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Doc1 · May 13th, 2008, 11:24 PM

I had to get off the computer and actually run some errands on my day off. Any way I was eating dinner with my wife, and I am pondering the statement that Former PFR said about the stacks being an obstruction for n/a applications. You see, I’m a science guy and things have to sound logical to me or it doesn’t work or I have to ask a hundred whys to satisfy my curiosity. But science and motors don’t always go hand in hand. I’ll start on 101 basics and see if it makes any since to you (Former PFR) and me. Now your max air flow depends on how much volume a cylinder can hold. As your pistons go down it pulls air with it and the exhaust valves close and intake valve opens. And depending on if it’s a stock or larger ported head, it can be a quicker filling up of air in the cylinder. So as air gets sucked through the tb, and through the head and into the cylinders, most of the air goes through the 1st few cylinders and less air to the rear cylinders meaning the rear cylinders run richer (in the case of the ROE). Therefore the egts would be lower. Most of the time we are more afraid of the cylinders going lean vs. rich. If I had to guess, the rear ones would probably lose 10-20 cfm. I am not sure if that makes a big difference or not. But that doesn’t solve the issue of having less air back there. Then I was thinking about some of the sheet metal manifolds that I have seen out there with the tapered ends. Maybe the tapered end design actually increases the remaining air velocity by decreasing the plenum space. I have seen those tapered designs on both n/a and turbo applications. But I believe in more of the larger plenum design vs. the tapered design for turbo applications.

Now back to my manifold design. Actually I was incorrect regarding the stacks. They are actually 2”, the same length as the runners. If you look at the front view, the dead center of the tb plate is above the stacks so obstruction of air flow is less likely to exist. I have seen other manifold with tall stacks for different car applications but can remember on what website. The stacks are most likely below the tb. I guess for my design to work for n/a applications, the firewall end will have to be tapered. Here’s another question, how steep of a tapered angle and where does it start. But for a true n/a manifold to work, the design must compliment the head porter’s art work in allowing for certain lifts and duration of air to pass by. Like I said n/a motors are not my cup of tea.

Now how do you back up your theory that an oval design for the runners works better than a transitional design that myself and exoticengine.net uses. Once the manifold is finished, I am going to give Greg Good a call to see if he can do a flow test on that runner design but I would have to make another bottom piece with the oval design for comparison. Maybe one day I’ll get a wild hair up my ass and fork out the money to do the oval design. Greg does flow testing on the heads and I’m not sure if the equipment is the same or not for flow testing intake manifolds, but I will give him a call.

Thanks for picking my brain.

May 13th, 2008, 11:24 PM	#33
Doc1 Enthusiast Doc1 is offline Join Date: Apr 2008 Location: Houston, TX Posts: 36 Rep Power: 0	I had to get off the computer and actually run some errands on my day off. Any way I was eating dinner with my wife, and I am pondering the statement that Former PFR said about the stacks being an obstruction for n/a applications. You see, I’m a science guy and things have to sound logical to me or it doesn’t work or I have to ask a hundred whys to satisfy my curiosity. But science and motors don’t always go hand in hand. I’ll start on 101 basics and see if it makes any since to you (Former PFR) and me. Now your max air flow depends on how much volume a cylinder can hold. As your pistons go down it pulls air with it and the exhaust valves close and intake valve opens. And depending on if it’s a stock or larger ported head, it can be a quicker filling up of air in the cylinder. So as air gets sucked through the tb, and through the head and into the cylinders, most of the air goes through the 1st few cylinders and less air to the rear cylinders meaning the rear cylinders run richer (in the case of the ROE). Therefore the egts would be lower. Most of the time we are more afraid of the cylinders going lean vs. rich. If I had to guess, the rear ones would probably lose 10-20 cfm. I am not sure if that makes a big difference or not. But that doesn’t solve the issue of having less air back there. Then I was thinking about some of the sheet metal manifolds that I have seen out there with the tapered ends. Maybe the tapered end design actually increases the remaining air velocity by decreasing the plenum space. I have seen those tapered designs on both n/a and turbo applications. But I believe in more of the larger plenum design vs. the tapered design for turbo applications. Now back to my manifold design. Actually I was incorrect regarding the stacks. They are actually 2”, the same length as the runners. If you look at the front view, the dead center of the tb plate is above the stacks so obstruction of air flow is less likely to exist. I have seen other manifold with tall stacks for different car applications but can remember on what website. The stacks are most likely below the tb. I guess for my design to work for n/a applications, the firewall end will have to be tapered. Here’s another question, how steep of a tapered angle and where does it start. But for a true n/a manifold to work, the design must compliment the head porter’s art work in allowing for certain lifts and duration of air to pass by. Like I said n/a motors are not my cup of tea. Now how do you back up your theory that an oval design for the runners works better than a transitional design that myself and exoticengine.net uses. Once the manifold is finished, I am going to give Greg Good a call to see if he can do a flow test on that runner design but I would have to make another bottom piece with the oval design for comparison. Maybe one day I’ll get a wild hair up my ass and fork out the money to do the oval design. Greg does flow testing on the heads and I’m not sure if the equipment is the same or not for flow testing intake manifolds, but I will give him a call. Thanks for picking my brain.