Fuel injection pressure relief valve

[Ozzydog]

Hi everyone. A question if I may for those who know such stuff,
What is the pressure that the relief valve operates at on a 2000 Jackal?
Thanks in advance
Andy

[Kev m]

I assume you mean the fuel pressure regulator (or "pressure adjuster" in the poorly translated OEM manual):

The pressure adjuster is a device which is necessary for
maintaining a constant pressure jump on the injectors.
The pressure adjuster is a differential type with diaphragm,
and is pre-set during assembly at 3 +/- 0.2 bar.
Upon exceeding the pre-set pressure, the internal duct
opens to allow the excess fuel to flow back into the tank.
Note that to keep the pressure jump to the injectors
constant, the difference between the fuel pressure and
the intake manifold pressure must also be constant.

40.6 - 46.4 psi  (280 - 320 kPa)

[Kiwi_Roy]

I assume you mean the fuel pressure regulator (or "pressure adjuster" in the poorly translated OEM manual):

40.6 - 46.4 psi  (280 - 320 kPa)

I note you mention it's a Jackal, if your pump seems extra noisy at times it could mean the main filter is plugging and the pump is relieving internally, it does that at ~70 psi.
My EV would run ok for a while then start losing power on the hills as the filter plugged off, easy fix.

The fuel injectors operate at choked flow, a few psi variation in delivery pressure has very little effect on flow.

[rodekyll]

42#.  +/- 2#.  More or less affects volume and spray form.

Pump will do 70+.

[Ozzydog]

Thank you Kev M, Kiwi_Roy and rodekyll. I’m chasing an idea, about a noise generated by the standard regulator which uses two washers acting with each other against a spring to regulate the flow/ pressure. (Non standard tank and mounting place prompts this as a possible source of a noise that starts to irritate)
Thanks again,,I really appreciate your taking the time to let me know, and in Kev’s cases, finding, then ungarbling the OEM manual.
Cheers from (almost literally) freezing Melbourne
Andy

[Rough Edge racing]

 42-50 psi is typical of port injection systems on most bikes and cars...Don't say I said this, but jacking up the pressure 3-5 psi can have a noticeable performance increase on some vehicles...Not to say you should do this or it will be ok on a Guzzi..But you never know...

[rodekyll]

On an open loop system like the Jackal that is true.  I have an adjustable regulator in the trike.  For me the performance advantage is negated by the drop in economy.  But you can get to the same place by adjusting the c/o trim.  Every increment of adjustment = 1ms of squirt  time.  It's easier to calculate flow volume using a known rate of flow, while keeping pressure as your constant.

[Rough Edge racing]

On an open loop system like the Jackal that is true.  I have an adjustable regulator in the trike.  For me the performance advantage is negated by the drop in economy.  But you can get to the same place by adjusting the c/o trim.  Every increment of adjustment = 1ms of squirt  time.  It's easier to calculate flow volume using a known rate of flow, while keeping pressure as your constant.

  What type of injectors are used on Guzzi's? Are they a cost compromise design?

[rodekyll]

 ?

[n3303j]

I find the last lines of the quoted manual text interesting.

"........excess fuel to flow back into the tank.
Note that to keep the pressure jump to the injectors
constant, the difference between the fuel pressure and
the intake manifold pressure must also be constant."

That explains the unused static port on my V11 regulator and the fact that the manual shows this unused port connected by tubing to both injector manifolds dowind of the butterflies.

Of course the bike is delivered to USA  with the static port open to the atmosphere and the manifold ports tied into the carbon canister vapor capture system.

Still wondering how it would run with the regulator connected as in the factory  diagram. I'd try it if I had a CO analyzer. Probably get 20 more HP, 11 more miles per gallon and chop 2 seconds off my quarter mile time!

[rodekyll]

No, that's not what the spigot does.  The manual is in error if it wants that spigot connected to vacuum.  The spigot is there to allow the ambient atmospheric pressure in for the regulator diaphragm to work.  There's been many topics about it here over the years.  Many have been caught in the apparent logic of the book, assumed that the spigot needed a hose, and suffered the bad running until they removed it.  It's easy enough to prove for yourself though.

[RinkRat II]

   

Still wondering how it would run with the regulator connected as in the factory  diagram. I'd try it if I had a CO analyzer. Probably get 20 more HP, 11 more miles per gallon and chop 2 seconds off my quarter mile time!

  Yeh Baby! I'm sure those are the minimums! Now where'd I put that 400mpg carb...............

       Paul B

[Charles in Lake Charles]

Still wondering how it would run with the regulator connected as in the factory  diagram

During high vacuum (idling and economy cruising), fuel pressure will be lower and the mixture will be leaner. During low vacuum conditions (accelerating), no difference.

[Rough Edge racing]

?

On some vehicles there are alternate injectors available that offer better spry patterns....

[rodekyll]

On some vehicles there are alternate injectors available that offer better spry patterns....

They use industry standard stuff.  Same numbers as some HD, Aprilia, and Ducati.  HD has options for flow.  Guzzi seems to use the same one for each class of injection and changes volume by pulse duration.  I don't see where - say - EV and Breva stuff would directly interchange.