My homemade PSE exhaust mod soon underway... input please
 

Hey gang,

So I was going to post this on the tech forum, but I thought there would be more of you here to have fun with this discussion. I'm waiting on a used Box S muffler to arrive which I plan to hack into my own version of PSE with valves and a dash switch. Even if it stays on most of the time, it will be nice to have the switch option, and since my car has to pass Spanish inspection every two years, the finished mod needs to look OEM and be quiet on inspection day. Since I can TIG weld stainless, the final solution is flexible (and will be a fun project.) Though I am sure the Pedro/Oettle/Fister bypass mods are great, I'm going for a different solution.

The question is: where in the exhaust flow will the valves go? Here are some pics to get everyone oriented:

OEM muffler flow diagram (pretty sure I have this correct)
http://www.evan.com/boxster/stock_cut_open_diagram1.jpg

Same flow diagram from the other side
http://www.evan.com/boxster/stock_cut_open_diagram2.jpg

Bottom of this pic is the factory PSE from MK1 Boxsters. Note the piping from the inner chambers, through the valve. Its then routed around the muffler and directly to the tips. (This is the one that had the polished piping visible under the rear bumper)
http://www.evan.com/boxster/mk1_PSE.jpg

Here is a shot of "facelift" PSE from a 2004 Box. Its not clear from the pic where the piping to the valve originates or ends up, but my educated guess is it comes from the inner chamber and gets routed to the outer chamber, where it will then go through the last curve of piping inside and out the tips.
http://www.evan.com/boxster/sport_exhaust_valve1.jpg


AND FINALLY: I'm debating where my 2.5" diameter valves will go. Option 1 (easiest to fabricate) is to go directly from the inlet pipe, through a valve and right into the outer chamber. Possibly damn loud, though maybe not any more so then the usual bypass mod. No matter what I'll have to weld in a reducer from maybe 1" to 2.5" so there may not be so much more noise getting through then with 1" tubing anyway.

Option 2 is to use the valve to connect the inner and outer chambers. With the big diameter valves here I think plenty of noise will end up going through the outer chamber and then out the tailpipes, hopefully with a more refined sound then a straight-to-the-tips bypass, but I don't know. This option is a bit harder to fabricate but will not be easy to spot even with the car on a lift for inspection.
http://www.evan.com/boxster/stock_cut_open_diagram3.jpg


I'm open to all ideas and suggestions! Also if anyone knows a supplier for vacuum actuated exhaust valves, let me know. The one on ebay looked sketchy and he always only has "one left."

Evan - Unfortunately, I don't have advice for you but I do want to thank you for all of the cut-away photos and explanation! I learned a lot and expect that many others did too. :cheers:

well, I saw the same ebay vendor as you and, while he only has one valve left, he has managed to sell 6 of the 5 units he has ... but yeah, if someone can find a better vendor.

otherwise, I was thinking of cutting-out the secondary cat on each side and putting cutouts in their place using easyseal exhaust clamps. attach the valve to the cutout so that muffler is bypassed when valve open. simple and easy to put the cat back if required.

regarding control, instead of using a switch, use the vacuum switch that opens the resonance flap on your intake (if you by an x51 power kit for your car it doesn't have the resonance flapper and the Porsche install instructions actually tell you to repurpose the rpm-activated vacuum switch to control the pse). so, you can use the same switch and split the vacuum line, or split the rpm signal and use multiple switches. the benefit of the latter is that you can turn off the pse by killing the signal to the switch. either way you should think about adding a second vacuum tank. using this method you get a pse that opens over 4000 rpm when hard on the throttle, but keeps back-pressure at lower rpm and keeps the muffler in the loop when driving sedately.

You're welcome! Thanks for reading. :)

Someone else did the hard work and actually cut open these mufflers, I just obsessed over the function and made some diagrams on their pics. Its going to be fun to get in there and try my own hacks now!

I thought so too. The ebay guy is cheap but I think I'll look elsewhere. There appears to be a vendor in the UK with nice valves.


Interesting. I'm not looking to do a total muffler bypass but rather to allow part of the flow past and part still through the muffler. No drone and more sound I hope. Being that I have a euro-spec car, I have only the secondary cats.


This part is all new to me and I'll have to learn more. Thanks for the info, I had no idea that there might be a resonance control in the intake that is vacuum controlled. Off the cuff I can say that since I'm only going to do a partial bypass, I think backpressure will be sufficient anyway, though time will tell. I want to enjoy the noise on demand, not only over 4k rpm. Carnewal has a kit I am considering for the vacuum connections, including a solenoid valve and wiring.

Please tell me more about the vacuum tank, I'm a noob when it comes to that part.

If I were you knowing what I know I would email or call these guys:

FD Motorsports

They got their start by modifying Porsche mufflers in their garage for their own edification, it has since grown into a decent sized shop with a thriving mail order market also. You cannot talk to better guys than Mark or Darin.

Excellent, thanks!

Also known as the DIY Pedro Sport Exhaust (PSE):
Make the Pedro Sport Exhaust

Been contemplating this since I'll be doing the second cat delete soon anyway.
Way too complicated to start hacking into a standard Boxster muffler. Won't improve the resonance (=exhaust sucking) characteristics of the exhaust either. The PSE just pipes a small fraction of direct noise to the outside world.

Yep, any information on exhaust valves would be appreciated.

Thanks for the link. You'll notice that I mentioned Pedro in the original post, so I'm well familiar with his mod and I like it. If it didn't matter for the bi-annual inspection, and if I didn't care about turning off the sound sometimes, then I would just weld up a similar mod myself. But since I can weld stainless, anything goes.

I am essentially after what you describe the PSE to be-- a little extra noise piped in. Though I'll probably go for something more aggressive, and of course with the valves to turn it on and off.

Regarding your comment about hacking into the muffler being complicated, I'm not reinventing the insides, just making a valved bypass. And I specialize in complicated. :D

if you just want the pse to be on/off with a switch, use an electric cutout instead of vacuum. vacuum is used when you want fast response (ie, actuating as you cross an rpm threshold); electric should serve your needs fine, is cheap, and is readily available on ebay. check out maxspeed motorsports who sell such a kit.

Good suggestion. I was seriously considering electric valves, and there are many on the market. I Googled extensively and unfortunately, these get mixed reviews regardless of manufacturer for being unreliable. They are also very long/tall, so space will be an issue. If anyone has direct (good) experience with these cutouts, I'd like to hear it. I haven't found the nicer ones to be so much cheaper then vacuum valves actually.

My original plan was to hide two electric valves down inside the muffer with the actuators outside, so if a gear motor craps out it can be replaced. However, these aren't made for that type of application, you really have to have access to the whole thing to change the motor. Also, the electric valves are aluminum, which I can't weld, while the vacuum valves are stainless, which I can. This matters if I want the valves mounted halfway inside a muffler.

One major bonus with the electric valves though: you can set the opening anywhere you like, not just open or closed. That could come in handy if the exhaust is too aggressive wide open, I can adjust it to taste.

Can someone take a measurement for me?

I'd do it myself but my car and I are 2000 miles apart most of the time, including right now. What I need is a rough measurement of the distance from the top of the exhaust piping to the underside of the heat shielding (see arrows.) I want to see how much space I have to play with for the bypass piping and valves.

http://www.evan.com/boxster/muffler_clearance.jpg


In other news, my donor muffler arrived today! Thanks to forum member itsnotanova for helping me out with a good deal.
http://www.evan.com/boxster/evan_donor_muffler.jpg

You could try your option #1 without even having to split the case. Leave the valve outside the case, drill a hole, and weld a stub/flange on for your connection.

I'm leaning in that direction too, with the valve being located in about the same place as the stock PSE has it. I'd possibly tap into one of the curved connection pipes, pipe through the valve, and then straight into the outer chamber. Stealthy and will look fairly OEM.

Any new progress on this?

As soon as the muffler shows up from you, then I'll start building version 2. :D