what is your opinion on my intake

[Dannyho]

I have had the idea to build my own intake manifold/plenum and have come up with a design that I like aestetically, I designed it on a cad program and would liker to know what problems might be in the design. the runners are long enough for the tuning i want, but I should stress that this was made without any measurements of the engine, so sizes and spacing are not in any way final. ie. the "throttle bodies are wayy too small. I'm just looking to see what the experienced guys think about the geometry of it. for instance, plenum volume too large maybe? or if the cross over pipe is even necisary.
I hope this can spawn a good discussion of intake design as well.

http://www.padlockhost.com/images/manifold.GIF

http://www.padlockhost.com/images/manifoldtop.GIF

thanks,
Dan

 

[patprimmer]

It seems unnecessarily complex.

Why not just copy OEM systems.

I see no reason for dual plenum.

There is no detail about throttles or about entry from plenum to runners, both of which can have a large impact on performance.

For multi point EFI and individual port runner throttle plates, the plenum size is not so important so long as it is big enough.

If you have throttle bodies on the inlet to the plenum, the size of the plenum can reduce throttle response if to big.

Individual throttle bodies are a major restriction to flow unless very carefully designed and sized.

Drag racing has generally shown more power by using tunnel ram manifolds with an injection hat. This gives individual runners, large single plenum and a very large throttle body into the plenum, but response is not an issue as they can bring up the revs before the light turns green.

Sprint cars and where allowed, circuit race cars use IR manifolds with individual throttles close to the valve.

Virtually all, normal production cars use a single throttle body to the inlet of the plenum.

Regards

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[xnicke]

I think you missed the point Pat. I believe it is supposed to look "cool" and hopefully work as well?
I´m far from being an expert on this, but my guess is that your plenum will work ok. I guess a volume of about 1.5-2 times the engines is normal (not sure about this though, just guessing).

 

[patprimmer]

But this is an engineering forum, not a stylists forum.

Regards

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[ornerynorsk]

Hood clearance?

 

[xnicke]

Pat, i agree. However, the design was due an aestetical point of view but the question technical.

 

[patprimmer]

Sorry Nick, I forgot the smiley.

The comment was meant tongue in cheek.

To combine the twin plenum's into one would not alter the height.

I am concerned about the transition from the plenum to the runner, and the excessive change of direction in the runners.

With a lack of detail, just taking a wild guess, the runners look very small diameter and VERY long, thereby making maximum power at quite low rpm, like maybe 3000 to 4000 rpm

Regards

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[Dannyho]

yes, the design looks a lot more complicated than it is. OEM designers have the added bonus of being able to make a mold for a part and having complicated surfaces inside of their intake. In this design the radii of the curves are all sizes I can find and purchase myself, and every curve is planar- there is no spiraling. that way I can cut the pieces and assemble it myself. The intake is a part of the engine that most visible and aestetics do play a role. As far as hood clearance. once i get measurements to work from I can design to that, but like i said its not the numbers I'm concerned about, its the geometry. I have all the formulas for tuning the runners, plenum, throttle bodies, and it's all pretty plug and chug.

in reality all 8 runners have the same parts to them, so its actually very simple, there are basically 6 parts to each one, and it will be easy to merely duplicate them each 8 times as opposed to having different designs for each one.

Does anybody know the usefulness or effectiveness of the cross over pipe, It will equalize the pressure in both plenums, but how necisary is this?

 

[GregLocock]

I imagine that would rather depend on the firing order of your engine.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Dannyho]

what are you referring to when you say it would depend on my firing order? all those numbers or the effectiveness of the cross over pipe, and if it's the pip, please elaborate

 

[Fabrico]

It should work OK. As far as tuning, the runners are kind of long and may provide a little extra pep in one area and a little disappointment in another. Separate plenums require precise matching of everything else. The smallish crossover won't go far in evening things out. Surely, one more ornate, full diameter, ramshorn tube can be added around the back or over the top.