A quick Q on fuel lines..

[GeoffM800]

Pulled the tank off my M800ie and ..can't recall which fuel line goes on which tank outlet (misplaced my sketch!)..one hose has a 'M' tag on it ..but which spigot does it attach to?

[slob]

M is delivery (Mandata)
R is return (Ritorno)
http://www.thelasturl.net/ukmoc/fuelhoses.png

[TimDW]

Just like slob said.

Sometimes the fueltanks are marked with IN and OUT

IN = Ritorno = R = Into the tank
OUT = Mandata = M = From the tank to the carb/throttle body

[GeoffM800]

brilliant!!..thanks so much Slob/TimDW for such simple clarity!! G

[Dukedesmo]

Just like slob said.

Sometimes the fueltanks are marked with IN and OUT

IN = Ritorno = R = Into the tank
OUT = Mandata = M = From the tank to the carb/throttle body

As above M & R but in tanks where the fuel pressure regulator is inside the tank it probably doesn't matter which way round they go?

Certainly on my 916 it works either way as it's just creating a pressurised 'loop' from tank back to tank (with injectors in the loop) so orientation is unimportant, of course if the regulator is external and therefore between injectors and tank then it won't if you connect it wrong run as you won't get any fuel to the injectors...

[350TSS]

Dukedesmo: what about the placement of the filter in the system if it ends up on the return to the tank it is too late?

[Dukedesmo]

Dukedesmo: what about the placement of the filter in the system if it ends up on the return to the tank it is too late?

In a 916 tank the filter is in the tank as is the regulator so the fuel is filtered, pumped out and returns to the tank to face the regulator on return, this creates the correct pressure in the 'loop' and therefore at the injectors . As such the orientation of the out/in lines makes no difference whatever as the fuel is always filtered on the way out.

I believe (at least some) Monsters are different? my (carby) Monster has a fuel-injected model tank and it too has an internal filter but no regulator.

I have set it to circulate a loop which has a 'T' (actually a 'Y') to feed the carbs and the excess fuel just returns to the tank but (I believe) the fuel injected Monster it originates from has an external regulator built into the throttle body assembly? In which case the out and in would matter otherwise you'd be pumping fuel to the backside of the regulator and not getting to the injectors? It would still be filtered though.

[Darren69]

In a 916 tank the filter is in the tank as is the regulator so the fuel is filtered, pumped out and returns to the tank to face the regulator on return, this creates the correct pressure in the 'loop' and therefore at the injectors . As such the orientation of the out/in lines makes no difference whatever as the fuel is always filtered on the way out.

I believe (at least some) Monsters are different? my (carby) Monster has a fuel-injected model tank and it too has an internal filter but no regulator.

I have set it to circulate a loop which has a 'T' (actually a 'Y') to feed the carbs and the excess fuel just returns to the tank but (I believe) the fuel injected Monster it originates from has an external regulator built into the throttle body assembly? In which case the out and in would matter otherwise you'd be pumping fuel to the backside of the regulator and not getting to the injectors? It would still be filtered though.

That's how my S4 is; the pressure regulator is between the throttle bodies and the filter is in the tank. I'm not sure but I imagine it is filtered before being sent to the injectors so as to protect them from particulate matter either from the fuel or the tank.

[TimDW]

Normally a fuelfilter has a direction. There is an arrow on the OEM filters... So I think theoretically it would not matter, but practical is does...

[Capo]

In a 916 tank the filter is in the tank as is the regulator so the fuel is filtered, pumped out and returns to the tank to face the regulator on return, this creates the correct pressure in the 'loop' and therefore at the injectors . As such the orientation of the out/in lines makes no difference whatever as the fuel is always filtered on the way out.

I believe (at least some) Monsters are different? my (carby) Monster has a fuel-injected model tank and it too has an internal filter but no regulator.

I have set it to circulate a loop which has a 'T' (actually a 'Y') to feed the carbs and the excess fuel just returns to the tank but (I believe) the fuel injected Monster it originates from has an external regulator built into the throttle body assembly? In which case the out and in would matter otherwise you'd be pumping fuel to the backside of the regulator and not getting to the injectors? It would still be filtered though.

The pressure regulator is after the injectors. The ECU 'assumes' there to be a constant pressure (which is the function of the regulator to maintain) and the controls the injector pulse accordingly. Its a bit micky mouse, the regulator is not that precise.

Additionally, there is a fine screen at the fuel connection on the injector

[Darren69]

Bit of a thread hijack. So can you change the standard pressure reg and get a bit more pressure/better performance?

[Dukedesmo]

Bit of a thread hijack. So can you change the standard pressure reg and get a bit more pressure/better performance?

Probably, if such a regulator is available (race version?).

I understand you can also 'adjust' it, by gently tapping it with a small ball-pein hammer to dent it and If done correctly it increases the fuel pressure a little.

You'd then need to do other mods; gasflow, remap etc. or you'll just run richer.