mileage computer for a carbureted engine

[dcb]

I'm gonna piggy back here too, or tell me to get my own thread

re: full flow vs full pressure. I picked up a used electric pump, and had a chance to play with it this evening, and about 10 feet of clear 5/16 tubing.
observations:
1. It takes a number of seconds to fill the tube at full flow.

2. The pump keeps running when max pressure is reached, and runs at the same speed regardless of the volume it puts out (function of differential pressure).

So let's say it takes 5 seconds to fill the coil of tubing back up to some safe distance from the top, and when the controller senses the level at the bottom, it will always runs the pump for 5 seconds. And keep track of how many 5 second runs it made. Given that there are variations from stroke to stroke, I think it makes sense to ONLY track how many times the pump was turned on for 5 seconds (for example), and not precisely how many times the piston moved.

I don't think it should be full flow though, I can't quite explain why though. Intuitively I think if the immediate pump outlet had a restriction, that would only allow a little more fuel than anticipated maximum demand would require, then it would give more predictable results as it would have to run longer to refill the tube/resivoir, and there would be less variation in the outlet pressure the pump sees.

Originally Posted by dcb

I like how far your drip counter idea has come

I think this will work, for my bike , the microcontroller just turns the pump on for a specific amount of time when the resivoir looks low, and keeps count. The pump doesn't run so long that it would overflow the resivoir, might even want a restriction on the pump outlet. I'm ready to go get a cheap fuel pump.


...

[diesel_john]

That's a good idea. the more restriction between the pump and measuring cylinder the lower the flow that it could measure accurately. restricting orifice would not have to be bigger than the sum of the main carb. jets, would it. high level detector would be redundant, with the timer, but would accomodate different pumps, but so would adjustable timing.

probably better to dial in the restriction as close as possible to get same accuracy with a smaller volume, because the smaller the measuring volume the closer to instant MPG.

i kept thinking i needed to limit the pump to single strokes, with an adjustable delay then count number of strokes to make a gallon. would almost be real time flow. maybe if i power it thur a signal light flasher it will single stroke.

on the recirculating ball flow meter (rbfm), the ball doesn't go around very fast, maybe 1 Hz.

[dcb]

Just thinking out loud here, trying to detect when fluid is in a clear tube. A laser LED would work, but so might a narrow angle LED. Might be an easier way to do this.

Get the bias right to trigger a 5 second pulse from a 555 timer (for example) when the laser hits the CDS cell. Add a relay/power transistor, and give the bike odometer a click on the same pulse.

The vent is going to be a pain.

[personx]

I'm planning to use a green LED as a sensor in my meter. The green ones are made from the same stuff as solar cells so they will generate a little current from light. The ones I have (green light but with clear lens) will put out 1.5 V from a white LED held about one inch away. I have a green lens one that will only put out .8 V at best so the clear lens ones are the way to go. I don't know what they would be after the sending light was filtered through two pieces of glass and an eighth inch of gas but that what I'm planning on using now.

[dcb]

Picked up some electronic bits on the way home:



Thought I would see how the clear tube behaved in the infrared spectrum:
the LED by itself:


the LED through the empty tube:


the LED through the tube with water in it:


Am I imagining things or is it much brighter with the liquid in the tube? That is not what I expected.


P.S. Here is the intended display device


Edit: Apparently water vapor is a good IR blocker, which explains the results. Will need to retest with gasoline.

[diesel_john]

So you will be counting how often the pump runs not how long the pump runs, correct. Or how many times the pump pulses over time to keep the tube full.

[dcb]

Originally Posted by diesel_john

So you will be counting how often the pump runs not how long the pump runs, correct.

Well, the pump will run for a fixed amount of time when triggered by the low level detector, i.e. 3 seconds, so lets call that a "pump cycle". I'm just counting how many pump cycles there were. But certainly you could deduce the total running time easily enough.

Originally Posted by diesel_john

Or how many times the pump pulses over time to keep the tube full.

just the number of pump cycles.

By playing with the "tire circumference" on the bike computer and/or the delay time I hope to come up with a useful reading on the distance travelled. i.e. 100 miles is really one gallon dispenced by the pump

[dcb]

Ok, tried the gasoline in a tube, I really should try and find one of these first next time



it is pretty much transparent at 950nm

I wasn't happy with the test, but I think that laser is going to be more of a sure thing, and I already have one.

[JohnnyGrey]

If you're confident you can design the electronics, all you need is a few inputs...

Wideband 02 / MAF

or

Wideband 02 / MAP / RPM

Meter the air going in and sniff the exhaust to figure out how much fuel was in that air.

[dcb]

Yah, but wideband O2 sensors are expensive. We were hoping for cheap