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Old 08-17-2009, 11:17 AM   #1 (permalink)
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AutoSpeed: "FuelSmart" device: sort of a live BSFC indicator

Julian Edgar has posted the first of a two part series about an electronic project device called "FuelSmart" that he's impressed with:

Quote:
If you have a manual transmission car and the engine uses a MAP sensor, this device can improve your fuel economy by up to 15 per cent.


To be clear, it's not a vehicle mod, but instrumentation using vehicle sensors to help the driver use the go pedal smarter to save fuel.

See: FuelSmart - Part 1

Essentially it monitors throttle position (via the TPS), and engine load, via manifold absolute pressure (MAP) sensor. If the unit detects inefficient engine operation, it lights up a red LED. EG, under low load and a mostly closed throttle. The LED is the driver's reminder that s/he can get better economy either by giving it more gas, or increasing load (upshifting) if you're trying to accelerate or climb.

Or if you're approaching a stop, it's a reminder to fully release the throttle and go into DFCO mode (Deceleration Fuel Cut Off), rather than very lightly motoring along in a very inefficient engine operating range.

The article also explains the pros/cons between this device and a simple vacuum gauge.

My main criticism with the piece is it muddies the waters about what "pulse and glide" is (discussion of BSFC often includes a P&G description, as this one does). It essentially describes "Pulse and DFCO", not Pulse and Glide. DFCO necessarily occurs in gear, with engine braking slowing the vehicle as a result. DFCO is not a true glide. A true glide occurs in neutral and will out-distance DFCO. Engine-off gliding will beat DFCO every time in terms of better fuel economy.

Full details: FuelSmart - Part 1

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Old 08-17-2009, 11:45 AM   #2 (permalink)
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Very cool.
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Old 08-17-2009, 12:10 PM   #3 (permalink)
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I'm not all that impressed. Its a neat little gadget, but the average driver won't use one. Plus, a scangauge's LOD reading is be infinitely better (and more expensive of course).
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Old 08-17-2009, 03:20 PM   #4 (permalink)
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Quote:
Originally Posted by Daox View Post
the average driver won't use one.
We're not average drivers.

And of course, anyone whose attention this thing seizes, is probably going to wind up stepping up to the SG ere long, as soon as they realize how big a difference knowing more can make.

That said, dang. Another gadget I can't use. For the first time in my life, I'm making enough to afford geegaws, but my ride is too ancient and I'm too stingy to actually buy or use one!

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Old 08-17-2009, 05:12 PM   #5 (permalink)
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Quote:
My main criticism with the piece is it muddies the waters about what "pulse and glide" is (discussion of BSFC often includes a P&G description, as this one does). It essentially describes "Pulse and DFCO", not Pulse and Glide. DFCO necessarily occurs in gear, with engine braking slowing the vehicle as a result. DFCO is not a true glide. A true glide occurs in neutral and will out-distance DFCO. Engine-off gliding will beat DFCO every time in terms of better fuel economy.
Fair enough. But I am reluctant to recommend driving in a way that is illegal for most of my readers. Rolling around in neutral is actively frowned upon here, and - I would have thought - in most other places as well.

Quote:
Its a neat little gadget, but the average driver won't use one.
It can be easily adjusted over a wide range, so is quite suitable for 'average drivers'.

Scan Gauge? Well, FuelSmart is far easier to use, far cheaper, and suits cars for which a Scan Gauge is not available. Locally, that's literally millions of cars.

Last edited by Julian Edgar; 08-17-2009 at 05:35 PM..
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Old 08-17-2009, 05:48 PM   #6 (permalink)
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Julian -

Quote:
Originally Posted by Julian Edgar View Post
...

It can be easily adjusted over a wide range, so is quite suitable for 'average drivers'.

Scan Gauge? Well, FuelSmart is far easier to use, far cheaper, and suits cars for which a Scan Gauge is not available. Locally, that's literally millions of cars.
Very interesting gizmo, when will part two be posted? Is it offered as a Jaycar kit?

In your article you write :

Quote:
Second, it is always easier to spot an indicator LED showing that something is wrong, rather than constantly watching the sweep of the gauge needle. In fact, the LED can be sensed without even directly looking at it.
I find that lights often become "invisible" to me over time. I have to consciously look at them to see if they are on. For hard core people like us, you could have some alternate wiring that might look like so :

Green LED = optimum driving (EDIT: You already have an Orange LED)

Red LED = bad driving
Buzzer (that can be disabled) = bad driving

With the "buzzer" option, the sound could be training the driver without having to look at the dashboard.

Also, are all MAP sensors the same? I get the impression that there are multiple flavors of map sensors. But maybe you are stating that limitation in the "At a glance ..." section.

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Last edited by cfg83; 08-17-2009 at 06:03 PM..
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Old 08-17-2009, 05:53 PM   #7 (permalink)
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- It will be available fully built from its manufacturer, eLabtronics.

- The current output is an orange LED that lights when 'bad' driving is occurring

- You can replace the LED with a buzzer if you like (I did that in testing) but it will drive you mad.

-Nearly all MAP sensors have a voltage output of 0-5V. Some rare ones use a frequency output, for which this device is not suitable.

- Part 2 is out in a week.
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Old 08-21-2009, 10:44 PM   #8 (permalink)
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...I, for one, am looking forward to seeing Part II, even though I have an automatic car, because the 'theory' behind the premis is worth understanding and learning about.

...anybody there in AUS working on an article about "gathering/creating" your own BSFC "map" for your car as you drive (universal (manual and automatic) application)?
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Old 08-21-2009, 11:07 PM   #9 (permalink)
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Quote:
...anybody there in AUS working on an article about "gathering/creating" your own BSFC "map" for your car as you drive (universal (manual and automatic) application)?
yes, but it will be some time away

FuelSmart is a suprisingly effective instrument, and does have some application in auto trans cars.
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Old 08-21-2009, 11:22 PM   #10 (permalink)
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Believe you me, I have thought about it plenty also. There are some major flys in the ointment and that is things like hills and wind.

It all starts with something like weighing the car, so that when it accelerates you can deduce how much (horse) power it took to effect that change in velocity in that amount of time.

Once you know the weight, you can then determine the CDA with some coastdown testing (which is dependant on careful conditions).

So lets say you have accurately weighed the car, and have (perhaps with the help of an onboard device) done the coastdown testing, and have good figures for CDA and CRR and Weight.

So, how do you then, assuming the world isn't flat OR windless, determine that a given peak in bsfc, hasn't been tainted by things like wind or terrain slope or drafts or reduced weight (low tank) or???

Problem with deducing power in the real world is that it doesn't make for a very controlled measurement. Something like coasting in gear downhill and seeing even a tiny bit of acceleration could throw the whole thing off.

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