dual plenum intake,yes or no

[Rikki Kitto]

With JP

[repo]

Android won't let me edit. I ment #35

[repo]

See post #36

[grundey]

CFD shows that the shape of the slot doesn't matters, I tested a simple square edged cut, it actually woks until it's a restriction.
How do you test those dual plenum intake to determine is it good/bad?

[AndyP]

The Jenvey one when testing one of the universal mitsubishi evo ones is one of the worst I ever tested.

My wallet just breathed a sigh of relief as I read that

[JP]

Now my 2p.

Single plenum intake great when volume is great enough to allow even distribution. This can only happen with perfectly radiused matching trumpets into the plenum floor. So volume has to be large. Now large volume means turbo has to spin more and for longer to make same boost pressure as manifold of smaller volume where cylinders see airflow from turbo sooner at set pressure.

So to make use of the oversized plenum one has to think as the engine and turbo as a compressor with a surge tank and airtools attached via pipework. Stand at beginning of quarter mile. Launch control, build up boost to desired level, surgetank stores pressure (intake manifold), desired pressure is reached and launch. By having a large plenum stored with pressure it is now easier to maintain constant pressure throughout the 1/4mile providing the compressor is large enough to exceed flow requested by the engine.
Fit a smaller turbo to this and now the engine empties the tank faster than the turbo can fill it causing gradual pressure drop.
So in a situation where you want a car to be fast and responsive like hill climbing rallying, circuit etc.... a large plenum suddenly becomes less than ideal.

So we go to the smaller plenum where the engine see's the flow from the turbo quickly. Boost builds up quick but the higher air speeds now cause turbulence that creates uneven cyl flow. Uneven cylinder flow means your engine is not running as smoothly as it can and this is represented in a lower torque figure. If each cylinder is operating 100% equal you end up with maximum torque for the application.

So this is where a dual plenum intake comes into play. It's a way of distributing airflow through the plenum on a small plenum design where the runners are more directly effected by the airflow entering through the throttle body in order to distribute it evenly across all cylinders giving a best of both worlds fast response and max torque delivery.

There is however very few proven good quality twin plenum designs out in the market place and the reason being is the transition between the primary and secondary chambers causes turbulence in it's own right. It is this transition that is the make and break of the manifold design. Firstly the volume that is allowed to pass through the partition is very important relative to engine turbo and pipe/tb size. Secondly the actual shape of the transition is very important. Just a slot is not the way to go about it as it introduces more turbulence than you are trying to get rid of. Just because the manifolds look the same on the outside doesn't mean the functioning components are the same on the inside.

Repo's is one of the better ones out there based on what I have seen of the internals cpl years back. The Jenvey one when testing one of the universal mitsubishi evo ones is one of the worst I ever tested. They will all however make similar peak hp figures as this is determined by the overal compresser flow providing cam head exh mani etc are all correctly matched. The difference is where it makes peak power and how long it stays in it's powerband as this will show the effectiveness of the manifold design and it's distribution amongst the cylinders.

I personally decided to make my own as wanted to do something different from what was available of the shelf. A lot of development time went into it with not flow testing but airspeed testing under pressure and cyl distribution. Didn't really care what the flow figures where as they here going to exceed anything that the I5 head was capable of maxed out anyway so it was never going o be a restriction and distribution and airspeed was king.
My final design came out better than anticipated (revision2 after some flaws where highlighted in version 1) not only do I have 1bar boost from 3250rpm I hit peak well before 4k and redline with no drop in pressure at 8200rpm. With a pretty flat power curve for almost 4000rpm. Car drives lovely launches hard ******ed my twinplate over the winter so of the road till further notice . However the benefit that wasn't expected on the first version as wasn't shure if tuned runners/air shockwave pulses etc would work on an fi engine. It did by bouncing the runner shockwaves of the back of the secondary plenum wall I managed to get increased cylinder filling at key points such as puling away, coming on boost and peak power area (although the latter was of by 400rpm of the exact peak due to a slight misscalculation).

For me I'm happy I went dual. No I don't want to make more. And in answer to the op's question if you buy a tried and proven developed item then the answer is 'YES'. If dabbling into territory that is not your forte though you can do more harm making one yourself than actually just keeping the stock setup ported.

JP

[repo]

It's purely because the flow in the plenum is not static. There is a mixture of pulsation, fuel vapors (changes in density and pressure changes due to liquid boiling), temp changes and boost fluctuations, the CFD can't predict.

[JP]

I have been doing CFD studies for while on dual plenum intakes. My data shows that it doesn't actually flow that well as many think. On a flow bench it wouldn't compete any better...But the magic is there and has nothing to do with flow... When flow is needed go for a single plenum, it can flow a lot.
Some shots of my flow simulations


P.S. Lehmann WRC 1.8T engine had 300hp and well over 700Nm....

I the past found that flow simulations and bench testing give improper results to relate to real life use. There is several manifolds on the market that have been developed in this manner and all the data looks really impressive. Then you bolt it to the car and it missfuels across cylinders and causes excessive lag due to extra turbulence introduced due to incorrect trumpet and plenum configuration.

[JP]

Have you seen Dutter racing new intake? Much more "simple" design and a single throtle body ( last year he had ITB's). Also he is making 1000+HP. Sorry if it's off topic

Love the idea behind the dutter one tried and proven concept when executed correctly. however he has 2 major flaws in the design. Middle cylinders will get more direct airfeed than outer cylinders unless internal baffles are present inside the plenum. secondly edged of the trumpets are sharp edged causing unnecessary turbulance reducing the effectiveness of the trumpet stacks

[JP]

For 550HP AAN intake manifold works well, very good twin plenum you can buy such jenvey one:

One of the worst ones I've ever tested! so much turbulence on transition between plenums meant the only way I could balance the flow was by running uneven trumpet stacks during testing.

[repo]

I feel like getting provoked by this guy, but perhaps better not.

http://www.quattroworld.com/wp-content/uploads/2012/05/Kuva-081.jpg

1450 eur

[vti2]

No is Not booring, because you can run it every Single day without Problems. Don't Need a 1000HP Monster wehre i have to pull out The Engine every weeckend.

[Thuppu]

It is alot more complicated has the most people thing, a dual plenung manifold will reduce velocity from the air being pushed to the engine and will also be able to distribute the same air better to the cilinderhead, throtle response will be better, another efect is that by reducing velocity the air get´s cooler, you can run more timing, this will produce more torque and HP and a better driveble powerband.
Most of the guys foget about how power should be delievered by the engine, they only matter about peakpower, for me doesn´t make sence to have 800+hp for only 500rpm and the rest of the rpms only 400, it doesn´t drive good.
Dualplenung is all about drivebility, throtle responce and torque.
On the track or street you will outrun a bigger HP lazy bitch :-D

Well, all depends on what you wan't and need. If you build a mile racer for 330+km/h or for 1/4 drag race you may need 1000+hp. And 1000hp from a 2.2l engine cant be delivered with a large power band. I'm sure OEM guys are pleased with their mapped stock setup or RS2'd setup. 500+hp with HX35S on street is a very nice and responsive setup and also great for trackdays, but quite booring in the end.

[Vorsprung durch Technik]

Most of the guys foget about how power should be delievered by the engine, they only matter about peakpower, for me doesn´t make sence to have 800+hp for only 500rpm and the rest of the rpms only 400, it doesn´t drive good.
Dualplenung is all about drivebility, throtle responce and torque.
On the track or street you will outrun a bigger HP lazy bitch :-D

I can't agree more!

[diesel des]

Repo can you post some more pictures of yours and costs please?

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