Plenums and ram pipes
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After reading though a few threads ie Joes 7 port and Rods 5 port i noticed that the ram pipes protrude into the plenum significently





Whats the theory behind this as i would have thought that this would not be ideal airflow or is it better to dirupt airflow in the plenum?

or is the heat getting to me

mine are like that as it was easier to do it that way,

there are some good pic's of flush stuff here, as you'd expect they are flush...

http://www.rossmachineracing.com/20vVWintake.html

Putting a proper stub stack type inlet has the same benefits in a plenum as it does in an air filer. Although having squared off edges like the two shown will not be as good as a stub stack or ram pipe design.

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I use these bellmouths, basically because the yelow bible suggests that it is one of the best shapes.



They stick into the plenum by about 30mm.

Coupled with a long runner, I seem to be getting good torque from low down on the 998T.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

where are they from Paul?

I machined them up from solid.

I recently made these for the 1293T:


A bit more here:

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Missed alot of your thread Paul bloody clever stuff!

Thanks.

I'm not sure why I put the bellmouths towards the middle of the plenum. the triple injector manifold is Version 15 of my designs. Version 2 had the bellmouths in the same place.

I must have read it somewhere, but can't remember where. I probably plaguerised TDs design :)

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I used them on mine as I read that the bell mouth design helps to keep air speed up as it changes direction. Sharp edges cause masive losses in air velocity.

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1/4mile in 13.2sec @ 111 terminal on 15psi

My machinist made an error interpreting my drawings, so I ended up with a comprimise to recover from said mistake, but, there is a 6mm radius leading to a bell mouth almost the full length, so it at least has to be better than just a straight 38mm opening :)

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Edited by Sprocket on 24th May, 2010.

http://www.minifreunde.at/harry/links/inletsystem.htm

Harry

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I didn't spot this when it was first posted....

The main reason I did mine the way you show in the first photo is that I'm copying (as far as possible) the Cossie design for all my injection system and they stick into the plenum/airbox.

However, the Cossie ones are much more rounded bell mouths than the ones I machined up, but mine is only a trial so far.

Also, it is a common modification on the Cossie to fit a spacer plate between the two halves of the plenum/airbox which would make the (four) inlets less intrusive in the box. It's not clear if this works because of changing the airflow into the trumpets or because of the increased size of the plenum.

I personally tend to think that once the plenum is under pressure (ie, boost) the exact shape becomes less relevant.

Having said that, I have built in a splitter plate (which you don't see in the photo) to ensure equal distrubition to the two runners......

Schrödinger's cat - so which one am I ???

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Yes, the rules still apply - my simplistic point is that on a normally aspirated engine the pressure difference (which drives the air mass flow) would be very low at that position and can't be increased, so optimizing the flow regime is very important.

Once you have forced induction you can compensate for poor flow just by increasing the pressure difference. I agree optimizing the flow path has to be beneficial as less boost will be needed to achieve the same mass flow but there are a lot worse restrictions in my nightmare of plumbing.

A good example of poor design in my case - and probably most standard factory items - is to look inside the intercooler header. Pretty much the same principle as the plenum, a large box feeding smaller tubes. The tubes are rectangular and pressed through the endplate leaving a small upstand and it is all sharp square corners.....

But back on the original point, like Paul, I too think I have read somewhere about having them protruding into the middle of the plenum but this can surely only give an advantage if they are fully radiused all the way around to the back (as Paul's first photo) which I did not attempt to do.

Final point, by having them protrude in, the runner length becomes longer for the same physical size of plenum and longer runners are supposed to improve torque.

Schrödinger's cat - so which one am I ???

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Interesting Robert,

Do you know if that is measured or computer modelled ???

And under steady state (flow bench) or real individual pulses ???

At least the ram pipes / stubs, whatever you want to call them, protrude a fair way into the plenum....

Schrödinger's cat - so which one am I ???

Well, this is the current state of the Miglia Turbo inlet:



As soon as I had tacked on the end plate, I realised that I need to change the design and move the TB plate further back with a taper from the plate to the plenum body. Never mind.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

What volume are you using inside there Paul ???

I've worked on 1.3 - 1.6 times the engine capacity which I've read on here and other sites is the optimum for forced induction but it is giving me lots of problems fitting it all physically in.

Yours looks smaller overall (although obviously a photo can be very deceptive).

Schrödinger's cat - so which one am I ???

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Schrödinger's cat - so which one am I ???

Schrödinger's cat - so which one am I ???

I guess that it is a constant flow simulation in CFD.

Any fluid in motion has a finite energy, either velocity or pressure or a combination of the two. If you speed it up, the presure will drop, converting pressure to velocity energy. If you slow it back down again, the pressure will return. That's why the pressure is higher at the trumpet furthest from the inlet.

It looks very fancy, but I have a distinct impression that they are not seeing a true picture, as the inlet velocity looks higher than the port velocity, whereas in reality the peaks would be much higher in the ports.

Edited by Paul S on 29th May, 2010.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Well it looks like Version 12 of Ansys CFX does transient simulations. I'm sure than when I looked at V9 it did not.



That means that you can put in time based boundary conditions rather than fixed flow or pressures.

I wonder if you could use it to identify the pressure pulses by including the whole inlet tract? I doubt that it will allow you to add a pressure pulse boundary condition in addition to a flow pulse. Maybe.

I'm tempted to try this on my manifold, just to identify if I actually do need to modify it. After all, this is similar to what I do for a living, so should not be too difficult.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."