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OBDI mpg meter? scanner?


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12 replies to this topic

#1 SVX_commuter

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Posted 16 May 2007 - 11:24 AM

Hello All,

Well I have been trying to find something for my Subaru's that I can hook up to the ECU and get mpg's. You know? A little meter that will let me read mpg when I am driving.

Does anybody know where to buy one of these?

#2 nipper

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Posted 16 May 2007 - 02:13 PM

OBDI thats really difficult. OBDI was not a universal code, so its very hard to neerly impossible to find what you want.

The simplist way to get a MPG gauge (if you want to increase MPG) is hook up a vacume gauge. Keep the needle high and thats when your using the least amount of fuel.

If you want something more high tech, i dont know if youll find any. Carberated MPG meters wont work since they measure the fuel moving in the fuel line vs distance. Fuel Injection circulates fuel to cool the injectors, meaning only 30-50 % of what passes through the fuel line at any given is burned. SO using the fuel flow method will give you dismal readings.

nipper

#3 Skip

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Posted 16 May 2007 - 02:34 PM

An interesting thought I had would be to build
a digital converter
to show the pulse width of the injectors.

Assuming it has constant fuel pressure
(unlike our turbo models).

The length of time the injector stayed open would/
could be converted to the fuel being used per time unit.

Not MPG but MPH

As for the units Nipper spoke of,
the ones I have seen have two "flowmeters".

One in the input line to the fuel rail and one in the return line.
They subtract the measurements to obtain
a fuel consumption figure.

Then using magnets on the drive shaft and a reed switch
for distance, they calculate MPG

A similar setup up could be done with my
pulse width monitor with no fuel line intrusion.

The man for this project IMO would be Vikash (vgr3) over at Leg.org

#4 nipper

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Posted 16 May 2007 - 02:47 PM

I havent seen them with two flow meters, that would correct that problem.

I dont know how often the injectors fire on OBDI subarus. It can be once per cycle, maybe 2 (Iv'e seen OBDI cars form other mfgs do weird things).

I do like the dual flow meters though.

I did a quick google search and i cant seem to find anything on the net for OBDI maybe ebay?


nipper

#5 Skip

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Posted 16 May 2007 - 02:54 PM

quote the Nipper
"I don't know how often the injectors fire on OBDI subarus. It can be once per cycle, maybe 2 (Iv'e seen OBDI cars form other mfgs do weird things)"

If coupled with the distance measurement
it would be a simple matter of calibration.

This calibration is needed for all the after market units I have seen/used.

#6 SVX_commuter

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Posted 17 May 2007 - 06:58 AM

Thanks for the replies!

I will keep this thread active for awhile as I wnat to see if anybody else has an idea.

I want to try some modifications to improve fuel ecconomy and I want to use the OBDI cars since they cost less. That way I burn something up it won't be a big loss.

They make the Scan Gauge II for OBDII cars...... but that's going to fit my Subaru. Very nice little programable meter, volts, rpm, mpg and more.

http://www.scangauge.com/

Maybe I should just get an OBDII Subaru :rolleyes:

#7 Skip

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Posted 17 May 2007 - 07:40 AM

That is a kewl tool.

Nipper runs one in his OB.


I keep saying I'm gonna get meself one.

I just graduated to OBD II
I don't like it only from the below stand point.

The PA emissions bit is no phun atoll.

#8 nipper

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Posted 17 May 2007 - 08:47 AM

Actually OBDII is SO much easier to diagnose then OBDI, since it is standardized in all mfgs.

nipper

#9 Skip

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Posted 17 May 2007 - 09:07 AM

that maybe the case

BUT

if there is anything wrong (a shift solenoid for the
conv. lock up in the project I have now)

PA emissions fails it - i.e. you must get the problem solved
no matter how trivial it is before it will pass.

Then if you do not have all the "readiness monitors" set
you fail again (speaking PA here, your state may differ).

Having only two chances before the big RED FLAG at the
DMV is thrown - pish aw!!

My OBD I Subes have no problems passing the sniff test.

A silly solenoid in the trans - messy and convoluted repair -
for what maybe 2 MPG when the car is used for city driving only??

Can't wait for OBD III, ---> don't let your car fart
might throw a code you can't clear!!!


#10 SVX_commuter

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Posted 19 May 2007 - 06:29 PM

Oh I think you may not have to wait too long for OBD III. I sense that manufactuers will want to make a change soon to force everyone into NEW diagonistic equipment just to make some money for the stock holders.

This of course will be a set back for the DIY people as well as the engine tuners. Well then again maybe not. The OEM's arn't going to make that much off this kind of a change for the investers because the OEM's don't sell the scanners!!!!!

It would have to be a OBD III with a special lock code that only dealers and inspection stations can read. Then they could sell high priced scanners. Well that may that won't work as well. There are so many scanner companies now that the codes would be cracked.

Heck we will most likely run out of gas in the not too distant future or not be able to afford the high priced stuff and so then the age of fun driving may be coming to a close.

Drive it like you stole while you CAN ! ! ! !

#11 nipper

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Posted 19 May 2007 - 10:55 PM

Oh I think you may not have to wait too long for OBD III. I sense that manufactuers will want to make a change soon to force everyone into NEW diagonistic equipment just to make some money for the stock holders.

This of course will be a set back for the DIY people as well as the engine tuners. Well then again maybe not. The OEM's arn't going to make that much off this kind of a change for the investers because the OEM's don't sell the scanners!!!!!

It would have to be a OBD III with a special lock code that only dealers and inspection stations can read. Then they could sell high priced scanners. Well that may that won't work as well. There are so many scanner companies now that the codes would be cracked.

Heck we will most likely run out of gas in the not too distant future or not be able to afford the high priced stuff and so then the age of fun driving may be coming to a close.

Drive it like you stole while you CAN ! ! ! !


OBDI and OBDII were federal mandates, not just something the automfgs whipped up. OBDII LAW was specifically written with the corner mechanic in mind. OBDI was attempting to put corner mechanics out of business (that was not the intention, but the mfgs wanted that). Congress mandated a universal OBD system, not only for the corner chops, but so that the states didnt need 20 different inspection machines.

There is an OBDIII being written up and researched, but thats just in response to newer emission controls and newer technology. That will be sidetracked now untill the green house emission limits are dealt with on passenger cars.

Or so my SAE membership tells me.

nipper

#12 SVX_commuter

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Posted 27 May 2007 - 03:40 PM

OBDI and OBDII were federal mandates, not just something the automfgs whipped up. OBDII LAW was specifically written with the corner mechanic in mind. OBDI was attempting to put corner mechanics out of business (that was not the intention, but the mfgs wanted that). Congress mandated a universal OBD system, not only for the corner chops, but so that the states didnt need 20 different inspection machines.

There is an OBDIII being written up and researched, but thats just in response to newer emission controls and newer technology. That will be sidetracked now untill the green house emission limits are dealt with on passenger cars.

Or so my SAE membership tells me.

nipper


I bought the ScanGauge2 and have it hooked up in my97 Astro. NOT a Subaru but it is all wheel drive. All my Suby's are OBD1.......

ANybody got a way to get OBD1 to read on an OBD2 ScanGauge2?????

Thanks :)

#13 jamal

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Posted 27 May 2007 - 06:13 PM

you can't. But vrg3 made a cool piece of software that allows you to splice a stereo harness to a serial cable and monitor various thing with a laptop.
http://bbs.legacycen...pic.php?t=16219

Might not work for non- firstgen legacies.

Also, the MPG gauges in older BMWs are nothing more than a vacuum gauge with calibrated mpg units.




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