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Scratchbuilt L6 EFI Intake Manifold

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One of the current projects is a pair of L6 intake manifolds. One of them is for Clint Barnts and his beautiful 280z. The other is for an anonymous 240z owner...

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Man2.jpg

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Man3.jpg

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Man1.jpg

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The completed plenum shape will resemble this red outline...

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Man4.jpg

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Runner ID is 1.5”.

Length, for this manifold, is 6”.

 

After testing, a decision will be made on lengthening/shortening them on the second manifold.

 

A Wolf3D EMS will be installed along with a 6-coil Denso ignition system...

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WolfV4.jpg

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coils.jpg

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There is still a large portion of work to be done, along with a couple of necessary adjustments.

 

I’m expecting to test late March or April. Pending favorable test results and enough interest, I may build a small batch of them.

 

I’ll try to update the progression periodically.

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Due to request's, the head flange dimensions...

 

HeadFlange-1.jpg

 

HeadFlange3.jpg

 

Radiuses (expressed in dia.)...

 

HeadFlange2.jpg

 

PM me for 'full size', easier to read prints if needed.

 

Caution: I take no responsibility for the success of these drawings. There are many header configurations available and its simply impossible for me to account for all of them. Use these prints as a guide.

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This manifold is heavily influenced by its throttle body.

 

A scenario I wanted to avoid....

 

Picture9.jpg

 

...When a TB is attached to a 'flat plate' the incoming air has a tendency to separate directly after the TB, leading to turbulence (which can lead to uneven cylinder distribution).

 

My decided approach was to use an oversized TB to attack this two fold. First by slowing the air down, and second by allowing the walls of the TB to closely match the inner walls of the plenum.

 

Using a 65mm Ford TB (‘95 Crown Victoria) I was able to keep the taper after the TB within 10 degrees...

 

AirFlow.jpg

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FordTB.jpg

 

 

Another 'feature' I wanted to avoid is protruding velocity stack's.

 

As demonstrated by "turbobluestreak" in this CFD....

 

Picture8.jpg

 

...there is a high pressure area that develops between the TB and cylinder one.

 

Certainly this does not happen with all internal velocity-stacked manifold’s. My point is simply... without laborious testing and expensive test equipment, it can be risky.

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Prior to designing this manifold, I consulted with a few people. One of them, not surprisingly, was Braap. I asked him to list the items he’d like to see addressed. Near the top of his list was raised ports.

 

I recently contracted Braap's services to properly blend the ports into the larger, raised runners, and also asked him to summarize his work....

 

 

Today after church I was able to focus a little effort on matching up the custom N-42 head to the intake manifold. When Ron started the design phase of this intake, he coordinated with me concerning specific details in an effort to meet his goal of building an intake that would be a definite performance improvement over stock taking into account several details that we both feel need to be addressed in a true performance induction system. One of which is an effort to straighten the port. To do that, we remove material from the roof of the port opening, leaving the floor alone. With that, Ron designed this intake manifold with a raised port centerline. This aligned the runner and port floors with each other so when port matching, material will be removed from the roof of the port effectively straightening the port a little aiding in air flow not only in port size but in port shape AND approach.

In these pics you can clearly see the concept and end result.

 

The manifold runners and plenum base mocked up on the head in the engine bay…

Intake1Medium-2.jpg

 

 

 

These next two shots show the port mismatch and centerline bias of the port. In the top shot, note the port offset bias… in the lower shot you can see the virgin port with scribe line on the left and the roughed in port on the right.

 

 

Mis-match1Small.jpg

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Mis-match2Medium.jpg

 

 

 

This would probably be a good time to mention runner size....

 

1) N42 manifold runner area is approximately 53% of the intake valve area (stock 280z).

 

2) In my observations, OE manifold equipped Z’s generally run out of breath shortly after 5500 rpm or so, depending on the build.

 

3) I’ve seen enough data to suggest that number 1 and number 2 are related.

 

4) A priority of the design was to build a modular manifold so that runner diameter and length could easily be tailored to the specific engine.

 

The manifold pictured above uses 1.5” ID runners. This puts runner area at 74% of valve area. The runners are also 6” long (OE averages around 7.25”). This should compliment the intended use of the first engine. Dyno testing will follow to confirm success or failure.

 

We’re looking into building adjustable length runners for the second manifold and, of course, we’ll share the results.

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The good news is that the manifold is fully welded and fits pretty well.

 

The bad news is that the plenum warped a bit. Next plenum will be of a heavier gauge... lesson learned.

 

Aside from having to fix my screw-up, its well on its way to being tested...

 

WeldedManifold.jpg

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Several people offered advice for fixing the warped plenum (thanks!). A close friend of mine had an unusual solution... dry ice.

 

The warp is caused primarily from the expansion of the material with no place to go. Dry ice contracts the metal considerably, and nearly instantly, I found.

 

A video illustrating the rough idea... http://www.youtube.com/watch?v=4rIKo6241vg

 

To aid the process I capped and pressurized the manifold to 10 PSI to help the 'valleys' come up. This seemed to help a little but probably wasn't entirely necessary (air was off for the 'peaks')

 

The larger 'dents' towards the center came out very readily. The wrinkles at or near the welds took substantially more effort and I wasn't able to get them out completely. I did find though, through a tip from Roostmonkey, that a large portion of the stress is in the weld itself and, oddly enough, using ice on the weld helped a surprising amount.

 

Although not perfect, here are results...

 

Before...

 

BarntsManifoldWarped.jpg

 

 

After...

 

Manifold_pressurized.jpg

 

 

Although I wouldn't do this on a painted surface, I would recommend giving it a try. Pretty slick.

 

Some clean-up work and its off to be ceramic coated.

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Picked up the manifold from Finish Line Coatings in Milwuakie this morning, Cerma-chromed...

 

 

ManA.jpg

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ManB.jpg

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ManC.jpg

 

 

 

Manifold is now mechanically finished. There are several revisions in the works for manifold #2. What's that saying?... Experience is that thing you receive immediately after you needed it.

 

The car is scheduled for a dyno session immediately following the All-Datsun Canby Meet... I'll post before/after results with a few more specifics.

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Fulfilling requests for more info on the EMS system...

 

Glovebox mounted Wolf3D (V4) provides the engine management, driving the coils through a J&S Safeguard. The Safeguard uses 'smart knock' technology to hold each cylinder below knock threshold, delivering a quasi-custom timing map on a cylinder-to-cylinder basis.

 

BarntsWolf_JS.jpg

 

 

 

 

Denso ignition system...

 

BarntsCoilsB.jpg

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BarntsCoilsA.jpg

 

 

 

CAS sensor, pried from a Z32, and adapted to fit the L6....

 

BarntsCAS.jpg

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Fired the car up last weekend. After some initial tuning, the car runs strong. With a mild Electramotive cam, 265 @ .465, the car pulls cleany through 7000rpm. A bonus is that low rpm performance is only slightly compromised. Dyno results in a couple weeks...

 

running.jpg

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"Turbobluestreak" was kind enough to produce some CFD work on this manifold (Thanks!).

 

One of the goals of the design was to reduce the turbulence immediately after the TB. Looks like success...

 

CFDa.jpg

 

 

Another high priority was equal cylinder distribution. *Almost* accomplished that. The generous short side radius was an effort to promote this. Seems I still ended up with a small stagnant area in the corner. Also, the unexpected detachment on the outboard perimeter wall seems to cause enough of a low pressure to effect cylinder's 3 & 4 to some degree. The consequences of the reversion in the low pressure zone I suspect to be pretty negligible... the least of my concern's anyhow.....

 

 

CFDb.jpg

 

 

I found this to be pretty enlightening. However, I must add that static testing like this is a serious over-simplification, completely disregarding Hemholtz, acoustics, valve events, etc... Interesting nonetheless.

 

In response to this, I've made some plenum revisions and TBS has offered to test them...

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Finalizing a revised plenum shape and construction method...

 

PlenumRevision.jpg

 

Compared to...

 

barntsmanifoldb.jpg

 

 

The overall footprint is largely the same. A slightly revised TB position and angle, coupled with a different build technique, will allow a better entry into cyl. 1 and *should* help reduce the high pressure 'ahead' of 3 and 4.

 

The strategy is to form the upper and lower plenum halves around an aluminum CNC'd buck, putting the only weld seem on the horizontal perimeter.

 

Stepping up to .125" material, reducing the flat surface area, and better weld placement will allow this manifold to take boost.

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