realtime monitoring tools for pre-obd2 cars
 

so, i have a 95 integra that is not supported by the scangauge. i'm not prepared (at this moment) to drop $165 into a superMID even if i could get it to work on my car.

so, are there relatively inexpensive tools available that will aid me in knowing how my car is doing as i'm driving?


i've heard of using a vaccum gauge. presumably this indicates the level of load on the engine, higher vaccum=lower load and less fuel consumption.



any suggestions?

I would like to find a cheap fuel rate (GPH) meter and install one in each of my vehicles...the only ones I've seen are appropriate for a boat, not a car, though I don't remember why I didn't think they'd work in a car when I looked them up.

Maybe because a lot of FPRs are integrated into the fuel rail, so you'd have to hack your fuel rail to get it in after the FPR?

On his Honda it has a return-type fuel system so the gph wouldn't really be relevant unless it read how much is returned back to the tank since the electric pump should be pretty much stable on the fuel that's being delivered to the fuel rail.

A had a vacuum gauge on my 95 Integra, and it shows little more than when you push the throttle, you make less vacuum. Be light on the gas pedal and you'll make more vacuum and get more MPG. There is a home-made MPG gauge I saw someone working on (look in the VX lean-burn monitor thread in the tech section on here for a link to it) but it looks quite complicated if you aren't electrically savvy.

I haven't gotten around to doing it yet on my 1991 CRX, so at the moment this is just theory, but...

It occurred to me that you could wire up a LED indicator light (for example "green" for "go") in parallel with the fuel injector (so that the LED is run by the same signals that trigger the FE to use fuel). In theory, this should give you an easy to see (and cheap to install and run) indicator light that gets brighter the more fuel you are using, and cuts out entirely when you get FE cutoff (coasting in gear). Not exactly the same as a real time MPG meter, but it should give you some fuel use feedback on the cheap!

NOTE: Some places will sell you LED indicator lights already combined with a simple regulator, so that you can directly hook them up to a car's electrical system (in this case the FE signals). For example, I've thought about using these LED modules ( https://www.superbrightleds.com/specs/wiredLED.htm ) from https://www.superbrightleds.com ($1.99 to $2.99 each, plus shipping, depending upon LED color) for a few indicator lights (including a FE indicator) added to my dash.

I read about someone who did this, and posted the following question in another thread:
How precise is the current that operates the injector? Could the LED affect the operation of the injector by diverting some of the carefully-measured current from it?

Thinking about it, you could probably rig a voltmeter through a capacitor to give you injector pulse width duration, would probably only be accurate to within a percent or two, but would be a good visual indication.

Nissan injectors seem to have about 15 ohms resistance..

Putting a superbright LED in parallel with the injector circuit with say a 5K ohm current limiting resistor shouldn't hurt the injector performance at all.

Things which move from electrical current, like an injector pintle, generally use a lot more current than a small LED is going to require..

Can you find out what the resistance of the injectors in your car is?

You would have to use a diode to keep current from the capacitor from flowing back into the injector when the capacitor had more charge than the injector drive circuit

Many Cadillacs and Lincolns from the early '80s on have an MPG readout built in. My first one was in my '85 Continental...along with a digital gas gauge which read in gallons (you could watch the gas being sucked right out!). Same with my '84 Town Car, although you got a bar-graph fuel gauge. If you went into diagnostic mode, you could even see the fuel flow rate.

My '83 Eldorado also has one built in. It's been really fun to use it to try out various driving techniques (got behind a truck one day on the freeway for about 20 miles and got my average MPG over 32). It is really nice to have that kind of instantaneous feedback. However, since these work off each car's computer, I don't know if it would be possible to get the appropriate parts from a junkyard and adapt to another car...