POP OFF, BY PASS, DUMP VALVE, POPOFF FAN
No need and I don’t want to bore anyone with useless explanations about pop off valves, (also called popoff ventile,dump valve …
No need and I don’t want to bore anyone with useless explanations about.
The pop off valves, (also called popoff ventile,dump valve Diverter valve,By pass,power pop etc etc) on the net and in the various forums there is enough information and not affordable and easy to find.So I will just give more technical info,trying to be as clear and simple as possible. So that even the neophyte can understand what I’m talking about and at the same time,fill in gaps or complete the information to those who are not.Someone will ask why this article,and I’ll satisfy them right away!We occupy a good part of our time giving answers and information. To those who ask us ” what do your valves sound like “.By telephone it is not at all easy to get across what you would like.So better to write it !!!!!!!!!!!!
The first thing to know about popoff ventile,dump valve, diverter valve, By pass,power pop etc. etc. is that on the sound characteristics they are exactlyparable to a wind musical instrument.Which will have the prerogative of being able to be conformed to the air passages in the best way.Built with suitable materials to produce resonances and vibrations.And finally tuned in the most perfect way….but all it will be able to produce will always be only a sound based on the quantity and air pressure that will pass inside it. Logically more air quantity and pressure will produce a louder sound and vice versa.
Having said that we have understood that the sound and puff of the popoff ventile,dump valve Diverter valve,By pass,power pop,is not 100% attributable to their facture.But we have not yet established what percentage of the component is valid to judge the peculiarities and goodness of the same.If we were to install a valve in a car with a naturally aspirated engine what would be the results?Absolutely nil,zero,nonexistent. There is no turbine that produces air !!!!But then at this point we should say that the goodness of the sound or puff produced by pop off valves is to be attributed 100% to the car in which it is installed ? and proportionally to the boost pressure ???This too would be an approximate statement.For if we had a valve made of bad materials,with unsuitable internal sliding,and perhaps not self-lubricating,it would surely have high friction such as to create delays in opening,thus preventing the air from producing the beneficial puff effect.This is because when a valve opens late,the air,instead of passing through its orifices,bounces like a ball between the three opposite ends.( closed throttle butterfly,air filter box and compressor impeller ).This bouncing phase also produces a sound,which many,indeed too many,mistake for sound created by the popoff ventile,dump valve,by pass,power pop etc. etc.
Below we can hear the sound of an overly restrictive valve (File 1).
Initially,it opens and makes a puff of about half a second,then it becomes saturated with air and,unable to discharge it,starts the bouncing between ( closed throttle butterfly,air filter box and compressor impeller).However,those who use it are fully convinced that it is the sound created by the valve,when it would be enough to eliminate it to have the same dangerous sound.So much so that then when they contact us to buy the valve,they are looking for that very sound.Whereupon we have to do our best to make it clear that that sound is not the valve opening,but rather a valve that does not open at all or opens badly behind the pressure wave that should be passing through it. Or with restrictive orifices for the amount of air that should pass.This can happen ( as we said before ) because of a poorly designed and poorly constructed valve.But it also happens when you want to apply a pneumatic valve in a car where there is an electric valve applied as standard.
Below we can hear another example of a pneumatic valve applied where there was originally an electric valve (File2).
In this case, you can feel the air bounce very well without any openings for the air to discharge to the outside.
For the sake of completeness, you should know that when we speak of electric or pneumatic valves, we always mean valves with exactly the same functions.The differences are only and exclusively in the opening control.In the electric one there is a magnet that, excited by the passage of current, pulls a shutter which in turn opens an orifice from which the air to be discharged will pass. The exhaust may be open ( valve with a puff ) or recirculating closed ( silent valve ).
In the pneumatic one,the opening and closing command is given by a small tube that must carry pressure and vacuum to fill or empty a chamber,with either a diaphragm or a piston inside it. In the pressure phase,the force of the same applied on the face of the piston or diaphragm keeps it pushed down closing the discharge orifice. While in the depression phase,a negative force will be applied to the face of the piston or diaphragm which will pull it upward,thus clearing the orifice below and causing it to discharge air. Having said that,anyone will be able to see for themselves that the speed of electrical execution is significantly faster than that of air.Wanting to go into the details of operation,let us also explain why this delay occurs.
In all the explanations that follow and explain the operation of the valves,contrast springs,which are part of the valve closure,will deliberately not be mentioned.This is trusting that the manufacturer of the valves has considered the spring as an essential element for closure and not for venting,as this option is to be controlled by the clearance of the sections and diameters at the design stage,avoiding inappropriate adjustments to others.
In the electric valve,the control unit sends a current pulse to the valve and the opening occurs in real time when the current arrives ( delay of little more than zero ) the response time can be compared from when we press on the clakson to when we hear the sound.
In the pneumatic valve,driven by the control unit what happens is that:the control unit sends a signal to the solenoid valve that switches pressure/depression waves, which waves then have to reach the valve.So if there was pressure in the valve previously,first the circuit has to be emptied of pressure and then saturated with depression and vice versa when closing ( delay of about a little less than 1 second ).
In the pneumatic valve driven by engine phases or throttle butterfly closure:the pressure that is in the intake manifold ( in turbo running phase ) is brought through the usual small tube to the valve,which being there pressure remains closed.Then when the throttle closes completely and in the manifold the wave phase sign changes and goes to vacuum,the same always through the small tube is brought to the valve ( opening it ).Here in addition to the delay of air movement we also have the slowness on the part of the engine to change wave sign,since the closing of the throttle does not cause a sudden change of sign.Because first the engine has to suck in all the air from the manifold,then as it continues to turn it has to suck in as much air as to send the manifold space into depression ( delay a little more than a second ).
There is also a third type of valve with different control.That is,the one with pressure both above and below the piston.The two pressures equalizing hold the piston still.Then just removing the upper pressure causes the piston to rise,pushed by the force of the lower pressures.
Considering that air velocities inside the engine are close to those of sound………..
We can guess for ourselves that opening delays are absolutely to be avoided.
Over the years,engines have progressively gained more and more power and torque,but without raising displacement or exaggerating boost pressures.This is thanks to a well-done study,of materials,friction,and especially volumetric filling.Designers have managed to make the engine “swallow more air “this by improving:Exhaust and intake ducts,bringing air velocities and pressure waves favorable to filling to really very high levels,compared to a few years ago.These velocities also require quick controls to manage and perhaps not quite as retroactive as they were in the past,especially with regard to supercharging.Starting with the electric or electronic waste gates,continuing with throttle butterfly completely released from the decisions of the driver’s foot and determined to follow the set program and continuing with the pop off valve that has since become electric ( the control ).
Now in the light of the above,it is possible to apply an “old pneumatic valve” where the electric valve used to be.But unquestionably on the performance and scenic level it is absolutely counterproductive.Would you be willing to change your smartphone for a cell phone only 2 years old?Maybe here I have to stop,I think no further comments and explanations are needed !!!!!!!!!!!!!!
Angelo Bonalume
File 1
File 2
