ECU signals for mileage indicator?

**Poops** · April 19th, 2005 01:40 AM

some cars have this meter which gives an estimate of the consumption (km/l) in realtime. I think even the range can also be computed.

Has anybody tinkered with their ECU's? Maybe we can tap some signals there to come up with a gage that will provide an immediate feedback on the car's mileage.

I was thinking a simple electronic gage (or a color-coded bar graph?) attached to the O2 sensor or pressure in the manifold?

Is there an off-the-shelf product available?

I figure changing driving habits can be significant but a feedback mechanism would help accelerate the learning process under various conditions (accelerating, cruising, braking, up/downhill, idle, w/ or w/o aircon, etc..). We can expect the price of gasoline to go up pa rin in the near future so I need all the help I can get.

Thanks...

**OTEP** · April 19th, 2005 01:52 AM

Most European cars have a 'fuel economy' gauge. Not that it is very accurate. I'm not sure how those things work.

On our W124, it's an analog gauge clustered with the fuel, temp, and oil dials.

**kinyo** · April 19th, 2005 02:19 AM

poops,

there is an off-the-shelf product that will show you INDIRECTLY fuel consumption in real time ... the vacuum gauge

install a vacuum gauge, not so expensive, then drive in such a way that the vacuum level is kept at higher reading at most times ... you'll find that fuel economy improves

you'll also find that keeping vacuum at high level necessitates that you must be easy on the gas pedal

if you want kinda high-tech stuff, the MAP (Manifold Absolute Pressure) sensor on modern engines sends out a signal proportional to the vacuum level ... this signal can be used to display vacuum into an electronic LED bargraph display ... i think i've seen such electronic vacuum gauge in the market (sa concorde yata), but i'm not sure if it uses the MAP signal or the usual vacuum line (it which case, it must be using some kind of pressure transducer for electronic display conversion)

i once found in the net a schematic for such display, built one, made some modifications to make it compatible with my civic MAP sensor signal and it worked ... which means it is possible to diy such project if you are electronically inclined and the whole project will not cost more than P1k

**ghosthunter** · April 19th, 2005 08:29 AM

if your car has the ODB II port...

www.scanguage.com

**endlessgwing** · April 19th, 2005 10:21 AM

ok yung scangauge a, kaso ang mahal, hehehe

sir kinyo, pede po ba makita circuit diagram nung nung ginawa nyo? ok na project to

**Poops** · April 19th, 2005 10:26 AM

thanks guys...

I was thinking of tapping into the ECU wiring for the MAP or something similar. Since I'm also electronically inclined, a simple opamp to condition/calibrate the signal before feeding it to a color coded display driven by an LM3914 (National) for linear or LM395 if logarithmic.

I just don't know the wiring harness of my Altis (1.6E '04 M/T) and if the input impedance to most op-amp's won't affect the ECU operations.

Salamat...should be less than 1K nga. More the aesthetics para matched sa dash.

**Poops** · April 19th, 2005 10:29 AM

thanks guys...

I was thinking of tapping into the ECU wiring for the MAP or something similar. Since I'm also electronically inclined, a simple opamp to condition/calibrate the signal before feeding it to a color coded display driven by an LM3914 (National) for linear or LM3915 if logarithmic.

I just don't know the wiring harness of my Altis (1.6E '04 M/T) and if the input impedance to most op-amp's won't affect the ECU operations.

Salamat...should be less than 1K nga. More the aesthetics para matched sa dash.

**endlessgwing** · April 19th, 2005 12:23 PM

found this one sa net, parang ok sya ...

http://www.pelicanparts.com/techarti...el_monitor.htm

**kinyo** · April 19th, 2005 11:37 PM

Originally Posted by endlessgwing

sir kinyo, pede po ba makita circuit diagram nung nung ginawa nyo? ok na project to

eto o ..

i don't have the original circuit i found in the net ... what i have shown is the actual circuit of my final prototype ... iirc, my modifications were: i used 5-volt power, added diode and capacitor at the input, used 100k trimpot at the input to be able to calibrate the display while offering high-impedance to sensor's output ... note that the 5-volt regulator is not shown but it is part of the circuit, including associated capacitors for stability ... using 5-volt power keeps the LM3914 chip run cooler in bar mode

**Poops** · April 19th, 2005 11:48 PM

You may have to add a limting resistor for each of the LED to keep the current to say 20mA. I usually use 220 ohms 1/4 watt depending on the LED. The sink rating I think is somehow limited.

The circuit from endlessgwing uses a 3915 for logarithmic. My guess the sensor is likewise log based.