most cars you will gain a good amount of power. i know the S is highly tuned already so will a header help out? also with the header i know it will lower the psi but does that mean that you can run higher and not have damage?

ie if the car blows at 12 psi with out a header will it blow at say 10 with the header?

tia

 

Not sure where you get this sort of information from. (Eating crow and removing this smilie.)
A header has no affect on a superchargers boost pressure. Boost pressure is governed by the blower itself and the speed at which it is driven. If it boosts 12 psi @9000rpm, it will still blow 12 psi @9000rpm with any header you put on. With a blown S2000, what a header will do, is to provide a better means of egress for the exhaust, thus making for a more efficient "pump". A more efficient pump will produce a better power output. Also, removing the cat on a blown S2000 will further the cause of exhaust egress.
I believe you are thinking "turbocharger".

ps. In answer to your other question: NO, you can't run higher boost on the "perceived" notion that a header will lower boost pressure and not have damage if you do nothing else. Anytime you increase boost pressure to any significant degree on the intake side, you need to do something to avoid damage.

 

thanks xviper i was given that infromation for ripp modds. they are a large supercharging speed shop.

 

The other factor affecting boost is restriction. That is, the design of the intake runners, head and valves affect how much resistance there is to airflow and hence how much boost is measured.

The theory above comes from the suggestion that an engine with valve overlap actually releases pressure out the exhaust valves during the early phase of the intake stroke. The extention is that the more efficient the header onwards is the more will pass through and hence less boost will be measured. Or conversely that back pressure from the exhaust is a factor in boost so less back pressure equals less boost.

I'm sure Alaniz or someone can answer this more definitively, but I doubt the overlap would have much effect and even if it did aftermarket headers won't change things much. They don't have much effect on NA engine simply because the stock headers are pretty good so I doubt they will have any effect on boost.

With regards to the idea of upping boost, assuming this theory held water (And I don't think it does) you could run a smaller pulley and bring the pressure back up and I doubt it would be any more or less dangerous. The cylinder pressure would be the same.

 

btw...
Doesnt aftermarket header lean out the A/F on S/Ced(no stand alone ECU) S2k? making it dangerous?

 

In my experience, if you have a bottleneck in the system after the combustion chamber and then remove the bottleneck you will see the boost drop.
I went from a factory exhaust system to Toda header, straight pipe and Amuse dual....... Lost boost. Additional fuel and timing adjustments recovered the lost power at lower boost and a few more rpms.

The bottleneck in the S2000 is in the exhaust ports and valves. The valves & passages in my head have been opened up enough (16%) to make the exhaust system the bottleneck. I am currently considering opening up the header back exhaust system. Then it's back to the intake to maximize the flow. 110mm throttle body and CF large plenum intake manifold plumbed for nitrous. It never ends. Be happy with the factory header unit unless you race or have money to burn.

 

As did I but I have the Fuji cat back instead. I could not observe such a loss but then, it is most likely very subtle and not measureable on my boost gauge.

In actual mechanics, it's hard to see that a freed up exhaust would contribute to lowering boost pressure as the combustion chamber presents a barrier between intake and exhaust. At no time is there a directly open passageway between intake and exhaust during the 4 cycles. What am I missing here?

 

The magic word is overlap. That period when the intake and exhaust are both open. On the '00-'03 S I believe it is somewhere in the neighborhood of 20 degrees. It is decreased to give more low end torque on the '04-'05.

 

Gotcha. 20 degrees seems like a lot to me. During that phase, would the exhaust gas pressure not also be applied back into the intake as well, thereby maintaining a bit of that "barrier" I mentioned? Could this be why the change in boost pressure from a freer exhaust be so hard to observe? On an S2000, it can't be more than 1/2 psi or you'd see it even on a crude gauge, no? 2 psi is somewhat inconceivable.

 

[QUOTE=Sideways,Dec 29 2004, 07:54 AM] and CF large plenum intake manifold plumbed for nitrous.