Honda intake manifold
I have a local guy who just finished a CNC plasma table who is itching for excuses to use it. If somebody can make a cad file in a format he can use I can get parts made for teh cost of material and shipping. Cheaper if somebody will send/ get me a piece of scrap aluminum to use.
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I have a local guy who just finished a CNC plasma table who is itching for excuses to use it. If somebody can make a cad file in a format he can use I can get parts made for teh cost of material and shipping. Cheaper if somebody will send/ get me a piece of scrap aluminum to use.
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ʎpunq qoq
Joined: Jan 2014
Posts: 604
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From: Western Australia
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My manifold is off for decking right now so I could check it for you.
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ʎpunq qoq
Joined: Jan 2014
Posts: 604
Total Cats: 202
From: Western Australia
Try this one for fitment (print it out 1:1, lay it over the manifold flange, align and rub your finger around it. You should see where the CAD is wrong. Just send me some photos and some measurements of where it is out and I'll amend it.
I have guessed at a 15mm difference in bolt hole location. I can't find it online but I'm sure thats what I've read at some point. Photos of gaskets look about right, maybe it's 12mm not 15.
I should note that my CAD flanges have a big area at the base to weld some triangular fins to support the runners. They aren't the same as a OEM flange. I'm assuming there is nothing to hit on the head like the earlier model but it would be worth checking that also. If it fits, I'll tidy it up before people use it.
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Bannisheded
Joined: Aug 2014
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Also, I can't open these at work, but I suggest splitting the bolt holes to make it easier on his plasma cutter. Punching holes through the .5" plate I'll probably use will be pretty hard on equipment. One continuous cut is much easier on his gear.
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Elite Member
Joined: Jul 2005
Posts: 2,502
Total Cats: 146
From: Anacortes, WA
Fundamental intake manifold design stuff. Just like you might have to search for a few minutes to substantiate a theory that rod ratio of 1.45:1 might make less power than 1.58:1 in a Honda B series.
The reason so many people build ultra short runner BP manifolds is twofold:
1. They start with B series manifold designed for a longer rod ratio engine that makes power between 7000-9000rpm and either don't know the difference or don't care. Boost tends to hide just how bad your manifold design is.
2. It's easier to make it fit in the bay without the plenum hitting the shock tower.
Regardless of high you rev a BP on the stock crank, an OTS B series manifold will have a hard time matching the area under the curve and peak power of a square top. I have a pile of Honda B series/BP flanged manifolds here. Our best one just matched a squaretop and barely cleared the shock tower. It has runners that are too short.
The ideal BP manifold has runners the same length as OEM average, about 1-2mm larger ID depending on cams, plenum 10-15% larger volume and most of all, a straight shot from the TB flange into the plenum. I say average runner length because every OEM BP manifold has 4 different runner lengths to work around packaging constraints (EGR, hood clearance, production line assembly). Fixing that one problem is worth a few %, and fewer blown F/I builds running one o2 sensor.
To get the correct runner length and still fit in the engine bay means starting from scratch or looped runners, sort of like the BEGI prototype. Honda B series based manifolds will always be too short because of the curve of the runners. I know of only one non-looped manifold in existence that is correct. It is sheet & tubular aluminum with some cool carbon trumpets epoxied inside the plenum.
The reason so many people build ultra short runner BP manifolds is twofold:
1. They start with B series manifold designed for a longer rod ratio engine that makes power between 7000-9000rpm and either don't know the difference or don't care. Boost tends to hide just how bad your manifold design is.
2. It's easier to make it fit in the bay without the plenum hitting the shock tower.
Regardless of high you rev a BP on the stock crank, an OTS B series manifold will have a hard time matching the area under the curve and peak power of a square top. I have a pile of Honda B series/BP flanged manifolds here. Our best one just matched a squaretop and barely cleared the shock tower. It has runners that are too short.
The ideal BP manifold has runners the same length as OEM average, about 1-2mm larger ID depending on cams, plenum 10-15% larger volume and most of all, a straight shot from the TB flange into the plenum. I say average runner length because every OEM BP manifold has 4 different runner lengths to work around packaging constraints (EGR, hood clearance, production line assembly). Fixing that one problem is worth a few %, and fewer blown F/I builds running one o2 sensor.
To get the correct runner length and still fit in the engine bay means starting from scratch or looped runners, sort of like the BEGI prototype. Honda B series based manifolds will always be too short because of the curve of the runners. I know of only one non-looped manifold in existence that is correct. It is sheet & tubular aluminum with some cool carbon trumpets epoxied inside the plenum.
I was thinking of building another one based on a 95 manifold for Naturally aspirated and was wondering about adjusting runner lengths a bit when I modify the flange.
Motor will be stock internal NB2. Then mayby I should just run a stock VCTS manifold which seems to work well for mid range torque I think without much drop at the top.
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I haven't cast a manifold yet but I did cast an NB head port. I measure my squaretop runner lengths and got ~12". Its hard to get an exact measurement since you would need to take the center line of the bend. I also have 3.85" for the NB intake port length.
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Elite Member
Joined: Jul 2005
Posts: 2,502
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From: Anacortes, WA
I'm contemplating cutting up an NB manifold to get the head flange portion and welding it to an NA manifold cut apart and ported reassembled and using the flange portion of the NB to add maybe an inch of runner length to make it closer to NB length. I like the cleanness of the NA manifold once you cut all the EGR features off and smooth it out. The square top has a bit bigger runner diameters but I think but I will have stock cams stock head and stock motor so I'm not sure that that will be a gain for anything other than very high RPM maybe peak power while I want area under the curve and mid range torque.
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