V2Rocket

You'll need to make a decent taper to open up from the AM intake to 928S4 head.

Credit for photos to Rob Edwards...

mark kibort

i think that will be fairly easy to flair and mate, but thats just what it looks like.

2 x 1.7" (S4) to 2 x 1.5" " should be doable. it looks pretty easy. since the width is near identical, all that needs to be done is the hole cut on the sides and opened up . (and then filled in. that would give a nice transition to the S4 ports. ) and, depending on the width from side to side of the 2 heads, this is a good thing to have to modify that way, to more accurately make the fit of the intake to the heads position wise.

the walls of the runners are very thin, and if you can imagine just cutting slits on either side of inside of the runners, you could just bend them inward and fill in the difference.

mark kibort

for the gross positioning of the runners, with aluminum, is it possible to heat them up and bend with some type of insert dowel? does cast aluminum bend under heat or just crack?

Mongo

Given that the walls are thin, you will need to be extremely careful with that procedure.

mark kibort

the heating and moving, (if possible) or the cutting and bending to port match.

either way, the port match seems to be a closer match than originally thought.
welding something that doesnt have to reallly reshape the port is much better than planned.. they are still oval at the base, and go toward a rectangle shape much higher in the runner, so the port match or fitting a flare, should be straight forward.

dr bob

Mark --

You won't be able to heat-and-move the cast manifold runners. the amount of heat needed to get that manifold to a plastic state is substantial, and by the time you get it to that state it will collapse in on itself from its own weight.

The matching at the head needs to consider not just the size of the hole but the profile of the port downstream and into the valves area. Hence my suggestion that you make silicone runner impressions from both the manifold and the ports in the head, and line them up to see exactly how much mismatch you'll need to correct. The finished runner would be the smoothest possible transition with no change in flow direction needed at the transition. There are of course some schools of thought that include a ledge at the junction to purposefully break the flow at the walls before the valves. Regardless, you'll want to see exactly how much "transition" will need to be corrected in the lower ends of the AM manifold runners to make a smooth fitup to the Hans flanges.

mark kibort

yeah, kind of thought that seemed too easy.. i was picturing the exhaust welder guy moving things around like puddy. ok, so yes, i get the picture and think we cut and angle the existing runners and flare the ends to meet the Hans adapters. that way, there is very little disruption of flow , with the exception of the S4 adaptation where the runners will have one side cut and bent outward to meet the new shorter radius sides. interesting that the S4 ports are larger here. (by about .20") thats ok, the runners get much larger as you go up into the plennum. there should be a venturi effect, but nothing that should be that much of a problem. if you look at the "problems" of flow and direction, and diameters of the stock S4 intake, the AM intake is light years ahead.

dr bob

Mark --

The runners are tapered to gradually increase charge velocity through the valves and into the chamber. Since friction losses increase with the square of the change in velocity (everything else being equal...) the longer runners needed for a little bit of beneficial echo have less friction loss that way. While maitaining a laminar flow. You won't really want to go from smaller-faster- to larger-slower right above the mating face. Instead, you'll work your way back up the AM runner until you get to a spot where the cross-sectional area is the same as the adapter's CSA, and start your direction adjustments there while maintaining that CSA.

You have a bit of research and design work ahead of you, grasshopper...

mark kibort

yes, there is a bit of flow care needed here that i am much aware of. but , when i want to find calm, i look at the right angles and turns and bends , some you couldnt make them any worse if you tried, of the s4 intake. look at #2 and #3 manifold ports and trace their paths, not to mention the U turns of #1

GregBBRD

Both of the intakes that Mark and Joseph had were carbon fiber pieces that literally had automotive "Bondo" and paint joining the pieces together. The first time I bolted throttle bodies on Joseph's manifold, fabricated the throttle linkage, and pulled on the cable, the throttle bodies (with the mounting flanges previously attached to the mainifold) literally fell off the plenum.....with me standing there holding the cable. Must have been quite a sight....grown man holding onto a cable with two throttle bodies and mounting flanges dangling down.

Yes, regular old automotive fender repair Bondo attached the flanges to the plenums. Definitely "ready for prime time".

Perhaps you can just cut off the flanges off of both the S4 manifold and the AM manifold and connect the S4 flanges to the AM manifold, using the same technique.....at least for testing.

My guess is that the AM manifold is going to act very similar to an "American Tunnel Ram"......good for drag racing at high rpms, but terrible for a long geared low rpm road race engine. (How many gears does an AM have and what is the RPM range of the engine?)

I'm just saying.....

James Bailey

Actually this concept makes a great deal of sense. Shape the inside of the transition pieces in foam, use S-4 feet . Coat them then use S glass/epoxy to cover the foam. Use solvent to melt out the foam and you have an intake !!!

James Bailey

S-glass can handle the heat, the fiberglass would have some flexibility to compensate for expansion contraction of the block and it requires no welding...... just simple skills to shape the foam plugs. Uses the feet of the S-4 and the plenum and upper runners from the A M (put my daughter's up for my avatar ) So the stock fuel rails fit. And we have a composite aluminum, s-glass, and magnesium intake.

mark kibort

actually, this style of intake is being used for the Mustang 5.0s , making near 450rwhp, and the larger engine size, aston martin v8. they have an almost identica shape HP curve to what mark and Joes car had. its fantastic for road racing, but obvously, if the porsche had 6 close ration gears like the Aston Martin, it would be better use of the available HP. the AM ratios are almost identical to the caymanGTS. as far as on track use, the gears and shift points are very close to the 928 for most tracks and speed ranges. sure, this intake wont have the "driveability " of the S4 with the flappy resonance, but for racing that isnt used anyway. (mine has been removed as i never see RPM levels below 4000rpm)

you have to remember, we are talking about much more direct ports with huge bell mouthed inlets. this will flow much better than the larger ports at the heads, than anything that the S4 intake can make. the larger displacement with a 5 liter and certainly the 6.4L , will kick up the torque levels and thus HP in the lower RPM vs the Am 4.3 or 4.7 V8

funny about mark and joe's intakes . yes, with no tuning and just slapping Home depot plumming pipes it made near 500rwhp. i especially like the intake plennum flexing like a breathing snake when he engine was reved ....... certainly ready for prime time!

OBehave2.0

Shame you don't have one of these.

GregBBRD

The stock intake manifold works adequately on stock (or near stock) engines making 300rwhp. The compact design Porsche came up with actually works as good as was needed.

I've proved many times (with my 6.5 liter engines) that the stock manifold is the limiting factor to making over ~420rwhp.

Just about anything with straighter runners will improve engine output at higher rpms. And since you say you never drop below 4,000 rpms, the actual design parameters that you require are pretty simple.

A "tunnel ram" style intake should solve your needs.

My needs are much different and require a different design.