driving efficiently

[Mike]

i'm pretty sure modern fuel injection doesn't do that.

All FI'd cars have a rich 'cold start' cycle.

Cold start being the operative word. If mike doesn't care about burning his starter, his car isn't dumping in more fuel on startup once the engine is warmed up.

righto. saving gas > saving starter.

[Andy]

Do you think you're saving enough gas to justify the cost of a starter?

[.RJ]

I'm not sure I get it - if your coolant is below a certain temp, you're on cold start - starting and stopping the motor several times doesnt change this.

[Mike]

Do you think you're saving enough gas to justify the cost of a starter?

i would think that the gas saved at a stoplight outweighs the cost of a single start on my starter, yes.

[Mike]

I'm not sure I get it - if your coolant is below a certain temp, you're on cold start - starting and stopping the motor several times doesnt change this.

drive around 10 minutes, car gets warm, come to light, turn off car, turn car back on, car is already warm, car doesn't do a cold-start.

[.RJ]

that must be a long stoplight...

[.RJ]

drive around 10 minutes, car gets warm, come to light, turn off car, turn car back on, car is already warm, car doesn't do a cold-start.

Whats the point of that exercise?

[Mike]

that must be a long stoplight...

or starters seem to last a really long time.

[Mike]

drive around 10 minutes, car gets warm, come to light, turn off car, turn car back on, car is already warm, car doesn't do a cold-start.

Whats the point of that exercise?

what's the point of this thread?

[.RJ]

I have a hard time believing you're going to save any gas by shutting off your car at a light - certainly not anything worth worrying about. It doesnt take much fuel to keep the motor running at idle and off load most cars run pretty lean.

[Mike]

math:

new starter = $195
number of starts on a starter (guesstimate): 10,000
cost per start = $.02

gallons burnt per hour of idling: .4 (found a site where a guy did the math, he was driving something that gets 33mpg combined so i likely burn more than that)
cost of gas: $3.30
cost to idle for an hour: $1.32
cost to idle for a minute: $.02

the break even point then become a minute... if all i was caring about was cost. the idea of not burning fuel makes me feel warm and fuzzy.

[Andy]

math:

new starter = $195
number of starts on a starter (guesstimate): 10,000
cost per start = $.02

gallons burnt per hour of idling: .4 (found a site where a guy did the math, he was driving something that gets 33mpg combined so i likely burn more than that)
cost of gas: $3.30
cost to idle for an hour: $1.32
cost to idle for a minute: $.02

the break even point then become a minute... if all i was caring about was cost. the idea of not burning fuel makes me feel warm and fuzzy.

The bolded word is the operative. I don't know mike, i appreciate the effort but it might be in vain. Can we get you to track how many times you start the car in a month and we'll do the math from there

[Evan]

my guesstimate based on when my miata starter died is about 5,000 starts and it died a little earlier than is probably typical for most cars. 10,000 is probably pushing it.

the engine could also be wearing a bit faster since your cylinder and head are de-lubricating after the oil drains in the pan.

and I do think mike is a retard.

[Mike]

math:

new starter = $195
number of starts on a starter (guesstimate): 10,000
cost per start = $.02

gallons burnt per hour of idling: .4 (found a site where a guy did the math, he was driving something that gets 33mpg combined so i likely burn more than that)
cost of gas: $3.30
cost to idle for an hour: $1.32
cost to idle for a minute: $.02

the break even point then become a minute... if all i was caring about was cost. the idea of not burning fuel makes me feel warm and fuzzy.

The bolded word is the operative. I don't know mike, i appreciate the effort but it might be in vain. Can we get you to track how many times you start the car in a month and we'll do the math from there

my car has been on the road for 7 years. i figure about 3 starts a day. 3x365x7 = 7665 and it is still going.

[Apoc]

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.

[ScottyB]

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.

(B) the forums have been slow as hell and i'm bored

new starter = $195

including installation? also as Evan mentioned you are relying on a thin film of residual oil on the top end every time you start after stopping, increasing wear (probably very minutely but still). and yeah, if you're cruising at 80 for 2 hours you've pretty much negated days worth of doing the stop/start thing. but then again i guess its better than nothing.

ultimately this is all "it works for me" theoretical guesstimating BS talk for the most part. just thought it might be interesting discussion.

[ViPER1313]

ultimately this is all "it works for me" theoretical guesstimating BS talk for the most part.

Thats why I beat the piss out of any car I drive, all the time. Takes all the guess work out of it.

Don't buy the car if you can't afford to put gas in it.

[D_Eclipse9916]

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%.

Also different cars turn back on the fuel injectors at different rpms, for the dsm its 1400 rpms, so go do a test on your car. Slow down in gear and wait till you feel the engine braking almost stop and the car keeps you going for the most part between 1000-2000rpms.

Second, your cold starts are richened up on fuel injection vehicles. Aside from it being rich, you are also at a higher idle because of your FAIV (Fast Air Idle Valve). This means more fuel burnt. Arguably, there are two arguments to this, let your car warm up almost completely to let everything warm up without putting load on the vehicle. Bunch of negatives, at idle your EGR is working and if your constantly doing this to your vehicle, you will have lots of carbon build up. Second your not warming up your transmission/rear end/ blah blah blah, so if you thinkn you can flat foot it out since your engine is warm? Nope.
Then the alternative, warming it up by driving slowly, yes this is the best way to get best gas mileage, gets you there faster. However, im not quite sold. My car certainly doesnt like it until its been warmed up for at least a few minutes, I wont go into the reasons why I dont like this method as they are in my own opinion.

Channing, I find it hard to beleive your getting better gas mileage. 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). But thats not the only variable, which is why im inclined to say I find it hard to beleive, but cannot prove or justify. Do you have to get up to speed, especially around town? Time it takes accelerating? Wind resistance as your are up to speed quicker you are inducing more wind resistance in your drive overall as your at a higher speed overall? Lots of variables more than that.


Gearing: This is a double-edged sword. As in the case of everything, extremes are not to your benefit. As I know my car well, I will explain this about my car. At 75 mph I am running at about 3100 rpms. Well you say, thats high, throw that 25% 5th gear reduction on that biatch! Now your running low 2000 rpms. Running less rpms=less gas? No, now you are having to maintain more throttle to keep the car at speed, inducing more throttle means more fuel....so? Where do you cut the line? I find a good speed is to keep the engine at 2900-3000 rpms, about 65-70 mph. I maintain between 9% and 14% throttle on I-81, where at lower speeds on hills I can see up to 22% throttle when at lower rpms. So a compromise is in order here.

Gas mileage comes down to a lot more than just drag coefficents, how about your coefficient of frontal area? This is a huge part of what we "know" as drag. tires? You know those awesome sticky tires that grip so well on your favorite corner in the morning? Yeah thats also killing your gas mileage. Toe is another big one, I personally have mine set to zeroed out front, 1/16 in the rear (or as close as they could get). Nobody mentioned rolling resistance? Huge factor here.


However, if your really bitching about gas hardcore, go get a fucking jetta diesel or something. I try to be gas conscientious but im hella guilty of on ramps, and any other place I can floor it. So pick your battles, I am good and do a few thigns to keep my gas bill down, but fuck im not gonna ruin a perfectly good on-ramp just so I can save myself $.20 in gas.


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

[Kaan]

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

The hate is strong with this one.

[.RJ]

What would Shep do?