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]

Should work...why wouldnt it?

 

[Neal R19]

Should work...why wouldnt it?

Yeah well that's what I thought... wanted to check if I'm missing something.

 

[DaveL485]

Yeah well that's what I thought... wanted to check if I'm missing something.

I would be tempted to set up a return system, just for personal preference... again that would work with the static reg @ 3.5 bar. Be easier to switch to rising rate in the future when its mapped.

 

[Neal R19]

I would be tempted to set up a return system, just for personal preference... again that would work with the static reg @ 3.5 bar. Be easier to switch to rising rate in the future when its mapped.

How would you do that though, using the stock fuel rail?

I'm thinking of running both feed and return lines to the engine bay and then regulate there, rather than regulate just near the tank and only run the feed line up to the front.

 

[DaveL485]

using the stock fuel rail?

I dont recall if they're plastic or alloy. Alloy, easy, weld in a fitting. Plastic, not sure how easy it would be to put a second fitting on the rail. Probably 'not very'.

 

[Neal R19]

It's plastic. This is why I was asking about the mk3 fuel rail... but it turns out I can't use of those because it wont fit a mk2 manifold.

Not sure what's actually different though or whether it could be easily modded to fit.

 

[DaveL485]

What are the chances that you could lop the end off the fuel rail, grind some light ridges in it and fit a pipe over the end with a jubilee clip...?

 

[Neal R19]

What are the chances that you could lop the end off the fuel rail, grind some light ridges in it and fit a pipe over the end with a jubilee clip...?

:gasp:

 

[DaveL485]

Sorry, autocorrect! It should have said "Make up a billet fuel rail with two fittings for a return system"

 

[Neal R19]

Sorry, autocorrect! It should have said "Make up a billet fuel rail with two fittings for a return system"

That's what I figured.

 

[Brigsy]

Does it have an in tank pump originally?

I would just fit a swirl pot and external pump instead of messing about with fitting something in tank. Fit a single pipe rising rate regulator to save messing about with a return on the rail. Rs tuning would be able to map it to suit a rising rate regulator or leave the vac pipe off as you have already said.

 

[Neal R19]

Does it have an in tank pump originally?

I would just fit a swirl pot and external pump instead of messing about with fitting something in tank. Fit a single pipe rising rate regulator to save messing about with a return on the rail. Rs tuning would be able to map it to suit a rising rate regulator or leave the vac pipe off as you have already said.

The original tank doesn't as it was a carbed engine. But I've got a 16V tank to fit which does have a pump (and baffles) in it.

I'm trying to keep things simple (and cheap) if I can. Since I want to run it on the OE ECU and therefore just need to replicate 3.5bar static, is there any advantage to doing it with an external pump and swirl pot etc?

Still trying to get my head around a non-return pressure regulator. How does that even work?

 

[Brigsy]

I think a cheapo swirl pot and use the original 19 16v pump as lift will be a better option, wont cost much more to be honest. If the baffle in the 19 tank is the same as the gtt it will be pretty poor.

Use a fpr with a return and a single pipe to feed the rail and whatever fuel pump you want i.e 255lph. Plenty of turbo cars run the same no issues.

 

[DaveL485]

Still trying to get my head around a non-return pressure regulator. How does that even work?

The dead head still pressurises as its part of the circuit behind the regulator diaphragm. Its not actually a returnless system, it does return, but the saving is in the fact the reg & return can be in the tank with the dead-head up to the front of the car, thus saving a run of fuel pipe to the front of the car for the return. If that saves a tenner a car over a million cars...
You'll notice a returnless system is a fecker to start after running dry, as the pump doesnt flow fuel through the line...you have to "inject" all the air before the fuel gets through.

 

[Neal R19]

The dead head still pressurises as its part of the circuit behind the regulator diaphragm. Its not actually a returnless system, it does return, but the saving is in the fact the reg & return can be in the tank with the dead-head up to the front of the car, thus saving a run of fuel pipe to the front of the car for the return. If that saves a tenner a car over a million cars...
You'll notice a returnless system is a fecker to start after running dry, as the pump doesnt flow fuel through the line...you have to "inject" all the air before the fuel gets through.

View attachment 16519

Yeah OK that all makes sense and that dead-head system represents what the mk2 runs as standard, and what I’m going to replicate in the 19.

What I meant was with reference to the mk3 setup – it has a similar non return/dead head system, but (apparently) with the addition of a rising rate fuel pressure reg on the fuel rail. I’m puzzled as to how this can regulate the fuel pressure down without having a return to dump excess fuel?

 

[Ewan]

I am also puzzled with the mk3 system. Seems the pump is regulated with a 5bar pressure in the tank (where the return is to bleed off excess pressure), but it also has a pressure regulator in the rail which is vacuum operated. Off high boost the rail has 3 bar and at high boost the vacuum regulator is activated allowing the rail to rise to 5bar.

I have no idea how that works. Perhaps the fuel rail internally has two channels that the 5bar feed is split into. Then the second channel is only activated when sufficient boost is applied?

 

[DaveL485]

What I meant was with reference to the mk3 setup – it has a similar non return/dead head system, but (apparently) with the addition of a rising rate fuel pressure reg on the fuel rail. I’m puzzled as to how this can regulate the fuel pressure down without having a return to dump excess fuel?

Good question.

@Red21 might be able to assist?

 

[tutuur]

You all make this way to complicated!

There are numerous of cars with the same setup, no it's not to cut down on costs. Running 5bar through a restriction of 1cm simply costs less energy than to run 3bar through 3m of fuel pipe constantly.

The rail pressure regulator does what every other regulator does, it works on pressure difference, when the boost rises it opens the valve more, when the boost is going lower is opens it less. This also depends on fuel pressure in the rail, by simply having an internal reference it's able to regulate and keep the pressure constant.

 

[Neal R19]

You all make this way to complicated!

There are numerous of cars with the same setup, no it's not to cut down on costs. Running 5bar through a restriction of 1cm simply costs less energy than to run 3bar through 3m of fuel pipe constantly.

The rail pressure regulator does what every other regulator does, it works on pressure difference, when the boost rises it opens the valve more, when the boost is going lower is opens it less. This also depends on fuel pressure in the rail, by simply having an internal reference it's able to regulate and keep the pressure constant.

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!

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