DIY plenum porting
05-12-2006, 09:04 AM
#181
Originally Posted by bilinghm
I'm not sure that it will make any differece either. However...
It may provide extra voulme in a way completely different and more benficial than a spacer. The spacer provides headroom over the cramped spot above the two front runners. Shaving the two front runners does the exact same thing. Untapered spacers also multiply the effect of the slanted lid of the 350Z plenum. They provide more room over 1&2 where is is needed, and even more room over the other runners where it isn't actually required. We also know that too much headroom can upset the pressure balance, potentially altering the velocity of intake air and harming low end torque.
Opening up the bowls along with shaving the 1&2 port roofs might be a excellent compromise. More headroom for 1&2, and a volume incease that effects all runners equally.
I'm beginning to believe that a properly modifed lower plenum will make spacers obsolete. I think many of the dyno results that we are seeing on the Mrev+ are providing the evidence.
Have I got the solution? Who knows?
It may provide extra voulme in a way completely different and more benficial than a spacer. The spacer provides headroom over the cramped spot above the two front runners. Shaving the two front runners does the exact same thing. Untapered spacers also multiply the effect of the slanted lid of the 350Z plenum. They provide more room over 1&2 where is is needed, and even more room over the other runners where it isn't actually required. We also know that too much headroom can upset the pressure balance, potentially altering the velocity of intake air and harming low end torque.
Opening up the bowls along with shaving the 1&2 port roofs might be a excellent compromise. More headroom for 1&2, and a volume incease that effects all runners equally.
I'm beginning to believe that a properly modifed lower plenum will make spacers obsolete. I think many of the dyno results that we are seeing on the Mrev+ are providing the evidence.
Have I got the solution? Who knows?
I will have another plenum to mess around with once i put this one on my buddies car. I know its going to make more power than stock, just not sure how much. So with the second plenum i can take from what i have learned and hopefully improve apon it.
Later
Aceman
05-12-2006, 10:07 AM
#183
OVER 10 HOURS OF CYLINDER HEAD & INTAKE MANIFOLD SECRETS
http://racingsecrets.com/speedtalk_head_porting.shtml
INTAKE MANIFOLDS
Tell us about the different manifold designs, and the advantages/disadvantages of each.
Give racers advice on picking the right manifold.
How to design a manifold from scratch.
Manifold Porting: How do you decide size and shape? How do you do the modification? Let's look at each part of the intake and get your thoughts.
Carb Flange
Plenum
Dividers
Runner entrance (at plenum)
Runner roof
Runner floor
Runner walls
Runner exit (at gasket)
What are your thoughts on fuel distribution?
What are your favorite formulas relating to intake manifolds?
What are the latest trends in manifold design?
What are the latest trends in manifold porting and modification?
What are the biggest mistakes people make when it comes to manifolds?
Biggest discoveries you’ve made working on intake manifolds?
Looks like these CD's would be very helpfull, and they are only $99 and it comes with a Vinyl Carrying Case ( very cool ) 
Later
Aceman
http://racingsecrets.com/speedtalk_head_porting.shtml
INTAKE MANIFOLDS
Tell us about the different manifold designs, and the advantages/disadvantages of each.
Give racers advice on picking the right manifold.
How to design a manifold from scratch.
Manifold Porting: How do you decide size and shape? How do you do the modification? Let's look at each part of the intake and get your thoughts.
Carb Flange
Plenum
Dividers
Runner entrance (at plenum)
Runner roof
Runner floor
Runner walls
Runner exit (at gasket)
What are your thoughts on fuel distribution?
What are your favorite formulas relating to intake manifolds?
What are the latest trends in manifold design?
What are the latest trends in manifold porting and modification?
What are the biggest mistakes people make when it comes to manifolds?
Biggest discoveries you’ve made working on intake manifolds?
Looks like these CD's would be very helpfull, and they are only $99
and it comes with a Vinyl Carrying Case ( very cool ) Later
Aceman
05-16-2006, 11:39 AM
#189
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Plenum corner
I have heard some comments and speculation that rounding off the corner shown in the photo would be a worthwhile modification. I have my personal doubts. There are two of these corners, one "corner" on the the left front by runner 1 and on the right rear next to runner 6. These little corners were very deliberately designed into this casting and NOT a mistake or overlooked opportunity. They are obviously designed to create a low pressure area below the lip and probably induce a swirl or vortex as the air cascades off the edge. The face of the corner below the lip is even slightly concave, further strenghtening my belief that this is a purpose designed arodynamic feature, not a mistake. I think the mistake would be to grind this off.
Polishing this area would probably be O.K. but I believe the original contours should be maintained unless somebody has either flow bench information or computer simulations that show an improvement with this area removed.
Polishing this area would probably be O.K. but I believe the original contours should be maintained unless somebody has either flow bench information or computer simulations that show an improvement with this area removed.
05-16-2006, 11:48 AM
#190
Originally Posted by bilinghm
I have heard some comments and speculation that rounding off the corner shown in the photo would be a worthwhile modification. I have my personal doubts. There are two of these corners, one "corner" on the the left front by runner 1 and on the right rear next to runner 6. These little corners were very deliberately designed into this casting and NOT a mistake or overlooked opportunity. They are obviously designed to create a low pressure area below the lip and probably induce a swirl or vortex as the air cascades off the edge. The face of the corner below the lip is even slightly concave, further strenghtening my belief that this is a purpose designed arodynamic feature, not a mistake. I think the mistake would be to grind this off.
Polishing this area would probably be O.K. but I believe the original contours should be maintained unless somebody has either flow bench information or computer simulations that show an improvement with this area removed.
Polishing this area would probably be O.K. but I believe the original contours should be maintained unless somebody has either flow bench information or computer simulations that show an improvement with this area removed.
LOL woooooops, well i guess we will see if it was a mistake to grind that down some
Later
Aceman
05-16-2006, 11:11 PM
#197
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Originally Posted by bilinghm
Here is a photo of where I plan to mill out the bottom of the "bowl" area. Inside the dotted line.
Are there any downsides to this??
Last edited by OCG35Coupe; 05-16-2006 at 11:16 PM.
