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Old 19-03-2019, 07:17 PM   #887
Darkness
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Join Date: May 2007
Location: Stockbridge
Bike: M900
Posts: 1,984
Quote:
Originally Posted by Mr Gazza View Post
I'm a bit surprised at your thoughts about a higher rate of return.
The volume of fuel can only go down once the cap is closed.(assuming a constant temperature.) There's nowhere for any extra fuel to come from.

The tank, along with the pump and fuel rail are full of fuel.
The pump pressurises the fuel rail (a very low positive pressure), and pumps fuel round it, back into the tank. Fuel exits via the injectors at a variable rate, but there is always an over supply and fuel constantly returns to the tank whether needed or not.

In order to return more than it has taken from the tank in the first place, it would have to draw from some other supply.... It's a loop. It just sucks in one end and squirts out the other with a bit lost in the middle on demand.

I have Capo's article on fuel caps, with pictures. But I have tried without success to post it before.. Sorry.
Yes, that’s my take on it too.

The only reason for petrol to come try to get out of the tank through the breather are if it’s got seriously hot since the tank cap was filled, or you are standing the bike on its front wheel braking, so all of the fuel rushes to the front of the tank.
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