Bill/Cory Exhaust Thoughts

[Jackpine]

Originally Posted by dplummer87

See, thats what i was thinking, i mean, IMO, by the time it gets to the muffler, the muffler is probably just being used as a "silencer" i mean, its already gone through the restricted headers and the restricted cats right?

So unless i put some headers and highflow cats, the muffler is probably just sound....? Logical thinking or no? Please correct me if its not. Im here to learn

Isn't a muffler simply for sound suppression? That's what I always learned. And the CAT is there to transform unburned hydrocarbons into something that's good for you like water vapor or carbon dioxide (as opposed to carbon monoxide).

But, the simple fact is, both these devices cause back pressure that prevents complete scavenging of the cylinders during the exhaust cycle. The introduction of Exhaust Gas Recirculation (EGR) sort of does the same thing, in the name of reducing Nitrous Oxide emissions I believe. So, for one reason or another, we're not going to get totally clear cylinders for the next intake cycle.

However, it IS possible, through a carefully tuned exhaust, to reduce the backpressure somewhat, which WILL increase the power available. You can even do it while staying within noise and emissions pollution limits. But, it takes a skillful exhaust specialist to make all this happen. I doubt it's any kind of simple "bolt-on" mod.

I think Lars and Cody posted a pretty good discussion of this a while back, but I'm too lazy to look for it.

What I took away from that discussion was that the results did not justify the expense, unless you're an absolute "purist" who doesn't mind throwing dollars in search of perfection!

One more thing that not everyone knows: You can't simply chop off the exhaust manifold and get a perfectly scavenging engine! This system is synergistic and needs to be TUNED to the engine to make things work properly!

- Jack