As a brief summary, the 3.0L C30A and 3.2L C32B are well-designed and generally flow pretty well from the factory. Honda spent a lot of time and money getting those engines to operate with maximum efficiency. That doesn't mean there aren't areas for improvement, but from a general standpoint it is difficult to get big NA gains from the NSX.
Exhaust
If you have a 3.0L NSX, then the biggest flaw is the exhaust system. The OEM manifolds are highly restrictive and tube headers can free up to about 20 whp. A good free-flowing exhaust like the Comptech or Taitec GTLW can net another 5-10 whp. NA1 NSXs with these exhaust mods typically dyno between 250 and 270 whp depending on the car and dyno. A 3.2L NSX does not benefit as much from these mods because it already comes with headers from the factory. However, slight gains may still be found from full-length headers and a good exhaust. A NA2 NSX with full headers and exhaust typically dynos between 270 and 290 whp depending on the car and dyno. The highest I've ever seen is Vance's NA2 (now the star of the FnF movies), which clocked in at about 305 whp.
Intake
This is an interesting area for NA mods. Early on, lots of vendors were releasing CAIs and snorkel mods that claimed to improve power. In recent years they seem to have backed off those claims. The OEM intake system is well designed and flows enough air for most stock applications. Based on some of my recent conversations, intake mods will do little to nothing for a 3.0L NSX. There may be a little more benefit for the 3.2L, since it displaces more air.
Engine Internals
If you don't go FI, then the only other place to find power is engine internals (pistons, cams, valves, ports, etc.) The benefit is questionable, however. In the late 90's and earlly 2000's, Comptech sold an engine package called the "IEM". The complete package gave you ported and polished heads with valve work, slight decking to bump compression, hot cams, etc. Mark Johnson, owner of Dali Racing, got the complete package and reported that it netted only about 22 whp on the dyno. Not much considering the cost. Even a 1st gen Comptech supercharger will get you 60 or more for less money.
If I were you, I would talk to Chris at SOS. If you are worried about stroke and piston speed issues, you could consider keeping your stock stroke/crank and sleeving your block with bigger pistons. SOS sells sizes that will get you to 3.3 or 3.4L without changing your stroke. This is the sort of displacement bump that combined with intake and cam/head mods, will get you close to FI power.
Exhaust
If you have a 3.0L NSX, then the biggest flaw is the exhaust system. The OEM manifolds are highly restrictive and tube headers can free up to about 20 whp. A good free-flowing exhaust like the Comptech or Taitec GTLW can net another 5-10 whp. NA1 NSXs with these exhaust mods typically dyno between 250 and 270 whp depending on the car and dyno. A 3.2L NSX does not benefit as much from these mods because it already comes with headers from the factory. However, slight gains may still be found from full-length headers and a good exhaust. A NA2 NSX with full headers and exhaust typically dynos between 270 and 290 whp depending on the car and dyno. The highest I've ever seen is Vance's NA2 (now the star of the FnF movies), which clocked in at about 305 whp.
Intake
This is an interesting area for NA mods. Early on, lots of vendors were releasing CAIs and snorkel mods that claimed to improve power. In recent years they seem to have backed off those claims. The OEM intake system is well designed and flows enough air for most stock applications. Based on some of my recent conversations, intake mods will do little to nothing for a 3.0L NSX. There may be a little more benefit for the 3.2L, since it displaces more air.
Engine Internals
If you don't go FI, then the only other place to find power is engine internals (pistons, cams, valves, ports, etc.) The benefit is questionable, however. In the late 90's and earlly 2000's, Comptech sold an engine package called the "IEM". The complete package gave you ported and polished heads with valve work, slight decking to bump compression, hot cams, etc. Mark Johnson, owner of Dali Racing, got the complete package and reported that it netted only about 22 whp on the dyno. Not much considering the cost. Even a 1st gen Comptech supercharger will get you 60 or more for less money.
If I were you, I would talk to Chris at SOS. If you are worried about stroke and piston speed issues, you could consider keeping your stock stroke/crank and sleeving your block with bigger pistons. SOS sells sizes that will get you to 3.3 or 3.4L without changing your stroke. This is the sort of displacement bump that combined with intake and cam/head mods, will get you close to FI power.
