19 Fuel pumps, pressure regulators

[Neal R19]

Alright chaps, been doing some thinking about the fuelling on my Turbo Shed.

Since I'm running a mk2 225 engine/fuel rail and planning to run it on the OE ECU (at least to begin with) I need to match the 3.5bar static fuel pressure from the standard in tank sender. Non return system.

The sender wont fit in the 19's tank, so here's what I'm thinking of doing:

- Fit a walbro GSS342 (or HRC equivalent - anyone got any 1st hand experience of these?) into the standard 19 sender unit in the tank (which has feed & return)
- At the outlet of the sender, pass it to a pre-set 3.5bar reg, which sends fuel back to the return stub of the sender. Like this one:



- T piece into the line between the pump and the reg and send that off to the fuel rail.

Any reason why this is a dumb idea?

I can just leave the vacuum reference port on the reg alone and it will just sit at 3.5bar exactly as the standard one does?

 

[DaveL485]

Ah yes of course! The rail reg doesn't need to return because the pressure goes back to the tank reg and the return there takes care of it!

...and the lightbulb switches on!

 

[Neal R19]

...and the lightbulb switches on!

Yeah proper lightbulb moment there!

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[Ewan]

Yeah proper lightbulb moment there!

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For the less than intelligent on here, or me, I still didn't quite understand the difference between the constant rate fuel system on a 225 and the rising-rate on the 250.

The 225 has a constant 3.5 bar in-tank regulated fuel feed to one end of the fuel rail (cylinder 4 end). The 250 has a constant 5 bar in-tank regulated fuel feed to an additional pressure controlled regulator in the middle of the fuel rail (between cylinder 2 and 3). This pressure controlled regulator is piped to the inlet manifold, and as the boost (positive) pressure increases will open the fuel regulator to allow up to 5bar on the fuel rail from a nominal 3bar.

Simples, unless you are a bit thick like me! I couldn't figure out how a regulator in the middle of the rail worked with a fuel feed on the end, until I realised that the fuel feed on the 250 is directly to the regulator. What a wally!

Edited this to say that it is exactly as Tutuur described a few posts above [emoji846]

 

[Neal R19]

Yep, that's the key thing - realising that the 2nd reg is before the rail, therefore needing no return itself but allowing the return on the tank regulator to sort it all out.