A Cars forum. AutoBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AutoBanter forum » Auto makers » Honda
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

"Real time" fuel consumption measurement



 
 
Thread Tools Display Modes
  #1  
Old April 7th 05, 12:40 PM
external usenet poster
 
Posts: n/a
Default "Real time" fuel consumption measurement

Given ever higher price for gas it would be nice to be
able to monitor ones driving habbits to get the best MPG
posible.

In a EFI engine the fuel consumption is based on the on
time for the injector(s). Has anyone seen any DIYS circuits
for intergrating the injector duty cycle.

I have been playing with a laptop PC versio, but it isn't
too healthy to be watching a LCD while driving.

I am hoping to find a way to reduce this info to a single
analog meter so that all you have to do is maximise or
minimisethe needle position.

Terry

Ads
  #2  
Old April 7th 05, 06:25 PM
halo2 guy
external usenet poster
 
Posts: n/a
Default

It is called a vacuum gauge and was done back in the 50's.

The higher vacuum you maintain, in theory, the better your mileage. When
you press the accelerator your vacuum drops and that means you are using
more gas.




> wrote in message
oups.com...
> Given ever higher price for gas it would be nice to be
> able to monitor ones driving habbits to get the best MPG
> posible.
>
> In a EFI engine the fuel consumption is based on the on
> time for the injector(s). Has anyone seen any DIYS circuits
> for intergrating the injector duty cycle.
>
> I have been playing with a laptop PC versio, but it isn't
> too healthy to be watching a LCD while driving.
>
> I am hoping to find a way to reduce this info to a single
> analog meter so that all you have to do is maximise or
> minimisethe needle position.
>
> Terry
>



  #3  
Old April 7th 05, 06:55 PM
Howard Lester
external usenet poster
 
Posts: n/a
Default


"halo2 guy" wrote

> It is called a vacuum gauge and was done back in the 50's.
>
> The higher vacuum you maintain, in theory, the better your mileage. When
> you press the accelerator your vacuum drops and that means you are using
> more gas.


Yeah, I had one in the early 70's for my '70 Chevy Nova - thanks for
reminding of those days!

Howard


  #5  
Old April 8th 05, 05:54 AM
Pars
external usenet poster
 
Posts: n/a
Default

Driving the car in way that'll maximize on ecnomy requires a standard
tranny. Otherwise, you're at the mercey of the automatic.

The posted city consumption for my car is 7.8L/100km, but if I put my mind
to it, I can get 6.5L/100km. However, I'm not able to shave anything off the
highway mileage which is 5.8L/100.

Pars
98 Civic Hatch

> wrote in message
oups.com...
> Given ever higher price for gas it would be nice to be
> able to monitor ones driving habbits to get the best MPG
> posible.
>
> In a EFI engine the fuel consumption is based on the on
> time for the injector(s). Has anyone seen any DIYS circuits
> for intergrating the injector duty cycle.
>
> I have been playing with a laptop PC versio, but it isn't
> too healthy to be watching a LCD while driving.
>
> I am hoping to find a way to reduce this info to a single
> analog meter so that all you have to do is maximise or
> minimisethe needle position.
>
> Terry
>



  #7  
Old April 8th 05, 09:41 AM
Randolph
external usenet poster
 
Posts: n/a
Default


wrote:
>
> Given ever higher price for gas it would be nice to be
> able to monitor ones driving habbits to get the best MPG
> posible.
>
> In a EFI engine the fuel consumption is based on the on
> time for the injector(s). Has anyone seen any DIYS circuits
> for intergrating the injector duty cycle.
>
> I have been playing with a laptop PC versio, but it isn't
> too healthy to be watching a LCD while driving.
>
> I am hoping to find a way to reduce this info to a single
> analog meter so that all you have to do is maximise or
> minimisethe needle position.
>
> Terry


This could be a fun project. I would start with a circuit like the one
below. Point A hooks to the switched side of one of the injectors, point
B to a high impedance voltmeter. Power supply to the 74HC14 should be a
regulated +5V supply, I am old fashioned and like the LM317 adjustable
voltage regulator for that purpose. The 180k / 100k resistors do several
things:

1. Voltage divider that converts the 14V / 0V swing at the input to a 5V
/ 0V swing for the 74HC14
2. Ensures that the circuit is a high impedance load on the ECU.
3. Provides high enough impedance at the input to the 74HC14 that
voltage spikes are effectively clamped by the protection diodes in the
74HC14.

The three inverters (with Schmitt trigger inputs) shape the potentially
ugly signal at the injector into a nice square wave with a 0 - 5V swing.
The 74HC14s are nice in that if they are supplied with 5V, the high
output voltage at moderate loads is very close to 5V.

The 100 k resistor and 10 uF cap form a low pass filter with -3dB point
around 0.16 Hz. This is a difficult trade-off. At idle you will still
see quite a bit of wiggle on your meter, and the response time is on the
order of 7 second. If you want faster response, you will get more wiggle
at idle. You could add more poles to the filter to get a better
compromise between response time and reading stability.

I would imagine that the duty cycle on the injectors is quite low, so
you might have to add an op-amp for gain between point B and your meter.
That will also allow you to add a gain adjust for calibration as well as
allow you to implement a more sofisticated filter.

Remember to ground the input of the three unused inverters.

74HC14
180k |\ |\ |\ 100k
A ---\/\/\/---------| >0----| >o----| >o----\/\/\/--------- B
| |/ |/ |/ |
| ===== 10uF
|---\/\/\/--- |
100k | |
V V

Now, if you like microcontrollers, you could hook the output of the last
inverter to the timer / counter input of your favorite controller (If
you still want to use the analog low-pass filter you probably would want
to use the second inverter rather than the third for your
microcontroller). Then you could time the pulses and calculate the duty
cycle that way. This will allow you to adjust your filtering to the
engine RPM so that you get a rock steady output regardless of RPM and at
the same time get quick response time on your meter.

A further experiment would be to use one resistive divider and one
inverter for each injector. Then use four diodes to OR the output of the
4 inverters together, and follow it with two more inverters. Then you
would get less wiggle on the meter at low RPM, or you could bump up the
cutoff frequency on the RC filter for quicker response. The
possibilities are endless...

Note: My 1:42 am engineering output is prone to errors. Use at your own
risk!



--
================================================== =====
A very modest collection of Honda tech info can be found at:
http://www.geocities.com/ng_randolph
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
R*volume*raduis2 c3po "Theroy of everything" zetasum Chrysler 0 February 18th 05 10:16 PM
Failed Smog Check 1981 Trans AM TheSmogTech Technology 0 January 30th 05 05:16 PM
Elantra fuel consumption syl Technology 6 January 20th 05 01:42 AM
Where to get Official Speed Limit Info [email protected] Driving 40 January 3rd 05 08:10 AM
In-the-tank fuel pumps cause death and destruction Silver Surfer Chrysler 293 November 7th 04 04:41 PM


All times are GMT +1. The time now is 07:43 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AutoBanter.
The comments are property of their posters.