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Engine Specific Info and Questions => IDI Engine => Topic started by: kane66 on April 24, 2009, 10:28:11 pm
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I've been following the jetta project 200 thread. And was really impressed by his plenum intake. I've also looked at the custom plenum the "935racer" offers. And I was sure that that is what I wanted. But I thought I would do a little research about how the fluid dynamics of a intake manifold works. I stumbled across this great thread where someone with more money than I built a custom plenum for his nissan. He did a lot of CFD analysis of his design, and also included a couple showing the fluid dynamics of a couple other intakes. One of them resembles the style of plenum both offered by 935racer and built by TurboJ. According to the CFD it seems that that plenum would deliver more air to the #4 cylinder than the #1 cylinder. Anyway wouldn't a design similar to the one built buy the guy on the Nissan forum provide more even flow to all the cylinder. Anyway heres the link.
http://forums.hybridz.org/showthread.php?t=127863
18 pages of reading but well worth it in my opinion. Any Ideas anyone
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the difference I see is that the dual plenum manifold you linked to uses a diminishing primary plenum and a consistent width transition between the two plenums.
the one used on the jetta 200(if I am not mistaken) uses a consistent sized primary plenum and a diminishing size transition between the runners, which accomplishes the same thing, but is easier to manufacture without specialized tools(the math is also easier)
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I don't know if I understand what you mean by "diminishing size transition between the runners" are the runners in the 1Y intake manifold different diameters, or different lengths. If you look at page 8 on the nissan forum you'll see the unequal air flow.
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no, the slot connecting the two plenums.
one has a consistent width slot and a tapered plenum and the other has a tapered slot and a consistent plenum
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libbybapa you beat me to it :lol: I was just about to ask the same question.
also it seems to me that the plenum slot is all the same width. The shot is from the end of the tube so Its hard to tell. May be the builder will chime in with a answer.
pic link of manifold in question
http://s232.photobucket.com/albums/ee303/TurboJanne/Jetta%20II%20TDIC/Tekniikka/?action=view¤t=P1000089.jpg
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I have done some looking on this as well. I have seen both styles, the straight slot and one where the added intake tube actually has a taper like a cone to ensure constant velocity across all of the runners. In my searching I have not seen the formula to figure out correct sizing. I should go see my old applied physics teacher from high school who just loves to play stump the chump with odd ball problems like this.
edit
I just finished reading the entire post of the build fr the dual plem that guy monster built. DAAAAAAAAAA-UUUUUUUMMMMMMMM!!!!!!!
Someone needs to interest that man in vw diesels!
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I've also seen a lot of different manifolds, but I've never seen any numbers showing exactly how much better these "upgraded" manifolds work. I'm sure there better than stock but were's the proof. For 600 dollars I sure would like some kind of proof. I haven't even seen any dyno runs with side by side comparisons "hint if anyone has any". That post was the first time I've seen any real hard evidence about how the shape of the plenum affects air flow.
I also agree that someone should get this guy interested in vw's.