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diesel_john 02-21-2008 02:19 AM

mileage computer for a carbureted engine
Is there a need for a DoItYourself flow meter on an engine using a carburetor? if so, i can tell you how one i had 30 years ago was built.

Using a circular track between two plates, with a marble or ball going around counted by an electric eye.

And a magnet on the drive shaft counted by a sensor for speed.

These two signal into a computer for MPG

personx 02-21-2008 02:35 PM


using a circular track between two plates, with a marble or ballbearing going around counted by an electric eye or counted by a crank sensor for flow.
Sorry if I seem not to bright but what moved the ball or how was it plumbed that the flow moved the ball bearing?

Why did you use speed instead of engine rpm?

How was it calibrated?

My ride is a carb version and I would love a flow reading

personx 02-21-2008 03:56 PM

Thinking about it I think I've come up with a flow meter design...

and of course the speed is for the distance part of the equation, duh.

so the big unknown for me is the computer impute part of it.

Rower4VT 02-21-2008 04:20 PM

There's already a product out there for non-OBD and/or carburated vehicles. If you go to a boating supply store/website you can get gps gauges that also have a transponder that you put in-line with your fuel line. These gauges will give very accurate speed, fuel flow, and typically have MPG readouts. Unfortunately I have yet to find one even close to the cost of a ScanGauge. :mad:

diesel_john 02-21-2008 07:14 PM

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Let's set a price goal of $30 for this flow meter, that should filter the ideas.

we are talking about non OBD engines.
the marble or epoxy ball is pushed around a circular track by the gasoline.
an electronics guy can tell you to make a light tach to count the ball passes(fuel volume)
the distance is pulses off magnet on the axle or drive shaft u-joint with hall effect or other sensor, a junk yard crank or cam sensor.
the calibration is like any MPG meter, count the pulses per gallon, and the pulses per mile. there are other threads on this site that tell how to use an old lap top to do the computation. but since this is just pulses and you don't have to decipher pulse width, the electronic minded can tell you how to use a divider chip (terminology) and display.

Below a very rough sketch. Visualize this stuff stacked up together and clamped with 4 bolts. The holes thur the outside ring are small enough so the ball passes over. So does some fuel, but it doesn't matter just takes more pulses to make a gallon. Next try to think of materails that are gasoline and alcohol proof to make it out of. A 1/2"x3" aluminum plate and ball mill would be nice, but lets try to think of something even more common and less expensive. Like maybe cut a 5/16" length off a piece of 3" seamless tubing for the outside ring. And 2 1/2" for the inside ring.

personx 02-22-2008 06:32 PM

I guess my question is about this kind of meter is what keeps the ball moving between the "out" to the "in" ? to get back into the start place again.

And if it is a steel ball the angle of the vehicle could throw off the readings, because there can't be a real seal between the ball and the wall. so you will get some flow around and if the angle increases or decreases that would I'm guessing cause differing readouts.

You had experence with one of these years ago how good did it work for you?

diesel_john 02-22-2008 10:25 PM

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personx, tell us about your idea.

Would the pulses of an electric (solenoid type with internal pressure sensitive shut off) fuel pump work?

The one i had in the 70's worked very well. it was two piece die cast, so each side had one half of a round groove. (your better seal) so i'm thinking we'll need to fill the corners in with epoxy, if we can't figure out an inexpensive way to cast or machine the groove. The ball was a plastic or rubber which was light weight. (your mass and acceleration concern). This may not be as much of a concern as we think because although the ball races around one side it would go slower around the other side. The old meter failed because the change gasoline formulation in the 70's melted the ball. so we need something round 1/4 to 5/16 in. diameter (approx. fuel line size) and immune to the chemicals in gasoline. So looking in the back of the Grainger's catalog chemical resistance chart, we see aluminum, kynar, teflon, polyacetal, nylon, tyton, carbon, ceramic, viton, epoxy. and i would add glass to the possible candidates, although on the heavy side. We are looking for a round ball made from one these material. Googling aluminum ball i find a lot of suppliers. 1000ea 5/16" weighs 1.6 Lbs. I am leaning towards aluminum right now any suggestions?

there is gasoline bypassing all the time that the engine is using gas, to take the ball pass the inlet port.

this pic of that 70's mpg computer, which still works by the way. Just no flow meter.

personx 02-24-2008 07:34 PM

what I was thinking about was something that I remember from fish tanks. they had a little spinning thing to show that the water was flowing, that the pump was really working. it was like the vane type air or hydraulic pumps. 6 (or more) vanes from a central hub all sealed in a clear plastic housing.

it would be easier to machine, just cut a round hole (1" to 2") in however thick stock you want and sandwich the sides as with the other one. drill inlets and outlets holes. you could mount a magnet on each side of the hub for balance or do a flat round plate that covers the vanes and color it to set off an optical sensor.

this is along the lines that I'm thinking now, but I not really married to any ideal right now. I had not even thought of doing this until you brought it up and now I think it's a great ideal.

I'm kind of a slow thinker and had some problems visualizing how that ball would get around the backside that is why I was asking about how well it worked for you. nothing like experience with something to see the way.

anyway I'm still building it in my head and have not come up with what I think is a good design so far.

ps where at in OH are you, I grew up in Franklin (between Cincinnati and Dayton) many many years ago.

diesel_john 02-24-2008 10:23 PM

the impeller would be gasoline proof, the bearing material would be what?
lets define the pressure to be 7 psi.
on the ball in a track design, an aluminum ball would be good, but all kinds of glass beads are available now. think glass would be to heavy? know any arts and crafters, a 6mm black glass bead would be good.
let's estimate the flow per min. @60 MPG @60 MPH would 1 gal,/ hr. or about 2 oz./ min.
@30MPG would 4 oz./min.
so 2 to 4 oz/ min would be a range to test over.

dcb 02-26-2008 08:47 PM

I have a need to get fuel consumption feed back on my bike. But without a fuel pump to keep the marble moving I might have to look elsewhere.

Hmm, fuel pump..., what about replacing the fuel pump with a 12v positive displacement pump and small accumulator that shuts off at a couple psi? Then keep track of the revolutions the pump turns and the distance traveled?

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