Thanks, Prime, for creating this forum.
Here are some of my thoughts for optimizing NA performance for our beloved cars, without tearing into the bottom end of the motor:
Airbox/Intakes/Throttle Body
I am encouraged by Prospeed's recent offering of an "alternatively plumbed" intake system. It has 2 of the 3 features (3.5-inch diameter piping, longer total pipe length) I always thought should have gone into such a system (the one feature it does not have is an integrated bell-mouth/velocity stack, but unfortunately there is simply no space for one).
There is still, IMO, a lot to be gained on the throttle body side. There are a few vendors that offer a boring-out service, but that is a band-aid, at best. The factor TB has a 68 mm opening that tapers down to 64 mm at the plate. This is simply not big enough. The limiting factor here is the size of the snout on the intake manifold that the TB bolts onto. However, others that were willing to do a little welding have retrofitted larger TBs onto their manifolds.
Bottom Line: I believe there is about 15 wHP to be found a properly designed and built intake system, along with a "proper" sized throttle body.
Intake Manifold/ITBs
Rahim (96cxt) is the only member here with proof of the benefits of porting the intake manifold. I am having my intake manifold ported, and will try my best to provide documentation (flow bench #s, and dyno testing) of how much the intake manifold can be improved upon.
There is also the (long shot) possibility of having a skilled fabricator come up with a no-compromise design from scratch. Some of the features I would include on my design are:
The verdict on individual throttle bodies ("ITBs") is ambiguous at best right now. I don't have any interest in running them, nor do I have the resources ($$$) to design and test a bunch of them to find the optimal setup with respect to horn length, width, and orientation.
Bottom Line: I believe there is about 8-12 wHP to be found in a ported and gutted intake manifold, and probably much more power to be found a redesigned piece.
Camshafts/Valvetrain
I think it's an absolute shame that no one has stepped up to make an affordable (cast) camshaft set for the NSX. The factory 10.2 mm/0.401 inch (intake) and 9.0 mm/0.354 inch (exhaust) VTEC lobes on the C30/C32 are, TIMID at best, when compared to what the B-series Hondas are able to run. As a point of reference, the Civic Type R (CTR) cams feature 11.5 mm/0.453 inch lift (intake) and 10.5 mm/0.413 inch lift (exhaust).
Based on the piston speeds of a 78-mm stroked C30 motor, it should be able to rev happily to 8500+ RPM. Yet, NA NSXs typically tap out at 7200 RPM. My research suggests that this is all due to the cam profiles.
Cylinder Heads
The KEY to power in any gasoline/piston engine. Honda heads flow great, but that doesn't mean they can't be improved upon. This will be one of my next projects, and will include flow bench testing, analysis, and dyno testing.
Bottom Line: Combined, there is probably 25-40 wHP to be found in a proper camshaft/cylinder head combination.
More to come!
Here are some of my thoughts for optimizing NA performance for our beloved cars, without tearing into the bottom end of the motor:
Airbox/Intakes/Throttle Body
I am encouraged by Prospeed's recent offering of an "alternatively plumbed" intake system. It has 2 of the 3 features (3.5-inch diameter piping, longer total pipe length) I always thought should have gone into such a system (the one feature it does not have is an integrated bell-mouth/velocity stack, but unfortunately there is simply no space for one).
There is still, IMO, a lot to be gained on the throttle body side. There are a few vendors that offer a boring-out service, but that is a band-aid, at best. The factor TB has a 68 mm opening that tapers down to 64 mm at the plate. This is simply not big enough. The limiting factor here is the size of the snout on the intake manifold that the TB bolts onto. However, others that were willing to do a little welding have retrofitted larger TBs onto their manifolds.
Bottom Line: I believe there is about 15 wHP to be found a properly designed and built intake system, along with a "proper" sized throttle body.
Intake Manifold/ITBs
Rahim (96cxt) is the only member here with proof of the benefits of porting the intake manifold. I am having my intake manifold ported, and will try my best to provide documentation (flow bench #s, and dyno testing) of how much the intake manifold can be improved upon.
There is also the (long shot) possibility of having a skilled fabricator come up with a no-compromise design from scratch. Some of the features I would include on my design are:
- Long runners with individual/integrated bell-mouths
- At least 4.0L of plenum volume
- 2 plenums (one for each "bank"), each with a centrally-located throttle body
- No square ("sharp") corners
- Relocated fuel injector ports
The verdict on individual throttle bodies ("ITBs") is ambiguous at best right now. I don't have any interest in running them, nor do I have the resources ($$$) to design and test a bunch of them to find the optimal setup with respect to horn length, width, and orientation.
Bottom Line: I believe there is about 8-12 wHP to be found in a ported and gutted intake manifold, and probably much more power to be found a redesigned piece.
Camshafts/Valvetrain
I think it's an absolute shame that no one has stepped up to make an affordable (cast) camshaft set for the NSX. The factory 10.2 mm/0.401 inch (intake) and 9.0 mm/0.354 inch (exhaust) VTEC lobes on the C30/C32 are, TIMID at best, when compared to what the B-series Hondas are able to run. As a point of reference, the Civic Type R (CTR) cams feature 11.5 mm/0.453 inch lift (intake) and 10.5 mm/0.413 inch lift (exhaust).
Based on the piston speeds of a 78-mm stroked C30 motor, it should be able to rev happily to 8500+ RPM. Yet, NA NSXs typically tap out at 7200 RPM. My research suggests that this is all due to the cam profiles.
Cylinder Heads
The KEY to power in any gasoline/piston engine. Honda heads flow great, but that doesn't mean they can't be improved upon. This will be one of my next projects, and will include flow bench testing, analysis, and dyno testing.
Bottom Line: Combined, there is probably 25-40 wHP to be found in a proper camshaft/cylinder head combination.
More to come!
Last edited:
![Infiniti-throttle-body[1].jpg](/data/attachments/75/75235-3778a15b8f9ef75a6afda82d323aa5b3.jpg)
