stoplights
09-21-2007, 04:23 PM
#1
Registered
Thread Starter
Turning off engine at stoplights
I understand the Prius turns itself off when stopped in traffic. I love that idea! I mean, to not sit there wasting fuel, spewing crap into the atmosphere… seems so obvious—like 'duh'!
Now… I know with ordinary engines, the rule of thumb used to be don't turn it off unless you're gonna be sitting in traffic for more than a minute (because you use more fuel starting it up than you would save not burning it). But do you think that's true for the Renesis?
As kind of an experiment, I'm now turning the engine off if I stop at what I know will be a REALLY long red light—say, 60 seconds or more (I leave the radio on). So… think that'll save much gas in city traffic? And will starting it up several times over the course of a trip stress the engine??
Now… I know with ordinary engines, the rule of thumb used to be don't turn it off unless you're gonna be sitting in traffic for more than a minute (because you use more fuel starting it up than you would save not burning it). But do you think that's true for the Renesis?
As kind of an experiment, I'm now turning the engine off if I stop at what I know will be a REALLY long red light—say, 60 seconds or more (I leave the radio on). So… think that'll save much gas in city traffic? And will starting it up several times over the course of a trip stress the engine??
09-21-2007, 04:35 PM
#2
The devil made me do it
iTrader: (1)
Join Date: Jul 2007
Location: Colorado Springs, CO
Posts: 3,708
Likes: 0
Received 2 Likes
on
2 Posts
The Prius does not shut off at a red light. It just simply uses the electric engine from a stop. I am going to say that you are going to burn less gas idling at 700 RPM than you will starting the car at every light.
09-21-2007, 04:36 PM
#3
Future Rotary User
Join Date: Oct 2006
Location: Chicago, IL
Posts: 567
Likes: 0
Received 0 Likes
on
0 Posts
My thought, even with a gas guzzler like a rotary, is that unless you're waiting several long minutes for a freight train, don't do it. What would happen if say you were in front of the pack and some idiot was barreling down the street out of control, with your only option to avoid a serious collision would be to move the car out of the way? By the time you'd get the car started, in gear, and moving, you'd be out of time.
Also in reality, even with heated O2 sensors and modern fuel injection, you're still running in open loop for maybe a minute or so, at startup anyways, thus dumping more crap into the air than you would have if you just sat and waited. Not to mention the drain on the charging system if you did it at every light.
My opinion, its not worth it for 60 seconds and you may wind up burning even more.
Also in reality, even with heated O2 sensors and modern fuel injection, you're still running in open loop for maybe a minute or so, at startup anyways, thus dumping more crap into the air than you would have if you just sat and waited. Not to mention the drain on the charging system if you did it at every light.
My opinion, its not worth it for 60 seconds and you may wind up burning even more.
09-21-2007, 05:02 PM
#7
I actually read an article about this some years ago. Based on limited research, it was found for the cars they tested that fuel was saved only if the engine was off for more than about three minutes. Just re-starting the engine used as much fuel as 3 minutes of idling.
It's been too long now to recall any other details.
I'm sure that for some engines, the time is much less than that, for some possiby more, but it does demonstrate that for each engine there is a window of ecconomy.
Another factor to consider is the lack of AC with no engine while you wait for that light or train.
It's been too long now to recall any other details.
I'm sure that for some engines, the time is much less than that, for some possiby more, but it does demonstrate that for each engine there is a window of ecconomy.
Another factor to consider is the lack of AC with no engine while you wait for that light or train.
09-22-2007, 12:01 AM
#8
Registered User
iTrader: (1)
Join Date: Aug 2007
Location: Portland, ME
Posts: 562
Likes: 0
Received 0 Likes
on
0 Posts
Saving the atmosphere is not up to the consumer. It's the manufactures. Making the choice to drive an electric car won't have any impact besides you save some money... having no choice but to drive an electric car will help change the atmosphere.
Although i'd consider running a hydrogen/gas hybrid in the 8 since apparantly it runs on hydrogen as is? (well only thing is hydrogen storage?)
Although i'd consider running a hydrogen/gas hybrid in the 8 since apparantly it runs on hydrogen as is? (well only thing is hydrogen storage?)
09-22-2007, 09:52 AM
#12
Registered
Some time ago (1970s, I think, during that era's rounds of fuel crisis) Volkswagen experimented with a conventional car whose engine shut down at lights. Started automatically when you stepped on the gas again. I think that re-starting a warm engine - one in good operating condition - does not really waste much fuel.
Ken
09-22-2007, 11:11 AM
#13
The devil made me do it
iTrader: (1)
Join Date: Jul 2007
Location: Colorado Springs, CO
Posts: 3,708
Likes: 0
Received 2 Likes
on
2 Posts
I would agree...if you consider it to be "off" while the electric engine is not producing power and the gas engine is not running. It is not like you have to restart the car by turning it to OFF and then back to the ON key position. The electric motor is there ready, it is just not providing power. It really is just symantics. Comparing this situation to turning on and off a gasoline engine is really comparing apples to oranges.
09-22-2007, 01:33 PM
#14
Registered
ICE = internal combustion engine
Motor = electric device.
Yes, I know that some people will refer to a car's engine as a "motor" and we do have "motorcycles," "motorists," etc. But an engine is the thing that burns fuel and a motor is the thing that eats electrons.
My high school engine shop teacher heaved enough water soaked erasers at us to make that point clear.
The Prius will turn its engine off, then restart it when needed. That VW turned its engine off. Not sure how much of a lag there was with the VW when the light turned green, but I'd hate to drive something like that when a tuneup was way overdue. Because the Prius has a motor as well as an engine, there wouldn't be a lag.
Ken
Motor = electric device.
Yes, I know that some people will refer to a car's engine as a "motor" and we do have "motorcycles," "motorists," etc. But an engine is the thing that burns fuel and a motor is the thing that eats electrons.
My high school engine shop teacher heaved enough water soaked erasers at us to make that point clear.
The Prius will turn its engine off, then restart it when needed. That VW turned its engine off. Not sure how much of a lag there was with the VW when the light turned green, but I'd hate to drive something like that when a tuneup was way overdue. Because the Prius has a motor as well as an engine, there wouldn't be a lag.
Ken
09-22-2007, 01:39 PM
#15
VRZOOMZOOM
Join Date: Sep 2006
Location: Central Jersey
Posts: 323
Likes: 0
Received 0 Likes
on
0 Posts
hmm....i only shut my engine off if i'm on those bridges where the middle portion opens up for the bigger ships to cross......and i know i'll be there for a good 5-10 mins.....before the light changes. Otherwise....i just leave it idle.
09-23-2007, 12:06 AM
#17
Registered
Join Date: Jul 2007
Location: Glendale, AZ
Posts: 101
Likes: 0
Received 0 Likes
on
0 Posts
09-23-2007, 05:51 PM
#18
ICE = internal combustion engine
Motor = electric device.
Yes, I know that some people will refer to a car's engine as a "motor" and we do have "motorcycles," "motorists," etc. But an engine is the thing that burns fuel and a motor is the thing that eats electrons.
My high school engine shop teacher heaved enough water soaked erasers at us to make that point clear.Ken
Motor = electric device.
Yes, I know that some people will refer to a car's engine as a "motor" and we do have "motorcycles," "motorists," etc. But an engine is the thing that burns fuel and a motor is the thing that eats electrons.
My high school engine shop teacher heaved enough water soaked erasers at us to make that point clear.
KenYour high school shop teacher wasn't from England, I'm guessing.
(I agree with you Ken, but I don't get my shorts in a knot if someone else doesn't follow the usage guideline and would never throw something at them. I'm suggesting that your high school shop teacher had a stick up his butt.)
09-23-2007, 06:32 PM
#19
Registered
Join Date: Mar 2007
Location: private area in south florida
Posts: 421
Likes: 0
Received 0 Likes
on
0 Posts
assuming the road is leveled you dont have to sit there with your foot on the brake pedal which enhances foot comfort...
and with the risk of flooding i wouldnt dare consider turning the engine off for a stop light....i live in an area where freight trains pass early in the morning and sometimes they coast with the engine off so they can commence stopping and they literaly are cruising at 10mph...and they are like 2 mile long trains...thats the only time i would shut it off and i would have to have just seen the train start to go by.
just thought of somethin, you know how dodge and others have the V8 that would run on 4cyl when hwy cruising...how difficult would it be for mazda to have a rotary that would run on 1 rotor when doing 60mph+...im still new to rotary engines but if this were at all possible this would be a great mpg and emissions booster for rotary engines.
and with the risk of flooding i wouldnt dare consider turning the engine off for a stop light....i live in an area where freight trains pass early in the morning and sometimes they coast with the engine off so they can commence stopping and they literaly are cruising at 10mph...and they are like 2 mile long trains...thats the only time i would shut it off and i would have to have just seen the train start to go by.
just thought of somethin, you know how dodge and others have the V8 that would run on 4cyl when hwy cruising...how difficult would it be for mazda to have a rotary that would run on 1 rotor when doing 60mph+...im still new to rotary engines but if this were at all possible this would be a great mpg and emissions booster for rotary engines.
Last edited by magikone69; 09-23-2007 at 06:42 PM.
09-23-2007, 07:41 PM
#22
Registered
Correct. Mr. Herfurtner was not from England.
More like he had one that he stuck up our butts.
I still cringe (and clutch my butt) when I hear someone refer to a twist drill as a "bit."
Ken
I still cringe (and clutch my butt) when I hear someone refer to a twist drill as a "bit."
Ken
09-23-2007, 09:22 PM
#23
Registered
Thread Starter
So… the consensus is that turning off the engine, if stopped for over a minute, WON'T save any gas. Is that correct?
(I'm not at all concerned about flooding. I only do this once the engine is warm. It ain't gonna flood, any more than an ordinary engine would. And if, for some weird reason, it did, big deal. I'm not doing it on draw bridges and over railroad tracks.)
(I'm not at all concerned about flooding. I only do this once the engine is warm. It ain't gonna flood, any more than an ordinary engine would. And if, for some weird reason, it did, big deal. I'm not doing it on draw bridges and over railroad tracks.)
09-23-2007, 11:04 PM
#24
bit, n. def. 3.Mach. the cutting or penetrating part of various tools: b. the movable boring or drilling part of a carpenter's brace, a drilling machine, or the like. -The American College Dictionary, 1968 edition.
I know exactly how you feel, Ken.
I used to have an English teacher who, referring to the past tense of the word "dive", would hold forth: "There is no such word as 'dove'. The past tense of dive is 'dived'. 'Dove' is a bird."
WTH? 'Dove' is a perfectly acceptable colloquial form of 'dived'. Maybe Mr. Kartchner and Mr. Herfurtner knew each other?
09-24-2007, 02:14 AM
#25
Registered User
Join Date: Mar 2005
Location: Stockholm, Sweden, Europe
Posts: 42
Likes: 0
Received 0 Likes
on
0 Posts
Result was that I automatically mashed the pedal and the car pealed off and jumped of like a drunk kangaroo. I ended up keeping my foot on the accelerator to keep the engine running since it was so d** annoying and that kind of made the whole set up pointless...
Apparently several car makers like BMW and eventually Mazda will implement a "when idle, shutdown" function, I hope it is greatly improved though...
Cheers, Niclas