You guys are thinking of an engine as a whole. I will be flowing a single port, think single cylinder engine, which has air pulsations due to the valve opening and closing. The valve opening/closing starts and stops airflow. If i don't come up with a simple method of interrupting airflow to somewhat simulate that event then i think that bleeding the pressure, from 100" to atmospheric, would work...at least well enough for my testing.
When a valve in an engine opens and closes it also creates pressures changes inside the port. Though it's not exactly the same this is why i believe that bleeding the air would work because there's a change in pressure and airflow.
I'll be creating a low pressure, at least 100" water and hopefully more, because this low pressure shows turbulence that you wouldn't see under higher pressures like the industry standard of 28".

I have seen those flow benches, thank you for the link. I already have my basic bench built but it is not operational yet. I know what i want it to do so i'm trying to figure all that out so i can, hopefully, build it one time rather than changing it around multiple times.

A throttle body, as mentioned, might work and i'm willing to spend some money, hopefully not a lot, on various methods to figure this out. The throttle body, gate valve and solenoid valve are all definite possibilities i'll be looking into. I think i've spent around $1700 on it so far over the last year.

If i were to use a throttle body or solenoid valve how do i control it? Can someone recommend an adjustable controller of some sort and are there any benefits of using 12, 24 or 120v?

 

I believe I've exhausted my thoughts on how to accomplish your task. As for the TB (Throttle Body), changing the return spring to something very low strength and then using a solenoid the same as a gas pedal cable might be doable. It should be able to swing 90˚ (relatively) and back to full closed in pretty short order. By that I mean about a tenth of a second travel time in either direction. I don't know if that would be fast enough for you, but I don't know of any other options.

Given that in my 4 & 8 cyl. diagram you can see airflow represented in sine wave format. Simply remove all remaining sine waves and just leave the single wave and you have what it sounds like you're trying to describe.

$1700? OK, you're not exactly looking for the cheapest solution. Rather, you're probably looking for something more specialized. The gate vac valve MIGHT be a workable solution, but it might not be as dependable as an auto TB.

I wish you well. Also hope you post your final solution so we can see what it is you've been working on. But you HAVE spurred an idea in my head for an experiment. Remember the movie "Crocodile Dundee"? Mick took a flat stick on a string and waved it over his head in circular fashion. Moving through the air caused the flat stick to rotate, presenting a flat surface to the air, then to continue spinning to present a near smooth surface. The result was a whirring sound. I wonder how well something like that would work in a tube with air being pushed through it. What kind of sound would it make and at what amplitude? Might be fun on Halloween. Ghostly sound emanating from who knows where. A copper disc cut to nearly match the ID of a tube mounted on a free spinning shaft.

 

I guess I don't understand what your trying to do. The friend I was talking about does cylinder head work along with a couple of brothers that compete regularly in the "Engine Masters Challenge" while they never win they do sometimes place. He also does work for local racers.

He uses the flow bench like it's supposed to be used, to test the flow in a port at a certain valve opening. And after finding that number matching the intake manifold to the cylinder port. I guess what I'm missing is what your trying to find out dumping the whole vacuum load that drastically.

 

The diagram below shows how air might flow through an intake tube for both 4 and 8 cylinder engines.

I think you forgot the valve overlap in that diagram. In real life the air is moving in both directions in an intake manifold. There is a thing called fuel standoff that happens because of the reciprocating nature of the air flow. That's why you see the velocity stacks on an unblown fuel injected racing engine.

 

I think you forgot the valve overlap in that diagram. In real life the air is moving in both directions in an intake manifold. There is a thing called fuel standoff that happens because of the reciprocating nature of the air flow. That's why you see the velocity stacks on an unblown fuel injected racing engine.

While I don't know for a fact the exact waveform of the airflow, my diagram does show some overlap. I believe in my statement I made that point as well that due to valve timing there should be some overlap. Maybe not expressed in these exact words, but that was my intent.

Velocity stacks - - - never fully understood them. But I have wondered why on my car there's an intake tube that has a box that has no airflow to it. I've assumed it has something to do with the changing pressures due to the choppy nature of the airflow going into the engine. Maybe it's to reduce noise, maybe it's to improve airflow and fuel efficiency. But I can't say I know these things.

 

But I have wondered why on my car there's an intake tube that has a box that has no airflow to it

Don't quite understand this. How can it be in the intake and have now airflow to it? Don't know what car or engine you have, but I have a 4 cylinder Colorado that is a 4 valve per cylinder engine. It has a box, called a "resonator" by GM in the intake track. This is to try and keep the intake pulses from being too noisy, it works until the engine is under a large load. My understanding of this is that it would be similar to a capacitor in electronics. A chamber that holds air to even out the pulses, instead of electricity.

 

I guess I don't understand what your trying to do. The friend I was talking about does cylinder head work along with a couple of brothers that compete regularly in the "Engine Masters Challenge" while they never win they do sometimes place. He also does work for local racers.

He uses the flow bench like it's supposed to be used, to test the flow in a port at a certain valve opening. And after finding that number matching the intake manifold to the cylinder port. I guess what I'm missing is what your trying to find out dumping the whole vacuum load that drastically.

That's the issue with standard flow benches, they don't duplicate the air pulsations.

Can anyone help me with recommending a controller?

 

@shortbus RESONATOR! YES - THAT'S IT! It's a box off to the side of the intake tube. I suppose it could mute certain frequencies, depending on its size.

 

That's the issue with standard flow benches, they don't duplicate the air pulsations.

Can anyone help me with recommending a controller?

Here's what I was suggesting with the butterfly in a tube. Imagine a disk inside your four inch tube. Imagine it's on a shaft. Imagine that outside the four inch tube is a gear and a motor. All that butterfly needs to do is spin. As it goes horizontal to the airflow the air moves freely. As it goes vertical to the airflow it restricts airflow. Depending on the speed in which you rotate the butterfly you simulate the airflow in an engine. One, two, three or four cylinder engines and you can simulate the airflow in each of those conditions. Unfortunately because of overlap in valve timing standard six and eight cylinder engines will be more difficult to simulate. I'd guess that you could make the butterfly smaller, thus allowing airflow at all times, but the spinning butterfly will allow greater airflow or greater restriction - depending on the size. And possibly shape. For a six or eight cylinder simulator the butterfly will need to be oval in shape and not circular.

All this is conjecture on my part. I don't KNOW this will work. But I imagine it will. As for timing - just vary the speed of the motor. Shouldn't be all that hard to come up with. 3D printing may be of value. You can print many different gear ratios and dial in on the one that best suits the midrange of the motor RPM. That way you can vary the motor speed easy enough and achieve the fine tuning you're after.

 

Here's what I was suggesting with the butterfly in a tube. Imagine a disk inside your four inch tube. Imagine it's on a shaft. Imagine that outside the four inch tube is a gear and a motor. All that butterfly needs to do is spin. As it goes horizontal to the airflow the air moves freely. As it goes vertical to the airflow it restricts airflow. Depending on the speed in which you rotate the butterfly you simulate the airflow in an engine. One, two, three or four cylinder engines and you can simulate the airflow in each of those conditions. Unfortunately because of overlap in valve timing standard six and eight cylinder engines will be more difficult to simulate. I'd guess that you could make the butterfly smaller, thus allowing airflow at all times, but the spinning butterfly will allow greater airflow or greater restriction - depending on the size. And possibly shape. For a six or eight cylinder simulator the butterfly will need to be oval in shape and not circular.

All this is conjecture on my part. I don't KNOW this will work. But I imagine it will. As for timing - just vary the speed of the motor. Shouldn't be all that hard to come up with. 3D printing may be of value. You can print many different gear ratios and dial in on the one that best suits the midrange of the motor RPM. That way you can vary the motor speed easy enough and achieve the fine tuning you're after.

 

Yes that is definitely an option. What i'm thinking at the moment is a driver like how a car PCM drives a fuel injector or vent solenoid with a duty cycle. What can i use to drive something like the how PCM does? Preferably a variable speed driver that i can adjust to my liking.

 

Fuel injectors don't work on full 12 volts. If memory serves, my wife's Toyota operated on about 7 volts. Don't ask me why I think that's the number. A little research will yield the correct voltage for whatever injector you use.

The point is that they open and close rapidly. Sounds like what you want. A 555 timer can probably be set up to give you the frequency you want the valve to open, how often it opens and how long it stays open. However, I just don't see that small an injector venting sufficient air to satisfy your needs.

 

I won't be using an injector, just referencing the type of driver i'm after. I'll look into the 555 timer

Thank you

 

Mentioned this before, the valve from an old washing machine. Operates on 120 VAC, so if you go with a 555 you'll also have to build a way of switching the 120 VAC. BE CAREFUL IF YOU GO THAT ROUTE! 120 VAC CAN BE DANGEROUS.

 

The bench will use 240v vacuum motors so i'll have what ever voltage i need available inside the bench to power everything.
So the 555 looks like it would work but i need a plug'n'play unit. I want to buy a module ( for lack of a better word) that i can mount to the bench with a rotary switch on it and a wire/s out one side that i can plug into..a modular unit i guess.

 

That's the issue with standard flow benches, they don't duplicate the air pulsations.

They also don't drop and pulse the full flow of the bench. In a carbureted engine the only place that see the more than one cylinders response is the area under the carb itself the plenum. In an modern fuel injected engine it has one cylinder per runner. So you must be working on some type of top secret stuff.

To get the pulses a normal engine sees you just need to use a engine valve sized valve.

 

Velocity stacks - - - never fully understood them.

Here's a good explanation of what a velocity stack is used for. There are formulas out there to figure the length need for a certain RPM range.

"Modern intake manifolds usually employ runners, individual tubes extending to each intake port on the cylinder head which emanate from a central volume or "plenum" beneath the carburetor. The purpose of the runner is to take advantage of the Helmholtz resonance property of air. Air flows at considerable speed through the open valve. When the valve closes, the air that has not yet entered the valve still has a lot of momentum and compresses against the valve, creating a pocket of high pressure. This high-pressure air begins to equalize with lower-pressure air in the manifold. Due to the air's inertia, the equalization will tend to oscillate: At first the air in the runner will be at a lower pressure than the manifold. The air in the manifold then tries to equalize back into the runner, and the oscillation repeats. This process occurs at the speed of sound, and in most manifolds travels up and down the runner many times before the valve opens again.

As a result of "resonance tuning", some naturally aspirated intake systems operate at a volumetric efficiency above 100%: the air pressure in the combustion chamber before the compression stroke is greater than the atmospheric pressure. In combination with this intake manifold design feature, the exhaust manifold design, as well as the exhaust valve opening time can be so calibrated as to achieve greater evacuation of the cylinder. The exhaust manifolds achieve a vacuum in the cylinder just before the piston reaches top dead center.[citation needed] The opening inlet valve can then—at typical compression ratios—fill 10% of the cylinder before beginning downward travel.[citation needed] Instead of achieving higher pressure in the cylinder, the inlet valve can stay open after the piston reaches bottom dead center while the air still flows in.[citation needed][vague] "
From - https://en.wikipedia.org/wiki/Inlet_manifold

Same thing in a smaller value is true of the length of exhaust headers and is why higher performance engines use headers and not exhaust manifolds.