i did some searching through the forum, and found a post from a guy back in like 2002/2003. he had stated that a true dual exhaust was better for non ported engines, but on a ported engine the collected exhaust headers would yield more power than true duals.

any truth to this?

 

There is only theory behind it. There has yet to be any reall numbers for either side to be posted. Back to back and multiple run dyno sessions would be the ONLY way to tell if it was true or not. Some people run true duals on p port motors so I don't know really. I'd stick my true duals though. I just need a car for them. Damn sport looks like a modern sculpture now.

 

A single can do better, but only if carefully tuned.

Since most of us don't have the resources to tune a header & it's collection point, duals work best.

 

4 port ported 13b twin turbo, 2/2.5in all the back to where it dumps into a 4in can for a muffler, if it could run better I'll never know

 

I was assuming duals were an NA issue.

Dual turbo's are a whole different story.
Flow is more of a factor then tune.

 

what do you mean tuned for a header????

 

The point at which the two pipes collect is how you "tune" a collected exhaust. But since the bolt on kits don't have complete freedom for max power they are probably not the best 'tune' setup you could use. In other words it has to be a custom made collected setup and you have to know what your doing to make it work better than true duals. Not just any collected system will be better automatically.


To the original poster if you have a turbo you can't really tune it unless you have separated twin turbos(I would think) and even then one larger turbo is more simple and can make just as much power(although laggy)


Santiago

 

With NA's tune generally has more benefit then just flow.
Duals are a "no-brainer" - with half the pulse frequency going down long pipes, they sort of tune themselves.

In a turbo, the exhaust turbine pretty much kills the tune, so flow is where you look for power.

 

uhhhh if the "tuned" setup is better, why are there no aftermarket setups?

 

I think it is because the "tuned" exhaust is for a certain RPM region. It has never really been answered how large the region is and/or how good/bad the 'tuned' exhaust does out of the tuned rpm range. So far only an oppinion set has been given. Unless I missed something.

 

SureShot and 1987RX7guy seem right. The racing engineers are saying that tuning size and length of the exhaust, much like intake velocity stack, develops a velocity column which helps pull and evacuate exhaust, where previous exhales help pull out the oncoming exhales, though causing early and latent backpressure, seems to increase low-rpm torque. Yes, the turbo manifold area distorts this, but can help before spooling just to hurt after spooling. Well tuned, I imagine this helps in pulling new breaths at the intake during port overlap.