Nathan's Road-Legal/Track BB4

[NafemanNathan]

Ok .... Here's another simpler explanation I've just found that I wish I'd found before pasting that other lot

Also I've just found out that Acoustic Supercharging is also referred to as "Resonant Conditions"...

Visualize the intake cycle of the engine as air flowing through the intake manifold runner, past the intake valve, and into the cylinder. Everything is fine and dandy until the intake valve shuts.

Here is where the law of inertia comes to play -- because the air was in motion, it wants to stay in motion. But the air can't go anywhere because the valve is shut so it piles up against the valve like a chain reaction accident on the freeway. With one piece of air piling up on the next piece of air on the next on the next, the air becomes compressed. This compressed air has to go somewhere so it turns around and flows back through the intake manifold runner in the form of a pressure wave.

This pressure wave bounces back and forth in the runner and if it arrives back at the intake valve when the valve opens, it is drawn into the engine. This bouncing pressure wave of air and the proper arrival time at the intake valve creates a form of supercharging.
In order to create this supercharging, all of the variables have to be aligned so the pressure wave arrives at the intake valve at the right time. This combination of synchronized events is known as 'resonant conditions'.

[NafemanNathan]

Very good info there bud.

I've touched on it a little before when I was looking into intake manifolds - the term 'supercharging' did somewhat catch my eye. But the explanations you've found are well described. As said though - good luck trying to achieve it without a mad scientists laboratory!

The only thing I wondered is why they design the back of the plenum flat (give or take the curve) to aim the sound wave/pressure back into the same runner. I assume it's the easiest way to do it and calculate it. I would think utilising this sound wave to the next opening valve would be the most efficient but I guess you'd end up with a jagged back plenum to bounce them into different directions which wouldn't be good for the flow of air in from the throttle body. So I guess I just answered my own query there!

Good to see some research going into this. I would question though whether you really need to keep the IAB's or not? If your remapping then your general increased airflow should compensate overall. Why do you think the more powerful Type R engines don't have them in the teg and accord? Would certainly free up some design ideas and make it easier for the guys to fabricate. Be interesting what you go for in the end whatever though.

I think the bodged looking one I posted where they welded onto the runners would be quite good in theory. I've also wondered about channelling the airflow into a vortex to spin around the inlet, into the plenum and down into the runners more efficiently. I've seen spacers that attempt to do a similar thing but don't know how effective they are. Do you understand what I mean?

Cheers,


Rob

[NafemanNathan]

Funny you should mention the vortex... Already on it ... and literally just kicked out a very rough design which also (possibly) utilizes the whole "Acoustic Supercharging" theory May even put a nice "twist" on the sound it produces to

Like you said, rebounding the pressure back down another runner would cause other issues. The hardest part about the whole theory is that you can only take maximum advantage (the peak if you will) at a certain rev range depending on the length of the runners and distance traveled back in the plenum. I have an idea involving a vortex and "a particular shape" ( ) that could simplify the entire theory and also peak over a broader rev range

My initial intentions was for whatever I designed to be suitable for a standard engine build (bar breathing mods) which would also include using a standard P13 ECU. This was because it would appeal to a broader market (being most BB1s and BB4s still use the standard P13 whether it's chipped or not) and also fill a gap in the market (being it would still have IAB functionality) for Dale to actually go into production. The more I look at it though, the more I think I might have to be selfish this time and design this one purely for my own build without the IABs

I guess this could always be a prototype ... I'd need to get a basic manifold dialled before advancing to IAB functionality right?

[NafemanNathan]

Ok, I've read this over and over. It goes in and I understand this but my mind boggles over the testing of this or even the equations to work this out mathematically. (Excuse me if some of this is in the clicky bits, not read them yet)!

Surely to test this it would be somewhere within the design process of all this. Some sort of sound wave gauge and precise air flow etc!!! Also along the lines of Type R I know a lot of money (and time) is spent on the intake processes.

Hmmm the mind boggles. =D> A bloody interesting read =D>

[NafemanNathan]

Here's a sum for you then ...


720 degrees - 288 degrees of cam duration = 432.00 degrees of crank rotation the the intake valve is closed.

3500 rpm / 60 degrees (full revolution) = 58.33 revs per second

58.33 rps x 360 degrees = 21000.00 degrees per second

432 degrees / 21000 degrees per second = 0.02057 seconds that the intake valve is closed @ 3500 rpm.

Pressure waves travels 1125.32808 feet per second

1125.32808 fps x 0.02057 seconds = 23.15 feet that the wave will travel before reaching the intake valve.

23.15 feet / 2 (up AND down) = 11.57 feet required.

11.57 feet x 12 = 138.89764 inches (=3528mm)

So basically I have to divide this number by a whole number (which will refer to each bounce of the pressure wave) to give me a distance from the closed valve to the next surface (Normally the back of the plenum).

Obviously this distance will change depending on the RPM I decide to peak at, so I need to find that out before I bother dividing that number.

On the otherside of things, I actually have a colleague who has a magazine with an article on how to build your own flow booth, so I think I may end up following that up to

[NafemanNathan]

im sure carol vorderman joined on here just the other day

If i remember correctly mazda have something pretty clever to do with vortex's and acoustic supercharging on their small v6 engines they put in the 323, 2.0l i think. Will have to have a read up again.

[NafemanNathan]

Cheers for that mate... I shall have a gander

EDIT:Or was that by chance the Mazda "Vortec" intake manifold?

[NafemanNathan]

Best link i've found so far is this http://en.wikipedia.org/wiki/Mazda_K_engine
Will have a better look later.

[NafemanNathan]

Brilliant! Cheers for that!

Acoustic supercharging has so many different names!

[NafemanNathan]

A more technical link about the mazda k series engine
http://www.tsentraal.ee/mx6/engine/SAE920677.htm

just sat for about 2 hours reading every post for the whole 27 pages lol

and im very impressed .. been some up and down but your lude looking amazing under the ****

not to sure about the patchyness of the pannels but its your choice,

i would have keept it all red

love this thread