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PostPosted: Sun May 24, 2009 9:07 pm 
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Location: Canada
I shut my car off when idleing, and I now shut my car off when I'm slowing to a red light. Keep in mind that since our brakes have boost, if you shut your car off, and pump the brakes a few times, they'll be hard.

I now also shut my car off if I'm downshifting from 100km/h or so on approach to a red light to stop. If I have to stop, I just stop, but if the red light happens to turn green as I'm slowing in gear, I just turn the car back on. You wouldn't even notice a difference.

I wonder if I save any gas doing that. The way I see it, since I'm hot-starting it or whatever, not cranking it, my injectors will just pick up where they left off. As for slowing with my car off, my injectors are still firing, even if only at idle.

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PostPosted: Mon May 25, 2009 12:50 am 
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Try going to http://ecomodder.com.
#55) Engine off coasting
Engine-off coasting (EOC) is one of the largest contributors to increased efficiency of hybrid vehicles, many of which automatically shut down the engine when the accelerator is released and the vehicle is coasting.
EOC can be accomplished in non-hybrids as well simply by shifting to neutral and switching the key from "Run" to "Acc" (being careful not to switch to "Off" and cause the steering to lock). As soon as the engine stops, return the key to the "Run" position so the odometer continues to count distance traveled and you're ready for a re-start.
This technique is best suited to cars with manual steering and manual transmissions. (Dramatically increased steering effort may be required in some cars with power assist. Also, most vehicles with automatic transmissions are not designed to travel with the engine shut off; the transmission may be damaged).
In non-hybrids, EOC is considered an advanced technique and should not be attempted until the skill developed away from traffic. In addition, coasting with the engine off is illegal in some areas.

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'91 Metro, rescued from trip to junk yard. SuzukiRD Underpulley & Header. 3Tech 9mm plug wires & 218/350 cam +10 gear, Bosch Plat. +4s, FlameThrowerII, synthetic fluids. K&N, Optima, Catco, Jones glasspack, & KYB struts. Vortekx Generators, Air dam, 7mm ground system, Ram Air. No TBI bridge. No A/C - roof scoop works.
'96 Metro - The Wife's car: SuzukiRD Underpulley, 3Tech econo cam +10 gear, K&N, KYB, Bosch, Syn. & grounded. No TBI bridge.


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PostPosted: Mon May 25, 2009 7:20 am 
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Location: Atlanta GA 30052
kaboler wrote:
I shut my car off when idleing, and I now shut my car off when I'm slowing to a red light. Keep in mind that since our brakes have boost, if you shut your car off, and pump the brakes a few times, they'll be hard...
I wonder if I save any gas doing that.

Likely no savings.

1. Red light idle: I have heard many times that starting a car takes the same fuel as idling for 10 minutes. Most stop lights around here are red for two minutes. It just seems longer! And the wear on the starter is increased by every stoplight. so on a trip 10x? 20x?

2. Slowing in gear: T3ragtop says slowing in gear with no throttle and engine ON does not fire the injectors. I have not measured that but I see 22 inches of vacuum doing this. If I shift to neutral, the engine idles at 1500 for 30 (?) seconds then drops. it is illegal here to go to ACC position (shut off) but how would they know?

It is hilly here so I try to build some speed with light throttle going downhill to help on the next up. I do slow and downshift at 1800rpm to 4th or 3rd on the upside. Everyone passes me going uphill and the gas/oil sellers are smiling. :roll:
If I had long down hill runs of a mile or more, I'd go to neutral or off and restart with the clutch -- not the starter.

I average 50+ mpg doing the above things in a 5sp 3 cyl. with 8 degree timing and 185/70-14 in the front. 175/70-14 would be better clearance and less resistance but I cant find them. :(

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daily driver: red 1991 Metro 3cyl 5sp, roof rack, 8 degree advance,
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completed frame up restoration: black 1994 Swift GT 5sp -- like new ! 45mpg


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PostPosted: Mon May 25, 2009 9:06 am 
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[quote="BadBent"]Try going to http://ecomodder.com.
[b]#55) Engine off coasting

Okay reading there. One thing I don't like about ecomodder is all the "don't inhibit other drivers" stuff. There's nothing better than being in front of a Ford F150 guzzling piece of shit with an idiot behind the wheel doing 92km/h when he wants to do 130km/h and can't pass!!!! WOOT!!!

Hey, I'm an environmentalist, that's my job!

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PostPosted: Mon May 25, 2009 9:16 am 
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xrw44 wrote:
1. Red light idle: I have heard many times that starting a car takes the same fuel as idling for 10 minutes. Most stop lights around here are red for two minutes. It just seems longer! And the wear on the starter is increased by every stoplight. so on a trip 10x? 20x?

2. Slowing in gear: T3ragtop says slowing in gear with no throttle and engine ON does not fire the injectors....


Yes, on the long downshifts, I'll shut my car off, let the engine slow me, and if I'm not stopped by the time I reach the intersection (light turns green and everyone is moving) I simply turn it back on. No starter required.

My concern is that shutting off the engine to save gas will end up costing me eventually with a new starter; hardly environmentally friendly hahahaha.

As for starting a car takes 10 minutes of fuel idle, I've heard that before, but it's complete bogus. Though, when starting, the engine does fire out of all 4 injectors instead of just 2 while idling. (I think. I really tried to understand what I was reading about my car's injectors.)

Apparently, my car will fire only 2 injectors at a time instead of 4 on a hot start, if my water temperature sensor says my engine is hot. I don't think my car stops injecting fuel when slowing down though, even high RPM slowdown. I assume it's idle speed.

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PostPosted: Mon May 25, 2009 10:05 am 
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Posts: 280
Location: Edmonton
You can save gas by getting up to 60KM/hr, then coasting down to 40. Then back to 60. I think it's called 'pulsing' by the hypermilers.

You can crank up your air pressure in your tires (55 PSI?). Or run space savers as long as you don't hit the highway much.

OR you could just disconnect one plug/injector :)


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PostPosted: Mon May 25, 2009 2:53 pm 
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I can't do that JP, I'm driving a GTI!! You're just jealous!

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PostPosted: Mon May 25, 2009 5:28 pm 
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Location: Edmonton
I wish I had an extra 300cc's!!!


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PostPosted: Fri Jul 03, 2009 11:33 pm 
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Location: winona mn
Starting a car uses about as much fuel as idling for 15-20 seconds. Not 10 minutes by any stretch. I have been engine off stoplight sitting, and engine off coasting with my Geo for years. I drive 58 miles each way to work on I90 in MN, and I get 37 mpg in the winter and 42 in the summer with the A/C on. I have 276,000 miles on my car, all still on the original starter, which I could get from any pick ur part for $25. I am pretty sure I am money ahead.
1999 1.3 L


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PostPosted: Mon Jul 06, 2009 9:06 am 
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According to my documentation, my car's injectors fire all 4 on startup only if my engine isn't at operating temperature. So, really, I don't think it costs anything on startup.

Which is why, I think, some people have trouble starting hot engines, because if the engine is hot, it fires only 2 injectors instead of 4 on a cold startup.

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PostPosted: Sun Aug 30, 2009 4:23 pm 
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xrw44 wrote:
1. Red light idle: I have heard many times that starting a car takes the same fuel as idling for 10 minutes.(

I'm quite skeptical of that claim. Oh, it's a common one in many areas. Many people have the completely incorrect notion that starting a fluorescent light takes as much energy as running it for 10 minutes. I think these kinds of memes are popular because they're such great over-dinner one line bits of "wisdom".

Why in the world should that 1 second of starting suck up 600 seconds worth of fuel? Is the injection system dumping hundreds of times the usual amount of fuel into each cylinder per cycle? Or is the rumor simply false?

I believe, but am not absolutely certain, that when the air conditioning is off, the Toyota Prius cuts the engine at stop lights.


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PostPosted: Mon Aug 31, 2009 12:01 am 
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sbergman27 wrote:
xrw44 wrote:
1. Red light idle: I have heard many times that starting a car takes the same fuel as idling for 10 minutes.(

I'm quite skeptical of that claim. Oh, it's a common one in many areas. Many people have the completely incorrect notion that starting a fluorescent light takes as much energy as running it for 10 minutes. I think these kinds of memes are popular because they're such great over-dinner one line bits of "wisdom".

Why in the world should that 1 second of starting suck up 600 seconds worth of fuel? Is the injection system dumping hundreds of times the usual amount of fuel into each cylinder per cycle? Or is the rumor simply false?

the amount of fuel you need to start the engine is probably closer to what it takes to run it for 10 seconds.
some articles on the topic:
http://www.treehugger.com/files/2009/08/idle-or-off.php
http://www.iwilltry.org/w/index.php?title=How_many_seconds_of_idling_is_equivalent_to_starting_your_engine%3F
Quote:
I believe, but am not absolutely certain, that when the air conditioning is off, the Toyota Prius cuts the engine at stop lights.

I'm pretty sure the 2nd gen Prius has an electrically driven A/C compressor, as well as a tank to store hot engine coolant, to avoid having to run the engine just for HVAC demands. There are even some non-hybrid cars that cut the engine off when you stop (The new Porsche Panamera will be the first such car to be sold in the US).


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PostPosted: Mon Aug 31, 2009 11:24 am 
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Location: McCall, Idaho (Native: So Cal)
sbergman27 wrote:
xrw44 wrote:
1. Red light idle: I have heard many times that starting a car takes the same fuel as idling for 10 minutes.(

I'm quite skeptical of that claim. Oh, it's a common one in many areas. Many people have the completely incorrect notion that starting a fluorescent light takes as much energy as running it for 10 minutes. I think these kinds of memes are popular because they're such great over-dinner one line bits of "wisdom". Why in the world should that 1 second of starting suck up 600 seconds worth of fuel? Is the injection system dumping hundreds of times the usual amount of fuel into each cylinder per cycle? Or is the rumor simply false?

Thank you for a most excellent demonstration of common sense. :D
My phrase is "Common sense isn't."
Have you seen 'Being There' with Peter Sellers and Shirley MacLaine.http://www.imdb.com/title/tt0078841/ I use the line "I understand." A lot. :D

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Bad Bent
'91 Metro, rescued from trip to junk yard. SuzukiRD Underpulley & Header. 3Tech 9mm plug wires & 218/350 cam +10 gear, Bosch Plat. +4s, FlameThrowerII, synthetic fluids. K&N, Optima, Catco, Jones glasspack, & KYB struts. Vortekx Generators, Air dam, 7mm ground system, Ram Air. No TBI bridge. No A/C - roof scoop works.
'96 Metro - The Wife's car: SuzukiRD Underpulley, 3Tech econo cam +10 gear, K&N, KYB, Bosch, Syn. & grounded. No TBI bridge.


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PostPosted: Mon Aug 31, 2009 11:56 am 
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Location: Saskatchewan
I don't know about stock ecus, but I idle warm with 3.3 ms fuel. and when I crank it's only 3.6. so how I would use 10min worth of fuel restarting I have no idea

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PostPosted: Tue Sep 01, 2009 8:55 am 
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Some of you don't have fuel injection. I suppose you might not want to turn your car off and on so much if you don't have fuel injection.

As for me, I shut my car off a lot because my car's energy demands is very low, so I can use my starter more without affecting mileage due to alternator output, and most of the time, I'm on the highway, so my long distance slowdowns are usually in 5th gear off, and I just turn my car back on when I get around 55km/h and saves me from startup (4 injectors firing asychronously).

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PostPosted: Tue Sep 01, 2009 9:03 am 
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kaboler wrote:
As for me, I shut my car off a lot because my car's energy demands is very low, so I can use my starter more without affecting mileage due to alternator output

The energy used by the starter is the same no matter what the other demands are placed on your alternator. But I'm pretty sure that what the starter uses is negligible, anyway.

Quote:
, and most of the time, I'm on the highway, so my long distance slowdowns are usually in 5th gear off

I believe that the ECU already cuts the fuel off when your foot is off the accelerator and the engine is still above a certain RPM.


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PostPosted: Tue Sep 01, 2009 12:32 pm 
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yeah im pretty sure it does too. ALL fuel injected cars either go by throttle position/map sensor or throttle position/maf sensor. being that these cars do have one or the other depending on the model, you can be damn sure its cutting all fuel off and you are slowing down from compression/friction alone. on carb cars its always drawing some fuel by the plate with the throttle closed.

a typical efi fuel cut off will run the motor down to 1500-1600rpms before activating injectors again. too low and it gets jerky bringing the fuel back in, and too high you just waste it.

it took me a few tries to get mine right. but lets say im at 3000rpm and I go to decelerate, that would put my engine vacuum down to the low 20 kPa mark. I "over-run" (as its called) down to 1600rpm and 37kPa, and only allow the slightest change in throttle (which will bring up the kPa) where if im on the gas more than 2%, it disables the overrun system until the next time I decel. its hard to describe what is all going on when you havent played with it yourself, but ive seen some aggressive overruns bringing it right down to idle, and the drivers just deal with the jerkyness, or clutch just before it comes back on.

you should feel the slightest change when the injectors come back on, do it in first gear. bring it up to say 3000rpm and just let it idle itself back down, youll see when it happens. and it is the #1 way to save fuel. with no overrun compared to my current aggressive overrun, ill see 8-10mpg difference over the whole tank.

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PostPosted: Tue Sep 15, 2009 12:36 pm 
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swift13b wrote:
yeah im pretty sure it does too. ALL fuel injected cars either go by throttle position/map sensor or throttle position/maf sensor. being that these cars do have one or the other depending on the model, you can be damn sure its cutting all fuel off and you are slowing down from compression/friction alone. on carb cars its always drawing some fuel by the plate with the throttle closed.

I had assumed that, too. The carbureted models do have a "fuel cut solenoid". But I always thought it was only to prevent dieseling. I didn't expect that it was any more sophisticated than that. But according to the 1986 FSM, the fuel cut solenoid also shuts off the fuel when the following 4 conditions are met:

1. The coolant temperature is normal.
2. The clutch switch (M/T) is off. (Clutch is not depressed.)
3. The idle microswitch is on. (Throttle is at idle position.)
4. The engine RPM is greater than 2500 rpm.

So it looks like the carbureted cars also enjoy this benefit.


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PostPosted: Wed Sep 16, 2009 9:51 am 
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kaboler wrote:
Hey, I'm an environmentalist, that's my job!


I'm suprised nobody noticed this; you actually appear to be a douche. While saving the environment is a great cause, you don't have to set aside common courtesy to do it :roll:

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You have a girlfriend? :shock:

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Last edited by HiTempguy on Wed Sep 16, 2009 11:25 pm, edited 1 time in total.

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PostPosted: Wed Sep 16, 2009 6:16 pm 
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I'm not sure if I have followed the thread correctly, but coasting to a stop with the car still running does not cut all fuel. The very act of idling uses fuel, so it stands to reason that fuel will be saved if your engine is off versus being on. Coasting to a stop with the engine on will save fuel over using engine compression to slow you down with the engine on.

The fuel cut solenoid I am familiar with is a safety feature used to prevent fuel from free flowing with the engine off in case of an accident.

Tom

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PostPosted: Wed Sep 16, 2009 11:05 pm 
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HiTempguy wrote:
kaboler wrote:
BadBent wrote:
Hey, I'm an environmentalist, that's my job!

I'm suprised nobody noticed this; you actually appear to be a douche. While saving the environment is a great cause, you don't have to set aside common courtesy to do it :roll:

That's a misquote. I never said that.

I told HiTempguy I'd edit this so you who are reading it, understand that it was simply a misquote, a typo if you will.

I agree with HiTempguy that we need to be courteous drivers while saving the environment. Upsetting a gas hog will do no good, they just wind up hating drivers of small cars and vowing never to get an economical small car. IMHO

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'91 Metro, rescued from trip to junk yard. SuzukiRD Underpulley & Header. 3Tech 9mm plug wires & 218/350 cam +10 gear, Bosch Plat. +4s, FlameThrowerII, synthetic fluids. K&N, Optima, Catco, Jones glasspack, & KYB struts. Vortekx Generators, Air dam, 7mm ground system, Ram Air. No TBI bridge. No A/C - roof scoop works.
'96 Metro - The Wife's car: SuzukiRD Underpulley, 3Tech econo cam +10 gear, K&N, KYB, Bosch, Syn. & grounded. No TBI bridge.


Last edited by BadBent on Thu Sep 17, 2009 12:33 pm, edited 1 time in total.

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PostPosted: Thu Sep 17, 2009 1:11 am 
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TomInOregon wrote:
The fuel cut solenoid I am familiar with is a safety feature used to prevent fuel from free flowing with the engine off in case of an accident.

The bit that I posted from the 1986 FSM is pretty clear. The FSM says the the Fuel Cut Solenoid cuts the fuel when the ignition is turned off to prevent dieseling. And also says it cuts the fuel when decelerating, provided that the 4 listed conditions apply, to improve fuel economy and to prevent the 3 way catalyst from overheating. I'm not sure how much good cutting the fuel with a solenoid inside the carb is going to do in a wreck. And the book doesn't mention that objective.

-Steve


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PostPosted: Thu Sep 17, 2009 8:27 am 
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BadBent wrote:
That's a misquote. I never said that.


Dude, I already sent you a reply PM plus I edited my post over 12 hours before you posted this one. Chillax, I'm pretty sure everyone knew who I was quoting :wink: My point simply is (for everyone) while its a noble cause, and I have respect for said cause, courtesy would dictate that you try to impose that cause as little as possible on someone else if they don't follow it, or expect them to get angry.

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This makes me wanna hurt someone, really bad. Where's Hitempguy, he's expendable
CJDavE wrote:
You have a girlfriend? :shock:

HiTemp Inc. ....... taking over the world one Sprint Turbo and Swift GTi at a time.

Chassis Flex Motorsports


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PostPosted: Thu Sep 17, 2009 4:11 pm 
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The modern cars that do this have much more efficient starter motors so there is less electrical drain. Any electrical drain has to be topped up by the alternator and takes power from the engine.


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PostPosted: Thu Sep 17, 2009 7:10 pm 
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Rhinoman wrote:
The modern cars that do this have much more efficient starter motors so there is less electrical drain. Any electrical drain has to be topped up by the alternator and takes power from the engine.

Let's see. 270 amps at 9.5 volts (the loaded test specs given in the '86 FSM) for 1 second is 2515 watt-seconds, which is only about 2.4 BTU. (Surprised?) A gallon of gasoline represents 125,000 BTU. If an engine is only 25% efficient, a gallon produces 31,250 BTU of work equivalent. So 2.4 BTU represents about 1/13,000th of a gallon or 1/100th of one ounce of gasoline.

Common electric motors, under full load, are about as efficient an energy conversion machine as you are likely to find. Up around 80-90% or better. And regular alternators are pretty efficient, too, I would think. But if you cautiously figure in 50% efficiency there, it still works out to about 1/50th of one ounce of gasoline (or 1/6400th of a gallon) to replenish the battery after starting the car. (There is going to be some inefficiency in charging and discharging the battery, as well. But I don't know the numbers.)

I wouldn't worry about that too much. I'd be more concerned about bendix wear, etc.


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