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Post by OziRiS on Apr 19, 2014 23:16:30 GMT
Here's yet another fuel efficiency myth.
This one started (for me) with my girlfriend's brother-in-law who's a real cheapskate. He wants to get as many miles to the gallon as he can possibly get, so he got this idea that turning off his engine while he was coasting down hill would save him a lot of fuel. Turns out he's not the only one who thinks this, as I've met many people over the past few years who say they do this.
Here's where I have a problem:
The guy in question drives a 2010 VW Golf 1.9 TDi station wagon with a manual transmission. A car that new has an automatic fuel cut off system that should set in when you take your foot off the gas, as long as the car is in gear and still at speed, effectively letting the car roll along without using any fuel. So why turn off the engine? Why not just let it roll in gear?
I see a couple of problems with turning the engine off:
Even if it does save you a few drops of fuel (and I'm not sure that it does), you're also turning off the ABS breaking system and the power steering system, which could potentially be dangerous in an emergency stop/maneuver situation.
I've also read somewhere that the starter wears out faster the more you use it (makes sense to me). When a car like this is new, the manufacturer apparantly guarantees you around 10,000 starts before it needs changing. If you cut off the engine every time you go down hill and start it again when the road either evens out or starts to go up hill again, then you're putting unnecessary strain on the starter and running the risk of having to replace it sooner/more often with added cost, effectively robbing you of all that money you saved (if any) each time you cut off the engine.
For my money the risk alone of not having properly working breaks and steering is enough that I'm not inclined to start doing this, but what do the rest of you say? Is there even any benefit to doing this in modern cars?
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Post by the light works on Apr 20, 2014 0:54:25 GMT
Here's yet another fuel efficiency myth. This one started (for me) with my girlfriend's brother-in-law who's a real cheapskate. He wants to get as many miles to the gallon as he can possibly get, so he got this idea that turning off his engine while he was coasting down hill would save him a lot of fuel. Turns out he's not the only one who thinks this, as I've met many people over the past few years who say they do this. Here's where I have a problem: The guy in question drives a 2010 VW Golf 1.9 TDi station wagon with a manual transmission. A car that new has an automatic fuel cut off system that should set in when you take your foot off the gas, as long as the car is in gear and still at speed, effectively letting the car roll along without using any fuel. So why turn off the engine? Why not just let it roll in gear? I see a couple of problems with turning the engine off: Even if it does save you a few drops of fuel (and I'm not sure that it does), you're also turning off the ABS breaking system and the power steering system, which could potentially be dangerous in an emergency stop/maneuver situation. I've also read somewhere that the starter wears out faster the more you use it (makes sense to me). When a car like this is new, the manufacturer apparantly guarantees you around 10,000 starts before it needs changing. If you cut off the engine every time you go down hill and start it again when the road either evens out or starts to go up hill again, then you're putting unnecessary strain on the starter and running the risk of having to replace it sooner/more often with added cost, effectively robbing you of all that money you saved (if any) each time you cut off the engine. For my money the risk alone of not having properly working breaks and steering is enough that I'm not inclined to start doing this, but what do the rest of you say? Is there even any benefit to doing this in modern cars? as you say, with a modern fuel injection system, if the ECU detects that the car is pushing the engine; it turns off the fuel. with the engine not turning, as you also say - you lose any power assist: I.E. brakes and steering. also, unless they changed the rule, in Oregon, it is illegal to coast with your transmission disengaged - whether the engine is running or not. additionally, if you have an automatic transmission and your car is newer than, say, an edsel, the transmission design is such that the lubricating system is powered by the input shaft of the transmission; which means if your car is moving without the engine turning, you are actively wearing out your transmission. so: if you have a manual transmission, no power steering or brakes, and no police around; and you don't mind a bit of extra wear on your brakes - because you will be using your brakes instead of your engine resistance to control your speed... |
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Post by silverdragon on May 1, 2014 6:48:03 GMT
Turning off the engine, other than stalling it, whilst moving, is illegal in UK, and parts of europe.
Mostly because of the Brake Assists and power steering and not being in proper control of the vehicle issues.
Therefore, any segment that has turning off the engine must address those issues before they start?..
Other than that, most engines have over-run fuel cut off's, in that when you are running down hill or slowing, the engine knows that, and cuts off the fuel supply to the engine anyway, as TLW has pointed out, so why would anyone want to try to save any more fuel than isnt being used anyway in the first place?....(Pick through the double-treble negatives in that one if you can?...)
Finally, if you turn the key too far the steering lock may engage.
Bit of a "Fail"..?...
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Post by the light works on May 1, 2014 14:27:23 GMT
Turning off the engine, other than stalling it, whilst moving, is illegal in UK, and parts of europe. Mostly because of the Brake Assists and power steering and not being in proper control of the vehicle issues. Therefore, any segment that has turning off the engine must address those issues before they start?.. Other than that, most engines have over-run fuel cut off's, in that when you are running down hill or slowing, the engine knows that, and cuts off the fuel supply to the engine anyway, as TLW has pointed out, so why would anyone want to try to save any more fuel than isnt being used anyway in the first place?....(Pick through the double-treble negatives in that one if you can?...) Finally, if you turn the key too far the steering lock may engage. Bit of a "Fail"..?... the bigger fail we had in the old boards was people with the knee jerk "but if the ECU stops delivering fuel, the engine will stop turning" reaction. so if you are ever on a downgrade and lose your brakes, just pull the fuel cut off handle on your truck, and it will bring you to a stop.  (how does proboards NOT have an eye-roll smiley?) |
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Post by silverdragon on May 2, 2014 6:10:42 GMT
Auto-correct is my worst enema. Onwards,  , I thought this one was?.... but they are dang hard to see?... To the auto fuel cut off, I have asked more than once if they could try putting the car on a steep hill in gear and letting it roll to see if the engine will turn or start even. I know it will, because I used to use that trick to start my Mini rather than bother the starter motor, which was an awkward sod at the best of times.
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Post by maxman on May 2, 2014 10:23:03 GMT
Just use an image of Captain Piccard doing a facepalm.
Or Jesus doing a facepalm.
Or anyone doing a facepalm, really.
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Post by the light works on May 2, 2014 10:37:32 GMT
Auto-correct is my worst enema. Onwards, , I thought this one was?.... but they are dang hard to see?... To the auto fuel cut off, I have asked more than once if they could try putting the car on a steep hill in gear and letting it roll to see if the engine will turn or start even. I know it will, because I used to use that trick to start my Mini rather than bother the starter motor, which was an awkward sod at the best of times. eyeroll has the pupils turned upwards. the emoticon is %) (we'll see if that pops a smiley) I've actually coasted my first pickup downhill with the ignition off and the transmission engaged - which is proof that not having the fire lit will still allow the engine to turn - but as I said, it was a knee jerk reaction form people with no critical thinking skills. |
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Post by kharnynb on May 3, 2014 12:11:53 GMT
That's only an idea of people who haven't thought of what a new set of brakes costs.....
Unsafe, stupid and useless.
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Post by ironhold on May 3, 2014 19:11:22 GMT
Last night I found myself in the position of having to get my car home w/o engine power.
I had virtually no capability to brake, and the steering was comparable to operating a tractor.
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Post by OziRiS on May 5, 2014 0:32:00 GMT
Last night I found myself in the position of having to get my car home w/o engine power. I had virtually no capability to brake, and the steering was comparable to operating a tractor. Just as I suspected. Now imagine rolling down a hill like that at 50 mph with the ignition on (for lights and such) but the engine off, getting ready to turn it back on when you get to the foot of the hill. Halfway down, a deer jumps out in front of you. Or someone fails to yield and turns out onto the road less than a hundred feet in front of you. Now what? Your reaction time is deminished as it is and you're willing to bet your own and everyone else in the car's life that you can turn that engine on quickly enough to brake/steer your way out of that situation? That's what my brother-in-law does and I've told him a hundred times that he's risking more than it's worth to save a few drops of fuel. I don't usually go around forbidding things, but I've actually forbidden my GF and son from ever getting in his car again. They're cool with it. |
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Post by ironhold on May 5, 2014 1:25:56 GMT
What happened was that my car broke down in the parking lot of the local movie theater, we didn't quite have the cash on-hand to pay for a tow truck, and someone bogarted the flatbed trailer at the mechanic shop where my dad works for their own ends.
We ultimately wound up having to use the family van to tow the car back to the house.
As near as my dad can figure, the computer isn't telling the fuel pump to activate. Best-case scenario is that I've got a bad connector (dirty, fouled, non-working, et cetra). Worst-case scenario is that it's the computer itself, in which case it might be time for me to let my car go due to how old it is.
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Post by the light works on May 5, 2014 1:56:50 GMT
What happened was that my car broke down in the parking lot of the local movie theater, we didn't quite have the cash on-hand to pay for a tow truck, and someone bogarted the flatbed trailer at the mechanic shop where my dad works for their own ends. We ultimately wound up having to use the family van to tow the car back to the house. As near as my dad can figure, the computer isn't telling the fuel pump to activate. Best-case scenario is that I've got a bad connector (dirty, fouled, non-working, et cetra). Worst-case scenario is that it's the computer itself, in which case it might be time for me to let my car go due to how old it is. ask a good mechanic for a quote on what it would likely cost based on the symptoms. if it exceeds the price of a replacement car, you have your answer. (currently my parents are keeping their minivan because it only costs them about $1000 per year to keep it running compared to the $30,000 or more it would cost for a decent replacement - but they are now needing to factor in the frequency of not being able to drive it because it is at the mechanic's.) |
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Post by ironhold on May 5, 2014 2:54:06 GMT
My dad's one of the people who helped design the diagnostic computer that mechanics use to read the error codes given by vehicle computers. The Army farmed him out to GE to help put together the prototype.
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Post by the light works on May 5, 2014 2:57:58 GMT
My dad's one of the people who helped design the diagnostic computer that mechanics use to read the error codes given by vehicle computers. The Army farmed him out to GE to help put together the prototype. and yet he does everything your brother tells him regarding his desktop? |
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Post by ironhold on May 5, 2014 2:59:49 GMT
That's why I keep wanting to scream.
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Post by the light works on May 5, 2014 3:05:07 GMT
That's why I keep wanting to scream. that does explain it pretty well. |
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Post by ironhold on May 5, 2014 3:09:26 GMT
Dad knows just enough about modern-day computers to ask a few questions here and there, but it's not his actual area of expertise and so he relents after a while.
My mom, meanwhile, keeps talking about having me go take some computer classes so that I can fix things for everyone. I've been trying to get her to go back to school, but even before the website of the local community college kept having issues (I've picked up malware off of the site twice) she would balk because she was afraid that she couldn't handle the coursework.
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Post by the light works on May 5, 2014 3:17:10 GMT
Dad knows just enough about modern-day computers to ask a few questions here and there, but it's not his actual area of expertise and so he relents after a while. My mom, meanwhile, keeps talking about having me go take some computer classes so that I can fix things for everyone. I've been trying to get her to go back to school, but even before the website of the local community college kept having issues (I've picked up malware off of the site twice) she would balk because she was afraid that she couldn't handle the coursework. I am getting the impression from your descriptions that she is one of those people who has spent her entire life specializing in making everyone else do all the work. |
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Post by ironhold on May 5, 2014 3:51:11 GMT
With my mom, it's pretty much "technology scares her because she can't understand it." She's comfortable with her little tablet so long as it works right, but the least little problem sends her into fits. That her laptop (which we pretty much had to march her into the store to buy) had Vista as its OS didn't help matters; if Vista wasn't screwing up then the laptop itself was having technical issues.
Heartbleed? The Internet Explorer breach? Stuff like that frightens her, and the way the mainstream media reports it doesn't help since it's all about causing panics.
The end result is that when it comes to anything tech-related, she gives up easily and wants somebody else to do things that she could easily do herself since she doesn't understand and is giving in to frustration.
The other issue is that her high school math teacher was mentally ill; he was a World War II veteran who had what we today would recognize as PTSD, and he would frequently experience flashbacks in the middle of the classroom. As a result, she associates math class with what she witnessed, and so appears to have some sort of psychological block when it comes to ever taking math again.
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Post by silverdragon on May 5, 2014 10:36:17 GMT
Get your dad to look at the error codes again....
I have an idea that he may need to discount, is it something to do with the immobiliser system.
I know from a little experience that fuel pump cut of is one method of immobilisation that can be quite effective... you end up with a dead car that wont start and a flat battery, but once the "Real" key is used to start it, (and you charge the battery) as soon as the fuel pump works, all systems are fine.
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(how does proboards NOT have an eye-roll smiley?)
, I thought this one was?.... but they are dang hard to see?...
