Cross wind power loss.

[posplayr]

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

Obviously line removal has been the accepted procedure. However it is also understood to also have some residual problems (i.e. in cross winds) as evidenced by Keith's comments.

So the question that I/AJ have been trying to answer: "Is there a way to sample the atmosphere (as Steve suggests) but make the sampling insensitive to speed and cross winds where based on Keith's post is know to be an issue even if minor. The sampling obviously has to supply sufficient air flow rate to meet the fuel demand flow rate.

In short, were trying to do something a little different to solve a know problem that an open vent pipe does not.

[Agemax]

i wait to hear the results of your filter experiment, see how that works out....

[posplayr]

i wait to hear the results of your filter experiment, see how that works out....

I have had petcock fuel starvation issues which I only found on a "closed circuit " track at sustained run over 100 mph.

So it might be a while; none of those around here.

[tkent02]

Has anyone tried connecting the vents to a nipple soldered onto the end of the K&N?

It seems the vent pressure would change exactly as the intake air pressure changes.

[Agemax]

Has anyone tried connecting the vents to a nipple soldered onto the end of the K&N?

It seems the vent pressure would change exactly as the intake air pressure changes.

good theory but under WOT acceleration would it not have a tendency to suck fuel up through the vents?

[tkent02]

good theory but under WOT acceleration would it not have a tendency to suck fuel up through the vents?

Yeah, maybe. Haven't tried it, I've always been OK with the little power variations.


Hmmm, the vent comes from above the fuel level in the bowl.....

[posplayr]

Has anyone tried connecting the vents to a nipple soldered onto the end of the K&N?

It seems the vent pressure would change exactly as the intake air pressure changes.

I thought about it but, did not want to ruin a K&N to try and not sure that is what you want in the first place.

The pressure inside the k&N is likely significantly less than that outside. As has been mentioned even a 1 psi differential is equivalent to several jet size change and this likely changes with RPM at max RPM being the highest which would likely cause a persistent high RPM lean condition.

Atmospheric venting is by all indications best , so the issue is how to get atmospheric pressure that is unaffected by speed, rpm or cross wind? The flow rate through the vents has to be much less than that through the throttle opening so if you can just provide a larger opening that the vent pipe you probably will not cause any significant additional pressure from.

[Dogma]

Has anyone ever tried terminating the vents up under the tank's frame tunnel? That should be some nice, non-turbulent air.

One thing from the Keith Krause post that I don't get is why the vents need to flow at all. The vent only connects to the air pocket above the fuel in the float bowl right? That should be a relatively static volume. No flow at all. Otherwise, the engine would be ingesting unfiltered air.

[AJ]

I just caught this thread was still going.

No disrespect to Keith Krause, but virtually no air should "flow" though the vent/equalization line on the carb float bowls. This is because

1. The bowls are tiny;
2. Air doesn't really flow through the bowls;
3. The air in the bowls resides above the gasoline, the level of which is set (nominally) by the float setting and then modified (slightly) by gasoline being drawn up through the jets, but as gas is drawn out, new gas comes in through the needle valve of the float system to more or less keep the fuel level constant; and
4. Any air flowing into or out of the vent line is only compensating for minor variations in the fuel level.

Thus the air volume above the fuel stays more or less constant, no air flows "through" the bowl, and any air flow through the vent lines flows to make up minor variations in the fuel level.

As to the source of the sensitivity: The jets want CONSTANT air pressure on the fuel in which they draw because the delivery of fuel is determined by (the diameter of the jet and) the pressure differential above and below the jet. Because the air volume in the float bowls is very small, even small variations in that volume will lead to significant variations in air pressure IF the vent line cannot compensate with sufficient speed (or if the vent is blocked off). Alternatively, pressure variations induced due to effects at the distal end of the vent tube will be magnified inside the float bowl because there is such a small volume of air inside the bowl. Having a bigger pocket of air would minimize these effects, but then the float bowl would need to become quite big.

I hope this was clear. As BCliff would say, thanks for your indulgence.

[Carter Turk]

I've experienced crosswind fuel starvation or uneven pressures on my 1150 with pods. This was with no vent lines. I've also experienced what I believe to be water getting into the float bowls from the vent ports. Fouled plugs as a result or that's what happened after a heavy downpour, as the vent line ports faced a 10:30 angle. This happened on a long trip when I neared my destination and encountered a torrential downpour, puttering in on 2-3 cylinders.

Since then, I've run two vent lines that terminate under the tank inside of the frame rails seemingly out of moisture that maybe pushed back behind the engine. Don't really know if this set up helps, but haven't fouled a plug for awhile. I still think I've felt a loss of power in heavy crosswind with or without the vent lines.

[WilliamGLX81]

The first thing I thought when I saw this was "I wonder if that guy is using pods....".

Cross-winds can lower pressure either at the pods themselves or at the vent tubes. How about running the vent tubes to an old oil bottle or something, open to the air, but shielded from wind, like peoples used to do for PCV systems. Or even constructing some kind of wind-break. Maybe even those little porous "rocks" for aquariums would do the trick.

If the problem is cross-wind blowing across the pods themselves.... I really don't know how that would work. The vent tubes seem more likely to me just because a lower pressure at the pods would still be a higher pressure than the inside of the pods, and because the air flow over the pods is at least shielded a bit more than the flat open end of a vent tube. Lower pressure at the vent tubes will immediately decrease fuel flow. Different game altogether.

[posplayr]

And yes the pods, act as a pressure equalizer as they accept pressure from all around. More importantly the pressure in the veturi has more to do with total INTAKE flow rate and RPM and less to do with atmospheric pressure. In contrast, The pressure at the vent ports will have a direct affect on fuel flow and AFR.

See my solution post 42. Uses a similar approach to POD filters and ticks back up nicely out of the way in one of the more sheltered areas of the bike.

http://www.thegsresources.com/_forum/showpost.php?p=1870527&postcount=42

The first thing I thought when I saw this was "I wonder if that guy is using pods....".

Cross-winds can lower pressure either at the pods themselves or at the vent tubes. How about running the vent tubes to an old oil bottle or something, open to the air, but shielded from wind, like peoples used to do for PCV systems. Or even constructing some kind of wind-break. Maybe even those little porous "rocks" for aquariums would do the trick.

If the problem is cross-wind blowing across the pods themselves.... I really don't know how that would work. The vent tubes seem more likely to me just because a lower pressure at the pods would still be a higher pressure than the inside of the pods, and because the air flow over the pods is at least shielded a bit more than the flat open end of a vent tube. Lower pressure at the vent tubes will immediately decrease fuel flow. Different game altogether.

[posplayr]

I just caught this thread was still going.

No disrespect to Keith Krause, but virtually no air should "flow" though the vent/equalization line on the carb float bowls. This is because

1. The bowls are tiny;
2. Air doesn't really flow through the bowls;
3. The air in the bowls resides above the gasoline, the level of which is set (nominally) by the float setting and then modified (slightly) by gasoline being drawn up through the jets, but as gas is drawn out,new gas comes in through the needle valve of the float system to more or less keep the fuel level constant; and
4. Any air flowing into or out of the vent line is only compensating for minor variations in the fuel level.

Thus the air volume above the fuel stays more or less constant, no air flows "through" the bowl, and any air flow through the vent lines flows to make up minor variations in the fuel level.

As to the source of the sensitivity: The jets want CONSTANT air pressure on the fuel in which they draw because the delivery of fuel is determined by (the diameter of the jet and) the pressure differential above and below the jet. Because the air volume in the float bowls is very small, even small variations in that volume will lead to significant variations in air pressure IF the vent line cannot compensate with sufficient speed or if the vent is blocked off). Alternatively, pressure variations induced due to effects at the distal end of the vent tube will be magnified inside the float bowl because there is such a small volume of air inside the bowl. Having a bigger pocket of air would minimize these effects, but then the float bowl would need to become quite big.

I hope this was clear. As BCliff would say, thanks for your indulgence.

The statement in GREEN is really the most pertinent.

If you consider the case of a blocked vent line, if the fuel level drops the volume above the fuel increases which lowers it's pressure which immediately lowers fuel rate and AFR(this assumes flow rate is proportional to the differential pressure between the venturi and the float bowl.).

If the bowl is vented then this effect is minimized as the air flow through the vent tube will bring the pressure above the fuel back to atmospheric pressure regardless of the fuel height maintaining more consistency in fuel flow rate and AFR.

I will agree that ON AVERAGE, there should be little air flow into the vent tube. But if there is any variation of fuel level (perhaps more specifically volume) in the bowl, then there needs to be flow in the equalization tubes to compensate.
So how much or how fast does fuel level in the bowl change? I don't have any data.

I have not done this test, but it may even be that no gas will flow through a jet if the vent line is plugged. Like liquid held in a straw by your finger over the upper end.

[KEITH KRAUSE]

I just caught this thread was still going.

No disrespect to Keith Krause, but virtually no air should "flow" though the vent/equalization line on the carb float bowls. This is because

1. The bowls are tiny;
2. Air doesn't really flow through the bowls;
3. The air in the bowls resides above the gasoline, the level of which is set (nominally) by the float setting and then modified (slightly) by gasoline being drawn up through the jets, but as gas is drawn out, new gas comes in through the needle valve of the float system to more or less keep the fuel level constant; and
4. Any air flowing into or out of the vent line is only compensating for minor variations in the fuel level.

Thus the air volume above the fuel stays more or less constant, no air flows "through" the bowl, and any air flow through the vent lines flows to make up minor variations in the fuel level.

As to the source of the sensitivity: The jets want CONSTANT air pressure on the fuel in which they draw because the delivery of fuel is determined by (the diameter of the jet and) the pressure differential above and below the jet. Because the air volume in the float bowls is very small, even small variations in that volume will lead to significant variations in air pressure IF the vent line cannot compensate with sufficient speed (or if the vent is blocked off). Alternatively, pressure variations induced due to effects at the distal end of the vent tube will be magnified inside the float bowl because there is such a small volume of air inside the bowl. Having a bigger pocket of air would minimize these effects, but then the float bowl would need to become quite big.

I hope this was clear. As BCliff would say, thanks for your indulgence.

Looking at my old post, I don't see where I said air flows into the vent. I did quote Dynojet using that term. Technically, there is a flow but maybe the word "entering" would be better?

[wymple]

I had crosswind problems up until the moment I got the factory airbox properly sealed