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Interesting Observation

  #1  
Old 01-22-2008, 04:39 PM
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Default Interesting Observation

Since gas prices cost an arm and a leg these days I, like most drivers, drive to conserve gas. I don't "gun it" unless I absolutely have to and take my foot off the accelerator if I see that the next traffic light is red. A long time ago a friend of mine told me to stick the car in neutral to conserve gas when stopped at a traffic light. Within a few weeks it turned into an habit with my old car (97 Camry).

Last month however I bought a the 08 V4 Accord Coupe with AT and noticed something that was somewhat of a shock to me. While the car is at a stand still, in neutral (w/ the brakes applied), the engine idles around roughly 900-1000 RPM. However if I put the car into Drive, while at a stand still, the RPM gauge stoops down to roughly 600-700 RPM. Now I'm no car fanatic but from the little that I know about cars and engines... the lower your RPM, the lower your gas consumption.

Has anyone else noticed this in their cars? Does it mean that more gas in being consumed in neutral?
 
  #2  
Old 01-22-2008, 04:44 PM
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Default RE: Interesting Observation

No, while the car is in neutral the tranny is dis-enguaged so the car is just spinning the engine, once you put it into drive it engauges the gears and has to rotate additional mass in the transmission, this is what drops your idle. So essentially, weather it's in neutral or in drive you're going to use about the same amount of gas at a stop light
 
  #3  
Old 01-22-2008, 04:50 PM
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Default RE: Interesting Observation

Ohhhhh so it is a common misconception then? Because I've heard a lot of people say that putting the car in neutral would save you gas at a stop light... Hmmm interesting. Thanks Sir nasty.
 
  #4  
Old 01-22-2008, 05:00 PM
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Default RE: Interesting Observation

It is a common misconception. I have a manual transmission, and I always put mine in neutral at a stop light. But that is not to conserve gas, it is so I don't have to keep the clutch mashed down with pressure from my left foot/leg.
I wouldn't put my auto in neutral at a stop light. It is pointless in my opinion.
 
  #5  
Old 01-22-2008, 05:01 PM
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Default RE: Interesting Observation

Oh...and it is an inline 4 or i4, not a V4. Just telling you before someone comments on that
 
  #6  
Old 01-22-2008, 05:20 PM
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Default RE: Interesting Observation

while we're on the saving gas/low rpm topic, i have a question,

i know how we're suppose to shift at around 3k rpm when we upshift, i do especially, when accelerating, but i have the tendecy, and i'm not sure if im the only one who does this, sometimes i would shift earlier, maybe like around 2k rpm, or in other words, i would already be in 5th gear going 35-40 mph, and i find this much a smoother ride, especially if your just driving in town, where you dont need to accelerate a lot, and keeping my rpm that low, i though was saving gas, because i had my theory of, the less you step on the gas, the less gas you consume, correct me if im wrong.. but of course, i still shift normally at the recomended 3k rpm, like if i'm trying to speed up, and entering freeways etc. and of course around 6k rpm, when beating the integ that pulls up next to me, hahah
 
  #7  
Old 01-22-2008, 05:26 PM
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Default RE: Interesting Observation

Couldn't that actually cause more damage as it has to keep slipping in order to engage?
 
  #8  
Old 01-22-2008, 05:35 PM
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Default RE: Interesting Observation

ORIGINAL: klrspz

Couldn't that actually cause more damage as it has to keep slipping in order to engage?
It doesn't sound like he's letting it slip, he's just not using as much throttle... unless I am mis-interpriting it... From what I've read/heard, when you run at around 2k rpms it's not as effecient because there is less inertia to help it get to that next revoloution so your engine is working slightly harder to maintain that, I've heard that 3000-3500 is the ideal point to run at since it has enough speed to maintain the rotational mass more easily plus it's a good effecient speed for complete fuel burning...

This is all based on theory and junk I've read, I have no way to test this but it's always made sense to me.... any other opinions?
 
  #9  
Old 01-22-2008, 05:45 PM
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Default RE: Interesting Observation

well, i'm pretty sure, i'm not hurting my car, i've been driving like that for more than a year, and i forgot to mention, this..maybe this will clear up..

i shift at 3000-3500 rpm for 1st and 2nd gear, and when i drive around 30-40, i just dont want to wait, till i reach to 35 for 3rd gear, 45 for 4th and above 50 for 5th..i find it smoother if i just shift it early, and the throttle is easy to coast on, and i find it easier not to speed, since you can only go so fast in each gear..so to sum of up all that inertia thing, im not lacking it..my car is moving already at a constant speed, and i slowly accelerate through the gears..
 
  #10  
Old 01-22-2008, 05:51 PM
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Default RE: Interesting Observation

I was refering to the rotation of the engine.... it's apparently more effecient to cruise around at 3000-3500 rpms than at 2000... Take a bicycle or stationary bike and push down on one pedal with a small amount of force, it won't make one full revolution.... now increase the force of that intial push until the pedal makes one full revolution, once it makes it around once it requires less of a force the second time to get it all the way around.... This is essentially the difference between running at 2000 rpm's or 3000ish as I understand it anyway....
 

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