Time spent at traffic lights - Engine OFF
 

Hey ecomodders,

I've been lurking about reading as much as I can. Tightening the nut behind the wheel was the single most beneficial MPG increase that I have made 26mpg prior to averaging 36mpgs now.

I have been shutting down the engine when I know that a traffic light is going to be long, and have read that it take about 11 secs. for the mpg benefit to set in. While sitting at traffic lights and counting in my head the amount of time the car is off, I figured I needed a stop watch to find out how much time I am off during the day.

Please understand I am a Field Service Engineer for IBM and drive a lot. This is my first attempt to make a contribution to this site.

Honda Accord 2.3l Auto

Todays numbers:

125 miles

27 Traffic light stops with engine shut down.

22:27 Time spent with engine off.

27 restarts @ .11 secs = 297secs inefficient start recoup


so I think I was shut down for 17:30

my scangauge says I burn .25gph at idle.


Is this worth it?


Is this valuable information to be tracking?

Ive been thinking about this as well and while I like the idea of saving fuel, I wonder how much fuel Im really saving with engine off at lights (of course every little bit helps and over time it will add up). My drives are probably far less hampered when it comes to time spent sitting, and I would be suprised if I would be able to actually save even 1/2 gallon of fuel over a complete tank, but others mileage will of course vary. I think the main improvement of engine off use is when coasting up to a red light from a distance and then continuing to sit with the engine off until its time to restart. Thats where you get the biggest gains assuming the car can be safely EOC'd.

I don't know about the 11 second thing. I do know that if it's a new car and the starter is expensive it's probably not worth it. The best thing you can do is EOC coast up to the light, and never stop. Popping the clutch to restart is a good idea to.

I think this depends a lot on the vehicle. In your case with the low GPH numbers you see at idle it may take a while for the savings to really add up(with luck it covers the new starter and then some). In the case of my Jeep I run about 0.79GPH idle. So it's sucking the gas like none other. So I have found short trips across town(about 5-6miles) it pushes the trip avg up 1-2MPG's if I turn it off at a 20-30second light.

I'm sure others may say it's not worth it. Claim it doesn't counter-act the cost of a new starter. But there are a lot of factors to take in to account, like the fact that in your case you spent 17:30 with the engine off, so the engine will last longer. If you want to get in to the nitty gritty, think about the money you just saved, how much intrest will that earn if you put it in the bank now to cover the new starter down the road?

...I don't shut off the engine at stop lights (need A/C when it's 100 F outside), but I have been "sensitized" to the fact that GASOLINE is "...going away..." while no MILES are being traveled, because the MPG digits keep "ticking" downward...slowly at first (short light) then rapidly (l-o-n-g lights).

...didn't realize I could "hate" stop lights so much (wink,wink)!

Really, when was the last time anyone had to replace a starter?

VW Rabbits had chronically weak starters, but since those late 70's / early 80's vintage vehicles, I've never had to.

I understand Wayne wore out the starter in his Accord, but the number of starts on his will vastly outnumber the typical ecodriver.

Not saying it can't happen, but I bet it's pretty unlikely.

Agree with Metro on the likelihood of replacing a starter...not likely.

And if the OP drives alot...imagine how much fuel he is saving by not idling the engine for 20 minutes a day. If you save a half gallon of fuel a week that's 26 gallons a year or more than $70 a year...just by simply turning your car off at lights. Well worth it in my opinion and just another piece in the puzzle to raising mpg, saving money, helping the environment.

Just to be a stick in the mud here - I just had to buy a new starter for the wife's Saturn. It had nothing to do with wear, though. Damn corrosion weakened the wire studs on the solenoid, and no one sells just the solenoid.

I did the math comparing NICE-on coasting with FASing, and idling while coasting can drop mileage from 60 mpg to 40 mpg. It's going to be worse when you're not even moving.

I found on my cross-country trip that shutting the engine off, but leaving the fan on, kept me cool through even 5 minute stoplights in FL and TX in my Scion. My Nissan isn't as effective, so 3 minutes is about the comfort limit.

Well, I've had to replace starters on several of my cars - 1988 Chevy Celebrity, 1995 Chevy Beretta, 2000 Chevy Impala. Granted, all of them were beyond 100,000 miles at the time of the replacement, but I take it more or less for granted that I'm going to have to replace a starter at least once.

Note that the above replacements were made before I made it a point to turn the engine off at long lights.

For what it's worth, BMW's owners manuals claim that four seconds of idling is the break-even point for idling versus shutting off. Of course, shutting down and starting up for every 4-second delay sounds like you're asking for trouble. My rule is that I'll shut down if I know the wait will be more than 20 seconds AND if the oil is at operating temperature.

A new starter for my Accord costs about $120. I've saved about $850 in fuel so far over what I would have spent getting EPA mileage. I'll risk it. :-)

jkp1187 -

I haven't replaced my starter yet (knock on virtual wood), but at 182K miles, it's gonna happen sooner or later.

I believe the 4 second idling number. In colder climates, one caveat to this is unheated oxygen sensors (aka oxygen sensors that only start to work when exhaust gases heat them up to "temperature X"). Heated oxygen sensors are heated using electricity from the battery, so they stay heated as long as the car's key is in the on-position. At extended stops in cold weather, an unheated oxygen sensor could cool off to the point where it is no longer operating normally. The ECU/PCM can detect this state and will spend more time in open-loop mode, which would burn more fuel.

I also wait for the engine to warm up before employing engine off. I won't using engine-off unless I already know the timing of the light. 20 seconds sounds about right for me too.

CarloSW2

I wish that I could EOC to traffic lights, but being an Auto and not on the list, I would damage the Torque converter.

I had read on another post that someone with at 1.5L had figured out the recoup of shutdown was 11secs. It would be great if it was only 4 secs!

I try to be smart about the shut downs, and today was mostly suburban driving and was able to see well ahead of my self so I could start coasting early, hate those traffic lights that jump yellow with no cars waiting. I made a few mistakes on the lights today, but did the same as yesterday tracking the amount of shutdowns and the time spent engine off:

26 Traffic shutdowns

15:51 total time shut down

11 sec recoup?(i'd really like to know the real number) = 286 secs

official time off = 11min 08secs

137miles driven today

So in two days you have saved about 30 minutes of idle time...in 4 days that would be an hour saved and 1/4 gallon of gas saved (by your numbers). Saving a gallon or more a month will surely impact your mpg positively over the course of a year.

You have to decide for yourself on it's impact on your starter and if the fuel savings by shutting down the car are most beneficial that any effect it might have on the starter...it's your car at the end of the day...but personally I don't think it's that big of a deal with the starter (again...it's your car at the end of the day).

I went through this process when I started hypermiling too. Was afraid to use higher psi for it's effect on tire wear/traction and slowly inched up from 35 to current 52 psi I'm running. I ran into a guy running 60 psi on the same tires the other day...so I pumped mine up to 52 yesterday. I was afraid to neutral coast in my former 4runner and slowly worked my way into doing it.

You find out what you are comfortable with and do it...what you are not comfortable with you search for more info until you're comfortable doing it or not doing it...certainly a process.

I replaced the starter in my Tercel last summer. Something in the electrical system wasn't working, so I replaced the battery, alternator, and starter, at around 170k miles. I think the starter was somewhere around $80, and pretty simple to replace.

I don't stop at enough lights to memorize the timing, but the ones that I do know, I shut the engine off.

My '88 Escort with 498K miles and 22 years old is only on it's second starter. I think the original starter lasted about 250K miles , that's lots of starts.

If you buy a replacement starter from an auto parts store, they come with a lifetime warranty.

I've had to replace a couple (long before I started shutting the engine to save fuel), and all you do is walk in with a faulty starter, tell them your phone number (because I had lost the receipt but they keep records in the computer) and walk out with a new starter (also with the same lifetime warranty.)

So for the cost of replacing the starter just once you get a lifetime of starting it at every stoplight.

Someone posted here recently pointing out that if you start accelerating immediately after starting, it is irrelevant whether the computer is compensating for the temperature because high-idle/open-loop have the most effect at idle or steady state (low throttle, low RPMs)
How many seconds of idling is equivalent to starting your engine? - IWillTry

EGADS Jacob! I forgot about the lifetime warranty...

That brings the score down to "if you can change it yourself, you've only got to save one starter's worth of gas in the WHOLE LIFE OF THE CAR!" (if you don't count your time.)

I'm pretty sure that the average person can save $200 worth of gas in the lifetime of the car (the cost of the Saturn's starter) with not too much problems.

what are you talking about ? i want to know if its easy and save gaz !!

and what is GPH ? a mesure of currect draw at idle ?

yanlapanic -

Page 8 in the Scangauge manual :

http://www.scangauge.com/support/pdfs/SGIIManual.pdf
GPH = Gallons-per-Hour
LPH = Liters-per-Hour
Fuel consumption rate in the selected units. This is
sensitive to throttle, gear and loading changes.

CarloSW2

Ho thanks ,

pretty nice info .

what is the second mod I should do with my car ... for aérodynamic or something ... what worth it the best ? *( sorry for english again )

i would like block grill , winter comming and -10 to -30 celcius is normal here so I should block it fully maybe ?

is dont want to do mod that are exagerated (i want stock look from ouside )

maybe coroplast under the car ? worth the job ? ... small miror (f1 style on ebay seem pretty nice and small)

Yanlapanic, why don't you go ahead and start a new thread in the forum with some pictures of your car if you have some. We would be more then happy to give you some suggestions there. It's ok we don't bite.

just because i will feel cheap to ask and get many good answer but I will not do all the mod ...

I wont delete a miror for example , Im 16 and just starting driving ... Ecomodeer interest me but I love performance too so I wont get my car hugly ...

you understand ??

FastPlastic was suggesting that you start your own thread for two reasons:

1. So you can get answers that are more devoted to what you're asking;
2. So you're not taking attention away from the person who had originally posted this thread.

Even if you don't do the mods that are suggested, you might get a few ideas that will help out in the future. You won't stay an inexperienced 16 year old forever, you know. You've got to grow up someday...

We like to help! Think of this as ecomodder university.

If you save some money later by getting better mileage think about donating and help us educate the next 16 year old newbie.

I'm on my way to donate right now...:thumbup:

Back on topic: Engine off at lights saves big. If you have a scanguage or mpguino you can watch the numbers fall fast. Savings are even greater if you are running alternatorless and you car does not have to recharge after each start.