VAP
08-19-2008, 10:38 AM
involving building a 3-piece cylinder head mounting plate(basically a very short intake manifold), an intermediate set of mandrel-bent equal-length runners welded to the base plate that gets bolted to the cylinder head with matching intake runner ports and a ITB mounting plate welded atop those runners that the ITB's will bolt to. The reason this "has" to be a full-blown 3-piece mounting base is that we have 2 intake runners in each head that are only 50mm apart center bore-to-center bore and even a pair of 40mm ITB's will require at least 80mm center-to-center spacing. So, even if 40mm ITBs were used and jammed together "bore-to-bore" they would be 30mm wider than the 2 cylinder head intake runner inlets they cover. Only way around that is to build offset runners that allow the ITB's to be mounted further apart and have only the IM runners converge at the cylinder head runner inlets. And for me 40mm ITB's cannot/will not make enough horsepower or flow enough CFM "per-cylinder" to achieve my design goal of closer to 55HP per-cylinder meaning I'll have to opt for a minimum 45mm bore ITB's which necessarily means I'll have to opt for "at least" 90mm spacing, and probaly closer to 110mm spacing on 2 of the ITBs with the 2 closely-spaced cylinder head intake ports. And of curse if I want to make equal HP/TQ in all 6 cylinders that also dictates I have to use an identically configured offset mandel-bend in the 3rd remaining cylinder head runner inlet that is spaced further apart. This in turn creates an inteference issue with the spark plug nearest the closely-spaced runner's end-most spark plug which is on the right rear and left front spark plug port (as viewed from the drivers' seat). Totally doable but "may" require a complete removal of both ITB intake manifolds any time the right rear or left front spark plugs need to be removed for ANY r4eason.
Another issue I see is trying to form the mandrel-bent runners into the shape of the runners that are in the head. Those runners are tall/narrow rather than perfectly round. A work-around for that "may" be to CNC the cylinder head runner inlets into a gradual concentric (round) taper at their inlet. The "unknown" factor in this approach is not knowing how deep one can go with that taper before running into a water or oil gally inside the head at any of the intake ports and only way to know for sure is to mount a "sacrificial head" in the mill and go for it even 1/8" to 1/4" deeper than the ITB setup will require as only going to a depth that meets the "needed" depth cannot reveal if there's adequate aluminum thickness and that you're not a "paper-thin" thickness away from a watery/oily grave.
Another concern for me and everyone who has to pass a visual as well as tailpipe emissions test is the crankcase recovery issue. Sure I can run individual "sock-type" foam oil filters but that aint gonna fly the visual portion of my e-test. And the only way around that means I must devise a plenum of some sort... just like the black plastic one our cars came with or the recovery sleeve many of us use to reintroduce blowby gases back into the combustion process. That literally dictates a single or dual plenum that is a sealed system between the ITB upper velocity stack inlets and the clean air intake. If individual foam "sock" filters are used within the plenum there won't be any additional filtration required. But that means all those blowby gases will now collect in the ITB sock filters insuring they get very dirty, very quickly. External filtration as we have now will allow only ITB inlets to get dirty while filter remains clean and dry but that in and of itself makes for a convoluted intake air path much like we have now where intake air has to follow a longer path with multiple bends to find its way into the ITB velocity stacks. And to further complicate things the latter method is the ONLY way to use ITB's with a stock OEM MAF system whereas the more efficient MAP system used with stand-alone would necessarily perform much more efficiently and make more power.
Bottom line is even if today we had someone making a manifold that would work for us as well as a clean air filtration intake system and planned on retaining stock engine electronics I don't believe this could be done using "new" products for less than $5k-$6k minimum. A stand-alone system would allow for perhaps a $500-$1,000 cheaper installation until you add back the $2k+ required to purchase a quality stand-alone plus installation if someone else installs it for you. Hell, I'll be at over $4,200+ international shipping "just" for the 6 ITB's, linkages, cable pulleys etc I want to use for this project if I can make it work. And I would still need to make the 3-piece intake manifold, dual fuel rails and adapt a TPS system to communicate throttle position sensing.
I'm going to proceed with this least for now for my own use and proceed VERY slowly. I'll first CNC a single cylinder head mounting plate. Next I'll pay someone to make me the required mandrel-bent runners for that plate that I can then CNC the throttle body mounting plate that will be affixed to the opposite end of the runners. I'll machine a sacrificial head before doing ANYTHING to determine if there's sufficient "meat" to hold back water/oil once cylinder heads are machined properly and known to work as-planned. Last thing I will do is buy ITBs as there's about a gazillion things that have to come together and be in place and working before I lay out almost $700 per ITB for the Jenvey ITB's I want to do this project with.
Another issue I see is trying to form the mandrel-bent runners into the shape of the runners that are in the head. Those runners are tall/narrow rather than perfectly round. A work-around for that "may" be to CNC the cylinder head runner inlets into a gradual concentric (round) taper at their inlet. The "unknown" factor in this approach is not knowing how deep one can go with that taper before running into a water or oil gally inside the head at any of the intake ports and only way to know for sure is to mount a "sacrificial head" in the mill and go for it even 1/8" to 1/4" deeper than the ITB setup will require as only going to a depth that meets the "needed" depth cannot reveal if there's adequate aluminum thickness and that you're not a "paper-thin" thickness away from a watery/oily grave.
Another concern for me and everyone who has to pass a visual as well as tailpipe emissions test is the crankcase recovery issue. Sure I can run individual "sock-type" foam oil filters but that aint gonna fly the visual portion of my e-test. And the only way around that means I must devise a plenum of some sort... just like the black plastic one our cars came with or the recovery sleeve many of us use to reintroduce blowby gases back into the combustion process. That literally dictates a single or dual plenum that is a sealed system between the ITB upper velocity stack inlets and the clean air intake. If individual foam "sock" filters are used within the plenum there won't be any additional filtration required. But that means all those blowby gases will now collect in the ITB sock filters insuring they get very dirty, very quickly. External filtration as we have now will allow only ITB inlets to get dirty while filter remains clean and dry but that in and of itself makes for a convoluted intake air path much like we have now where intake air has to follow a longer path with multiple bends to find its way into the ITB velocity stacks. And to further complicate things the latter method is the ONLY way to use ITB's with a stock OEM MAF system whereas the more efficient MAP system used with stand-alone would necessarily perform much more efficiently and make more power.
Bottom line is even if today we had someone making a manifold that would work for us as well as a clean air filtration intake system and planned on retaining stock engine electronics I don't believe this could be done using "new" products for less than $5k-$6k minimum. A stand-alone system would allow for perhaps a $500-$1,000 cheaper installation until you add back the $2k+ required to purchase a quality stand-alone plus installation if someone else installs it for you. Hell, I'll be at over $4,200+ international shipping "just" for the 6 ITB's, linkages, cable pulleys etc I want to use for this project if I can make it work. And I would still need to make the 3-piece intake manifold, dual fuel rails and adapt a TPS system to communicate throttle position sensing.
I'm going to proceed with this least for now for my own use and proceed VERY slowly. I'll first CNC a single cylinder head mounting plate. Next I'll pay someone to make me the required mandrel-bent runners for that plate that I can then CNC the throttle body mounting plate that will be affixed to the opposite end of the runners. I'll machine a sacrificial head before doing ANYTHING to determine if there's sufficient "meat" to hold back water/oil once cylinder heads are machined properly and known to work as-planned. Last thing I will do is buy ITBs as there's about a gazillion things that have to come together and be in place and working before I lay out almost $700 per ITB for the Jenvey ITB's I want to do this project with.