Exhaust Bypass Valves

[djomlas]

so you want your car to sound louder than a fartcan on a honda? am i getting this right? and y are you even trying to impress honda boys anyways...they already got it bad
there is a difference b/w a nice sounding exhaust that is pleasant to listen to, and annoyingly loud.

[John V]

This is true. And I can tell you from experience that a Boxster with no muffler sounds absolutely terrible. When I was building my custom exhaust I tried it. Not good.

It wont be 100% without a muffler, there will always be flow through both pipes, just more through the valve. If it does suck then I can just open it a little bit like the PSE bypass.

[David_J]

When I took my car in to get the exhaust installed, I removed the 2nd cats prior to dropping it off. OMG, is was crazy loud. Did not sound good at all. Having the valve that you can adjust should make it sound better as you can control the flow. Since there was no backpressure, the car drove poorly. That was the worst 5 minute drive I have ever had in my Boxster.

Ferraris use this valve type technology. The sound of the valves slamming shut sounds kind of cool. Like a shotgun! You can hear this on FabSpeed's web site in the Ferrari section.

[noone986s]

I have been looking at ordering one of these

http://cgi.ebay.co.uk/Porsche-Boxster986S-3-2-986-Sport-Sound-Muffler-Exhaust_W0QQitemZ290056062535QQihZ019QQcategoryZ38 786QQcmdZViewItem

Might be a different way of installing the valve in the bypass pipe. The video shows what effect the bypass has.

[djomlas]

Originally Posted by noone986s

I have been looking at ordering one of these

http://cgi.ebay.co.uk/Porsche-Boxster986S-3-2-986-Sport-Sound-Muffler-Exhaust_W0QQitemZ290056062535QQihZ019QQcategoryZ38 786QQcmdZViewItem

Might be a different way of installing the valve in the bypass pipe. The video shows what effect the bypass has.

how much would a muffler shop want to add these to a stock exhaust? its just 2 pipes...
i may just look around, i really liked that sound clip, no reason to pay all that money for one already made IMO

[z12358]

Originally Posted by noone986s

I have been looking at ordering one of these

http://cgi.ebay.co.uk/Porsche-Boxster986S-3-2-986-Sport-Sound-Muffler-Exhaust_W0QQitemZ290056062535QQihZ019QQcategoryZ38 786QQcmdZViewItem

Might be a different way of installing the valve in the bypass pipe. The video shows what effect the bypass has.

The Box on that video sounded like crap.

I feel many people are not really familiar with what goes into designing a complex acoustic system such as the exhaust. It has been years, but I remember how in high school Acoustics, we used to build Acoustic curcuits equivalent to electric curcuits. The idea was that the formulas describing the physics (dynamics) of sound waves (air pressure) in enclosed spaces are equivalent to the math describing the current in passive electric RLC (resistor, inductor, capacitor) circuits.

That math is not simple, and far from straightforward. You take one resistor out of an electric circuit and the circuit will stop doing what it was meant to be doing. There are issues of frequency bands and filters, harmonics distortion, and resonance. When all that gets combined with the physics of the car that surrounds the system, it gets even more complicated. Pockets of resonance (amplification of a certain frequency band) can fall right on top of the frequency bands defining the car's structure and rigidity -- and that's when the whole car starts shaking at certain rpms.

I doubt that ANY of the after market exhaust vendors has modeled any of these things the way I'm sure Porsche has.

My point is, these exhaust mods are not trivial, and sound level is not even close to being the most important factor to consider.

Z.