Input on Porting an NSX Intake Mani
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From: Austin, Republic of Texas
Input on Porting an NSX Intake Mani
Tried this in a different section and didn't get much input, so I thought I would re-post it here.
=====================
For starters, please only comment if you have experience porting intake manifolds. I really need sound input here, not just speculation. I don't mean that to sound rude or anything, I have just seen so many tech threads gummed up with ill-informed comments.
ANY input by professional porters would be very, very much appriciated. Thanks to all of you in advance for your help with this.
So heres the sitch: I have done basic porting on nsx intakes several times and had good results with FI cars, but I have an NA motor going together soon and I really need to get serious about sorting this part of it out. Now that SoS is offering their stroker kits, aggressive nsx NA builds are getting much more popular. The general opinion on the motors built so far is that the stock intake design is a limiting factor. ITB's offer a big inprovement, but are pretty spendy.
So far, I have been basically cleaning up the runners, port matching them and putting a knife edge on the divider in the entrance. I also ditch the VVIS plate and replace it with a billet part that maintains the depth and volume of the plenum with all the butterlies and associate junk removed completely. Lastly, the TB is bored out and the inake entrance is bored to match.
I will probably move to a custom intake at some point (getting flanges made soon), but I need an option based on the stock intake in the mean time.
I have included several pictures of a completely stock intake below so that anyone wishing to comment can get a good idea of what we are starting with. I also have several specific questions.
1) Do you think I should continue to put a knife-edge on the divider at the entrance, or should I lose the divider completely? I am really tempted to do that and to also remove the divider 'wall' that continues the length of the plenum. I think that without the VVIS assembly, the divider is pointless.
2) I was also thinking of welding in some material to build a slight radiused lip (like a velocty stack) on the runner opening that faces the plenum. It would only be on the bottom half, but it might be better than the extremely tight radius there now.
3) There is room to make the plate that replaces the VVIS assembly a few millimeters deeper than it is now. This would increase the plenum volume slightly, but I am not sure if it is worth the hassle.
Anyway, on to the photos.
First, here are some pictures of the complete stock intake assembly with the VVIS plate and lower plenum.
Looking into the plenum entrance:
Plenum entrance from inside. This shows the divider pretty clearly. When the manifold is assembled, that divider rests up agains the VVIS plate.
So, you can all see how the stock system works, this is the VVIS assembly. Again, you can see where the internal divider matches up to it. The butterflies open at high rpm to increase plenum volume. I generally remove this whole assembly.
This is the inside of the intake manifold:
And a closer look at the runner entrance:
If any of you need to see a different angle to get a better idea of the mani's design, let me know and I will do my best to post up a better photo.
So, let's hear from the experts - what would you do if you were porting this thing?
=====================
For starters, please only comment if you have experience porting intake manifolds. I really need sound input here, not just speculation. I don't mean that to sound rude or anything, I have just seen so many tech threads gummed up with ill-informed comments.
ANY input by professional porters would be very, very much appriciated. Thanks to all of you in advance for your help with this.
So heres the sitch: I have done basic porting on nsx intakes several times and had good results with FI cars, but I have an NA motor going together soon and I really need to get serious about sorting this part of it out. Now that SoS is offering their stroker kits, aggressive nsx NA builds are getting much more popular. The general opinion on the motors built so far is that the stock intake design is a limiting factor. ITB's offer a big inprovement, but are pretty spendy.
So far, I have been basically cleaning up the runners, port matching them and putting a knife edge on the divider in the entrance. I also ditch the VVIS plate and replace it with a billet part that maintains the depth and volume of the plenum with all the butterlies and associate junk removed completely. Lastly, the TB is bored out and the inake entrance is bored to match.
I will probably move to a custom intake at some point (getting flanges made soon), but I need an option based on the stock intake in the mean time.
I have included several pictures of a completely stock intake below so that anyone wishing to comment can get a good idea of what we are starting with. I also have several specific questions.
1) Do you think I should continue to put a knife-edge on the divider at the entrance, or should I lose the divider completely? I am really tempted to do that and to also remove the divider 'wall' that continues the length of the plenum. I think that without the VVIS assembly, the divider is pointless.
2) I was also thinking of welding in some material to build a slight radiused lip (like a velocty stack) on the runner opening that faces the plenum. It would only be on the bottom half, but it might be better than the extremely tight radius there now.
3) There is room to make the plate that replaces the VVIS assembly a few millimeters deeper than it is now. This would increase the plenum volume slightly, but I am not sure if it is worth the hassle.
Anyway, on to the photos.
First, here are some pictures of the complete stock intake assembly with the VVIS plate and lower plenum.
Looking into the plenum entrance:
Plenum entrance from inside. This shows the divider pretty clearly. When the manifold is assembled, that divider rests up agains the VVIS plate.
So, you can all see how the stock system works, this is the VVIS assembly. Again, you can see where the internal divider matches up to it. The butterflies open at high rpm to increase plenum volume. I generally remove this whole assembly.
This is the inside of the intake manifold:
And a closer look at the runner entrance:
If any of you need to see a different angle to get a better idea of the mani's design, let me know and I will do my best to post up a better photo.
So, let's hear from the experts - what would you do if you were porting this thing?
Thread Starter
Honda-Tech Member
Joined: Sep 2003
Posts: 3,234
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From: Austin, Republic of Texas
Re: Input on Porting an NSX Intake Mani (Bense)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bense »</TD></TR><TR><TD CLASS="quote">It would probably be easier to just go custom than it would be to try to work with the OEM manifold</TD></TR></TABLE>
That is already the long-term plan. I am having flanges made now and have already done most of the prep work like math on runner length, sourcing parts, etc. However, I may need to work with a stock mani for the mid-term and I know there are a lot of guys who are (or have done) doing similar builds who not ready to jump to a custom intake yet and are running stock intakes with moderately bored-out TBs. I am very aware that it is not a great solution, but it is one I need to deal with for now.
That is already the long-term plan. I am having flanges made now and have already done most of the prep work like math on runner length, sourcing parts, etc. However, I may need to work with a stock mani for the mid-term and I know there are a lot of guys who are (or have done) doing similar builds who not ready to jump to a custom intake yet and are running stock intakes with moderately bored-out TBs. I am very aware that it is not a great solution, but it is one I need to deal with for now.
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