PRESSURE ADJUSTER

[Ryland3210]

I agree it's not proven but the few reports I've heard are positive. Also, some FWIW facts:

• The WHB (both yours and mine) says it should be connected. It's never pictured and it's not in the parts manual but still, it is clearly in the text (using the word 'must'). In the generation before mine, it was pictured too, routed to both manifolds.
  
• Connecting it will not result in richer mixture at any time, just leaner at low load.
  
• The specs for the injector says it will atomise the fuel forming a cone of 30° at a fuel pressure of 3±0.2 bar (44±3 psi). This must be referenced to where it injects to, not free air. Without connecting this hose we will get well out of this range at certain conditions and the way I read it, this may result in bad atomising at low load or decel.
  

Anyway I have ordered what I need to do this mod. and I will report back.

 

Please clarify, Raz. I do not reach the conclusion of "bad" atomising, but I have not seen the specs. Here's my analysis:

 

We know that obviously the injectors pump fuel into the same location, regardless of whether the hose is connected to the regulator or not. Therefore, connecting the hose results in reducing the absolute fuel pressure at low load or decel, so there should be less atomizing with the hose connected, since atomization increases with pressure. Do the specs indicate that 3 bar is the minimum required for atomizing, or is it merely saying that an atomized cone of 30 degrees will be formed at that pressure? Does it indicate a lower pressure below which atomizing will not occur?

 

Given that good atomizing is achieved at WOT and low RPM by design, where intake manifold absolute pressure is almost the same at atmospheric, then I believe the same degree of atomization should occur when intake manifold absolute pressure is close to zero, since the pressure difference between fuel and intake would be the same. I expect you will find fuel economy will improve with hoses connected, and look forward to your report.

[Ryland3210]

Wasn't this just covered in another thread??

 

I tried connecting the fuel regulator pressure reference to the intake "recovery canister/balance" barbs many years back. There was ZERO noticeable difference after a few days. No, I didn't do an exhaust gas analysis or dyno before and after. Instead, I simply re-plugged the barbs. It occurs to me that the .030" bore of the intake barbs is inadequate to handle throttle transitions.

 

Your right, buddy. Much of this was covered in an earlier thread, but Paulo may not have noticed that, and this one is perhaps a useful summary.

 

Are the "intake "recovery canister/balance" barbs" you mention the ones on the intake manifold used for throttle synch? If not, then little change should be expected, if connected where there would be very little vacuum created. Moreover, if connected to the airbox, the variation in absolute pressure would be opposite that of the intake manifold, and provide a reverse signal to the regulator.

 

Whether the .030" bore is adequate depends on the volume within the connecting hoses and the chamber in the regulator. There is no steady state flow here to create a pressure loss except in transients. If the bore was determined using engineering principles (which is open to question), it might have been sized intentionally to optimize the tradeoff between adequate response time, and dampening pulses. In that case, the length and inside diameter of the hoses should be the same as indicated in the manual.

[raz]

Please clarify, Raz. I do not reach the conclusion of "bad" atomising, but I have not seen the specs. Here's my analysis:

 

We know that obviously the injectors pump fuel into the same location, regardless of whether the hose is connected to the regulator or not. Therefore, connecting the hose results in reducing the absolute fuel pressure at low load or decel, so there should be less atomizing with the hose connected, since atomization increases with pressure. Do the specs indicate that 3 bar is the minimum required for atomizing, or is it merely saying that an atomized cone of 30 degrees will be formed at that pressure? Does it indicate a lower pressure below which atomizing will not occur?

It may very well be me jumping to conclusions, I don't have qualified knowledge. Also, the text just explains the system, it's not really a spec.

 

This is the exact quote from a V11 WHB: "Finally, from a hydraulic point of view, upon a fuel compression of 3±0,2 bar, the jet brakes down as soon as it comes out from the nozzle (atomizing), thereby forming a cone of about 30°."

 

It does say the pressure should not exceed 3.2 bar or go below 2.8 bar, but it's not very clear what happens else.

[Guest ratchethack]

Given that good atomizing is achieved at WOT and low RPM by design, where intake manifold absolute pressure is almost the same at atmospheric, then I believe the same degree of atomization should occur when intake manifold absolute pressure is close to zero, since the pressure difference between fuel and intake would be the same. I expect you will find fuel economy will improve with hoses connected, and look forward to your report.

John, I'm sure you know this, but for the benefit of others, it's a little vague from the above. I would respectfully point out that as soon as the engine is running, intake manifold absolute pressure drops to much lower than atmospheric (ambient) at low RPM. That is, relative to ambient pressure, intake manifold vacuum is highest at idle and lowest at high throttle openings. Ambient absolute pressure being one bar (at sea level), intake manifold absolute pressure approaches one bar as closely as it ever gets (when the engine is running) at WOT.

[Dan M]

I agree it's not proven but the few reports I've heard are positive. Also, some FWIW facts:

• The WHB (both yours and mine) says it should be connected. It's never pictured and it's not in the parts manual but still, it is clearly in the text (using the word 'must'). In the generation before mine, it was pictured too, routed to both manifolds.
  
• Connecting it will not result in richer mixture at any time, just leaner at low load.
  
• The specs for the injector says it will atomise the fuel forming a cone of 30° at a fuel pressure of 3±0.2 bar (44±3 psi). This must be referenced to where it injects to, not free air. Without connecting this hose we will get well out of this range at certain conditions and the way I read it, this may result in bad atomising at low load or decel.
  

Anyway I have ordered what I need to do this mod. and I will report back.

 

I believe the injector spec given here is to show the cone shape at the given psi. The cone shape is determined by the injector's nozzle design. It will narrow with reduced pressure but not much in the range of the regulator. (I'm guessing a 7to10 psi change which is typical of a 40psi system) Narrowing of the cone to the point of lost atomization won't occur until the pressure drops way below regulated pressure. Fuel will still be adequately atomized at the reduced regulated pressure, just less will flow for a given pulse-width.

 

A fuel map with a vacuum operated regulator takes into consideration the reduced flow at closed throttle. Using (the loss of)manifold vacuum as the trigger to raise pressure makes for an instantanious increase in fuel flow. This bump in fuel delivery at throttle opening (which is greater than simply increasing duty cycle) helps reduce any hesitation. Hence the accelerator pump effect. With the regulator disconnected it is just rich all of the time.

 

I still wonder why a so many of these bikes have vacuum regulators installed from the factory but not connected.

[Guest ratchethack]

I still wonder why a so many of these bikes have vacuum regulators installed from the factory but not connected.

This is the same Q I've always had. It would seem so easy (and inexpensive) to've plumbed it in to start with. The only conclusion that makes sense is that these motors are so "primitive" compared to closed-loop auto systems (for example) that it doesn't make enough difference in practice either way. After my little "experiment" with it connected (no detectable difference), I figure best not mess with it unless I want to re-map just for this, and there's no identifiable benefit, so why chase another phantom here when I could be riding??

 

BAA, TJM, & YMMV

[dlaing]

I still wonder why a so many of these bikes have vacuum regulators installed from the factory but not connected.

I did not know that any of these bikes had the vacuum regulators connected by the factory.

Did these bikes have a different ECU part number?

Did they have evaporation canisters?

And were any of the bikes US models?

Sorry if I missed these points in some other thread.

[Ryland3210]

This is the same Q I've always had. It would seem so easy (and inexpensive) to've plumbed it in to start with. The only conclusion that makes sense is that these motors are so "primitive" compared to closed-loop auto systems (for example) that it doesn't make enough difference in practice either way. After my little "experiment" with it connected (no detectable difference), I figure best not mess with it unless I want to re-map just for this, and there's no identifiable benefit, so why chase another phantom here when I could be riding??

 

BAA, TJM, & YMMV

 

Hi Ratch,

 

I think you may have missed my earlier question, as copied below. I'm interested in correlation your results with the location of hour hose connection, as follows:

 

"Are the "intake "recovery canister/balance" barbs" you mention the ones on the intake manifold used for throttle synch? If not, then little change should be expected, if connected where there would be very little vacuum created. Moreover, if connected to the airbox, the variation in absolute pressure would be opposite that of the intake manifold, and provide a reverse signal to the regulator."

 

Thanks, John

[Ryland3210]

I did not know that any of these bikes had the vacuum regulators connected by the factory.

Did these bikes have a different ECU part number?

Did they have evaporation canisters?

And were any of the bikes US models?

Sorry if I missed these points in some other thread.

 

The service manual does show these connections and emphasizes their importance. This was covered elsewhere, along with a picture of the assembly diagram. I'm sure you can find the detailed information with a little research.

[Ryland3210]

I believe the injector spec given here is to show the cone shape at the given psi. The cone shape is determined by the injector's nozzle design. It will narrow with reduced pressure but not much in the range of the regulator. (I'm guessing a 7to10 psi change which is typical of a 40psi system) Narrowing of the cone to the point of lost atomization won't occur until the pressure drops way below regulated pressure. Fuel will still be adequately atomized at the reduced regulated pressure, just less will flow for a given pulse-width.

 

A fuel map with a vacuum operated regulator takes into consideration the reduced flow at closed throttle. Using (the loss of)manifold vacuum as the trigger to raise pressure makes for an instantanious increase in fuel flow. This bump in fuel delivery at throttle opening (which is greater than simply increasing duty cycle) helps reduce any hesitation. Hence the accelerator pump effect. With the regulator disconnected it is just rich all of the time.

 

Sounds reasonable to me, and consistent with my knowledge. My Cafe Sport has the regulator inside the tank along with the fuel pump, so there is no access. With the stock map intact, I added Stainture mufflers without baffles, and took off the airbox cover. The orginal filter is held down by a clamp generously provided by Ratchethack. When checked on a dyno, the mixture was still on the rich side, in spite of the leaning effect one would expect from these modifications. My exhaust pipes have always been black with soot. I believe that if I were able to connect the regulator to the intake manifold ports, fuel economy would improve, with no adverse effects to WOT performance, and would still not be too lean.

 

As to why wouldn't Guzzi continue to connect these hoses on bikes with external regulators, I have no idea. The cost is surely low, but there has been at least one opinion expressed that the frequent changes in pressure to the regulator might wear them out faster. Perhaps Guzzi had some problem with failing regulators, or perhaps they just wanted to made assembly easier, or perhaps it was purely accidental.

[dlaing]

The service manual does show these connections and emphasizes their importance. This was covered elsewhere, along with a picture of the assembly diagram. I'm sure you can find the detailed information with a little research.

But other than the manual there is no evidence of a production V11 being hooked up that way.

I have done more than a little research.

All I am asking for is someone to speak up who had their bike come from the factory set up that way.

I don't think anyone has, unless their dealer was trying to be extra clever with the bike setup.

Comments like this tend to lead us into believing that SOME bikes were set up that way from the factory:

I still wonder why a so many of these bikes have vacuum regulators installed from the factory but not connected.

I suspect it is misleading, and that no bikes were set up this way from the factory, except for maybe some 1999 Europe only models.

I certainly could be wrong, and that is why I ask.

Yes, I have searched for the answer, but I can't find evidence and the more I don't find, the more I believe that not bikes were delivered that way.

[raz]

Whether the .030" bore is adequate depends on the volume within the connecting hoses and the chamber in the regulator. There is no steady state flow here to create a pressure loss except in transients. If the bore was determined using engineering principles (which is open to question), it might have been sized intentionally to optimize the tradeoff between adequate response time, and dampening pulses. In that case, the length and inside diameter of the hoses should be the same as indicated in the manual.

I have tried to determine what (size) nipples were used with the P8 bikes, but without success. The ones I have ordered are normal ones with no damping. Maybe I will need to add dampers as those used in my Carbtune. But I suspect they will damp far too much, delaying the acc-pump effect. The canister nipples should be better, or maybe even those are too small. Note to self: 0.030" is 0.75 mm.

 

Hmm, of course, I could put it all togeather but connect the regulator side of it to a gauge and see how it looks.

[raz]

But other than the manual there is no evidence of a production V11 being hooked up that way.

I have done more than a little research.

All I am asking for is someone to speak up who had their bike come from the factory set up that way.

I don't think anyone has, unless their dealer was trying to be extra clever with the bike setup.

Comments like this tend to lead us into believing that SOME bikes were set up that way from the factory:

 

I suspect it is misleading, and that no bikes were set up this way from the factory, except for maybe some 1999 Europe only models.

I certainly could be wrong, and that is why I ask.

Yes, I have searched for the answer, but I can't find evidence and the more I don't find, the more I believe that not bikes were delivered that way.

I believe (on the same vague basis as you) that no Sporti or V11 ever came with it installed from the factory. I do believe that Cali P8-equipped had them installed, but actually I have no particular evidence of that either.

Maybe what killed it was the US canister thingies. When they had to use the nipples for that they quit connecting the regulator. For some reason they quit connecting it for the non-canister bikes too.

[Ryland3210]

I have tried to determine what (size) nipples were used with the P8 bikes, but without success. The ones I have ordered are normal ones with no throttling. Maybe I will need to add dampers as those used in my Carbtune. But I suspect they will damp far too much, delaying the acc-pump effect. The canister nipples should be better, or maybe even those are too small. Note to self: 0.030" is 0.75 mm.

 

Hmm, of course, I could put it all togeather but connect the regulator side of it to a gauge and see how it looks.

 

Keep in mind that if you increase the total hose length or inside diameter, that will increase the volume within the hose. Adding a pressure gauge will also increase volume. Any increase in volume will delay the response time for a given size "nipple". As the vacuum suddenly increases, the gas in the hoses and regulator has to flow through the nipple to relieve its pressure. The more gas there is, the longer it takes.

[Guest ratchethack]

Hi Ratch,

 

I think you may have missed my earlier question, as copied below. I'm interested in correlation your results with the location of hour hose connection, as follows:

 

"Are the "intake "recovery canister/balance" barbs" you mention the ones on the intake manifold used for throttle synch? If not, then little change should be expected, if connected where there would be very little vacuum created. Moreover, if connected to the airbox, the variation in absolute pressure would be opposite that of the intake manifold, and provide a reverse signal to the regulator."

 

Thanks, John

Sorry I missed this John. Yes, the same. As I've observed many times, It's not that very little vacuum could be created, because this is NOT the case. Full intake vacuum would be the normal state of pressure at the regulator, even thru the restrictive .030" bores in the barbs. The point I've been making is that rapid enough change in absolute pressure may not be possible to achieve any significant difference in real-world fuel delivery. It might be interesting for someone to bore the intake barbs out, but that someone ain't me, because I apparently lack sufficient interest. The barbs work fine for balancing the TBs as is, and boring them out would likely destroy this. I don't know of any discussion about connecting the fuel regulator air reference to the airbox, nor any reason why anyone would be interested in such a thing??