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 Fuel pipe size 
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Firing on two.

Joined: October 12th, 2019, 6:40 pm
Posts: 128
Location: Limburg Belgium
Post Re: Fuel pipe size
Roger, do you know if a submersible pump is self-sucking ? If so why not mounting it close to the engine ?


October 28th, 2020, 10:42 am
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Firing on two.
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Joined: March 21st, 2013, 12:04 am
Posts: 1131
Location: Exeter, Devon
Post Re: Fuel pipe size
I bought the one I have some time ago. In hind sight I may have selected an in line one.

My thoughts for submersible was that it should be quieter. I have a BMW K100 motorcycle, and its a replacement part for that.

The requirements for a FI pump are different to a carb pump.

With a carb, there is a reserve of fuel in the float bowl. If you get air in the system from the pump pumping air rather than fuel, then the float bowl will purge the air out when you start pumping fuel again.

With FI you do not have that purging effect. you have a closed system that needs to maintain a constant pressure for it to work correctly. If it has any air in the system, then the injectors will inject air rather than fuel.

For the constant pressure, a regulator is required.

There are a variety of flavours of fuel pump.

Submersible and In line. Some come with regulators built in, some don't.

The pump is probable best placed near the fuel tank, so as to run dry for the least amount of time when pulling up fuel.

So its the location of the Fuel Pressure Regulator (FPR) that is more important. generally speaking, the closer to the injectors as you can is better. The down side of that is you require a return pipe to the tank from the the FPR.

There are other issues regarding surge that need to be considered, but for the moment, I will submerse the pump, and place the FPR near the tank.

I still have to sort out the pipe work and connections to the injectors yet ..... :)

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If you can't fix it with a hammer, it's probably electrical (or, an electric fuel pump!) ....


October 28th, 2020, 11:51 am
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Firing on two.

Joined: October 12th, 2019, 6:40 pm
Posts: 128
Location: Limburg Belgium
Post Re: Fuel pipe size
Roger, I have a fuel rail with FPR from an old Toyota. The FPR seem to have a underpressure line to a throttle body . But the new body I bought does not have a connection . Some pics will follow later, as I wait for some components still to arrive. The answer to my question is partly answered because your BMW pump seems to be self-sucking too.


October 28th, 2020, 12:07 pm
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Firing on two.
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Joined: March 21st, 2013, 12:04 am
Posts: 1131
Location: Exeter, Devon
Post Re: Fuel pipe size
You can try the fpr without the map connection. It will work ok, or it wont. :)

Its to extend the range of the injectors, and to help them open against high vacuum. I would only bother with it if you have a problem with idle, or cant get enough fuel at wot. :)

_________________
If you can't fix it with a hammer, it's probably electrical (or, an electric fuel pump!) ....


October 28th, 2020, 12:34 pm
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Firing on two.

Joined: October 12th, 2019, 6:40 pm
Posts: 128
Location: Limburg Belgium
Post Re: Fuel pipe size
Indeed the map connection is for changing the opening of the FPR, or better closing longer. The connection is towards a porting throttle between the first main throttle and the manifold. This porting is openend when more power is needed Instead of one open throttle plate each inlet will have two open trottle plates. With two open plates the FPR will open later or not at all and it means that more fuel is pressed through the injectors. So in my case I will not need the map connection.


October 31st, 2020, 11:51 am
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