Fuel Pressure Regulator

[Guest ratchethack]

Ratchet detected no difference, but apparently only used his subjective feel for how it rode.

Uh, "apparently" on the basis of wot, Dave? Your conclusion is, again, more of that ever-so-familiar, well-worn, Forum Trademarked, Dave Speculation®, of which there seems to be no limit. I tend to leave measurement of A/F by "how it rides" to those with far better developed senses of extra-sensory perception.

 

I didn't specify how I arrived at "no perceptible difference", but here it is. I figured mileage on the road would be minimally impacted to the point where I wasn't interested in doing a mileage comparison that would be accurate enough to show any difference, and trips with lots of idling (where the effects would theoretically be the greatest) ain't my normal fare. Now if it were as much as 5% (even in stop & go traffic), this would've been significant enough, but it would be an order of magnitude beyond the maximum of anything I'd reasonably expect. Simply not enough for Yours Truly to be curious about.

 

What I did was what I've done for decades on a dozen moto's to look for changes in A/F. I looked at the plugs after in-traffic riding, including a series of l-o-n-g signal lights, where any change would be most apt to show itself with all the idling. No perceptible change wotsoever on a plug read.

 

Now if I had seen something that looked like a leaner burn signature at idle, that'd be one thing. But as fate would have it, it was at that point where I reckon I decided the universe as we know it is simply chocker-block stuffed to overflowing with so very very many things so incredibly much more interesting -- and how thankful we all can be for that! -- that I promptly re-plugged the intake barb, and Bob's y'er Uncle. Frankly, it'd become such an item of non-concern at that point that I hadn't given it much of any thought for years until this thread came up.

I suppose you could put a vacuum guage on it, divide the fuel pressure by the vacuum pressure in atmospheres and subtract the result from the fuel pressure at 1 atmosphere to give you a theoretical estimate of the change in fuel flow. Actual flow variation from a change in pressure will offset the answer.

Err, WOT?!?! That last statement was a Lu-lu.

 

Long as y'er at it, why not throw in a multipilcation by pi, an addition of Avogadro's number, and a division by Alfred E. Neuman's hat size?!

[Dan M]

Thought I'd jump in here.

The chamber is very small and doesn't take very much "flow" to actuate it. A .30" port should be plenty, the longer the run through fine tubing, the slower the response but we're splitting hairs. Remember the vacuum pulls the diaphram against the spring, when the throttle plate is opened the vacuum falls off instantly and the spring slams closed. It is not like there is a large flow. It obviously has to be connected to manifold vacuum. I'm guessing the spring is overcome at about 10"Hg. If you are going to hook it up you should tee it to both manifolds as the v-twin pulses vacuum quite a bit. A vacuum tee should be available at any auto parts store. A fish tank tee will probably deteriorate rather quickly in this environment.

Since it only reduces pressure at closed throttle, the likelyhood of a noticeable performance difference is nil. We've discussed before how the operation of the vacuum regulator is to increase fuel at throttle opening, kind of an accelerator pump effect. If you leave it disconnected you have the higher flow at all times which means with a stock map you are going from too rich at closed throttle to a more proper mix at open throttle. In theory, hooking it up will improve fuel economy but since it will only lean things out at closed idle the difference will be negligible.

I posted long ago about the difference CO output at idle with and without vacuum to the regulator but I forget the numbers now. As luck would have it I rode the V11 to work today and should have time to sample exhaust gas. I'll report the numbers later.

 

 

 

EDIT: OK here's the numbers at idle:

Regulator disconnected - CO 4.74%, HC 64PPM, Lambda .883 ~ Quite rich

15"Hg applied - CO 1.73%, HC 32PPM, Lambda 1.01 ~ Pretty good for a non feed back system.

 

Two things to think about.

I connected a vacuum gauge tee'd to both manifolds. The pulses are huge. The gauge shows about a 7"Hg bounce at 1100RPM. That is a lot of stress on that diaphram. I don't like it.

While 1.73CO is clean and green and 1.01 Lambda is about as efficient an your going to get, in the world of air / fuel cooled engines, that is a little lean at idle. Running it fatter (2.5-3%) is probably healthier especially in really hot weather.

[Guest ratchethack]

Thought I'd jump in here.

The chamber is very small and doesn't take very much "flow" to actuate it.

Correct enough, Dan. But as John pointed out, "as designed", the US version system has the volume of the charcoal canister connected to the vacuum circuit with the FPS. So this needs to be added to the volume of the FPS in consideration of how changes in vacuum at the intakes were intended to effect the FPS.

[Dan M]

Correct enough, Dan. But as John pointed out, "as designed", the US version system has the volume of the charcoal canister connected to the vacuum circuit with the FPS. So this needs to be added to the volume of the FPS in consideration of how changes in vacuum at the intakes were intended to effect the FPS.

 

 

Additional duty for the circuit just means slower reduction in fuel pressure (as vacuum builds); once the throttle plates open the vacuum falls instantly providing the boosted pressure.

[Guest ratchethack]

Additional duty for the circuit just means slower reduction in fuel pressure (as vacuum builds.

Exactamente! But far more importantly, this likewise means a slower response to a need for increase in fuel pressure.

 

It was in consideration of exactly this by what I concluded to be a restrictive size of the .030" intake ports, that no conceivable configuration of this vacuum circuit -- charcoal cannister or no charcoal cannister -- would be likely to respond fast enough to sudden throttle openings from idle to have anything but a detrimental effect on acceleration -- at exactly the conditions where the OPPOSITE EFFECT is needed the most, that being an "accelerator pump" effect.

 

Not so sure about "instantly" coming up to pressure. While it would appear from wot you've observed that the diaphragm can be acted upon rapidly, wot of the fuel pressure in the pump circuit? I figure better do without the low fuel pressure effect of the FPS at idle altogether and leave it disconnected as you pointed out above, and have the fuel pressure already up to pressure in preparation for producing max system fuel flow, rather than strangling off its ability to come up to pressure ASAP by a control that's always lagging behind the need for response.

 

FWIW, Dynojet Rep and Guzzista Extraordinaire Todd Eagan has an "add on" software program for PC III's that does exactly wot would make sense here as an enhancement to any pre-existing map. It's referred to as an "accelerator pump", and works ONLY with sudden throttle openings from low throttle openings, but I haven't seen any review of it, nor scarcely a mention in several years.

 

EDIT:

EDIT: OK here's the numbers at idle:

Regulator disconnected - CO 4.74%, HC 64PPM, Lambda .883 ~ Quite rich

15"Hg applied - CO 1.73%, HC 32PPM, Lambda 1.01 ~ Pretty good for a non feed back system.

 

Two things to think about.

I connected a vacuum gauge tee'd to both manifolds. The pulses are huge. The gauge shows about a 7"Hg bounce at 1100RPM. That is a lot of stress on that diaphram. I don't like it.

While 1.73CO is clean and green and 1.01 Lambda is about as efficient an your going to get, in the world of air / fuel cooled engines, that is a little lean at idle. Running it fatter (2.5-3%) is probably healthier especially in really hot weather.

Nearly missed this EDIT! Interesting about the 7" Hg pulse bounce! Wot d'you figure it'd be with a 2-3 mm bore in the intake port barbs?!

 

It'd be informative to get a read on it with the charcoal cannister in the circuit. I don't suppose you have yours handy?

 

I don't like the fluctuations, either. As you point out, this has to be stressful on the FPR, and not wot you'd get in a multi-cylinder motor, for which the FPR was likely designed in the first place.

 

Thanks for doing this Dan. Putting some numbers on it the way you've done here is informative. D'ya reckon it'll satisfy John M./Ryland? We're still left with the Q about common .030" intake barbs across all models. But with two .030" orifices at work here, instead of the single one I've connected for my observations, I reckon there's considerably more of an effect -- and quicker response capability -- than I'd concluded.

 

But alas and alack! Even after pushing back the frontiers of ignorance another coupla big steps here (many thanks for the effort! ) I find I'm even less interested than I was before in using the intake vacuum reference on the FPR -- but o' course, that's just me.

[Dan M]

Exactamente! But far more importantly, this likewise means a slower response to a need for increase in fuel pressure. <_>

 

It was in consideration of exactly this by what I concluded to be a restrictive size of the .030" intake ports, that no conceivable configuration of this vacuum circuit -- charcoal cannister or no charcoal cannister -- would be likely to respond fast enough to sudden throttle openings from idle to have anything but a detrimental effect on acceleration -- at exactly the conditions where the OPPOSITE EFFECT is needed the most, that being an "accelerator pump" effect.

 

Not so sure about "instantly" coming up to pressure. While it would appear from wot you've observed that the diaphragm can be acted upon rapidly, wot of the fuel pressure in the pump circuit? I figure better do without the low fuel pressure effect of the FPS at idle altogether and leave it disconnected as you pointed out above, and have the fuel pressure already up to pressure in preparation for producing max system fuel flow, rather than strangling off its ability to come up to pressure ASAP by a control that's always lagging behind the need for response.

 

With a fairly long hose to reach manifold to manifold over the seat tee'd in to a vacuum gauge, the vacuum dropped as fast as you could open the throttle. Doing this sort of testing on a car where it is easy to hook up a fuel pressure gauge and a vacuum gauge, I can assure you that the vacuum drops and the fuel pressure raises instantaneously. It is almost as if there is a mechanical connection between the throttle and the gauge needles. What happens with the canister installed in indeed unknown.

 

FWIW, Dynojet Rep and Guzzista Extraordinaire Todd Eagan has an "add on" software program for PC III's that does exactly wot would make sense here as an enhancement to any pre-existing map. It's referred to as an "accelerator pump", and works ONLY with sudden throttle openings from low throttle openings, but I haven't seen any review of it, nor scarcely a mention in several years.

 

I have the accelerator pump feature on my PC3, I cannot tell the difference enabled or not. Perhaps with a custom map it can be of use. If enrichment is needed for what we've been discussing (on throttle opening) there would be a noticeable hesitition, bogging or even a backfire. If there is not a hesitation, adding more gas is just more gas. There will be no more power, just an overly rich mixture.

 

EDIT:

 

Nearly missed this EDIT! Interesting about the 7" Hg pulse bounce! Wot d'you figure it'd be with a 2-3 mm bore in the intake port barbs?!

 

It'd be informative to get a read on it with the charcoal cannister in the circuit. I don't suppose you have yours handy?

 

Sorry, no

 

I don't like the fluctuations, either. As you point out, this has to be stressful on the FPR, and not wot you'd get in a multi-cylinder motor, for which the FPR was likely designed in the first place.

 

Thanks for doing this Dan. Putting some numbers on it the way you've done here is informative. D'ya reckon it'll satisfy John M./Ryland? We're still left with the Q about common .030" intake barbs across all models. But with two .030" orifices at work here, instead of the single one I've connected for my observations, I reckon there's considerably more of an effect -- and quicker response capability -- than I'd concluded.

 

Watching how fast my gauge moves, (without the canister of course) I'd say .030 is fine. The flutter of the diaphram that is surely happening with the extreme pulses of the large bore twin is reason enough to abandon the thought of putting the regulator into service.

 

But alas and alack! Even after pushing back the frontiers of ignorance another coupla big steps here (many thanks for the effort! )

 

No problema.

[Skeeve]

I didn't specify how I arrived at "no perceptible difference", but here it is. I figured mileage on the road would be minimally impacted to the point where I wasn't interested in doing a mileage comparison that would be accurate enough to show any difference, and trips with lots of idling (where the effects would theoretically be the greatest) ain't my normal fare. Now if it were as much as 5% (even in stop & go traffic), this would've been significant enough, but it would be an order of magnitude beyond the maximum of anything I'd reasonably expect. Simply not enough for Yours Truly to be curious about.

 

What I did was what I've done for decades on a dozen moto's to look for changes in A/F. I looked at the plugs after in-traffic riding, including a series of l-o-n-g signal lights, where any change would be most apt to show itself with all the idling. No perceptible change wotsoever on a plug read.

 

Gotta call "No Joy" on this one, Ratchet: plug reads for this minimal change in fuel burn are going to be impossible [not merely "hard" to detect, but impossible to the unaided human eye] while fuel mileage is the only pertinent datum & oh-so-easy to determine [if you keep track of your avg. as a habit, as I tend to do.]

 

Avg. mpg jumps from 40 to 41mpg? Yippee, you got a 2.5% improvement [ie, not really worth much trouble, & easily ascribed to random variations (favorable tailwinds & the like)] - but a jump from an avg of 40 to 42? Now things start getting interesting. And at no time will there be a discernible difference in plug color btw these conditions.

 

Plug reads are only valid for steady-state running conditions & then only for ball-park determination of carbueration (fueling, whatever you want to call it: I know our bikes don't have carbs! ); they're supremely unsuited to track the transition throttle conditions that are precisely the point of this hypothetical hookup for the pressure regulator.

 

Ride on!

[Dan M]

STOP PRESS>

 

After thinking about the whole .030 orifice question I decided to hook a vacuum gauge directly to the manifold with the brass nipple removed. The pulse on one cylinder at idle is more than 15"Hg! With the nipple off you can feel a puff of pressure between the vacuum pulses. The gauge bounces from the slightest amount of positive pressure to just past 15" vacuum.

So, you are not getting the range of vacuum through the small orifice. Will it slow the operation? perhaps yes. Still, that regulator hooked to this engine will be useless, dancing between applied and not with every pulse of the engine.

[Guest ratchethack]

Plug reads are only valid for steady-state running conditions & then only for ball-park determination of carbueration (fueling, whatever you want to call it: I know our bikes don't have carbs! ); they're supremely unsuited to track the transition throttle conditions that are precisely the point of this hypothetical hookup for the pressure regulator.

Well, Skeeve, we'll likely disagree on this one.

 

It's a matter of degree, ain't it? Wot's tolerable "within the ballpark" to one will only be tolerable "within the infield" to the next. This might just be me, but I find that in this day of bit-mapped fuel delivery, we can "see" lots o' things on fuel maps in great detail that have little and ZIP real-world effects on the road. Just because something can be accurately measured doesn't necessarily mean it's necessarily always significant, f'er cryin' out loud! We seem to have people hereabouts who believe that regardless of how a motor runs, unless the map has such and such a profile, and if there are any "outliers" to some sort of ideal -- Well then! It's inherently "wrong"! Methinks such folks typically have no background in tuning carburetors, where the "ballpark" is one walloping huge place relative to the infield, and an "inside the park" home-run counts the same as one hit out o' the park.

 

Not directing this observation at you wotsoever, Skeeve, but I reckon if one has little experience with or knowledge of how motors work, gazing at fuel maps becomes one's primary perspective, and one quickly gets deceived about wot's important, lacking much (if any) comprehension of the underlying principles??

 

Of course a 40-42 mpg difference won't be visible on plugs! I'd be surprised if I could even get a consistent run on the same road anywhere near within +/- 2 mpg (a 4 mpg variance) on the same day at the same ambient temperature, with the same wind strength and direction, with no change to A/F a-tall!

 

Now whilst the following is INTERESTING (thanks again to Dan with all due appreciation already acknowledged previously), it doesn't amount to the kind of consideration I b'lieve is necessarily all that important on the road:

Regulator disconnected - CO 4.74%, HC 64PPM, Lambda .883 ~ Quite rich

15"Hg applied - CO 1.73%, HC 32PPM, Lambda 1.01 ~ Pretty good for a non feed back system.

Wot you can most certainly see on plugs, is significant changes in A/F, including at idle -- if you know how to read plugs, and particularly if you're familiar with how the "pre" state of the plugs look before you take a "post" change read.

 

This ain't rocket science here, despite the number of those who want to b'lieve it is. I reject the idea that A/F has to be exactly precise or it's necessarily "wrong". Sure there are far better ways to evaluate the effects of connected or disconnected FPR on idle A/F than reading plugs! Many's the highly tuned carbed motor for nearly a century that got that way without gas analyzers, fuel maps, and yes! (gasp) -- NO dyno! Reading plugs is certainly crude relative to today's capabilities -- but it's by no means useless -- particularly on a relatively "crude" donk such as the V11! Put it this way -- if the A/F is affected in some way at idle that I can't see on the plugs, as long as it's not having a detrimental effect on how it runs on the road, and the mileage ain't too far out o' whack, it's too minor for me to have the slightest concern about.

 

I agree with you that the off-on transitions are the most important. These can't ever be read on plugs.

 

I also agree with Dan here:

While 1.73CO is clean and green and 1.01 Lambda is about as efficient an your going to get, in the world of air / fuel cooled engines, that is a little lean at idle. Running it fatter (2.5-3%) is probably healthier especially in really hot weather.

If this is the case -- and I b'lieve it more'n likely IS -- we have a "ballpark" of somewhere close to 300% of "ideal" where it's not only acceptable to run, but where it's safer, and likely hardly -- if at all -- detectable via mileage! Now how "important" or "significant" is accuracy here, I most obstreperously ask?????

 

But now I'm gettin' tired o' so much ado about not very much a-tall, and I b'lieve we've well flogged this one into a grease spot.

 

BAA, TJM & YMMV

[raz]

Thanks Dan, that was a lot of real facts. Discouraging though. It appears that we would have to even out the nasty pulses to an extent where the effect of this whole thing becomes useless. It will be either too little or to slow, I guess. Yeah Ratch I know you told us so <_ src="%7B___base_url___%7D/uploads/emoticons/default_happy.png" alt="^_^">

 

Still, I intend to hook up a fuel pressure gauge and check what the real effect on that side will be. Just because it's easy, and I wanted to check my pressure anyway.

 

Another thought: Why would the alpha-n system not be enough by itself? Why would this FPR connection, or a MAP sensor, ever be needed? Say you have a map cell at 3000 rpm and three quarter open throttle. Could you be running at that very cell with completely different manifold pressures? If so, how? Why? Other than the effect of dirty filters, of course.

 

Say you cruise on 3rd gear at exactly 3000 rpm. Then wind on 75% throttle. This results in a pressure of x in the intake manifolds before rpm actually increases.

 

Now, say you cruise on 5th gear at exactly 3000 rpm. Then wind on 75% throttle . Will this produce a totally different manifold pressure? How?

 

Or, to have even more differing scenarios: When hitting that cell during acceleration (low gear) from lower rpm, will the manifold pressure be significantly different from when hitting it during deceleration (too high gear) from higher rpm? Sorry if I'm being a complete moron, I just can't picture this.

[jtucker]

Still, I intend to hook up a fuel pressure gauge and check what the real effect on that side will be. Just because it's easy, and I wanted to check my pressure anyway.

 

I'd be curious to hear how this goes, as this is something I've often wondered about.

 

Long ago, I purchases an adjustable fuel pressure regulator from evoluzione.net (I think they actually sold some Guzzi bits at that time). Anyway, they indicated that the fuel system on the Guzzi was the same on some Aprilias, and those were known to deviate wildly from spec, hence their aftermarket solution.

 

I never got around to installing it prior to my bike going in for the "never-ending rebuild" project. Now that the bike is back, its running so nice that I'm reluctant to mess with anything. Even if the stock regulator on my bike is correct, I'm still tempted to put the adjustable one on, just so I *know* it's correct. Or, I guess I could probably figure out how to fit the gauge from the kit with the stock regulator just to see what it's doing.

 

__Jason

[Guest ratchethack]

Why would this FPR connection, or a MAP sensor, ever be needed? Say you have a map cell at 3000 rpm and three quarter open throttle. Could you be running at that very cell with completely different manifold pressures? If so, how? Why? Other than the effect of dirty filters, of course.

 

Say you cruise on 3rd gear at exactly 3000 rpm. Then wind on 75% throttle. This results in a pressure of x in the intake manifolds before rpm actually increases.

 

Now, say you cruise on 5th gear at exactly 3000 rpm. Then wind on 75% throttle . Will this produce a totally different manifold pressure? How?

 

Or, to have even more differing scenarios: When hitting that cell during acceleration (low gear) from lower rpm, will the manifold pressure be significantly different from when hitting it during deceleration (too high gear) from higher rpm? Sorry if I'm being a complete moron, I just can't picture this.

Raz, these are very good Q's, all of 'em.

 

In fact, though I b'lieve I've got a fair handle on most of 'em, they deserve far better than I can properly respond to, and I'm as interested as y'erself in how someone more deeply experienced and knowledgeable in this area would answer 'em. Yes, you might say I've managed to Peter Principle me way into territory wot's far better left for others.

 

Where's Pete lately?

 

Man's gotta know his limitations. . .

[Ryland3210]

Wow! A lot of water under the bridge since the last time I checked in.

 

First, Dan M's reading of 15" Hg at idle, is about - 0.5 Bar, while the fuel pressure regulator target is 3 bar. So if its reference port is connected to the intake manifold, it becomes 2.5 bar. Fuel flow would be reduced by 8.7%.

 

Improvement in economy would not only occur at idle or closed throttle decels. Part throttle cruising economy would also be improved, although to a lesser degree, if the vacuum is less than at idle. By the way, that isn't necessarily so. Had Dan M's idle vacuum reading been in the 20-21" Hg range, I would expect it to be far lower during cruise, but at 15", I'm not sure at all. I've seen engine vacuums ranging anywhere from 10 to 16" under cruise conditions. Under deceleration, fuel flow would decreased by a higher percentage, due to the higher vacuums achieved.

 

With smart enough software in an ECU, anything which can be done by connecting the FPR to the intake manifold could be duplicated, since it has data on TPS and RPM, BUT only if the air filter pressure loss and barometric pressure is consistent with the software's assumption (there's that dangerous word again!), OR if an ECU's absolute pressure sensor is working and connected to the airbox between the filter and the throttle body, then there's no problem.

 

So under those conditions, mapping the ECU can do the same thing. So why bother considering connecting the FPR to the intake manifold? Because it's cheap!

 

Ratch's comment that his water manometer (Mercury's density is 13.6 times higher) does not fluctuate much lends some comfort that the FPR diaphragm might not be unduly fatigued. Moreover, the worst case for engine pulses would be at idle, wherein the frequency would be lowest. The 0.030" orifices act as a low pass filter, so the higher the RPM, the less the fluctuation. Also, the farther open throttles are, the less the fluctuation. Idle is the worst case for both reasons.

 

If this regulator is constructed in the conventional fashion, its diaphragm is controlling a needle, with fuel pressure on one side of the diaphragm and ambient pressure and a spring on the other. So it's not as though the diaphragm makes a sudden movement when the ambient pressure (vacuum) reaches a threshhold. Still, it is a concern that I don't wish to discount altogether.

 

Would I do it anyway in the name of science and fuel conservation? You bet! I like the cleaner exhaust as well. Based on Dan M's analysis, it's as if the idle mapping was done with it in mind.

[emry]

Speed Density systems are able to calculate the volumetric efficiency of an engine courtesy of the Ideal gas law. Alpha-n systems are simple preprogrammed fueling maps. Intake airflow does vary under different operating conditions, such as engine load. SD systems can provide much better fuel mapping for low throttle settings and slight changes in TP. Many SD systems revert to a Alpha-n system during acceleration or above about 30% throttle opening where airflow through the engine to changing too quickly for a MAP sensor to be accurate.

[dlaing]

Correct enough, Dan. But as John pointed out, "as designed", the US version system has the volume of the charcoal canister connected to the vacuum circuit with the FPS. So this needs to be added to the volume of the FPS in consideration of how changes in vacuum at the intakes were intended to effect the FPS.

Maybe we need a poll to determine how many people still have the canister(s).

I kind of assumed most people considering the mod had no canister(s).

The diagram shows no canisters.

Was your test done with or without canisters?

If you have canisters, that would certainly explain why you noticed no difference!!!