Nevada 2006 - external fuel pump config

[Boichat]

Hi all.
We have looked through many Posts here and can’t quite get a definitive answer.
I am looking to replace my Nevada fuel tank and need to have an external fuel pump.
From what I can see the engine runs at 3 bar, fuel pump 3 bar or similar but the pressure To the injectors is regulated by the regulator. I have three options for setting this up.
1) all items in line with the pressure regulator return at 5 bar to the tank. (Regulator needs and in,out and return)
2) no return to the tank - could this blow the engine?
3) Regulator in return line. Would this regulate the pressure to the injectors ok? (Regulator only needs an in and out)
I have attached a drawing of these three configs  (hopefully)

If anyone Has any help on the configurations or parts I would be extremely grateful. This is my first guzzi and the first efi I have worked on.

[chuck peterson]

I'm pretty sure as far as Nevada's go...

There is me, and Sir Ed, and...

That's about it.     

I gave up doing anything on mine except riding and polishing

You might try the smallblock forum

I believe your question would apply to most in tank pump V7 new generation

[Kiwi_Roy]

Sketch 3 is the way to go. The regulators control the upstream pressure, downstream of the regulator the pressure is quite low as there is no restriction going back to the tank.
The In Tank scheme is very similar to that.
An external pump can generate 70 PSI if the filter plugs then it relieves through a relief valve inside the pump itself.
Take a look through this document, its an early one but still very relevant.
https://dpguzzi.com/efiman.pdf
There is one thing wrong with the document, if you look at the diagram on page 3 the pressure regulator is shown (yellow) connected to the inlet manifolds, all modern guzzles have it going to atmosphere.
If you look at the pump diagram you can see the internal relief valve I mentioned, it vents back through the hollow motor shaft.
The pressure of 45 PSI at the regulator ensures that the injectors operate in the choked flow region, the flow rate is not effected by manifold pressure as it would be if the injector pressure was only 30 PSI

[sign216]

You might try the smallblock forum

When Yahoo Groups died I started a new Smallblock Group, for the older smallblocks (V35, V65, etc):  https://groups.io/g/Moto-Guzzi-SmallBlock 

And also the MG750 Group for more modern, (Breva, Nevada, V75):    https://groups.io/g/Moto-Guzzi-750

Joe

[Boichat]

Thank you all for the links and quick replies.
Does anyone have a product code for the 3bar pressure regulator?

[sign216]

Thank you all for the links and quick replies.
Does anyone have a product code for the 3bar pressure regulator?

Boichat,
Do you have Guzzi part no. for that?
Joe

[guzzisteve]

From a search

https://wildguzzi.com/forum/index.php?topic=70628.0

[Boichat]

Thank you all.
I have settled on this configuration. Using a 3 bar fuel pump. filter and an adjustable return fuel regulator at 3 bar.
From what I can see the injector system is dead head style in the original set up. So this system with a 3 bar return should be an improvement in terms of pressure stability.

[Kiwi_Roy]

I'm not sure your regulator will have 3 ports as you show typically one port is open to atmosphere and may be fitted with a hose barb which you leave unconnected.
The hose between the filter and regulator is where the injectors should be connected, this type of regulator is referred to as a Backpressure Regulator because it controls the pressure
behind (upstream) of the regulator. The pump puts out a fixed flow and the regulator lets excess back into the tank.
A downstream pressure regulator as you show would cause the pump to overpressure because it only allows enough flow to raise the pressure down stream like what you would use on
a gas bottle.
Actually I'm wrong, I just looked at page 3 of the document I posted but that regulator has 4 ports but two are directly connected together to save having to add a tee fitting.
The yellow hose is not connected to the manifold as they show, I suspect that was a very early idea, before ECUs became so sophisticated, I have never seen it done on a Guzzi.
I quote from page 7
Note that to keep the injector pressure stage steady, the difference between fuel pressure and intake manifold pressure must also be constant. This is achieved by running a tube between the seating of the calibrated governor spring (3) and the intake manifold. Not for your Guzzi
The manifold pressure changes as you open and close the throttle but the regulator pressure remains constant and the flow through the injectors is strictly determined by how long the injector
is open. The injector instantaneous flow rate is not effected by the manifold pressure as it operates under choked flow conditions.
The flow over time changes as the injector open time changes or its open more times per second.
The ECU knows how much air is passing into the engine by the revs the throttle position and atmospheric pressure (elevation) so it adds fuel to match.
------------
BTW the ECU on a modern Guzzi calculates the fuel consumption just by adding up the time the injectors are open over distance traveled.