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Scratchbuilt L6 EFI Intake Manifold


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#21 RTz

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Posted 14 March 2008 - 12:47 PM

Monzter was kind enough to run a CFD analysis on the proposed plenum revision. The goal was to improve three areas... entry into #1, 3 and 4, while reducing the swirling mid-plenum. It seams reducing the swirling was the only item that became 'reality'... it was also of my least concern.


Velocity chart at 20psi...


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Thanks again Monzter!
Regards, Ron

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#22 RTz

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Posted 14 March 2008 - 08:51 PM

Monzter was able to calculate individual runner CFM.

1. 129
2. 170
3. 156
4. 141
5. 136
6. 138

These correlate well with the pictorial view in the previous post.

A runner-runner disparity of nearly 32%. Ouch.

Here's the crux... these are static flow numbers and an intake is anything but static. Valve events and acoustics play a significant role in manifold function.

For example, a friend of mine was relaying a story of intercooler flow testing, using an inlet 90 degrees to the core such as below....

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They found that the air passing by the first row's actually created enough negative to cause backflow through the core. The CFD on my manifold shows a tendency to do this as well.

However, a large number of 'successful' manifolds are built with a 90deg. entry, both OE and aftermarket (Ferrari, Porsche, Lingenfelter, etc, etc). That, in itself, isn't definitive proof, but it does build suspicion that static flow is only a small part of the picture... in fact, it may be so skewed as to be nearly useless.

Maybe some testing would shed some light...
Regards, Ron

HybridZ; Some diligence required.

#23 RTz

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Posted 13 July 2008 - 05:40 PM

Finally getting around to posting a pic of the amended manifold, installed...

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Regards, Ron

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#24 RTz

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Posted 12 September 2008 - 02:46 PM

After a heap of procrastination, I decided to have a go at a carbon fiber plenum...


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CF has a number of attractive qualities that make it a nearly ideal candidate for manifold use. Aside from the obvious weight and thermal advantages, it has a nearly unlimited fatigue life. Fatigue resistance is one of my primary motivations as a boosted plenum is subject to significant stress. A well built CF plenum should survive many lifetimes. Add in nearly infinite shaping possibilities and an audible resonance that can't be duplicated by any other material.

Of course CF comes with its own drawbacks, mainly cost, manufacturing complexities, and a limited heat range.

Anyhow, the first step is to build a plug that mimics the final shape. A mold resembling the 'silhouette' was constructed, filled with 8lb expanding foam, and the plug extracted...


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Next up, hand shaping...
Regards, Ron

HybridZ; Some diligence required.

#25 RTz

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Posted 12 September 2008 - 06:41 PM

Rough shaping is going well...

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Note: inlet is intentionally longer than the final piece to aid in vacuum bagging.
Regards, Ron

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#26 RTz

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Posted 13 September 2008 - 11:35 AM

One of the critical elements of the plug is the TB interface. A bonded aluminum flange is the plan (a proper bond will shred the CF before the adhesive fails). Dimensionally, I have some wiggle room in machining the flange to final diameter. But, the plenum needs to be ROUND for the adhesive to work correctly. An easy way to get it close was to remove the backside of a hole-saw, and power by hand...



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Its not *exact*, but its close enough to finalize during the finishing steps.




Blended in the new inlet...


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About another hour or two of roughing in and it will be time to start the finishing stages.
Regards, Ron

HybridZ; Some diligence required.

#27 RTz

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Posted 13 September 2008 - 03:57 PM

Fortunately, I came to my senses and realized I was making this harder than need be. New strategy...


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As round as round gets.

Where the aluminum 'cap' begins is where the CF will visually end and the TB flange begins. This will give me a short, perfectly round neck to bond to.
Regards, Ron

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#28 RTz

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Posted 15 October 2008 - 08:05 PM

A serving of Bondo and more shaping...

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Overall shape is where I want it. Next on the list... attending to all the imperfection's.
Regards, Ron

HybridZ; Some diligence required.

#29 brianZortiz

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Posted 11 May 2010 - 04:15 PM

Sorry to bring old thread but man I was you can make me an intake manifold. If you have an extra one please quote me.
1973 260z GC coilovers 200f/225r tokico illumina. 3.9 LSD+extra clutches. ZG flares. upcoming engine L28et SDSem46f.
1972 240z no engine. in storage. Just waiting.

#30 RTz

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Posted 12 May 2010 - 04:31 PM

I have no plans of building another, for a while.
Regards, Ron

HybridZ; Some diligence required.

#31 G-rib-73-240z

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Posted 11 October 2010 - 07:27 PM

may i ask what your rough angle is from your throttle body to port 1(cylender one) this is similar to me and my roommates plans for my intake.

Thomas Gribble

#32 RTz

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Posted 12 October 2010 - 06:08 PM

It's a little hard to read, but the angular dimension noted in post #20 is a frogs whisker over 49 Deg.
Regards, Ron

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#33 z2go

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Posted 18 October 2010 - 11:37 PM

Ron, what happened with the CF version of the project? Was it scrapped for a different design?
1972 240Z SBC 350 ground-up resto-mod

http://forums.hybrid...post__p__878147

#34 RTz

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Posted 19 October 2010 - 02:13 PM

Was it scrapped for a different design?


Yeah, it was scrapped for a BMW manifold...

http://forums.hybrid...-bmw-m-powered/



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:mrgreen:


The CF plug is sitting high on a shelf. When I'm feeling nostalgic I may pull it down have another go at it. The BMW conversion comes first, as well as one other large project, so it may be a few decades ;-)
Regards, Ron

HybridZ; Some diligence required.

#35 z2go

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Posted 19 October 2010 - 09:56 PM

Nothin' wrong with that!
1972 240Z SBC 350 ground-up resto-mod

http://forums.hybrid...post__p__878147

#36 BRAAP

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Posted 20 October 2010 - 10:01 AM

Better yet if he builds a CF intake for that 240 HP N/A 3.2L. (should be upwards of 260 with the other BMW intake, unchoked exhaust, and no compromise tune of the aftermarket EFI). :2thumbs:




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