Supernatural 3.7L 9,000RPM Project (Page 6/18) La fiera JUN 12, 02:04 AM quote Originally posted by fishsticks: I'm worried air rushing into the plenum is going to (partially) disrupt the spray pattern from the injectors since they're so high up and put fuel on the plenum walls. You see a similar effect in cylinder head ports, which is why a lot of shaping is done to the ceiling, and sometimes the floor is raised. I think that airflow is going to push fuel to that back wall, and possibly the other walls of the plenum. That will not happen, this intake is designed to "STALL" incoming airflow speed to maximise pressure and eliminate turbulance inside the plenun so the fuel goes were it is design to go. It is plain physics. I've been modeling this approach for a couple or years now. Same story with the intake I use now, I started that back in 2014. Blacktree JUN 12, 10:28 AM Rei has a good point. The air isn't going to fly straight back and bounce off the back wall, like a ping-pong ball. That's not how aerodynamics works. The top part of the plenum will act like a diverging nozzle, and the bottom part will act like a converging nozzle. The middle of the 90-degree bend is where airflow will be the slowest. There might be a dead spot, up in the corner. But I don't think that will push the fuel spray around. fishsticks JUN 12, 01:17 PM quote Originally posted by La fiera: That will not happen, this intake is designed to "STALL" incoming airflow speed to maximise pressure and eliminate turbulance inside the plenun so the fuel goes were it is design to go. It is plain physics. I've been modeling this approach for a couple or years now. Same story with the intake I use now, I started that back in 2014. We will agree to disagree then. There's little about a box with sharp corners that's going to do much to shape airflow, and your throttle body opening is too large to cause that plenum to be much of an expansion chamber. Where does this massive charge deceleration happen, especially at significant RPM and high air velocity? "Plain physics" says you'll have a low pressure area that air is going to try to fill as quickly as possible, and also that air likes to travel in a straight path. quote Originally posted by Blacktree: Rei has a good point. The air isn't going to fly straight back and bounce off the back wall, like a ping-pong ball. That's not how aerodynamics works. The top part of the plenum will act like a diverging nozzle, and the bottom part will act like a converging nozzle. The middle of the 90-degree bend is where airflow will be the slowest. There might be a dead spot, up in the corner. But I don't think that will push the fuel spray around. You are taking a diagram which I warned was bad (with exaggerations drawn in) literally. I'm kinda over this, so let me bring one last point up and I'll be on my way. OEMs, even in performance motors, have been moving point of fuel entry closer and closer to the combustion chamber for decades, to the point that GDI is commonplace now. There are reasons for that - charge precision and detonation resistance among them. F1 cars are on the wagon, so this isn't entirely a CAFE driven move. What Rei's done is the opposite of that, and he's going to experience situations that were rendered moot by port injection and GDI. But hey, maybe he's found some secret sauce in "plain physics" that everyone else missed. I HOPE that I'm wrong and he makes 500whp on this thing, but I suspect I'm not. La fiera JUN 12, 11:45 PM quote Originally posted by fishsticks: Basically, incoming air is going to ignore the radiused part of the plenum below the TB and head straight for the back wall. So, if that's the case airplanes would not fly! Instead of me drawing what my intake concept is designed to do lets allow a physics simulator to do it. Velocity and pressures are for reference only but regardless of the values the result is the same, velocity goes up and pressure will drop and vice versa. And by varying the shape and volume in the plenum you can achieve either result. https://youtu.be/WFtkAZQCy7A Incoming velocity= 43.1ft/s @ 8.9psi hi velocity and low pressure Plenum velocity= 4.6ft/s @ 18.87psi low velocity and high pressure. That's a 89% velocity decrease and 100+% pressure increase. If an airplane gets this percentages changes on its wings in mid air it would cause the plane to stall and fall to the ground. That's what this intake is designed to do. Pay attention how the black dots follow the contour or the radius below the "TB". Joseph Upson JUN 14, 06:58 AM quote Originally posted by La fiera: So, if that's the case airplanes would not fly! Instead of me drawing what my intake concept is designed to do lets allow a physics simulator to do it. Velocity and pressures are for reference only but regardless of the values the result is the same, velocity goes up and pressure will drop and vice versa. And by varying the shape and volume in the plenum you can achieve either result. https://youtu.be/WFtkAZQCy7A Incoming velocity= 43.1ft/s @ 8.9psi hi velocity and low pressure Plenum velocity= 4.6ft/s @ 18.87psi low velocity and high pressure. That's a 89% velocity decrease and 100+% pressure increase. If an airplane gets this percentages changes on its wings in mid air it would cause the plane to stall and fall to the ground. That's what this intake is designed to do. Pay attention how the black dots follow the contour or the radius below the "TB". I get what you're saying, I don't believe laminar flow over an airfoil (wing) is the best example. All else the same, the same quantity of air would need to flow faster through a smaller throttle body than with a larger throttle body to maintain equilibrium for the same engine output, or to maintain the same flow rate on the backside of a smaller throttle body, the media would have to move at a higher velocity, than with a larger. Likewise, a larger plenum has more reserve, so the pressure drop as cylinders pull air in from it, will not occur with as much velocity through the throttle body as it would with a smaller plenum, basically, you're less likely to feel one cubic foot of air being sucked out of the back door of a house, while standing in the front door way, than you would while standing in the doorway of a small room as it's being sucked out of a window. So yeah, I can see how inlet air on a plenum that size will not likely affect the fuel injection stream. Is that correct, or close? zkhennings JUN 14, 09:23 AM Let’s also not forget that it is not pressurized air entering the throttle body but a vacuum formed at the mouth of each runner, that alone will encourage the air to bend around the short radius of the intake. As demand increases at higher rpms there will of course be some momentum that the air will have that will send air at the rear wall of the plenum, but I don’t think it will be drastic due to the large plenum volume relative to the size of the intake ports. There will be some vortices that form at the dead spot in the corner that could disrupt the spray pattern, but with each runner demanding air and fuel it should help guide the injector spray where it is trying to go. At the same time I don’t think the suggestion of texturing the walls is a bad idea as regardless of plenum shape, spraying fuel near shiny surfaces will probably result in some puddling of fuel. I just want to hear this thing on the dyno. Will JUN 19, 09:58 PM quote Originally posted by fishsticks: OEMs, even in performance motors, have been moving point of fuel entry closer and closer to the combustion chamber for decades, to the point that GDI is commonplace now. There are reasons for that - charge precision and detonation resistance among them. F1 cars are on the wagon, so this isn't entirely a CAFE driven move. OEMs, yes. Not so in motorsport. High RPM race engines with a throttle per cylinder have been using shower injectors ABOVE the throttle plates for a long time. This was every F1 engine before the new turbo era. Also race bikes as well. DI works better with forced induction, which is why F1 cars have DI in the new turbo era. thesameguy JUN 22, 12:51 PM I think the relationship is the other way.... turbos are better with DI. No? Will JUN 22, 03:19 PM That's what I said. Notorio JUN 23, 11:33 PM quote Originally posted by Blacktree: That's what I like about the Falconer lower intake... no injector bungs. Also, there's no cold-start or idle air passages. So the intake ports can be bigger. It also has a big port on the end, for crankcase vacuum. That's what the blue fitting is for. I had to go look at my stock lower to see the injector bongs indeed taking up a chunk of vertical space. So in the much different Falconer intake it must have a different Middle and different Upper as well?