Plenum Theorum

[Adam]

Thread cleaned.

Could we please keep this factual and informative about the original subject.

Ben started a good thread in hope of getting some good info, can we try and keep it that way.

Thanks.

[F6 UTE]

Thread cleaned.

Could we please keep this factual and informative about the original subject.

Ben started a good thread in hope of getting some good info, can we try and keep it that way.

Thanks.

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Cheers m8.

I'll peruse tomorrow, when I've recovered from the eagles loss

[ebs_4l]

what, I ask for actual calculations and I get my post deleted??

all I wanted was to separate the theory from the technical data

[F6 UTE]

Thanks DW, and others for posting.

Spiko, cheers for the pix, yours looks like a hefty piece of kit. Nice. It looks as though your design is the shorter runner approach, with decent volume..

It also is a design I have contemplated- ie resembling that of an intercooler end tank..

GTjake, there are not really many websites dedicated to the subject, as an example of what we see happen in this thread. Everyone has different views on what is needed, what's deemed necessary, and importantly, what Spiko mentioned, what works for the individual, and there setup.

I would also like to know if the 27hp gain from Simon Gs' plenum on an NA was including a tune, or just bolted on, and not tuned. Then what was the difference with a tune + plenum Vs Tune only on an NA??

CHeers guys.

[aiboart]

Just thought the other thread was starting to detract from the purppose of it's incarnation, so started this one.

Plenum design discussion..

No where do I expect someone to disclose there volumes, dimensions or the like, but an open technical discussion should be an interesting read.. Thoughts and opinions are free.

© Helmholtz resonance effect. This is a phenomena which occurs when tuned length runners are used to increase the volumetric efficiency of the engine under NA conditions to over 100%. This produces a very strong pulsing effect within the plenum.

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<edited>.... I have nowhere seen anyone relate to Helmholtzs' theory openly in a Ford Forum, or relating to these cars. I see Simon G alluded to it, without actually mentioning it one time. It makes me think he used the formula to some degree, with engine dyno testing to come to a final spec on his plenum design.

I have seen no real literature to support the use of the formula in boosted applications. Plenty for N/A, as you mention.

One reason being, will the return pulse from the intake valve be enough to overcome the ~20psi in the runner, and the forces directed against it?? I am not sure, but every reaction has an equal and opposite reaction, so maybe, atleast untill the pressure in the runner is equal, then yes, maybe a return pulse?? I assume the benefit would be small, but worth looking into. Not that hard to work it out..

Also, tuned length gets bandied about alot. Well, tuned to what length?? Bottom end, midrange or topend??

Alot of guys pride themselves on there 'tuned length' manifolds, or extractors, (which are more commonplace) they have bought, but to what rpm range are they tuned to?? Are they aware if they even meet there own requirements? Does the 'tuned length' of the intake runners match the exhaust, if it's been done??

....<edited>....

Runner Length. Short runner are good for top end, longer runners give excellent torque down low, this is fact, not an opinion.. I am waiting to see a Nitto plenum back to back on a Ford Lower half and aftermarket upper half, of any brand.

If the XR6T revved to 8500rpm even 9k, as Jap 6's do, I would call it a winner. There powerband is alot higher in the rpm range than the Barra engine, and they predominantly boost late. They also launch VERY hard at the drags, generally on antilag.

But the design, in my opinion is based on upper rpm, which some people will be looking for, so it will fill a market neiche..

My only arguement to this, I've experienced better results looking at peak torque, and where it occurs ( lower rpm ), as opposed to peak power high in the rpm.

<edited>

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What effect does the variable length intake runner system have in the turbo? As per the above post, tuning the intake lengths has positive effects on a NA application and therefore being able to vary the tuned length is a undisputed good thing to do in a NA variable speed (car) engine.

However, I understand that the variable length runner system is turned off for our XRT/F6/TT applications, why?

1/ it doesn't matter in this turbo application

2/ it does matter

3/ it matters but the effect of boost is overwhelming

4/ it matters, the effect of boost is overwhelming, except when the engine is running at low boost and low rev

5/ it matters at low boost low rev conditions, however the extra volume of long runners improves cylinder filling whilst inducing runner fill time lag, so there is a net zero effect trade off involved

6/ it matters, but the effect of variable boost and intake temp creates a variable compression wave velocity in the intake runners, which in turn creates a variable resonant frequency that is difficult to tune.

7 it is a factory fitted power/torque restriction device

8/ it is something the factory is keeping in reserve for as part of a staged model upgrade sequence. (as per the independent variable valve timing system?)

9/ there is so much other tuning head room and low rev torque with this turbo application no one is bothered with further improving low rev, low boost, (eff. NA performance)

10/ there are other variable involved

Regards,

aa

[phildub]

I believe Simon did bring this up in one post and believes this would help economy in the T. Torque once turbocharged, I think you are right be saying

"3/ it matters but the effect of boost is overwhelming

4/ it matters, the effect of boost is overwhelming, except when the engine is running at low boost and low rev. "

I guess Ford decided that there was little point as the engine had already meet its design parameters, so there was little need to improve it further.

I think you will find that XLNT6's Helmholtz resonance effect,is fairly accurate and tested and maybe not theory any longer.

It seems funny that engines like Honda's v-tecs that rev to well over 8500 and make 100 hp plus per litre still have quite small plenums they are still made from thick cast alloy while less powerful cheaper cars are now plastic something I also think also simon posted about having a ridget plenum.It would also be cheaper than a high expence composite.

[Guest]

what, I ask for actual calculations and I get my post deleted??

all I wanted was to separate the theory from the technical data

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that's ok I had my pyhagoris plato and aristotle vs columbus micheal angelo and mozart deleted too!!!

and that was at least hilarious!!!!!!

[F6 UTE]

what, I ask for actual calculations and I get my post deleted??

all I wanted was to separate the theory from the technical data

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that's ok I had my pyhagoris plato and aristotle vs columbus micheal angelo and mozart deleted too!!!

and that was at least hilarious!!!!!!

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It aint so funny woggie if it weren't true.

On my mock up 'jig' I have written on it

" E=MC2 "

I am serious..

lol.

[turbotrana]

I'd like to see Nizpros 27hp increase from their plenum independently tested.

The E series Falcon have both the broadband manifold on the EF onwards and the single band manifold from EA to ED. Both give very similar peak power. This has been shown many times over. The single band manifold has some similarity in design to what Nizpro have on offer. Ford may not always do things because of cost/time restraints but I certainly believe if there was a 27hp increase from a manifold, Ford would want to hear about it and use it in their production engine.

Edited 10/09/06 03:48 AM by turbotrana

[Guest]

It seems funny that engines like Honda's v-tecs that rev to well over 8500 and make 100 hp plus per litre still have quite small plenums they are still made from thick cast alloy while less powerful cheaper cars are now plastic something I also think also simon posted about having a ridget plenum.It would also be cheaper than a high expence composite.

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I'd watch what you say as this is far miles light years away from the truth!!!!

the humble hyundai and daewoo plastic shark skin intakes can and do show the honda cast manifolds a thing or two!!!! this from as early as 94 production models!!!