|Quote, originally posted by silvercar »|
|would you care to detail the reasons that you used "stock" injector bosses? I have laid hand to every manifold in this test, and several have perfect injector placement in billet, properly sealing bungs that arent killing off the port area.|
Sure. For one, they give more flexibility with injectors (large body injectors will work, for instance.) Second, some injectors will perform more reliably with the plastic insulating insert. Thirdly, I understand how geometry effects flow and ultimate power and can incorporate design features not readily accepted by the layperson but still make more power in my design. This is because I can separate the vital criteria from the not-so-vital criteria or minimally vital criteria.
|my second question to the apr runner is: Why is the curve so drastic? It seems to me by the shape that it would hurt port velocity and create turbulence rather than promote it.|
Packaging, placement of inlet runner to plenum intersection, third part from the last answer and probably other reasons that I don't recall now.
|As to your remarks about engine builders liking straight plenums(maybe in a later post than the one i have quoted here): the guys who did the testing liked the shape of my 007 plenum... and all due respect... but i have no doubt that they have a more intimate knowledge of power gained by flow than anyone at APR.|
I would certainly challenge that statement. I have no doubt that they could determine by looking at a design what would work better on a flowbench more quickly than I can but their statements lead me to believe that they aren't nearly as good at determining what works on an actual engine. I don't know how many times I or other people need to say this but what works on a flowbench IS NOT what will necessarily work on an engine. Furthermore, spending hours on a flowbench gets you absolutely no closer to determining what will actually work on an engine. Only individually testing the different designs on an engine will. Even then, you will likely be confused because design parameters which are NOT tested in a flowbench test will skew the results.
What is much more important is understanding what is going on in a dynamic state with the engine. Many complex and highly accurate engine analysis programs do not take things like plenum taper, and injector boss protrusion into consideration at all and yet the simulation results are extremely accurate. Yet parameters like plenum volume, runner length, runner cross-section, throttle body cross-section, etc. are taken into consideration. These programs are able to calculate the results without solid geometry of the manifolds or even cylinder heads (although there are many valvetrain specific parameters involved and the more entered the more accurate the results.) I would almost guarantee that the R8 intake manifolds in the picture that I posted were never tested on a flow bench. Why? Because that particular component did not need to be flow tested. The engineers understood the vital parameters required in the design, they knew the best basic manifold design, and did not need to waste time on such a test. Furthermore, the results would not be valuable (and potentially would be misleading) if run in the same manner as the test performed in this thread as they do not represent how an actual engine operates. (This is not to say that flowbenches are not very valuable tools in other situations!) I do not doubt, however, that much consideration was given by the Audi engineers on the runner length, plenum volume and other vital manifold parameters and I am sure many wave simulations were performed to optimize the design and likely a number of iterations were tested on an engine dynamometer.
What this comes down to is being able to separate the bulls**t from what constitutes good solid design. As one of the original founders of APR and the engineering lead for the company I have been trying to do this since day one. Any product that we design that goes under the hood is designed for performance- not by the latest fad or by going by the latest market trend. We apply solid engineering and nothing else. The basics of what makes an optimal intake manifold has been understood for a very, very long time. These fads such as heavily tapered plenums, velocity stacks, dual plenums, etc. are nothing more than that - a fad. People buy into them because they look cool and in some cases (certainly not all) they may give better numbers on a flowbench or because they have some other unique feature that appeals to the consumer but whose existence is based on flawed logic.
By applying solid engineering and logic we determine precisely what are the vital parameters and what are the not-so-vital parameters. We prioritize these parameters and then come up with the best design that works within all of our constraints. With the 1.8T intake manifold project we designed it the way it is because it was the best manifold design. Any compromises needed for fitment, etc. were minimized and are negligible. Again, the results speak for themselves. I don't know of any other manifold that has shown the gains that many people are seeing on our manifold. This is not to say that other manifolds don't work and have big gains, I expect many of the designs do but I would expect our design to outperform any of the designs that I have seen in most all real-world scenarios.
Modified by Brett@APR at 7:55 PM 2-27-2007