Gas mileage training aid
 

I saw a little device in a video recently that teaches the driver how to save fuel. It's a little box with LEDs that mounts on the dash, and the LEDs light up red if the driver accelerates or decelerates too quickly, thus teaching the driver how to drive more efficiently. I've searched and searched and can't find this thing anywhere, has anyone seen this thing? I would like to suggest this to people I know who are pretty much clueless as to how to drive efficiently, I think it would prove very helpful.

I've never seen it, but seems like it would be easy enough to make.

How in the world could it know what the optimal acceleration rate is for a specific car? It might do more harm than good.

Unless it works similar to a vacuum gauge.

I think I saw it through a link someone posted recently.

I bet for a GPS receiver hardcoded with generic values. The GPS receiver gives not only the position, but also the speed and the acceleration.

A few weeks to design, a few dollars to build and you can sell 50. Will pay for itself rather quickly even if people save only 10%.

Far less powerful than a SG, but will be enough to a lot of people. With a SG you have to analyze numbers in real-time to know what you have to change... People do prefer something telling them what to do, or what they are doing bad.

Even if you only say people when they are accelerating too quickly or driving too fast, this is enough because that box is looking at it all the time. It's still hard to me to have always good accelerations and good speed.

People will not become hypermilers, but will meet EPA and will be happy to save money.

Denis.

you could make that for 15 dollars worth of parts on a circuit board 1" x 1". Analog output 1-axis accelerometer, 2-channel comparitor. Set the light to turn on when the accelerometer outputs a certain level on accel and decel (one comparitor each), and you're done.

If doesn't have to be "optimal", it just has to be a help for people that care less than your typical EM reader.

If P&G is a good FE technic then what is so wrong with fast acceleration? Isn't the Pulse in P&G just fast acceleration?

No, I don't htink so. Correct me if i'm wrong as I am new here, but i believe that in P&G, the time taken the accelerate should be the same as the time taken to coast. A hard accel is just a huge fuel dump with little efficiency.

You want acceleration is a certain range - too low is as bad as too high. "slower the better acceleration" is a myth.

I agree that an accelerometer would be useful input for maintaining optimal acceleration rates.

I suggest that car manufacturers:

1) allow the cruise control "resume" button to work from a standing stop.
2) tweak the resume to maintain optimal acceleration

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).

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?

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.

http://forum.ecomodder.com/attachmen...9&d=1205914740



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 ;)

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. :D 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. http://www.ls1tech.com/forums/images...r_banghead.gif

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...

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.

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.

That's ok, I got my answer, highjack away. :thumbup:

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.

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.

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 :)

I think that the important difference between fast and slow acceleration is the time spent at lower speeds. If your goal is to get to 100km/h then the most efficient way to get there is to religiously follow the BSFC to keep your engine running efficiently, this means you can glide for a longer proportion of your driving and you get great FE. On the other hand if you accelerate slowly then the time you spend at low (efficient) speeds where aero and rolling resistance losses are smaller is greater. Since aero losses increase cubically with velocity the lower drag from the lower average speed can make up for the decreased engine efficiency (i.e. you are getting less power per kg of fuel but still using less fuel over all because the power requirement is less).

I guess if you prefer a simple rule without having to work to hard to get decent FE.

If you hate slow acceleration and are willing to work harder (watching throttle and rpm carefully, possibly EOCing or P&G) then it may be better to accelerate with the BSFC map.

Probably the best thing for each driver to do is to test both methods and see which one works best for him/her. (or downsize your engine so you get high load/slow acceleration! ;))

re: lights to turn on: I'd say have 2 lights. One for "you are accelerating too friggen hard" and one for "you are braking hard, you should have begun slowing sooner". Get a "typical" driver to avoid those two lights and they will save 20+% on gas, easily.

btw, what the heck is bsfc? Linky to thread or webpage? Or maybe just a non-acronym so i can find out for myself?

Kiwi?
Includes handy marketing video.

Sorry for being late to the party but the Digital Fuel Mizer might be the item in question. I remember seeing it a while back when I was looking up info on the scangauge and vacuum gauges. Not sure how effective it is but it's cheaper than a SGII and requires no looking (since it also beeps at you besides the flashing).

In this article, I think the boiling hot cup of open coffee in the cup holder or between the legs might be an even easier motivator for controlled accelerations/deccelerations. But from the article I read on Ben's other site about accelerating and FE, slow and steady isn't always the best bang for the MPG.

Without a doubt, experimentation and practice seem to be the order for the day... and burning cups of coffee to the groin for the more adventurous. :thumbup:

BSFC = brake specific fuel consumption

I read about them here

On my car (mid size sedan, automatic transmission) I cannot control the rpm and load like I want to to maximize BSFC. Even so, accelerating at a moderate rate in the 2200-3000 rpm range and accelerating at less than 2000 rpm give the exact same MPG over a 1/2 mile stretch. I've repeated the test a few times.

I encourage others that have the right guages to test this also. Perhaps we can put to bed the "very slow acceleration gives best MPG" myth.