Cross wind power loss.

[AJ]

well i am just going to leave mine as it is, vent tubes removed completely. it runs fine and i am happy with it.

if it makes any difference at all, i have a stainless plate mounted covering the gap in the frame where the air box used to sit. whether it helps or hinders, i dont care, it looks nice

And thanks to your help, I have gone to the same route (so far ).

It has stimulated some interesting discussion.

[Agemax]

And thanks to your help, I have gone to the same route (so far ).

It has stimulated some interesting discussion.

indeed it was, although starting to get a tad to tecnical on where to stick your pipes, considering there is a tried and tested method that works!

[posplayr]

I appreciate your thoughtful analysis, but am not totally convinced of your conclusions (not necessarily disagreeing, either).

Unfortunately, I don't have a stock ESD airbox to look at. However, on many other bikes, there is no overt "plenum" on the stock setup. The "reference tubes" merely run up near the point where the air enters the airbox, so it's sampling the air at the inlet (while being oriented so that the inlet air is NOT directly drawing across the reference tube endface and the problems that would cause). This is the main reason I'm concluding that the sampling should be done close to the air inlet, but it makes intuitive sense to me.

When you have an air-box the fundamental approach to controlling air flow is to mix the flow through a common plenum and so the logical way to control the differential pressure between venturi and the float bowel is to pick a point to sample (for float bowl equalization) is a point up stream to that air intake mixing process. a port on the inside of the rear chamber is apparently adequate.

Certainly there is an attempt to regularize this differential pressure across all RPM and road/wind conditions. However, I don't think that trying to maintain a particular differential pressure specific to a particular carberator or cylinder is needed or even wanted. In other words you don't want to adjust the pressure inside one float bowl v.s another because there is an apparent drop in pressure at one pod v.s. the other.

From my discussion it would seem clear that the flow rate of air through any cylinder at a given RPM is going to be little effected by changes in pressure at the inlet of carb. The strongest evidence there is that you don't need to precisely balance the airflow between cylinders is that fact that individual pods work at all. In fact they seem to work quite well with the possible exception of these cross wind issues.

I think we are in agreement as Steve initially pointed out that with or without Pods the equalization tubes are important and so that really is my focus, how to provide a stable or regular float bowl pressure in response to RPM/Speed and riding/cross wind conditions.

I wrote "overt" plenum wrt the stock setup because it may indeed be that the top of the airbox, the frame rails, and the bottom of the seat form an "effective" plenum to stabilize and normalize the air pressure in that region. Please post a picture of the ESD setup you described, as it wouldn't surprise me a bit if Suzuki worked to optimize the system. Most stock systems became very well engineered progressing through the 1980's and beyond.

Now, as to sampling near the air filter inlet vice merely providing a point of fairly undisturbed air to sample atmospheric pressure, there are a couple items to note.

Removing the stock airbox and replacing with pod filters drastically alters the airflow up under the seat. In my case, I installed a plastic tool tray covering most of the area where the airbox used to be and then ran the vent tube up under the seat into an area I thought was relatively stable - an "effective" plenum. However, that's no guarantee that the air really is stable up there. Indeed, the disturbed air cascading off the engine may actually be trapped by the side covers of the '82 1100E and be ducting that disturbed air up to the "stable" place up under the seat at higher speeds. It is also no guarantee that the air pressure at that location is similar to what is available at the pods filters.

I'm thinking that the best thing to do is regularize the flow into the equalization ports with a single K&N style breather filter like you originally suggested.

It inherently creates a plenum effect inside of the filter and the oval/round shape is inherently less susceptible to local pressure changes because it samples all around. The flow requirement is low enough that a single filter will equalize all of the float bowls. My port inlets are about 6 mm and so a 3/8" vacuum line has more area than two 6 mm ports. Basically all you need is a 1/4" T with a 3/8" port (min) to go into the breather.

Looking at my bike at least it is kind of a toss up about where is best for the breather. Down behind the cylinders, right behind the pods on the cross support or all the way back to the top of the battery and shielded behind the side covers.

Airplanes have a big problem with carburetion because they experience huge variation in atmospheric pressure as they climb and descend. The simple answer is that *most* carbureted aircraft use a manually-controlled mixture setting so the pilot can adjust for optimal operation. This is a little bit like manual 'chokes' on our bikes. There are special aircraft "pressure carburetors" that automatically adjust to air pressure, but they are complicated and relatively rare. It would be interesting to look at the mechanisms of their operation.

I mention all this because what is being "balanced" is the differential pressure across the jet (and, if the atmospheric pressure is changing over a wide range, the air density).

I think that's exactly the purpose of the pods, that they do flow appreciably more air into the engine. (Side note: Everybody thinks you should get better gas mileage from this, but that is incorrect. More airflow means you need more gasoline to maintain mixture, so the engine makes more power instead of providing reduced fuel consumption. Of course, you can "throttle back" to recover some of the lost mileage. These things are much easier to experiment with on an airplane than a road vehicle, but tests - both reported and my own experience - prove this to be true. Optimal efficiency for the vehicle occurs when the engine is operated WOT with minimal restriction, and the engine is sized to make the appropriate amount of power for the application.)

I think this is probably correct. I've already noted that my simplistic attempt to make an effective plenum by installing the tool tray was not sufficient. But it is more than simply having a "stable" sampling.

One could conceivable make a sampling port using a ram-air horn in front of the bike, sampling stable, high pressure air, and this would probably fail to maintain the appropriate pressure balance across the jet. Similarly, one could make the sampling location in a nice stable location like, say, up under the seat, but if this proved to be a low pressure area due to air flow (as I suspect it is), then you would again be mismatching the pressure balance across the jet. This is why I think it's best to sample in and around the area where the air is drawn into the filters, not some disconnected location. Sampling at the filter seems logical to maintain the pressure balance across the jet. I further think that either a filter or a plenum (or even an in-line resonance filter) would be a useful addition to stabilize the 'reference' the tube provides.

This is something that is just prime for experimentation because it would be so easy. It would be easy to move the end of that tube around to different locations, adding an air filter, building a plenum, whatever, and observing the effects. Getting more sophisticated, one could add some electronic sensors and a data logger. What fun!

But, alas, if my immediate problem is solved by removing the damned tube running up under the seat or placating my carburetor pixies (I have started leaving a cookie on the starter cover when parking my bike), then I will move onto more immediate projects, such as painting my forks, rebuilding the headset, polishing the swingarm, getting a fairing, and maybe retrofitting modern brakes.

Offered in the respectful tradition of technical discussion.

I don't think that the problem is as bad as might be envisioned in that there really is kind of a bubble of stagnant air behind the motor where the pods are and probably further back. (I previously described this with the slip streams going well around the bike/rider). If it was not so then you would see different acceleration/power in each gear. If you were tuned correctly for air flow at low speed but high RPM, then it would surely change as you started going much faster but the same RPM's/throttle position.

Soto a large extent the primary objective of the breather type filter is to regularize what ever pressure/flow there is required going into the float bowls for equalization and to provide a protective guard against any occasional cross winds that might affect the differential pressure of the vent pots.

I still think it is a good idea to do something other than just leave them open (although that works pretty well also), although I'm not sure if I will ever really be able to prove or even notice any improvement.

[AJ]

Agree with all the above. Note that I wasn't suggesting that one try to sample for each carb individually.

I too am liking the idea of using a small filter as a stabilizing plenum.

Especially since I already have one to try....

And I am sure it will help me pick up at least 7 horsepower....

And increase fuel mileage by 4 mpg.

Cheers!

[posplayr]

Agree with all the above. Note that I wasn't suggesting that one try to sample for each carb individually.

I too am liking the idea of using a small filter as a stabilizing plenum.

Especially since I already have one to try....

And I am sure it will help me pick up at least 7 horsepower....

And increase fuel mileage by 4 mpg.

Cheers!

Sorry, that is why I though you were suggesting a sense point near the carbs?

Further to your comment earlier about dyno testing/tuning. As I have read following dyno tuning you still always have to do some "real world" riding.

I wonder if this has anything to do with pressure changes at speed behind the engine changing the float bowl pressure (and effectively the jetting) from what it is on a dyno with just a fan blowing.

I did my tuning with a WBO2 sensor so it is real world as it were. Well worth the effort.

[AJ]

Sorry, that is why I though you were suggesting a sense point near the carbs?

Further to your comment earlier about dyno testing/tuning. As I have read following dyno tuning you still always have to do some "real world" riding.

I wonder if this has anything to do with pressure changes at speed behind the engine changing the float bowl pressure (and effectively the jetting) from what it is on a dyno with just a fan blowing.

I did my tuning with a WBO2 sensor so it is real world as it were. Well worth the effort.

I was suggesting having a single pickup point roughly around the air filters, mimicking the stock arrangement.

Agree about the limitations about the dyno tuning (thought I mentioned that in an earlier post, but perhaps not).

One interesting observation is that the sensitivity I experienced is at partial throttle opening at high speed. Whack the throttle open and the surginess would go away, or at least be hidden. I think this is why the dynojet tech guy initially recommended going back to the stock size air jets. He didn't even mention the vent tube until I raised it.

All this suggests to me that the "balance tube sensitivity syndrome" is magnified at high vacuum (partial throttle) condition, which is when the differential pressure across the jet is maximized, but also when the effective jet size is smallest (due to the low needle/slide position). Airflow velocity is more or less constant due to the CV carb, but the pressure in the carb is low relative to atmospheric. There are a couple factors at play here (differential pressure, air velocity, and effective jet size), so I need to think on this a little longer.

Finally, I'd be REALLY interested in learning about your O2 meter setup. I was trying to figure out how to make a poor man's meter using a cheap O2 meter and automotive sensor, but even that was difficult without a bung in the header collector pipe.

[gsrick]

well i am just going to leave mine as it is, vent tubes removed completely. it runs fine and i am happy with it.

if it makes any difference at all, i have a stainless plate mounted covering the gap in the frame where the air box used to sit. whether it helps or hinders, i dont care, it looks nice

Picture please.

[posplayr]

I ordered one of these. It already has a built in T and I only have to adapt from the 3/8" down to the 6mm at the float bowl ports.

http://www.ebay.com/itm/290901111625?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

I also considered that if it is in fact side pressure due to changes in angle of attack that it would at least be better to not have the filter pointing that way. This way the filter pulls from front and back and not from the sides. Minor effect perhaps.

Forgive the references to a Hawley

I'll just run individual lies from each carb pair to this on either side and tie strap it somewhere just behind the pods or as far back as the battery

[posplayr]

I was suggesting having a single pickup point roughly around the air filters, mimicking the stock arrangement.

Agree about the limitations about the dyno tuning (thought I mentioned that in an earlier post, but perhaps not).

One interesting observation is that the sensitivity I experienced is at partial throttle opening at high speed. Whack the throttle open and the surginess would go away, or at least be hidden. I think this is why the dynojet tech guy initially recommended going back to the stock size air jets. He didn't even mention the vent tube until I raised it.

All this suggests to me that the "balance tube sensitivity syndrome" is magnified at high vacuum (partial throttle) condition, which is when the differential pressure across the jet is maximized, but also when the effective jet size is smallest (due to the low needle/slide position). Airflow velocity is more or less constant due to the CV carb, but the pressure in the carb is low relative to atmospheric. There are a couple factors at play here (differential pressure, air velocity, and effective jet size), so I need to think on this a little longer.

Finally, I'd be REALLY interested in learning about your O2 meter setup. I was trying to figure out how to make a poor man's meter using a cheap O2 meter and automotive sensor, but even that was difficult without a bung in the header collector pipe.

I think this is the final configuration

http://www.thegsresources.com/_forum/showpost.php?p=1303763&postcount=12

http://www.thegsresources.com/_forum/showthread.php?t=164565&highlight=AFR+Info

http://www.thegsresources.com/_forum/showthread.php?t=161402&highlight=innovate

Made a sniffer ; there is about 3 ft of copper pipe up inside the header aboy to the collector. The only bung is welded into the peice of 3/4" steel black pipe that is part of the sniffer.

[posplayr]

I have been taking a new look at the old data and I seem to be getting clutch slip at WOT 9300 RPM.

[AJ]

I ordered one of these. It already has a built in T and I only have to adapt from the 3/8" down to the 6mm at the float bowl ports.

http://www.ebay.com/itm/290901111625?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

I also considered that if it is in fact side pressure due to changes in angle of attack that it would at least be better to not have the filter pointing that way. This way the filter pulls from front and back and not from the sides. Minor effect perhaps.

Forgive the references to a Hawley

I'll just run individual lies from each carb pair to this on either side and tie strap it somewhere just behind the pods or as far back as the battery

Mine looks just like that, but is only a single tube, so will use my plastic T fitting.

I expect to pick up some serious horsepower with this configuration. Posplayr guarantees results!

(looking forward to reading the other links you posted. thanks!)

[posplayr]

OK I finally got around to installing my filter. I used a double port breather off of ebay. It is 3" in diameter and as you will see i had to do a frame mod to locate it high up under the tank where it is essential fully shielded from any cross winds but will still be subject to any air flowing below the gas tank.

I used a 3/8" ID clear tubing (1/2" OD) as this is basically just vacuum line. The carp inlets are 6mm which I found some 1/4" vacuum line fit that pretty well. I stepped up to the 3/8" OD using some 7mm gas line on top of a connector that just fit snug inside of the 3/8" tube.



On the GS1100ED's there is a little metal bracket welded across the top of the frame to serve as a anchor point for bolting the rear of the tank down. There is a flange that sticks off, not sure what it was for but it was slightly too small for the 2" filter. So I pursuaded it up with a sledge and block of wood so the filter would fit there





This is picture shows a side view of the filter mouned about 8" above the carb center lines. When you look at a side view of the bike with side coveres mounted it is obvioulsy going to be pretty sheltered at least from cross winds.



No ride reports, not expecting any big changes unless I'm chocking off the vent lines

[Agemax]

well, be interested to see the ride reports. although i guess you will have to ride in a few different weather conditions to get a complete picture of any changes

[posplayr]

I found this old post by Keith Krause (the local expert on carbs)
which represents a lot of work and exploration on this topic by him.

http://www.thegsresources.com/_forum/showpost.php?p=455591&postcount=35

Well, some days my brain works better than others and today my brain has the day off. I wonder why I didn't see your post for all this time?
I've tried to give my opinion on this a few times in the past and I'm sure someone could use the right words to explain better than me or actually knows the entire sequence of events that explains what's happening.
I just know that when you greatly increase air flow into the stock carbs, you're also changing the vacuum and the pressure. These changes will effect the venting and the fuel flow. These changes effect some models more than others but it effects them all. Some models only seem to have problems in crosswinds or other windy conditions, while others will have serious fuel starvation just cruising down the street on a calm day.
I called up Dynojet many years ago to ask why they suggest removing the float bowl vent lines when running pods (part of their stage 3 and 7 jet kit info). They said "a vortex will compromise the air flow into the vent if the lines are left on." That's about it.
I don't know how much of this problem is related to air travelling across or around the pods or how much is related to increased air flow INTO and THROUGH the carbs but on a few of the bikes I've tinkered with, the problem was there regardless of outside wind speeds.
I can see how a vortex could be created at the line end, such as blowing across an open tube. A vortex would create a resistance in the tube and any resistance could compromise the venting and this would make it harder for the jets to draw fuel from the bowl. I don't know why this same vortex wouldn't be as bad when acting upon the vent nipple.
I've read where this vortex can be strong enough under some conditions to actually create a vacuum at the vent line and this will draw on the bowl and defeat the venting to at least some degree, if not completely.*
I've also considered that the stock venting system, just a float chamber and tube, could be inadequate to allow for the increased flow the carb is experiencing with pods. If more fuel is exiting the bowls then the stock venting may not be adequate to keep up with it under some conditions. In this case, the best thing we could do is remove the vent hose and that would at least MINIMIZE resistance to best venting. Line/tube length obviously factors in but I've had no luck by "shortening" the lines either. It's either remove them completely or don't run pods on many models.
It could be a combination of things or something else than the above. You'd be amazed at how much air your bike sucks in and it relies on proper venting.*
I do know that even with very good jetting, most pod equipped bikes will show some mild hesitation and fuel flow problem while in stronger crosswinds. It's not a true mixture problem. It's because the jets can't draw fuel easily under this condition. Fuel starvation.
I remove the lines because it usually must be done if you want the bike to run well. I or my friends have never had a problem with the open nipples getting bugs or dirt in them or water either. Obviously, it could happen though. I've never had a serious problem from crosswinds either, but I've felt hesitation and even got a few "spits" out of the filters at the time. Just a minor annoyance in my case. I know what it is and that it will pass quickly. Even if expecting it, it can be difficult to tell if any hesitation is from the pods or just the wind hitting you and buffeting you around.
Hope this helps.

The surprising point he makes is that with pods you need to remove the line al together as that the increased fuel flow through with pods requires more flow through the vents and the 1/4" line is too small.

I only used a small 1/8" section to attach a 3/8" ID hose to the 6mm nipple. So the area of the hose is essentially twice as large as stock and relatively short (6-8" going up to the filter).

I still need to do a road test to ensure I don't have fuel starvation issues with this setup.

[Agemax]

I found this old post by Keith Krause (the local expert on carbs)
which represents a lot of work and exploration on this topic by him.

http://www.thegsresources.com/_forum/showpost.php?p=455591&postcount=35

The surprising point he makes is that with pods you need to remove the line al together as that the increased fuel flow through with pods requires more flow through the vents and the 1/4" line is too small.

I only used a small 1/8" section to attach a 3/8" ID hose to the 6mm nipple. So the area of the hose is essentially twice as large as stock and relatively short (6-8" going up to the filter).

I still need to do a road test to ensure I don't have fuel starvation issues with this setup.

isn't that what we have been saying all along??