Motorcycle petrol tank fuel gauge

[djsb]

I have a motorcycle that does not have a fuel gauge. If I want to estimate fuel usage I need to zero my trip meter when filling up the tank and then take note at what distance I switch the petrol tap to reserve. At a busy petrol station I often forget to do this or just cant be bothered.
I'd like to fit some kind of gauge that gets it's reading either from fuel flow or some kind of sender in the tank. The tank is plastic and has a narrow fuel filler hole so access to the inside of the tank is going to be difficult. I know most car sender units use some kind of float to measure the fuel level. I've not seen any thing similar for motorcycles (but I havent looked too hard yet).
It would be great if there was a measureing device similar to that used in car wheels for tyre pressure. This is embedded in the wheel and is probably self powered. I've seen a few fuel flow projects on the internet for small aircraft. The only problem is the fuel flow sensor is too large or too expensive or both. Does anyone have any wisdom or ideas that I can persue. I'm not worried about the MCU side of things, the sticking point is using the appropriate fuel flow sensor.

Thanks,

David.

[mikeselectricstuff]

I wonder if you could sense through the plastic wall, e.g. by change of dielectric constant or acoustic properties of the petrol inside - probably only practical for a few specific levels but might be useable. Is the plastic translucent ? If so an optical method may be viable.

Static pressure of fuel ? May not work when flowing, and may be issues with vibration, but potentially quite simple and accurate ( may need compensation of the pressure vs. content curve to correct for the profile of the tank).

Optical triangulation sensor in fuel cap?

[djsb]

Not sure if optical triangulation will work as the petrol is almost clear (pale to dark straw colour) and the inside of the tank is white/cream. The colour of the tank inside is useful as it will reflect light but only in a diffuse way. The tank is made of nylon and is painted dark red. I'm not sure if light can shine through it as I've not tried it.
There is an air vent under the tank, I wonder if air displacement could be measured in some way, just thinking out loud.
Or an air bubbler measurement system

Air bubbler (from wikipedia)

An air bubbler system uses a tube with an opening below the surface of the liquid level. A fixed flow of air is passed through the tube. Pressure in the tube is proportional to the depth (and density) of the liquid over the outlet of the tube.

Air bubbler systems contain no moving parts, making them suitable for measuring the level of sewage, drainage water, sewage sludge, night soil, or water with large quantities of suspended solids. The only part of the sensor that contacts the liquid is a bubble tube which is chemically compatible with the material whose level is to be measured. Since the point of measurement has no electrical components, the technique is a good choice for classified “Hazardous Areas”. The control portion of the system can be located safely away, with the pneumatic plumbing isolating the hazardous from the safe area.

Air bubbler systems are a good choice for open tanks at atmospheric pressure and can be built so that high-pressure air is routed through a bypass valve to dislodge solids that may clog the bubble tube. The technique is inherently “self-cleaning”. It is highly recommended for liquid level measurement applications where ultrasonic, float or microwave techniques have proved undependable.

David

P.S A picture of a similar tank

http://cgi.ebay.co.uk/MZ-MUZ-Skorpion-Sport-Cup-660-01-Fuel-Petrol-Tank-/390187062108?pt=UK_Motorcycle_Parts

[Kiriakos-GR]

Post an picture of your tank ..

Some times just the shape of it , does not help to add an gauge .

[rossmoffett]

Maybe you're not concerned about this anymore because it's an old thread, but just FYI..

Fluid level is measured by ( density * gravity * height ) = ( pressure )

With 10 inches (25 cm) you're looking at only about 0.4 psi (2.75 kPa) or less for fuel pressure change.  You'll see much larger variations than that just from the fuel sloshing around or backpressure from the evaporating fuel.  Much larger changes than that will occur just from barometric pressure shift in absolute pressure gauges.  Air bubblers or pressure measurement on the outlet are out.

You're pretty well stuck with floats or dielectric measurement.

Another low-tech solution I see a lot in the oil/gas fields is an external measurement tube.  You could do that just by making a three-way outlet on the bottom, running a clear tube up above and back into the tank.

[Zad]

My first reaction was to fit a pair of capacitative strips to the side of the tank, and measure the capacitance of the pair. Possibly by running it in an oscillator and measuring the oscillator frequency/period. It would need to be pretty sensitive though. I really wouldn't trust anything electrical inside the tank that wasn't custom made for the job.

[NiHaoMike]

What about a self-heating PTC glued to the outside of the tank? It would get hotter if there isn't any fuel cooling it down.

[Zad]

That would only work for one point in the tank, and any sloshing would instantly cool it. Tricky things motorboke tanks, they aren't as linear as car tanks, and are even more prone to the fuel moving around.

[Koubek]

I was dealing with the measuring level of the petrol trough the hydrostatic pressure. With some kind of pressure sensors it is the working way. Only bigger problem was finding of the pressure sensor for reasonable price that can be used with petrol. Device worked as well as i decided to offer it for others. It was some years ago. I must do some advert for me  Today i have an manufactory, this device is tuned into perfection and still in production.  😎 https://www.lskelectronics.com/fuelgaugepro1
I also described there some restrictions of this system so maybe it can also help to someone with constructing his own.

[ken246810]

Have you seen this product?
Hydrostatic pressure fuel gauge

I know this subject is old but this could help someone, there are various styles if you look at the products

https://www.lskelectronics.com/fuelgaugepro1

edit oops I just saw the post before this and it is the same product

[langwadt]

I was dealing with the measuring level of the petrol trough the hydrostatic pressure. With some kind of pressure sensors it is the working way. Only bigger problem was finding of the pressure sensor for reasonable price that can be used with petrol. Device worked as well as i decided to offer it for others. It was some years ago. I must do some advert for me  Today i have an manufactory, this device is tuned into perfection and still in production.  😎 https://www.lskelectronics.com/fuelgaugepro1
I also described there some restrictions of this system so maybe it can also help to someone with constructing his own.

does that really work reliably? gasoline is lower density than water and the tanks isn't very tall so there is not a lot of pressure differential to work with

[CatalinaWOW]

I think the external tube approach is by far the easiest and most reliable posted so far.

Depending on how you want to use the gauge there may be a number of options worth considering.  A binary indicator (above or below reserve level) would be much simpler to make and calibrate.  A simple pair of capacitive plates at the appropriate level.

Another approach which might work would be to directly measure the mass of the gasoline with a load cell.  This approach gets rid of all of the complications of relating depth to volume in a complicated tank shape.  You can get adequate load cells for well under 20 USD.  Vibration, bumps and the like can be filtered out.  But there are lots of issues to sort out.  Is the tank supported in such a way that the load cell can weigh it?  Will your body weight or saddle bags or the like sometimes rest on the tank?  How much dynamic range do you need to handle the various bumps and jiggles?  What are the appropriate time constants?  I can see this working on some bikes and being totally hopeless on others.

Back when I was riding a motorcycle a lot I was like you and would often forget to reset the reserve valve.  But I always filled the tank to the top.  If you are consistent in filling your tank each time you might even get away with an open loop approach, using a counter on the crankshaft to represent petrol usage and a switch on the gas cap to do a reset.  Could justify a lot of fun test rides to calibrate the revolutions per liter ratio and evaluate its variability.

[Fred27]

I've had a lot of motorcycles and never seen one with a fuel gauge - even on bikes like BMWs where it would be a welcome feature. The best I've seen is "X miles since the low fuel light came on". This leads me to believe that the dynamics of the fuel sloshing around makes it impossible to do well.

Actually, that's not quite true. I have had a bike with a fuel gauge - it was a Zero FXS. 

[AndyC_772]

My Ducati Diavel had a perfectly good fuel gauge.

[Fred27]

My Ducati Diavel had a perfectly good fuel gauge.

Fair enough, then! It seems it has and can be done. Odd that my Hypermotard 950 (with the latest colour dash as on the Panigale V4) hasn't got a fuel gauge.

[BurningTantalum]

I faffed about with fitting a fuel gauge to my Triumph T160 bike back in the late 70s. After much experimenting with a metal can of petrol on the workbench I settled on a float sender from a car fitted through a hole in the bottom of the tank. I fitted the gauge in the tacho, in the space where the odometer would fit in the speedo version of the instrument. A simple Letraset white 'o' and white dot show the full and empty position. It is still working today and has never been touched. I had to fit a voltage reg to accommodate the variable supply voltage, but used the thermal 'ticking' unit from the car.
More recently I fitted a dual float and reed switches in my skid steer loader, which is all that is needed really for a bike. 2 LEDs on the panel.
BT

[floobydust]

It seems the Ducati uses a float sensor and 10 reed switches. Part 1

[Circlotron]

Back in 1982 we had a Honda Melody scooter that had a fuel gauge.