driving efficiently

[Maengelito]

Edit: I reread it and kind of came off a little mean, im a nice person, just trying to help, its 2 am and I just got home so cut me some slack :o

DSM guys :roll:

but in all seriousness, DJ is right about all the different factors involved. we all drive different cars with different motors that have different fuel maps and different gearing and different drag coefficients at different altitudes with different air temps, etc.

gas all comes from the same sources as it would be very cost prohibitive to have an exxon holding tank next to a sheetz holding tank next to a BP holding tank and different trucks to go to different stations. most gas stations are privately owned and refilled by one local distributor. the proprietary additives are what makes brands of gases different but what you get out of it is most likely a factor of how well you take care of your car. winter gas and summer gas are different though as someone mentioned because of the temp change, as well as an increase in ethanol content during the summer months. the drawbacks of this (or benefits) were discussed in that turbo thread awhile back.

some cars might shut off their injectors while coasting, but i'd dont think i've ever owned one. any factory gauge that shows "mpg" is essentially a vacuum gauge on the intake tract. i'm sure it doesnt pump much fuel while coasting to save gas, but you need a little bit of rotating force to keep the alternator spinning, vacuum for power assisted brakes, etc. if you can push start a car, then that car pumps a little bit of fuel while coasting.

as for gearing, i dont know what the parameters are for the advertised fuel consumption test when looking at the sticker of a new car. i know its been talked about that they're going to revise the test, but as it stands now, its not very indicative of how most people drive. regardless of that fact, most car manufacturers want to sell lots of cars and 90% of cars are going to have gearing that has a good trade off between fuel econ and power when going between 55-65 mph as well as going from a stoplight to say like 20 mph. where that trade off is depends on what kind of car you have and the demographic you're aiming for.

as stated earlier, i think the true answer that applies to any make and model of car of how to save gas is to not drive like a jackass. we're all guilty of it sometimes, but if you're truly concerned about a penny here, or a nickel there, then you probably dont drive very quickly or aggressively. sure a nickel or penny here and there add up over the lifetime of a car, but i'm willing to pay that for the smile i get when i take an offramp.

[ScottyB]

The hate is strong with this one.

hate leads to anger
anger leads to suffeerrinngg

mmmmm

*end yoda voice*

[HAULN-SS]

A LOT of confusion and misinformation in this thread.

First Deersty, your wrong. Most cars do shut off the fuel injectors when your in gear and slowing down. First clue that your injectors are off, is wideband A/F. When you are in gear and slowing down, you will notice the wideband goes straight to LEAN. This is because no fuel is being injected. Also, next personal experience and clue aside from talking with many knowledgeable people about it.....is OMG, look at your injector duty cycle. When I am slowing down in gear, it goes to???????? Yes! 0%.

This is only true for manuals. For automatics, there would be no hydraulic pressure to keep the clutches engaged to keep the RPMs high enough so that the injectors stayed shut off. So the RPMs drop to just above idle, and fuel is delivered. Now, I'm gonna go out on a limb here, and say that most cars are automatics.

[BLINGMW]

Now, I'm gonna go out on a limb here, and say that most cars are automatics.

In this club? They better not be. :|

When you are at full throttle, that mini is running between a 11:1 and 13:1 a/f ratio, while if you are light throttle/cruising/idle, it should be between 15.2:1 and 14:2:1 (around).

Yeah, that's the question I hoped to answer in the other thread, but I still really don't know. I know it's richening the mix when the full throttle switch kicks in, so it seems that 99% throttle, just before that would be perfect, but I don't have an easy way to test that. :dunno:

any factory gauge that shows "mpg" is essentially a vacuum gauge on the intake tract.

I don't think that's usually true, most are digital and do it by summing up each firing of the injectors. Very oversimplified, the ECU knows what duty cycle each injector was at when it opened, so it just keeps a running tally of that. It should be, and I've found usually is, a pretty accurate method.

[Mike]

the idea of not burning fuel makes me feel warm and fuzzy.

Then why did you drive from Arlington to Philadelphia fast enough to make it in 2 hours? Turning your car off if you're going to sit more than 10 seconds seems a little silly when you're willing to do 80+ on the highway.

i'm not sure i follow. i never said "i strive to be the most efficient person in the world at all times." if i did, i wouldn't own a car and i wouldn't be a part of this club. it would be silly to live like that, but am i wrong for trying to do little things when i can?

[.RJ]

am i wrong for trying to do little things when i can?

Yes :lol:

[Ginger]

I don't think that's usually true, most are digital and do it by summing up each firing of the injectors. Very oversimplified, the ECU knows what duty cycle each injector was at when it opened, so it just keeps a running tally of that. It should be, and I've found usually is, a pretty accurate method.

+1

The BMW motorcycle gauges (calculate mileage achieved, fuel remaining, and miles remaining) are accurate down to the mile these days.

[Mike]

what's the point of this thread?

(A)

does anyone else try to consciously make their everyday drives pretty efficient? any cool tips? maybe we can learn something.

i knew that, he didn't. he was arguing dollars in my pocket, not efficiency.

some links on the subject:
<!-- m --><a class="postlink" href="http://hamiltonianfunction.blogspot.com/2007/06/turning-off-engine.html">http://hamiltonianfunction.blogspot.com ... ngine.html</a><!-- m -->
<!-- m --><a class="postlink" href="http://hamiltonianfunction.blogspot.com/2007/11/stoplights-revisited.html">http://hamiltonianfunction.blogspot.com ... sited.html</a><!-- m -->

fwiw, the labor for replacing my starter will be done by me. even using this tactic, i suspect i'll replace one starter on every car i own before moving to something newer. interestingly, i've driven for 10 years now and have never replaced a starter hrug:

[ScottyB]

i've driven for 10 years now and have never replaced a starter hrug:

that's pretty cool...if you're doing the work yourself i guess it's not a bad tactic to use.

[.RJ]

How much extra gas is used on startup though?

I think mythbusters needs to put this to the test!

[Ginger]

How much extra gas is used on startup though?

Why would there be extra gas when the vehicle is already warm?

[.RJ]

Once the engine is running, it wont dump extra fuel, but just starting the engine uses gas - does it use more than idling? I dont know - thats the question

[Ginger]

Once the engine is running, it wont dump extra fuel, but just starting the engine uses gas - does it use more than idling? I dont know - thats the question

I don't think it uses extra gas just to start... I can't figure why it would. It uses up 'lectrical juice, though.

[.RJ]

It uses up 'lectrical juice, though.

Which takes away HP (and fuel) from the engine to replace (the alternator). I hadnt thought of that one.

[Ginger]

It uses up 'lectrical juice, though.

Which takes away HP (and fuel) from the engine to replace (the alternator). I hadnt thought of that one.

That's not a relational draw, though. The motor will spin the alternator at the same resistance whether the battery recently had a heavy draw or is fully charged. Fuel use to for the current replacement would be not effected.

[Kaan]

the old tail my grandfather told me... was that if you are sitting for more than a minute... you should have shut the car off. bascially the fuel it takes to start up = 60 seconds at idle.

[Mike]

It uses up 'lectrical juice, though.

Which takes away HP (and fuel) from the engine to replace (the alternator). I hadnt thought of that one.

i don't know squat about alternators, but it seems to me that since it is driven by a constant belt (always on, doesn't change speed), it doesn't matter if it's charging something or not, it's always sucking up the same amount of motor. yes? no?

[Ginger]

the old tail my grandfather told me... was that if you are sitting for more than a minute... you should have shut the car off. bascially the fuel it takes to start up = 60 seconds at idle.

Every time I do that on a bike (since I'm hyper paranoid about my bikes overheating) it's time to go within 10 seconds - without fail.

[Mike]

It uses up 'lectrical juice, though.

Which takes away HP (and fuel) from the engine to replace (the alternator). I hadnt thought of that one.

That's not a relational draw, though. The motor will spin the alternator at the same resistance whether the battery recently had a heavy draw or is fully charged. Fuel use to for the current replacement would be not effected.

we posted at the same time

[.RJ]

That's not a relational draw, though. The motor will spin the alternator at the same resistance whether the battery recently had a heavy draw or is fully charged.

For a generator (most motorcycles) - yes. It takes more 'work' to spin an alternator if its charging the battery though - the voltage regulator will take feedback from the battery's voltage and reduce the draw on the alternator if it doesnt need any juice.