Wikipedia:Reference desk/Archives/Miscellaneous/2015 March 6

= March 6 =

Stalling and modern car engines
Sort of an engineering issue: Why do many modern cars stall so easily?

I don't have any hard numbers on the issue, but I have witnessed a lot of stalling lately, say during the last 10 years. This includes both other cars and my own.

My car is a modern electronic model, and I found that stalling is not always connected to the lower displaceent (my first car was an old model, OHC engine with close to twice the displaceent, i.e. more power at low RPM), but also to the fact that the engine seems to quit around 700rpm even with no load.

The old car, which was 17 years old when I got it but in great condition, could recover from 300 to 400rpm with no problem if I disengaged in time, but with new cars, it's different: no matter what load, if the rpm drop below 700, the engine calls it a day. I don't know the exact rpm figures; I'm extrapolating from the internal RPM meter, so the figures could be off. However, it's definitly about twice the rpm I could recover from with my old car, i.e. roughly the same power, and with a smaller engine with lighter parts.

Now, why does the engine chip give up? Is it dangerous to run an engine at low RPM, to an extent that it's less dangerous to stop the engine completely and let the user restart than to try to keep it running? Is there some code in it like

if (time_since_last_rev >= 90 milliseconds) { stop; // don't risk engine damage }

OTOH, I always thought that stalling an engine is bad (as in, potentially damaging)...

Our article on stall (engine) claims that electronic engines are less plagued by stalling, but in my experience, that's not true, not at low RPM.

Pleas note that I'm not really a "car guy". The most complicated car maintenance I ever did was an oil change - ¡Ouch! (hurt me / more pain) 12:19, 6 March 2015 (UTC)


 * I'm not a car guy either, but I think any modern car that stalls at low RPM needs a tune-up. I think idle RPM is still something that can be adjusted. &#8213; Mandruss  &#9742;  12:25, 6 March 2015 (UTC)

Thanks but sorry that's not it; it didn't drop below 700 without load. It's just that it never recovers once it drops that low.


 * When reversing or otherwise when going very slowly, with the old OHC I could disengage around 400rpm and push the gas only so slightly, and it would recover 99% of the time.
 * Now when I fail to disengage in time and it drops below 700, it's already dead (as in it didn't recover 'once). It does restart just fine, and it never drops below ~950 without load.
 * Yes I am part of the problem; I'm so used to engines with more power at low RPM that my reflexes don't kick in in time to save a modern engine. :(
 * And when I bought that one,
 * Vendor: Oh, you're from America, please wait while I pull up the pricing of our AT cars...
 * Me:     No thanks, I'm looking for manual transmission.
 * Vendor: *wat*
 * And it happened twice.

Back to the main issue, I don't stall that often, I'm down to about once per month, but that's much more than I did before. And the amount of stalling in other cars has increased, too, but now that I think of it, drivers who are still adapting to a newer engine could be to "blame" for most of these.

p.s. I reformatted Stalling (disambiguation). - ¡Ouch! (hurt me / more pain) 13:06, 6 March 2015 (UTC)


 * May I ask what cubic capacity the engine is. What I'm thinking is that some modern cars have very small engines. What with their engine management system trying to keep the revs low and their resulting  low rotational kinetic energy, the the OP's model may well have stalling problem – if it fits into this category. However,  if he own a Humvee, then that theory go out the widow as not even a traffic patrol vehicle  blocking the road ahead will course a stall.--Aspro (talk) 22:47, 6 March 2015 (UTC)


 * Does your modern car have airconditioning? Did your old car *not* have A/C?  The deal with most modern small-engined cars (certainly my MINI Cooper) you need the engine power you get at around 700 rpm to keep the airconditioner pump running.  The engine management computer on my car sets the idle to 500rpm when the A/C is turned off and 700rpm when it's turned on.  So it doesn't stall no matter what.  But if you had a car that didn't detect when the A/C is turned on, then the idle would need to be set to 700rpm to avoid stalling in the worst-case situation.  Older cars without A/C can obviously idle with lower rpm, all other things being equal.


 * But there is a trend toward higher rpms in order to have smaller cylinders without compromising power output - hence you can have a smaller motor, less weight, etc. It's not a bad thing.  If your car stalls, then if it's an automatic, or if it's stalling while idling - then you need to get it serviced.  If it's a stickshift and it's stalling as you pull off the line, then you simply need to adjust your driving style.
 * SteveBaker (talk) 19:24, 7 March 2015 (UTC)


 * My gut reaction is that the OP does not have a stickshift, as one quickly learns how to manage the gas pedal within the first 10 hours of driving. --Aspro (talk) 23:02, 7 March 2015 (UTC)


 * I learned on automatic but switched to manual within a year (both the "old" and the new car are manual, too); the "rotational kinetic energy" seems to be really low even at about twice the RPM. That's a thing I never thought of – but it's possible: smaller cylinders, smaller pistons, crankshaft and last but not least, smaller and lighter flywheel.
 * More than half the cases happen when parking and stop me two feet short of the spot :(
 * Most of the other cases during winter, when it's cold and I pull off in 2nd gear; these usually happen less than a mile from home, in the morning. I blame temperatures and "Driver needs coffee badly" syndrome.
 * Sometimes I'm just not paying attention, or I'm distracted, and whoops.
 * These add up to about once per month. Quite bad but not a disaster either.
 * I wonder how precise the timing is with electronic engines? It probably varies between manufacturers, but 90 milliseconds is less than twice the PC timer overflow interval; maybe the timer since last rev (or since last ignition, or whatever) just overflows and that, rather than an "emergency stop" statement is what kills the engine. Or maybe I thought of that because I'm better I suck less at computers than at cars... - ¡Ouch! (hurt me / more pain) 08:19, 9 March 2015 (UTC)


 * As you have learnt on automatics, then maybe you have still not got the hang on slipping the clutch/ riding the clutch at slow speed -such as parking and uphill starts. One just uses the gas pedal to keep the revs a little bit higher. See: &  . This  may not always intuitive to everybody – and you, maybe are one of the unlucky geeks that needs to switch off the logic part of  brain and 'just feel' the cars response and act accordingly. Try some up-hill-starts. First forward then backwards. If this is the problem you are  experiencing, Then, through the seat of your pants you will soon judge the right revs to maintain. It is just practice. Have a go and report back to us please, as this question may come up again. P.S. Those higher revs and good clutch control negates any millisecond delay inherent in the engine management system. Forget that, until we have engine management systems using quantum computers. --Aspro (talk) 17:09, 9 March 2015 (UTC)

Judicial Sentencing for Witchcraft
Context: https://en.wikivoyage.org/wiki/Wikivoyage_talk:Joke_articles/Time_travel#Witch_Trials

What was the historical sentence and methods of carrying out used in history? ShakespeareFan00 (talk) 14:52, 6 March 2015 (UTC)
 * Which country? KägeTorä - (影虎) (Chin Wag) 15:16, 6 March 2015 (UTC)
 * in the Context pre-colonial United States. ShakespeareFan00 (talk) 15:22, 6 March 2015 (UTC)
 * It appears to be Salem, Mass, in what would become the United States, at the time of the Witch Trials. Thus, in 1692. Did you read our article on the Salem Witch Trials, ShakespereFan? LongHairedFop (talk) 15:23, 6 March 2015 (UTC)
 * I'd also recommend Entertaining Satan - Witchcraft and the Culture of Early New England by John Putnam Demos, an excellent read and very comprehensive. Demos has written several other books on Witchcraft as a historical study.  -- Jayron 32 15:29, 6 March 2015 (UTC)
 * In the U.S., burning, hanging and pressing under stones were used as methods of execution of convicted witches. The Espy File (Executions in the U.S. 1608-2002) lists 33 people executed by hanging, one by pressing and one by burning. The only African American convicted of witchcraft was the only one executed by burning. 20 of the 35 known executions for witchcraft occurred at Salem. No executions for witchcraft occurred after the Revolutionary War, so arguably none occurred in the United States. Rmhermen (talk) 19:44, 6 March 2015 (UTC)
 * I'd always figured old-timey Americans leaned toward burning blacks over whites, but not by that much. Damn. Seems the only thing so vile a white person could do to get that is "slave revolt". Makes me think witchhunting fell out of fashion more for finding an easier scapegoat than finding rationality or humanity. Need to torture test a witch to see if she's black. Checking the skin instead must've seen some prosectors' conviction rates skyrocket. InedibleHulk (talk) 21:18, 6 March 2015 (UTC)
 * What the fuck are you rambling on about? -- Jayron 32 03:56, 7 March 2015 (UTC)
 * The Espy File. And race in the United States criminal justice system. And moral panic. Not allegedly magical Tanzanian albinos. InedibleHulk (talk) 19:40, 7 March 2015 (UTC) InedibleHulk (talk) 19:38, 7 March 2015 (UTC)
 * The fact that those things are possibly true doesn't mean it is relevant to bring them up in unrelated discussions. If the OP has a question about racial aspects of crime and criminal prosecutions in the modern United States, they can ask it and we can provide references.  Making broad political statements in an oblique manner is not appropriate behavior for the reference desk, and only serves to make this place less friendly for people who just come by for straight answers.  Please don't do that.  -- Jayron 32 13:56, 10 March 2015 (UTC)
 * Not totally irrelevant, just a bit tangential. And not a direct answer to the OP, a follow-up on Rmhermen's observation. Some straight answers cover a lot of ground. When the colony was young, the xenophobes had to look for the darkness under the skin, and go to great lengths to prove their findings to the women's similar-looking kin. There seems to have been a discomforting feeling that anyone (mostly any woman) could be a wolf in sheep's clothing, and the suspicion led to familial and community dissension.
 * As blacks became more common, the scapegoat became clearer and more disconnected. Easier to prove guilt and justify punishment for the whites, without fear of a counter-allegation. The mass persecution of blacks seems to have directly filled the witchhunt niche, and completely eradicated the practice, like how an influx of deer will stop wolves from digging for mice. Since the mid-eighteenth, the American courts have yet to return to the smaller, harder targets.
 * No political statement or unfriendliness intended, beyond "some humans continue to suck at humanity". Sorry for any offense. InedibleHulk (talk) 19:45, 10 March 2015 (UTC)

Mysterious fuel gauge
I recently bought (in the UK) a second-hand Toyota Yaris which has a digital instrument display. The fuel gauge has the letters "I/I" at the top, and "R" at the bottom. Is this from another language or some sort of international code? Just curious. The speed is given in Miles Per Hour, and it's a right-hand drive so you would think it was optimised for the UK market. Alansplodge (talk) 17:58, 6 March 2015 (UTC)
 * Have you checked the car's manual? Maybe it explains there what these mean? -- Jayron 32 18:02, 6 March 2015 (UTC)


 * Checking this out in various car forums, mentioning other Toyota models too, such as the Scion tC, I saw consensus that "1/1" stands for 100% (not 1/2-full, not 2/3-full, but 1/1-full!), while "R" appears to stand for reserve (though at least one person suggested "refill" too). One reason for this choice might be that they're more universally understandable outside the Anglophone world (reserve is called something similar, starting with the letter "R", in many languages, while the words for "full" and "empty" usually don't start with "F" and "E" in those languages. ---Sluzzelin talk  18:20, 6 March 2015 (UTC)


 * Thanks Sluzzelin, that makes perfect sense. Unfortunately Jayron, the manual wasn't supplied, but I've been able to work most of it out so far.... Alansplodge (talk) 18:24, 6 March 2015 (UTC)

FYI @Alansplodge, user manuals are available here.   → Michael J Ⓣ Ⓒ Ⓜ 01:50, 7 March 2015 (UTC)
 * Thank you kind sir. Alansplodge (talk) 18:21, 7 March 2015 (UTC)
 * By the way, the Japanese drive on the same side as we do, so the car would not be optimized necessarily for the UK market, it would just be normal. If it had been changed to left-hand drive, then it would have been optimized for certain other countries. KägeTorä - (影虎) (Chin Wag) 11:38, 8 March 2015 (UTC)
 * I think both of Alansplodge's comments were meant to be taken together not seperately. Japan and some other countries may have right hand drive vehicles, but they instrument panels probably don't have Miles Per Hour as the primary speed units. In fact, probably one of the only ones which would is the US, but they would have left hand drive. Japanese used vehicle exporting and other sites like seem to confirm that having MPH probably means the speedometer at least was changed for Japan imports edit: exports, or I'm guessing anywhere else which exports many vehicles to the UK (Singapore perhaps?). Of course it's possible only the speedometer was changed rather than really being optimised for the UK market. Nil Einne (talk) 13:31, 8 March 2015 (UTC)
 * Indeed. I was assuming that MPH + RHD = UK. Even the Republic of Ireland has gone over to those funny kilometre thingies. Why are we writing in tiny letters? Is it an eye test? Alansplodge (talk) 19:23, 8 March 2015 (UTC)
 * <Small><Small><Small>Yes, just to see if you can drive, dear chap. <font face="MV Boli" color="blue">KägeTorä - (影虎) (Chin Wag) 19:38, 8 March 2015 (UTC)
 * Point me in the direction of Specsavers please... Alansplodge (talk) 11:22, 9 March 2015 (UTC)
 * You have two options. Either zoom in, or copypaste to your preferred Wordprocessor. Then, dear chap, you shall pass your test for being a worthy driver. Believe me. <font face="MV Boli" color="blue">KägeTorä - (影虎) (Chin Wag) 17:11, 9 March 2015 (UTC)
 * I cheated and read from the "edit". Alansplodge (talk) 21:04, 9 March 2015 (UTC)
 * Bah, immediate failure, for not following instructions! :) <font face="MV Boli" color="blue">KägeTorä - (影虎) (Chin Wag) 04:34, 10 March 2015 (UTC)