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Re: Intake manifold volume and design


JNR
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Galant VR-4 org Post #: 543477 posted 10/03/07 11:29 AM     Remind Me!  Send Private Message   Edit Post      
OK, here's a crude sketch, to give you an idea...note it is not meant to represent any proportions, actual workings of the 'flapper', etc. and should be treated only as a diagram...also, it is not 4G63 specific.




BTW - can anybody convert a PDF or TIF imagine into JPG, for a better quality? I don't have any graphics programs here! Edit, nevermind, it came out *OK* for now; just don't blow it up, lol.


Edited by JNR (10/03/07 11:31 AM)

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Galant VR-4 org Post #: 543482 posted 10/03/07 11:32 AM     Remind Me!  Send Private Message   Edit Post      
^sure can, but that one is a jpeg. you got another one?
edit:NVM



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Edited by VRausch4 (10/03/07 11:33 AM)

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Dialcaliper
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Galant VR-4 org Post #: 543483 posted 10/03/07 11:33 AM     Remind Me!  Send Private Message   Edit Post      
Actually, a lot of modern n/a cars use dual stage, or even triple stage intake manifolds. On a dual stage, the fact that both runners are open is intentional. You don't get the same oomph at high end that you would from a large single short runner, but having two different runners open actually gives you *two* additional wave tuning frequencies, not just the one from the short runners. That's why the cyclone opens around 4700-5000 RPM instead of waiting until much higher RPM (6000-7000). There's not good way to have a rapid changeover without cutting off airflow and creating funky effects. The extra runners have to shut off at low RPM so that the intake velocity isn't too slow, which would hurt low end torque. At high RPM, there's enough airflow to fill both sets up runners and still keep the speed up.

So ultimately, the cyclone should give you a bit more low end torque than the stock manifold, and a total of 3 tuned RPM ranges, but because of design comprimises, it will still be inferior at the top end than a single fixed short runner design. A Triple stage intake would give you either 5 modes or 6 modes, depending on how it's designed (two runners open at once or all three open)

If you had larger short runners and a second set of butterflies to close the short runners, you'd have better top end, but your midrange would suffer during the changeover period.

The other way to do a multi-stage intake is to have adjustable trombones (probably stepper motor driven, or vacuum driven against a spring with a ) to increase the runner length at low rpm and shorten it at high RPM, but the compromise in that situation is that you can't really shrink the runner diameter at low RPM.

I don't think anyone's come up with a truely variable geometry intake yet that can vary both adjust length and runner diameter. If they have, it's either custom, very expensive, or both.


Quote:

As a general rule: The longer, smaller diameter runners are beneficial to low and mid-range power (mainly torque) and short, larger diameter runners are for higher rpm power (horsepower).

so, a true dual runner intake would have a 'flapper' that would close off the short/large runners until a higher rpm/load (depending on how you set it up) and when it hits that variable (rpm), it opens the short/large runners and closes the long/small runners, giving it the best of both worlds...In a good design, it would have a 'fail closed' on the short runners, so in the event of failure, it goes thru the long, giving it better drivability, etc.

A Cyclone manifold is a dual runner design, with compromise for the sake of simplicity...Yes, it shuts off the shorter runners, but when it opens, it still uses the long runners and the diameter of the shorter runners is not that much bigger.

(I'll see if I can find a good pictorial of this)





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Edited by Dialcaliper (10/03/07 11:35 AM)

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Galant VR-4 org Post #: 543487 posted 10/03/07 11:36 AM     Remind Me!  Send Private Message   Edit Post      
^ didn't Bimmer have a variable length intake runner set up? no diameter change, but runner length?



Rance lives here...
Founder of Sold out to BMW Cru, then sold out there too.


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Dialcaliper
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Galant VR-4 org Post #: 543494 posted 10/03/07 11:44 AM     Remind Me!  Send Private Message   Edit Post      
The most commonly available aluminums these days are probably 2024, 5052 and 6061.

A lot of BMWs have multi-stage intakes. The 330i I think has a triple, and some of the pricer ones might have variable length runners.

A surprising number of cars have them these days. A lot of the fancy names for engines actually refer to it. (Mazda "VICS/VRIS", Porche "VarioRam", Ford "Duratec", even Hondas and a whole slew of other brands that didn't name the engine after it.

click

Edited: Yeah, I meant 5052, not 5054



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Edited by Dialcaliper (10/03/07 12:14 PM)

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digit
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Galant VR-4 org Post #: 543496 posted 10/03/07 11:48 AM     Remind Me!  Send Private Message   Edit Post      
I think you mean 5052, 5054 is not that common, at least on this coast it's not.

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Galant VR-4 org Post #: 543497 posted 10/03/07 11:48 AM     Remind Me!  Send Private Message   Edit Post      
^ oh yeah, the SVT has a variable intake...oops.
no production variable diameter though, eh?



Rance lives here...
Founder of Sold out to BMW Cru, then sold out there too.


Posts: 12049 | From: Cleveland, OH | Member Since: 12/21/04 | IP: (64.118.153.66) | Report this post to a Moderator

JNR
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Galant VR-4 org Post #: 543500 posted 10/03/07 11:58 AM     Remind Me!  Send Private Message   Edit Post      
No doubt the way I drew the sketch would not work, as you mentioned the changeover to completely off to on would cause some turbulence, etc...However, I think with the right design and/or progressive linkage, it could be done.

There was an aftermarket Ford "5.0" manifold (kind of like the GT-40) in the early 90's that had a neat approach to the dual runner design, but I can't seem to find it right now...And, yeah, there have been a few factory examples, but I think a true functioning manifold 'design' is out there and IMO, give you some great overall results.

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Dialcaliper
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Galant VR-4 org Post #: 543516 posted 10/03/07 12:25 PM     Remind Me!  Send Private Message   Edit Post   
Now that I think about it, one way to circumvent the variable diameter problem is what Honda did with VTEC - having a low-lift cam profile doesn't help you with runner airflow velocity, but it does help with air velocity into the cylinder, which helps your low end torque (maybe not as much as having the airflow velocity through the whole runner)

Quote:

^ oh yeah, the SVT has a variable intake...oops.
no production variable diameter though, eh?





1269/2000 Summit White

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