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| What Would Use More Fuel... | |
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| Tweet Topic Started: Nov 6 2008, 07:43 PM (168 Views) | |
| ScoobaJon | Nov 6 2008, 07:43 PM Post #1 |
J
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..a car going down a hill with the clutch in or out? does anyone know
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| paullen | Nov 6 2008, 07:45 PM Post #2 |
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Paul Lennox
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Clutch in should use more fuel as you are keeping the engine ticking over. |
![]() Gone is the 200, New project...1987 L200 www.lennoxservices.co.uk | |
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| tom | Nov 6 2008, 07:50 PM Post #3 |
Doesn't have a home to go to!
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yer if its in gear the wheels are spinning the engine effectivly using no fuel. depending on year of car the car can actually use very little or apparently no fuel if the clutch is out as the wheels going round is keeping the engine ticking over rather than it having to fuel it to keep it goin. |
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| ScoobaJon | Nov 6 2008, 08:03 PM Post #4 |
J
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but the car will go slower and be on the hill for longer + the injectors never shut off completely and as the engine is going faster it may end up injecting more fuel
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| cyman | Nov 6 2008, 08:11 PM Post #5 |
Here to stay
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if you keep the clutch out and the revs are higher than at tick over then the car will use more fuel than if you had the clutch in and are running at tickover. reason is as the revs increase even with no throttle the engine will keep the mixture correct thus more fuel will be used (although for the amount of time you get going down hill its not really going to amount to much either way) other things you need to take into account if the clutch is out the engine is trying to slow the car with what is refered to as engine breaking therefore you will travel a shorter distance as the car will slow sooner. but if you have the clutch in (or even better knock it out of gear so you have no clutch drag) you have no engine resistance therefore you would travel further therefore increasing your mpg. heheheh hope that makes things clear as mud
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| rob99 | Nov 6 2008, 08:20 PM Post #6 |
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Dead rising
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From recent reading I believe that keeping the car in gear rather than neutral is more economical. A quick google found these couple of quotes..
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Everyone you meet is fighting some kind of battle. Peter David Edwards. 15/10/1947 - 26/05/2008. R.I.P. | |
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| cyman | Nov 6 2008, 08:36 PM Post #7 |
Here to stay
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all but the most modern cars continue to burn fuel when in gear it is only in the last few years that the fuel injectors cutting off completley. obviously due to the whole global warming co2 thing. i found this whilst looking earlier. The following is based on info I gathered using a Scangauge automotive computer while helping my wife write a book about fuel economy: Coasting in neutral, fuel consumption is equal to idle fuel consumption. In the smallest passenger car engines, idling with AC and accessories off might consume .15 to .20 gallons per hour. In very large engines, you may be looking at .5 gal/hr. Now with AC, headlights, rear defroster and stereo blasting, fuel consumption rises by another .15 to .3 gallons per hour, depending on the car. At highway speeds, almost every car on the market will achieve over 100mpg while coasting in neutral. Coasting in gear is even more impressive. In most modern cars, if you're off the gas pedal and in gear, and the RPMs are above 1500 or so, your car turns off the fuel injectors entirely and you burn zero gallons per hour. Unless you drive an old car, you're getting infinite MPG coasting downnhill in gear. Keep in mind it's not free energy, and your car will coast to a stop much sooner due to the engine drag. But as a bonus, your car's momentum can drive the AC and accessories too, and your fuel consumption remains zero. |
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| 3ROTA | Nov 6 2008, 08:55 PM Post #8 |
Here to stay
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Most fuel injection engines cut fuel when throttle is closed. I know for a fact that an RX7 will cut fuel and that is 16 year old design. Even my Microtech has the option to cut fuel above 2000rpm with throttle closed. Mine had problems stalling with this on, so I have it switched off. I can entertain the people behind me with some flamage instead
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[GK-customfield]Kevin Bailey[customfield-GK]
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| cyman | Nov 6 2008, 09:02 PM Post #9 |
Here to stay
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heheh i dont think its worth us even trying to save fuel in our rx7's the only way ive found so far is to get it towed by a diesel
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| ScoobaJon | Nov 6 2008, 10:20 PM Post #10 |
J
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interesting stuff. so in conclusion.. if your cars clever enough to cut the injectors then its probably better to leave the clutch out. i'm pretty sure mine isn't though as i can always hear the exhaust quite loudly even when going down very steep inclines. it also pops and bangs a lot on run off which would indicate quite a bit of fuel is getting through. |
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| Julian | Nov 6 2008, 10:46 PM Post #11 |
Doesn't have a home to go to!
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I think this is why the majority of automatics are worse on fuel than the manual equivalent. |
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| rob99 | Nov 6 2008, 10:48 PM Post #12 |
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Dead rising
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Only if left in Drive all the time. If they shifted into a lower gear then it would be the same. (providing all the other dicussed paramiters are the same!) |
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Everyone you meet is fighting some kind of battle. Peter David Edwards. 15/10/1947 - 26/05/2008. R.I.P. | |
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| amnesia | Nov 7 2008, 03:17 PM Post #13 |
There's no replacement for displacement !
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If you're that desperate to save fuel you'd better buy a push bike
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| [GK-customfield]Daniel[customfield-GK]If you're good at something, never do it for free... | |
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[GK-customfield]Kevin Bailey[customfield-GK]
8:22 PM Jul 11