Exhaust Bypass Valves
 

Hey guys, I just bought these electric bypass valves and will be doing a write up along with dyno tests over the next couple weeks. I bought the valves and will have them installed within a week or two. I contacted PorscheDoc and got the low down on doing some dyno runs. So everything is falling into place. I bought dual 2 inch valves from Charles (http://www.badlanzhpe.com/index.html) and they are the best value out there if you want sound and maybe some top end (we will find out when I dyno them). I spent a total of $270 and that is a drop in the bucket compared to a $1000 muffler, and it will be louder and resonance free... if I want it to be. Any feedback will helpful. Let me know what you think. :)

Expect Updates!

Exactly where do you plan to put these?

I'm looking forward to this!! Having not wanting to drop thousands on an exhaust and not wanting to take a chance on resonance and the constant drone of a cat-back type system this can be the perfect solution! Quiet or loud depending on the mood of the moment. My only concern would be the placement in the exhaust system (ground clearance) and the motors freezing/breaking in the "open" position. As far as gains in power...I doubt it...like all the other exhaust systems on the market this would be great for sound only... :cheers:

Since the pipe to the muffler makes a U after the cat, we were going to cut that section out and add a pipe to make it a Y pipe. The actual vavle would be inside of that U. There will be plenty of space considering the valve is relatively small. I plan to just run the wires where the stock O2 sensors run into the car.

So, to be clear, you're going to have a 2" straight pipe which can be used to bypass the muffler using your valves?

I can tell you from experience that a 2" diameter straight pipe positioned right there will be loud. And incredibly droning. :D

Wow, looking forward to it! Good luck!!

Heck yes its gonna be loud. :D But droning can be easily fixed with a flick of a switch. Its almost all for the sound, but if I get any top end it will be of good use at the track. Heres a picture of the planned layout.

It would be a heck of a lot cheaper and easier just to pull the U tube out from the muffler when you get to the track than go through all you're doing now IMO.

But how will I do that while driving next to a fart can honda and blow them away with my awesome sounding engine? I want a louder exhaust like 98% of this forum, by getting bypass valves, I can get loudness, mediumness, or quiet instantly and keep the woman happy or open the valves as soon as she gets out of the car so I can scare small children.

I can't wait to see the outcome of this project. :cheers:

The only problem is that it doesn't really sound good when the muffler is off. It's just boomy and obnoxious. Given that there is no performance increase at all to running straightpipes (with the possible exception that with real straightpipes you can eliminate the weight of the muffler) it doesn't seem worth it. But, your car.. knock yourself out!

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 :cheers:
there is a difference b/w a nice sounding exhaust that is pleasant to listen to, and annoyingly loud.

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.

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.

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

Yeah I thought about that too. There is a guy here who did it himself.

http://www.ppbb.com/boards/ppbbphp/showflat.php?Cat=&Board=ARCHIVES&Number=1067764&pa ge=8&view=collapsed&sb=5&o=7&fpart=1

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.