Quoting alansupra94:
I am confused. *flame suit* what does this add to our VR4s?
I'm not sure if you are asking specifically about this manifold or the cyclone in general, so I will answer for both but knowing you, I think you understand the standard cyclone concept ok.
I've looked at cyclones for a long time and in Muskrat's cam choices thread, I and DR1665 had quite a discussion regarding both standard and AMG cyclones.
A cyclone has two sets of runners one set is long the other short. The second set is closed below about 4000 rpm using butterfly valves. Below 4000 rpm during the period off boost and the transition to full boost (in a stock car) the longer runners increase velocity of air into the head and give a 40lbs increase in torque over the stock 1G manifold. At 4000 rpms the butterflies open and the air now under boost takes the shortest most direct route into the head. The longer runners remain open allowing additional flow although I am unsure if any air actually passes through these until the short runners are overrun (air taking the path of least resistance etc). The concept works. The increases in torque are documented and the cyclone flows within 1 cfm of the stock 1G up top, so on a stock setup should give no loss in power in the upper rev range.
My research is nowhere near finished on these but what evidence I have so far suggests to me that the standard cyclone isn't just a turbo specific design. They have been used on NA Galants in Europe where they were installed on NA AWD vehicles similar to your GGSX and again it seems they provide no additional power but bring in much needed torque at lower rpms to help the lower power NA engine deal with more parasitic loss from the AWD drivetrain.
Now where Brian and I disagree is when it comes to the AMG cyclone. He believes it is a NA specific design that won't benefit a turbo setup. I believe that since the standard cyclone works well in both NA and turbocharged engines, any improvements in the design that benefit the NA engine ought to similarly benefit the turbocharged engine. It should be noted here that Brian knows a thing or two and I could be wrong but real world experience with this manifold suggests that it does work well with turbocharged engines, I am just not sure why because some of the design doesn't make sense to me for either an NA or turbocharged application.
Anyway, I digress. When I started building my 'ultimate' build, I was talking about putting a cyclone on the 2.3 litre stroker to help spool the big turbo. A few guys helped me do the math and it was a no go. No doubt It would have helped down low since the theory is sound but with the additional capacity it seemed the cyclone was going to reach it's max cfm long before the theoretical 8,000 rpm rev limit and was going to create a huge bottleneck that made the big turbo pointless. I ended up getting a Forrester IM and basically forgot about this. Then the AMG cyclone with much higher flow came up in discussions and I asked Curtis about fitting one of those. He had already built one modified cyclone with a larger plenum on stock runners for another guy at that stage and had an unfinished one sitting in the shop. After some discussion he agreed to modify that specifically for the stroker. He hasn't been totally forthcoming with you guys on this, to be honest he keeps a lot back from me most of the time until stuff is finished (kind of a moot point because most of this guy's stuff is well over my head).
All I can really say is that he is working on the principle of the cyclone to improve low end torque whilst trying to move away from the stock runner setup which isn't very conducive to high end flow. He is using a combination of velocity stacks on the head of the runners, a manifold plenum/runner setup designed to utilize the Helmholtz ram effect and possibly a dual butterfly throttle body in order to retain low end torque gains with considerably better throttle response but allow airflow to rip past about 6000 rpms. I was a little dubious I admit. I'm more a low end lots of torque kind of guy and I think that I went with too big a turbo, but if Curtis is correct with his math (and I don't think he got to be crew chief on Apache helicopters by making mistakes) this thing should spool close to an EVO III and make close to 65lbs up high without missing a beat.
I admit that in some respects this design has to be a compromise because we are reducing 'some' velocity by going to a shorter runner design overall. What you need to remember is that this isn't going on a stock car, it is going on a 2.3 litre, 9.0:1 compression engine with a lightened rotating assembly. It isn't really going to suffer too much off boost. Think of it a bit like cam design. You could theoretically produce 'more torque' lower down by putting tiny cams in a huge V8 but at some point it becomes counterproductive. What Curtis is doing here is using alternative design in parallel with the standard cyclone design to retain most of the low end benefits (the remainder being made up by capacity and higher compression etc) and then adding much better off idle reponse and a killer midrange and top end.