Haven't read all of the new posts yet. We did test the header against another design with different primary and secondary diameters and we are by no means done in terms of testing. Our next test is going to be the existing design with secondaries length matched to the primary, they're about 1/2 of the primary currently, clearly a suboptimal solution for keeping the catalytic converter in the stock location. This was something that in preliminary discussions many of our SCCA Solo 2 customers were interested in seeing based on Solo2 Rules.
R/TErnie, I'm not entirely sure why you think it's tough to design a header around an engine that cannot be tuned yet. We have evaluated all of the details of the factory cam timing range on intake and exhaust and the variance in terms of primary and secondary diameter across that range as well as the overall primary and secondary length don't change enough to make a major impact on the phsyical design of the header. Our header is making pretty substantial power as-is, I'd say. And it seems to me that the overall design of the header is going to work whether the engine is tuned or not. A tune doesn't alter cam timing out of the available range of advance/retard of the cam timing and spark angle doesn't impact header mechanics as far as I know. The overall length of the system is based on target power and port centerline length which also is static.
I apologize if I gave the impression that the dip was related to resonance, it is clearly not, but the resonance may certainly be related to a change in ignition or cam timing. My goal was to simply reduce that for sound sake. The concept of scavenging by altering the acoustics of the pipe that I mentioned were related to a secondary design that we have been looking into. There have been a few companies who have been successful at accomplishing this. All of this is not an attempt to correct some harmonic imbalance in the engine that we assumed was causing the torque dip. If you look in other threads our assumption is just the same as yours - that area is for economy at cruise. Our goal was to simply increase the midrange torque to ameliorate this issue until a tuning solution comes about. At that point, the gains we see by having a good mechanical design on the header will be just as good if not better than they are on the stock tune.
As for the AVCS maps being just as funky as the stock ignition and fuel maps, I can adjust my calculations to the full range of adjustment of the AVCS and the design constraints make only slight changes which still land in the primary and secondary length ranges as well as the primary and secondary diameters. What would you allege would change mechanically in our header design based on cam timing changes? Altering target peak HP rpm, port centerline length, as well as lobe center angle (LCA) change the length slightly, but as LCA goes up, the range of optimal primary and secondary length widens, landing my pipe sizes in the range just as well as it does when LCA reduces and my pipe sizes are designed within that constraint.
I suppose I'm not understanding your point. It's far beyond my intention to act like I'm an expert on this, I'm not by any means - which is why we have asked for input. This community is pretty awesome and has a number of people on board who have a lot of knowledge and real world experience with a variety of similar applications to the FA20 engine. So please, let me know what your thoughts are on this rather than asserting that building a header that makes power on a non-tuned engine would not work on a tuned engine. Because quite frankly, I am not following the important part - the 'Why?'
As for LC being a small place, yeah pretty much BFE. I've lived here for 9 years and have worked in the Aircraft Industry (Fixed Wing/Rotorcraft Aeromedical Systems Design & Manufacturing) as a Mechanical Engineer, Motion Control Industry (Absolute & Incremental Linear and Rotary Encoders, Accelerometers and High Accuracy Inclinometers) as a Senior Mechanical Engineer and Director of Engineering as well as the Automotive Industry (EFI Ancillary Control Systems, as well as the type of thing we do here with another sport compact company). I've not worked at ETS. My business partner John did indeed work at ETS for a number of years, but it's just coincidental that I bought property and a home in the same town that they were located in.
The other thing I would point out is that comparing to the factory header specifically, there is no trade off in a well designed tri-y design. There may very well be a trade off when we compare the stepped 4-1 design vs. this stepped tri-y design, but as things stand, there is a steady gain of power across the powerband as well as a substantial increase in torque across the powerband as well.
Again. We are going to build a NUMBER of other header designs to test. This is something that is quite fascinating to us and we thought it'd be a good approach to discuss these design ideas with the community and get their feedback and act as the hands in the process of changing a theoretical discussion on the forums into visible, real world testing of a number of products, bringing enthusiasts in on the development process and not being afraid to speculate about things even if they pan out to be false or inconsequential.
If I questioned every possible thing that went through my brain and didn't write it out in this thread for fear of being wrong or saying something that wasn't perfectly thought out, there are a number of ideas that may never come to fruition. I'm not afraid to make mistakes in a discussion. I'm certainly not afraid to speculate about things that are beyond the scope of my understanding, it's just part of my own learning process.
Here's the thing - I want to be open about this process and I can't do that if I'm not willing to postulate. So I may say some things now or in the future that aren't well thought out. I do think that acoustics and resonance can impact power, and that use of one or more helmholtz and other styles of resonator could feasibly positively impact scavanging. Case in point:
[ame="http://www.youtube.com/watch?v=1Fr00GjghnU&feature=relmfu"]ThermalPulse 180 - 18 Valveless Pulsejet High Throttle - YouTube[/ame]
There are a number of resonator designs used in the gas industry that impact flow and gas velocity based on changing pulsewaves in a compressed gas system. Why not fiddle around with some of these while we're at it? Or at least think about them. Might seem kinda wild, but they probably said the same thing about Alfred Büchi's ideas. Or Daimler or Rudy Diesel for that matter. What's the harm? Invest some money in something to test that doesn't pan out?
We're already invested in making a damn header and exhaust that doesn't sound like a bag of chainsaws (the funny part about this statement is that I know that video above is still running as you're reading this). I have always hated that when we have designed exhausts to the factory header and then somebody swaps out a catless 4-1 and our exhaust note goes to shit. And perhaps you can explain to me why our dual helmholtz axleback exhaust on the Genesis makes more power than a straight pipe or most of the catback systems on the market? I can't get my head around it, to be honest, unless the resonance of the exhaust is improving flow better than allowing the exhaust pulses to simply exit an open pipe. Obviously tuned exhaust length and the primary/secondary/tertiary harmonics of a length of tube at a given diameter have an impact on power, perhaps the use of the helmholtz simply makes the sixth harmonic act like the fourth.
Bottom line: the next step is to test this design without a cat and with the appropriate secondary lengths as calculated based on the data we have for the specs on the engine.
Jason