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L28 custom intake flange


JustinOlson

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What do you guys think of the plenum design above. I think this will be the standard unless others have design input. With this design, the plenum base is a full 3" wide, and the plenum is built on top of it. This is different from Rons design where the plenum material actually wraps around the plenum base, making it made narrower then 3". I'd like input before I go ahead and order the prototypes. The problem with Ron's first piece was the material thickness of the plenum (0.065"). By going up to 0.120" I think we will have much less trouble with warpage when welding as well as less flexing and cracking when used in boosted applications.

 

Justin

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What do you guys think of the plenum design above.

 

Picture doesn't come in for me.

 

By going up to 0.120" I think we will have much less trouble with warpage when welding

 

 

That's a fact!

 

 

as well as less flexing and cracking when used in boosted applications.

 

 

Even at .120", I think internal stiffeners, for big boost applications, would be desirable. Just a few pieces of 1/2" round stock strategically welded in vertically, would probably suffice.

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Ron I e-mailed you a picture of the plenum design. I think the internally welded 1/2" tubes couldn't hurt. I"ll have to do some research and see how many cracking issues people get into once they step up to thick walled material like this. My main goal by design this plenum is to finalize the plenum base so I can get it out for prototype. I'm not married to the current design as far as shape goes. By all means I'm open to suggestions.

 

 

Regards,

Justin

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Hi Justin,

Why not just make it Monocoque style / sheet metal? One pc would be cheaper than cutting up expensive mandrel bent tubes and running a mile long weld bead - also none of the warpage. The shape is simple enough that you could bang it out over a wooden buck. Aluminum is easy to anneal and age after. Check the pics below for a better explanation. The first one shows the small weld seam, the second one shows the end cap, but I think you could form this in also with a small center seam, and the last one shows it unfolded. I designed a bike years ago that the downtube was made this way / graphics and all. BTW .120 wall? how much boost ya gunna run?

 

Best Regards, Jeff

 

justin1.jpg

justin2.jpg

justin3.jpg

 

p-61%5B1%5D.jpg

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Jeff,

 

Thanks for the renderings. I really like that idea. How thick of material realistically can you form up from one sheet? I'd love to give it a try. Maybe I could carve out a wood form to use.

 

0.120" wall thickness seems to be what a lot of manifold fabricators are using for these intake manifolds. It seems like overkill to me, but I'm worried about the heat cycling and pressure cycling a intake manifold sees over its lift time. Aluminum doesn't have an endurance limit to fatigue, so I'm worried about cracks developing over time. I worry that if I don't make it sufficiently thick, I will have problems with manifolds failing down the road a ways.

 

Justin

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Forming the sheet with match dies and then folding it half with a break for production would be cake for .125 wall. I think hand forming .063 over wood will be easy and plenty for prototyping. It is amazing how strong a small boxed in shape like your plenum design is. FYI the BMX bike I showed was race by 220lb pro riders who could squat hundreds of pounds. If you have ever seen a BMX gate start you would be amazed how stiff and strong a monocoque tube can be. The wall thickness on the downtube for the bike was only .050. I think .120 will just make manufacturing and handling easier when it is time for a production run.

 

Jeff

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Monzter,

 

I had something similar in mind for manifold number two... with the exception of being two-piece, top and bottom halves. I like your idea much better. Sadly, I'm adjusting the shape of the plenum such that it will no longer work as a one-piece.

 

I think hand forming .063 over wood will be easy and plenty for prototyping.

 

Keep in mind that we are somewhat past the prototyping phase, as one has already been completed and running. As for .063, I really feel this is a poor choice for boosted app's. I've personally seen ballooned .120" manifolds. I know of BWM folks, running manifold's of similar shape, that have had trouble with .120", hence the internal stiffeners.

 

I'd be happy to have someone prove me wrong. All I'm saying is, if I were building one with boost in mind, it would not be less than .120" and there would be internal reinforcement.

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I was a bit concerned about the clearance between the injector ports and the slip fits for the runners. I made the slip fits slightly less deep to add some material there. It wont be an issue when the manifold is all welded up, but I just feel better having more material there.

 

Justin

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Found another mistake I think. The number 3 and 4 injector ports are offset the wrong direction. I'll have to correct that when I get home tonight.

 

What are your guys thoughts on using the carb bolt holes along with the efi bolt holes so that the manifold is setup for both bolt patterns? On the heads drilled for both you would have extra clamping force. Just an idea I've been kicking around.

 

Justin

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