ok, a little discussion on plenum design;

There is a lot of info and oposing thoughts when it comes to plenum design. Size, shape, volume, trumpets etc.

Not enough volume can effect the top end, too much volume robs throttle reponse (throttle response is dependant on using all available air to create a vacuum to suck in more faster) so there will always be a compromise between top end/throttle response.

Shape of the plenum will effect the way air flows to the runners, a straight even plenum will have air flow problems to the furthest runners, as each runner that the air passes has a gulp. This is the reasons that 90% of plenums taper from the air inlet to the back, this allows the air reaching the back runners to still be moving at the same speed.

There is also an argument for and against velocity stacks in the plenum, one side argues that trumpets inside the plenum will cause turbulence and slow the air speed down, whilst the other side of the argument is that air travelling down plenum will be fastest in the centre, and slowest along the walls (due to friction), so the air speed enterring a runner at the join of the plenum will be slower, than if the intake stack is raised off the floor.

My current design came out of a mix of all the above criteria, as well as material and space limitations in the engine bay.

However, I have now sourced some 4mm wall thickness mandrel bends, so i will be making one more final design using 4mm material all round.

The first design was made to have the maximum runner length, which lessoned the amount of taper I could use, so for the next one I will use shorter runners and a larger taper.

Original design on top, has a volume of 4 litres (not including the pod), new design is slightly larger volume, shorter runners and more taper.


This is still being designed to use with a turbo, running it NA until then is just a cheaper way of not buying more filter socks until it's done.

Comments, rants, welcome.

that new profile looks Heaps better!

if you wanted to increase the volume further, you could make the body of the plenum 100mm tall instead of 76mm, that would get you close to 6 litres.

from a turbo point of view B is the better one.


N/A i would change the entry into the plenum, and few other things,

Design B looks like some of the after market plenum chambers I have seen on the E series cars.

Cheers

ToranaGuy

Impressive work dsyfer!!!

Get her on the dyno or track and report back here ASAP...

top job mate!

i just want the 6 ITB for the au

make me some pleeeeaaasee????

The Fordmods dyno day is coming up in less than two weeks, I think we get two runs, I dont think I will have the next plenum done by then, so will run with the current one.

I am working on a new design manifold for the ITBs, I will probably make a couple when I get holidays near to xmass.

Started on the design for the turbo manifold,

To buy a merge collector ready made is anywhere from $150-$320, so I figured it wouldn't be that hard to make one.



It's pretty much two straight cuts, at a 15 degree angle, 60 degrees apart. Just need to figure out a jig so I can cut them on the band saw or drop saw.









The runners will be the same length, all made from butt weld elbows aka: steam pipe bends

I will be using a 12mm Pacemaker head flange, and using pipe through flange so I can weld both sides of the head flange (less chance of cracking)

Bit more, should work out to be pretty spot on equal length runners.

I figure it will take me less time building it scale on the computer then I will know exactly what materials angle etc, rather than pissing around tacking and untacking bends to get it sorted.

Final design for now:

12 x large radius 90 degree elbows.
6 x short radius 90 degree elbows.

So including the flange I estimate under $200 for materials.

that looks good,
it looks like the same design as the 6 boost manifold..

 

 

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I just had a good look at a 6boost picture, looks like they have 1 & 6 joining the collector at the back instead, that was the original way I planned, but was worried about number 5 getting in the way of the dump pipe.

Back onto the plenum for a minute, I just found a New Zealand site that makes plenums for RB's, they have a very similar design to mine and same construction method, so I must be on the right track. They have an RB30 with one of the plenums pushing 1300hp.

Rips is meant to be the shiz in NZ.
With your turbo manifold, is it possible to shorten the merge collector a touch to drop the flange down a bit?

yep, RIPS are top dog when it comes to anything to do with performance with the RB motors over here. Good to see the plenum work coming along nicely. I'm liking the look of this turbo manifold too, you could easily go into business making manifolds, plenums and ITB setups for the i6 guys

Keep up the awesome work