Accurately measuring fuel flow (2 litre petrol injection)

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Purple Pixie
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Accurately measuring fuel flow (2 litre petrol injection)

Post by Purple Pixie » Sat May 03, 2014 10:47 pm

Greetings

I have tapped into a source of supply of flow meters that can be fitted into fuel lines

HOWEVER as I understand it our injection systems have a feed line and a return line, with a meter in both lines showing how much fuel has passed through, the difference between the TO and the RETURN is the USED, taking this and the distanced travelled gives an accurate MPG

Now the question is how accessible are the lines to/from and what pressure are we talking? can the unpressured line to the pump and (unpressured?) return be tapped?

unpressured meaning not at injector rail pressure

Thanks

Dr B
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Simon Jones
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Re: Accurately measuring fuel flow (2 litre petrol injection

Post by Simon Jones » Sat May 03, 2014 11:04 pm

You could fit the flow meters at the tank end. That way you could get away without cutting the fuel lines.

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Re: Accurately measuring fuel flow (2 litre petrol injection

Post by Purple Pixie » Sun May 04, 2014 12:33 am

Simon Jones wrote:You could fit the flow meters at the tank end. That way you could get away without cutting the fuel lines.

Image
Anyone decode which one goes where as there is probably:
  • A breather
    A feeder
    A return
    and others?????
And the diesel might well differ from the petrol
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Re: Accurately measuring fuel flow (2 litre petrol injection

Post by Simon Jones » Sun May 04, 2014 9:19 am

This is from V6 but i would expect it to be the same. From left to right (in the previous photo) the pipes passing thru' the top plate are:

To engine
From engine
Filler neck vent

You can see the other end of the pipework here:

Image

The pipe that runs over the top is probably something to do with vapour management and would not be relevant for your purposes.

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Re: Accurately measuring fuel flow (2 litre petrol injection

Post by rita » Sun May 04, 2014 2:28 pm

Hi Purple Pixie, sounds like an interesting project, what type of meter do you intend to use. The normal unit is a Duel flow supply and return, usually wee bit expensive.

Good luck.
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Re: Accurately measuring fuel flow (2 litre petrol injection

Post by Purple Pixie » Sun May 04, 2014 4:42 pm

rita wrote:Hi Purple Pixie, sounds like an interesting project, what type of meter do you intend to use. The normal unit is a Duel flow supply and return, usually wee bit expensive.

Good luck.
They are rotary vane in-line meters with remote display units which are capable of taking inputs from multiple sensors, I am just trying to work out if they work at the low litres/hr level
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Re: Accurately measuring fuel flow (2 litre petrol injection

Post by Simon Jones » Sun May 04, 2014 5:10 pm

Are you going to take a feed from the speed sensor so you can calculate consumption per mile travelled? If you want to know if you are driving economically rather than an absolute consumption figures then a vacuum gauge on the inlet manifold would be the simplest option.
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Re: Accurately measuring fuel flow (2 litre petrol injection

Post by Purple Pixie » Sun May 04, 2014 6:59 pm

Simon Jones wrote:Are you going to take a feed from the speed sensor so you can calculate consumption per mile travelled? If you want to know if you are driving economically rather than an absolute consumption figures then a vacuum gauge on the inlet manifold would be the simplest option.
... vacuum gauge meets with my "Occams Razor" approach to solving technical problems

I am more interested in average consumption over a day or week.........
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Re: Accurately measuring fuel flow (2 litre petrol injection

Post by Gasy » Sun May 04, 2014 7:09 pm

Mighty complicated way of doing average
Why not just brim your tank full to top and zero your mileage
Do your day / weekly mileage and then brim your tank again which will give you the amount of fuel you have used
You can even put these figures into a app thingy which does all the maths for stupid people like me
Think the app is called fuelly
Some peeps on here have it displaying on there pages
Gas safe heating engineer / plumber if you need any advice just shout.
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Re: Accurately measuring fuel flow (2 litre petrol injection

Post by Simon Jones » Sun May 04, 2014 7:13 pm

Are you planning on using some form of data logger, or programmatical solution using something like a Pi or Arduino? Do the meters have a perpetual counter such that they record total volume of flow since day 1?
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Re: Accurately measuring fuel flow (2 litre petrol injection

Post by Purple Pixie » Sun May 04, 2014 8:04 pm

Simon Jones wrote:Are you planning on using some form of data logger, or programmatical solution using something like a Pi or Arduino? Do the meters have a perpetual counter such that they record total volume of flow since day 1?
Meters have inbuilt batteries and a perpetual counter like a water meter - no embedded technology
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Re: Accurately measuring fuel flow (2 litre petrol injection

Post by teenmal » Sun May 04, 2014 8:53 pm

Purple Pixie wrote:
Simon Jones wrote:Are you going to take a feed from the speed sensor so you can calculate consumption per mile travelled? If you want to know if you are driving economically rather than an absolute consumption figures then a vacuum gauge on the inlet manifold would be the simplest option.
... vacuum gauge meets with my "Occams Razor" approach to solving technical problems

I am more interested in average consumption over a day or week.........

A lot easier and cheaper using the garage / filling station Pump and the vehicle trip meter.

Any extra you spend you get it in the tank.
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Re: Accurately measuring fuel flow (2 litre petrol injection

Post by Purple Pixie » Sun May 04, 2014 11:17 pm

teenmal wrote:A lot easier and cheaper using the garage / filling station Pump and the vehicle trip meter..
Ah, agreed, but I am doing it for the hell of getting an end result that works!
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Re: Accurately measuring fuel flow (2 litre petrol injection

Post by GreenBongo » Mon May 05, 2014 7:59 pm

You need to ensure that the flowmeter on the supply is rated for EFI pressures, usually around 3bar, how are you estimating the flow rate?
If you have diagnostics then you could perform an estimate based on the injector pulse width.
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Re: Accurately measuring fuel flow (2 litre petrol injection

Post by Simon Jones » Mon May 05, 2014 9:35 pm

The pressure in the fuel lines is not going to be too great at the tank end (I would have thought) as it uses conventional rubber fuel hoses rather than metal pipework.
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