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Old 12-04-2009, 02:15 PM   #11 (permalink)
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My dad's car 2001 Impala, seems to do best with "hard" acceleration. (80% or so)

As long as you don't brake, your car will keep similar gas mileage. Everytime you brake, you are turning momentum into heat.

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Old 12-04-2009, 02:38 PM   #12 (permalink)
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Originally Posted by wagonman76 View Post
If you can tell what your shift points are, then you've got a good start. My take on it is when you're under 35 or whenever your TCC kicks in, take it easy. Pushing it harder just churns more fluid and is more wasteful. But once your TCC kicks in probably right after it goes into 3rd gear at 35 or so, push it a little harder to get it up to 45-50 and into OD. Just dont push it hard enough to downshift or your gains are lost for the moment.
What's TCC? You'll have to go easy on the acronyms with me. I know very little about cars to start with.

No problem noticing gear changes at least. I'm not deaf.


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justjohn-

When you're accelerating from a dead stop, remember that the greatest amount of friction occurs when you are starting from a stop. Moderate acceleration from a dead stop is a good way to eat up tires and gas. It's better to take your foot off the brake to allow the car to move forward a little and slowly apply gas until you're in 2nd gear. Remember 1st gear is the least efficient. Once you're in 2nd gear, you can apply a little more gas to achieve your moderate acceleration.
I've been doing the rolling stops. According to those graphs though, shouldn't I be holding the throttle near max and just keeping the rpm low?
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Old 12-04-2009, 02:39 PM   #13 (permalink)
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Originally Posted by MadisonMPG View Post
My dad's car 2001 Impala, seems to do best with "hard" acceleration. (80% or so)

As long as you don't brake, your car will keep similar gas mileage. Everytime you brake, you are turning momentum into heat.
Impala specific info always welcome, thanks!
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Old 12-04-2009, 02:41 PM   #14 (permalink)
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Originally Posted by justjohn View Post
What's TCC? You'll have to go easy on the acronyms with me. I know very little about cars to start with.

No problem noticing gear changes at least. I'm not deaf.




I've been doing the rolling stops. According to those graphs though, shouldn't I be holding the throttle near max and just keeping the rpm low?

Technically that's the perfect situation, but how do you plan on doing that with an automatic transmission?
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Old 12-04-2009, 02:57 PM   #15 (permalink)
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Technically that's the perfect situation, but how do you plan on doing that with an automatic transmission?
Not possible, as I understand it. So you're saying that the method you suggested will be most efficient because it will keep the rpm lower, is that right?

Is there a way to tell if that will make up the penalty for staying in a lower gear longer?
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Old 12-04-2009, 03:56 PM   #16 (permalink)
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This is an interesting discussion. I still feel you use less fuel if you take off from a slow start. From what I can see on my little gauge on my 944, using far less throttle and going to a SLOW acceleration puts me in the "20mpg" area with my foot down just a hair from a dead stop, than if i accelerated quickly to speed and then leveled out, my meter goes to into my black area which is "Errrr what miles per gallon...." zone.

Seems the same on my little escort. Starting and stopping is a large amount of the fuel consumption on the trip, even cutting down on this very subject can make an enormous change in your mileage.
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Old 12-04-2009, 04:44 PM   #17 (permalink)
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Originally Posted by Winfield1990 View Post
1. Pretty much all engines their maximum efficiency is where their peak torque is. Trying to drive in the RPM's where you have maximum torque is where you will get the best MPG. whatever gear your cruising in try to stay in that maximum torque rpm range.

2. accelerating at 3g is pretty much double the gas needed to accelerate at 2g..
1. Sounds plausible

2. Isn't that saying basically the opposite of the article I linked? Are you saying it's wrong then?


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Not to mention when you are accelerating with more force you are disturbing the air..
If you mean that accelerating harder creates more drag I'm pretty sure that's wrong. Drag is dependent on speed, not acceleration.
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Old 12-04-2009, 05:01 PM   #18 (permalink)
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justjohn - what he might mean is if you accelerate harder, the weight distribution changes. For instance if I accelerate lightly, the nose of the car raises slightly, raising further if you accelerate harder. However, since the co-efficient of drag is the most important thing, and you are correct on speed vs wind speed vs drag is the biggest variable, I think rolling resistance would be a bigger factor. But i think he is talking about the angle of the car when the weight distribution changes. Sort of like if you took a brick in the wind, with the wind driving at you straight forward the surface area exposed is simply the front. Change the angle and the other portion exposed will be underneath, then the wind would be also flowing along other variables under the car. However, at a low speed, I don't see how this would be a very large variable. I think a light foot is better still
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Old 12-04-2009, 05:04 PM   #19 (permalink)
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Quote:
Originally Posted by justjohn View Post
Not possible, as I understand it. So you're saying that the method you suggested will be most efficient because it will keep the rpm lower, is that right?

Is there a way to tell if that will make up the penalty for staying in a lower gear longer?
My method keeps you slow in 1st gear and then moderate acceleration throughout acceleration after that. By moderate acceleration, I mean that you should accelerate as fast as possible with the shift points staying around 2000 rpm. If you accelerate REALLY slow throughout, you're going to be spending too much time just short of the shift points, which wastes gas. Generally with a V6, anything over 2000 rpm is going to eat up gas quickly.

The only way to see the penalties of different acceleration is by using a Scangauge, but this is what has worked for me and several other people.
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Old 12-04-2009, 06:28 PM   #20 (permalink)
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You could try letting the car roll a bit, then stabbing the throttle hard briefly. These are large cars, they roll very well.

Do you have the 3.4 or the 3.8?

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