>>I still say a servo control unit would be the way to go.

I'll build one if you'll test it.

What parameters do you think should be adjustable?

5 *****:

1) Pressure to begin closing the diverter valve.
2) Rate to close diverter valve.
3) Pressure to open diverter valve.
4) Rate to open diverter valve.
5) Mysterious damping factor. (to prevent oscillations)

If I can get the range of pressures people see in normal operation, that would help.

I am nowhere near qualified to test an engine part. The best I could do is tell you if it worked at all. I am surprised that no one has thought of this before. A servo could be calibrated much more accurately than a vacume system, not to mention that a servo would not be subject to the yo-yo oscillation that the vacume system exhibits. Would be great if it could be ECU controlled or maybe controlled by a unichip. I'm no engineer, I don't even play one on TV.

Thinking out loud:
Does the vacuum line and the diaphram form a closed system?
If so, then it is the amount of air that is a function of time.
I guess if I could attach a coke can to the diaphram, then I need to pump more air out to achieve the same amount of vacuum.
I suppose that adding a smaller tube would have less volume and less air and cause the diaphram to be more "connected" with the vacuum source.
I am not sure if it is a closed system or not.

EDIT: whoops just read the post from Spiderknight. he pretty much made my point but since I did all that typing, I'll just leave it for posterity

>>Trippy,
>>
>>I agree with you. The restricted one takes longer because the vacuum has to build up. The same holds true for the bypass valve. It takes longer to open the valve because of the restriction.

Not wanting to copy all that vacuum experiment post, let me just reply to this one...

one more thing to consider here. in the vacuum cleaner test you propose, bear in mind that you are working against the whole room full of air (when I say working against I really mean trying to change the pressure of)

In the valve scenario, you have very small chamber that is apparently well sealed by the diaphram (diaphrgm? what the heck is a diaphrgm?). I think Trippy said earlier something to the effect that the position of the diaphram is determined by the pressure in that little chamber

to make the dvd/vacuum experiment the same, youd have to seal off the tube and have a little disk in the tube that could move. I suggest cutting apart a tupperware lid. Actually this is not a real apples-to-apples cause we dont have a spring.

Now I think that getting the manifold pressure is a capital idea. Andy you out there?

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Motorin' ... right now!

Here ya go, this run should be pretty self-explanatory.

http://www.ross-tech.net/andy/mini/t...eopenclose.csv

What are the units on the pressures?

SAE j1979 say kiloPascals, but 1000 kiloPascals is 145 PSI which is too big.

What about instead of a restriction, making the bypass valve lighter? That would increase the speed of both the open and close. Not sure if you can make it lighter. I think M7 has the right idea going one way, but it would be good to have a solution that not only closed it quickly, but opened quickly, or at least not affect it's ability to open as fast as in the stock scenario.

No one has shown why restricting the vacuum signal will make the valve open faster yet.

Do people think restricting the tube will really make it open faster somehow?

Thanks Andy,

Ok I'm not really sure how to read this but I'll take a guess:

I imagine DRIVER DEMAND = 100 means your at WOT and =0 means you'vce let off the gas.

I dont know where Air pressure is measured. Is manifold and upstream before and after the IC respectively? Which is more appropriate for the vale I dunno but they trend pretty much the same way so I'll go with Manifold Air Pressure (column K)

Now looking at rows 30 and 31 it looks like you went from flooring it to no gas with a time lapse of 0.5 seconds. We also see that RPMs went from 6934 to 7022. hmmm an increase. The measurement must have just taken just when you let off.

So lets instead look at 30 and 32. 6934 to 6184 RPM drop, 2045 to 301 pressure drop. wow. I think its safe to say the valve opened quickly.

Lets compare row 27 to row 32. RPM 6139 to 6184, pretty similar. Pressure diff? 1997 vs. 301. Well that is definitely asymettric behaviour.

The overall trend seems to be "slow build up pressure while at WOT then rapid drop when let off".

What do we want our "device" to do? Increase the rate of pressure build up while keeping the same rapid drop.

Alas, someone will have to smuggle a "device" or a ryphix spring to Andy for the apples-to-apples comparison.

any volunteers (assuming Andy is willing of course)?

I can post more logs with better sampling (by recording fewer variables) under a variety of driving conditions.

Driver Demand is exactly that, how much oomph I am asking for on a scale of 0 to 100. Air Pressure is measured in mbar of absolute pressure. Typical ambient air pressure around these parts is 1013 mbar. The Upstream Air Pressure is recorded by the Upstream MAP sensor (located next to the airbox ... kinda sorta) that is tapped into the inlet of the supercharger. It shows the air pressure between the throttle body and the supercharger. Manifold Air Pressure is from the TMAP sensor located in the manifold.

oh right. kinda got bamboozled by that whole up/down stream thing.

Still not sure about which (manifold or upstream) is more representative of the pressure that would be used to compress the spring and open the bypass value.

any thoughts?

i just wish it would bypass to else where, but to do it would lose its function by loss of vacumn for it, but i would be so much better if it were more like a blow off valve than a bypass, i would rather lose that hot air than recirculate it... i know before anyone says it, if i dont recirculate, the supercharger will be working all the time there loss of "gas" milage wouldnt happen or would it, hmmm if it were to blow out(into engine bay or something) rather than recirc, it would not build boost unless the valve was closed, there for negating the "drag" of the supercharger, it would be free spinning( but i would have to retain the vacumn controled valve, so that when you mash the gas it would close, but then again if it blows out, air would take the shortest route therfore none going into the engine

A true pressure regulator would effectively do what a stiffer spring would do. IMHO, all a restrictor does is to dampen fluctuations which would cause butterfly flutter during the transition period. These do exist but seem to dissipate with the higher pressure generated by a 19% pulley. Why has no one commented on the effects of higher pressure on this valve?

Does the butterfly have to open fully? I think not. It probably only has to open enough to relieve the pressure. A shorter travel would give you a quicker response and less chance of flutter on closure.

I think that the "fix" is either a stronger spring or pressure regulation.

I may buy another butterfly and change the spring.

Ryan and others did a bunch of work here and they deserve the credit.

without trying to sound defensive... credit? credit for what? I think its pretty obvious that all we're doing here is reinventing the wheel. Somebody already knows the answer to Trippy's original question, probably somebody (or bodies) on this very forum, it just isn't me. So we do what we can to try and figure it out.
Besides, pretty much the first thing Trippy did was reference Ryan's work.

Now that said, butterfly flutter isnt something I considered. Is this transition period where it occurs opening or closing or both? I would think closing because that is where we see a slow pressure build-up (as opposed to a rapid drop which causes it to open). In that case yes, I agree that a restrictor would probably reduce fluttering. but I've only got the stock pully and I cant say I've noticed any fluttering on ye ol' boost gauge.

So Andy, what pully were you using when you took that data?

Interesting thread -

What you have to remember here is that it is vacuum that drives the valve not air pressure (unless you think of it as negative air pressure) - By constricting the vacuum line to the valve it will indeed take much less effort for the spring to overcome the lessened vacuum and the response of the valve closing will be quicker. Conversely it will take longer for the valve to open up again as it will take longer to build up the required.

What I wonder is will having a delayed valve opening really cause a problem. The valve is only shut on acceleration so either your racing and the valve is shut all the time - or you're driving on the streets and the valve is open most of the time except when accelerating. If the 'dampened' vacuum line is only 'slowing' the opening of the valve slightly then I should think it would cause no problems. If on the other hand it is slowing it by a few seconds, I guess it could cause some harm over time (although I am not sure of this either) -

Vacuum is our friend

>>What you have to remember here is that it is vacuum that drives the valve not air pressure (unless you think of it as negative air pressure) - By constricting the vacuum line to the valve it will indeed take much less effort for the spring to overcome the lessened vacuum and the response of the valve closing will be quicker.

Could you explain this idea.

I think several people have explained step-by-step why the action of the restrictor will cause the valve to close more slowly.

I would like to read a clear explanation of why you think the restrictor will cause the valve to close more quickly.

You have pointed out the mystery here, and I'd really like to understand.

PLEASE READ>>>

The valve will not open more quickly. Because the valve diaphram is sealed and air velocity is zero at any one specific throttle position the air pressure(vacuum) will be the same on either side of the restriction in the tube, meaning that the valve will be at the same position with or without the restriction. The only thing the restriction will do is as Trippy said, slow the change of vacuum on the valve side of the restriction when there is a change in vacuum on the engine side of the restriction. This will cause the valve to react slower to change in vacuum when opening or closing.

Will this help with throttle response? I would think so. When you accelerate the valve starts to close. This causes an additional load on the engine because of the additional air pressure being pumped into the engine. Delaying the close of the valve should increase the throttle response from before because the engine is free to change RPM without additional load from the SC that is not instantly burning more fuel. It should allow the entire engine Air/Fuel to be more balanced during acceleration by dampening the engagement of air into the engine. That additional air added during the split second you begin pressing down on the accelerator is a restriction until the air burns more fuel. My guess is that the restrictor in the tube helps this process along by slowing the valve action allowing the air/fuel ratio to be maintained more consistantly benifiting throttle response for split second the valve is instructed to close. Throttle position control of added fuel should be almost instantainious but MAP sensor control of fuel has to be measured and then reacted to. Show that process down and you will get better throttle response Because you have more accurate Air/Fuel ratio. my $.02

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The valve should operate slightly faster because of the "device" inserted into the tube. The device only takes up air volume space within the tube. If there is less volume of air to vacuum, the faster vacuum will build.

Take it to a larger scale:

If you have a 10 foot length of PVC pipe 3" in diameter, you will have X amount of air volume. Cap one end of it and suck with your mouth on the other. You will suck out several breaths of air before any significant vacuum will occur. Now, take a length of 2" and 1" pipe, insert them within each other. You have now reduced the volume of air within the 3"pipe. When you suck on the end, vacuum will build faster as there is less volume to remove.
Does that make sense?

Let me edit before someone beats me... Yes, the size restriction also "slows" the airflow in both directions.
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MCS, with some stuff. Stuff. Just stuff, alright!

So sorry Uncle, but I cannot agree with you. During normal operation the valve is open, meaning sufficient vacuum has been generated to overcome the force of the spring. When the throttle is opened, the vacuum in the intake is lessened, but because of the restriction in the hose, it takes longer for the air to flow through the hose into the diaphragm chamber and relieve the vacuum, allowing the spring to close the valve. The converse is also true. When the throttle is closed, it takes longer for the air in the diaphragm chamber to flow out through the restricted hose to the intake manifold, lowering the pressure(increasing the vacuum) in the diaphragm chamber and opening the valve. The pressure of the spring is a constant, both in compression and relaxation. The restriction will only change the rate at which the spring is compressed or relaxed. The spring is used to determine how much vacuum/pressure is necessary to open/close the valve a certain amount.

Compare the flow of water through a garden hose and a fire hose. The garden hose can only flow a certain amount of water in a certain amount of time, it doesnt matter in which direction, ditto for the fire hose, but because of its larger diameter, at the same pressure and in the same time, it will flow far more water than the smaller garden hose. So, for a given pressure/vacuum change in the intake manifold, the restricted hose will take longer to transfer that change to the diaphragm chamber, just as it will take the garden hose longer to flow the same volume of water as the fire hose.IMHO

here are a few other thoughts:

any restrictor in the vacuum line will tend to filter out-average out- pulses, just like the restrictions needed in the vac gauges or just about any pressure gauge. this function would enable the butterfly movement to be more direct, without hunting, trying to follow the vac pulses;

a problem with the butterfly style of valve is that it does not close air-tight, even when spring loaded. You can check this by holding the closed valve/bore up to the light. this would argue for a more positive closing valve, like a poppet;

it seems like a good idea to dump extra air pressure when off-load, but the idea of re-circulating it back into the blower intake seems un-necessary and may have been done for sound reasons (read that aural)

Without regurgitating all of Super's point, in addition to throttle response, the people with the device have reported building boost faster. Not really sure if these two quantities are the same thing but I'd tend to believe not.

So if boost is building faster, I think one could assume that the SC engagement is not delayed.


and not to be a smart-*** or anything but I find that I get confused when I think about vacuum being negative pressure. Really there is no such thing as negative pressure, or at least it only exists in the same way that negative temperature exists (oh if only we could all use Pa and K).

Here's an idea I haven't heard on this discussion yet.

What if the suction-side of the bypass valve diaphragm chamber is not completely sealed?

If there is a tiny pinhole bleed orfice to the outside, then the situation is quite different.
It is not just a pressure difference that drives the diaphragm position, but some air must continuously FLOW out the vacuum tube for the diaphragm to move all the way to the open position.

In this situation, I think restricting the vacuum hose would be very similar to installing a stiffer spring.

In addition, depending on the size of the orfice, and the size of the restriction (And all other constants of the universe), the valve may not go completely to the fully-bypassed position.

If that was the case, the supercharger would "kick-in" faster since it was never completely bypassed.

Could Ryan or someone check to see if there is a bleeder orfice somewhere in the suction-side of the diaphragm housing?

Could someone verify that restricting the vacuum tube allows the bypass valve to go completely to the bypass position?

The orfice would be somewhere in the half of the diaphragm chamber that is connected to the vacuum line in this image from Ryephile

I THINK it's the far-left black round part in this image, but I can;t quite tell for sure.

The diaphragm itself might also have an orfice in it as a teensy-tiny hole.

In his post of May 26 to the yoyo chronicles, Ryephile includes a picture of the valve. He is holding the line pinched shut after inducing a vacuum at the diaphragm to open the valve. The valve stays open, implying there is no orifice in the diaphragm chamber or diaphragm to relieve the vacuum.

From Yo Yo Chronicles

Rats. I almost thought the restriction in the vacuum tube could possibly match some owners responses to the mod.

I simply can't explain how this mod could cause the supercharger to react faster.

Can you see that I'm being as open-minded as I can be on this mod? I'm trying as hard as I can to explain how it could possibly perform the way it is being described, and even when I propose a possibility, it gets shot down with the facts of the situation.

Any new ideas or is this turning into a nother "Placebo-mod" ?
I'm not accusing any of the modders of lying about it at all.
It's just that the Placebo-effect is incredibly powerful after making a mod you want to work.




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Team: Rational thought

i still think a cadidate is valve flutter eliminated by throttling the vac line