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Old 07-07-2008, 06:55 PM   #11 (permalink)
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Originally Posted by Gregte View Post
I understand this, but I thought a big part of the FE gain in P&G was the fact that the motor is running at its peak efficiency, with regard to power generated vs. fuel consumed, at a 2/3 to 3/4 throttle opening (pulse mode).
It is a large component

In order to accelerate efficiently, you need to know what efficiently IS. A typical interpretation of a bsfc chart like the one below is to hold about 3/4 throttle and shift at 3000 RPM. So you never really get into the "power band", but you make the most power from the fuel consumed.





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Originally Posted by Gregte View Post
Slow accel and decel never operates the motor in its peak power/fuel efficiency range.

Having said all this, I do indeed accel and decel gradually and I know I get better mileage for it. I guess my main question is, how is it that P&G can be so FE effective since it goes so contrary to slow accel/decel ?

Put another way, why wouldn't it be best of all to use a 'slow accel then glide' since slow accel is better than hard accel?
The other gains from P&G, that I am aware of are that the engine friction is effectively reduced since it is not turning for most of your voyage (or is idling). AND that it takes carefull attention to traffic patterns and anticipating possible obstructions so that you do not waste your acceleration.

Think of the acceleration as a billiards shot, and you have guessed well where the next stop is. There is one and only one best tap you put on the ball to leave it where you want it. Likewise there is one and only one most efficient acceleration curve. It is up to you to not to hold to that accleration curve too long so that you don't waste the fuel used during acceleration.

Note, keeping in the best bsfc range is a lot simpler with a manual. If you are serious about economy then try and make your next car a stick shift. I'm not going to dwell on autos here suffice it to say that smarter cars make for dumber drivers

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Old 07-07-2008, 08:30 PM   #12 (permalink)
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Fuel Mizer, it's an inertia gauge. The harder you brake the more LED's you light up. The harder you accelerate the more LEDs you light up.
Hardly worth $82.45 with shipping. I'm spending that much money might as well go for the Scan Gage.
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Old 07-07-2008, 08:46 PM   #13 (permalink)
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Originally Posted by ALS View Post
Fuel Mizer, it's an inertia gauge. The harder you brake the more LED's you light up. The harder you accelerate the more LEDs you light up.
Hardly worth $82.45 with shipping. I'm spending that much money might as well go for the Scan Gage.
Thanks for foiling the thread highjacking that was taking place. Yeah, not worth that much. I just thought it would be useful for people who are totally oblivious to how wasteful their driving style is, some of whom I occasionaly ride with.
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Old 07-07-2008, 10:12 PM   #14 (permalink)
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Search for it on Jalopnik.com, and Autoblog.com (though their search feature is a pain to deal with).

I know it was featured on both sites. Though, contrary to it's main goal, we at Jalopnik figured that a fun game would be who could keep it in the red the longest...
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Old 07-07-2008, 11:41 PM   #15 (permalink)
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A real time MPG number even if innaccurate or an estimate is more important to me. Atfer watching the numbers go up and down under different driving conditions I could probably drive a car all day and not go red led with that product. We can always write scangauge and have more lights bells and whistles put into a SG3.
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Old 07-08-2008, 08:44 PM   #16 (permalink)
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Gregte - what leads you to believe that very slow acceleration leads to better overall MPG?
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Old 07-08-2008, 11:37 PM   #17 (permalink)
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Quote:
Originally Posted by jonr View Post
Gregte - what leads you to believe that very slow acceleration leads to better overall MPG?
Oh, I don't. All I was asking was in reference to two seemingly contrary ways to achieve better FE. One way is P&G the other way is slow accel and decel.

If slow acceleration is good for FE then it would seem that a slow accel followed by glide might be better than fast accel followed by glide (P&G).

I am definitely not arguing, just asking for clarification or explanation.

Also, I apologize for hijacking the thread. It was not my intent. I was not paying attention.

To get back on the subject of simple fuel economy devices, one that can be made quite easily, and in my opinion is very useful, is to feed the fuel injector signal to a voltmeter through a simple resistor/capacitor circuit. This allows you to monitor the voltmeter to see the relative amount of time the injectors are firing. You can learn when they are completely off (high speed deceleration) and when you are better to use a higher gear or lower gear, or when it is better to have engine off or left on regarding intended decel with engine braking.

If you have access to an o'scope to make yourself a chart/table you can then tell more precisely how much actual fuel you are burning per second per the reading on the voltmeter. This allows you to determine if voltage n1 at 55 MPH is a better or worse than voltage n2 at 65 MPH etc.

My only point I am trying to make is that it is not absolutely necessary to buy a scangage (although they are quite nice) to be able to actually know the amount of fuel you are using under varying conditions.

However, the accelerometer, as this thread is about, is likely going to be a much better general type of tool for many people to actually make good use of.
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Old 07-09-2008, 12:00 AM   #18 (permalink)
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Quote:
Originally Posted by Gregte View Post
Also, I apologize for hijacking the thread. It was not my intent. I was not paying attention.
That's ok, I got my answer, highjack away.

Quote:
Originally Posted by Gregte View Post
To get back on the subject of simple fuel economy devices, one that can be made quite easily, and in my opinion is very useful, is to feed the fuel injector signal to a voltmeter through a simple resistor/capacitor circuit. This allows you to monitor the voltmeter to see the relative amount of time the injectors are firing. You can learn when they are completely off (high speed deceleration) and when you are better to use a higher gear or lower gear, or when it is better to have engine off or left on regarding intended decel with engine braking.
Funny you should mention that. One of the manufacturer specific X-gauges I have access to on my Escort is Fuel Pulse Width. However, I have limited understanding of how to interpret it and thus how to use this data to improve my driving style. One thought I had was that if my injectors do shut down under certain coasting situations (the much discussed "cutoff") that perhaps I would be able to see this by looking at fuel pulse width. But all I really see happening is FPW rising and falling somewhat in line with throttle position and RPM. I can see slightly different values by coasting in neutral vs coasting in drive, but that doesn't really tell me much.
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Old 07-09-2008, 08:38 AM   #19 (permalink)
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I suppose an accelerometer could be useful as long as the user understood that the goal isn't to keep the minimum number of lights lit. The goal is to keep approximately 1/2 the leds lit or none of them (for positive acceleration).

For braking, ideal is none of them lit.
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Old 07-09-2008, 09:30 AM   #20 (permalink)
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I don't know if there are any generalizations that can be made about how many LEDs should be on for accelerating, but you are spot on for braking

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