modifying exhaust

[Myst]

Hello,

I live in a country (Portugal) where I can't change most of any car parts.
Wheels sizes, noise leves, height ride, etc, have to meet the factory standard or else I don't get my anual IPO (that's the place where I have to take the car) certificate... and if I don't have such a certificate, the car can't be on the streets.

So, my question (maybe a stupid one, but I really don't know anything about mechanic) is:
- is there a cheap way to add a bypass to the cats, in a way that I can control from inside the car (with a push of a button) what exit is used ? This has to work in a way that I can have a better "sound" when I want it :revs: , and turn it off when I need it off.

Thanks for your help, and I apologise for my bad english :hihi:

[Bigglezworth]

Hello,

I live in a country (Portugal) where I can't change most of any car parts.
Wheels sizes, noise leves, height ride, etc, have to meet the factory standard or else I don't get my anual IPO (that's the place where I have to take the car) certificate... and if I don't have such a certificate, the car can't be on the streets.

So, my question (maybe a stupid one, but I really don't know anything about mechanic) is:
- is there a cheap way to add a bypass to the cats, in a way that I can control from inside the car (with a push of a button) what exit is used ? This has to work in a way that I can have a better "sound" when I want it :revs: , and turn it off when I need it off.

Thanks for your help, and I apologise for my bad english :hihi:
What you are asking 'can' indeed be done - but is not well supported in your situation. Exhausts can be manufactured to have an auxillary bypass channel funnel the exhaust vs. the main channel. This type of a system has been used by many a hot-rodder over the decades to bypass the entire exhaust system with mufflers. Sometimes referred to as hot pipes or dump pipes.

This noted there are lots of things that you would need to consider prior to ever entertaining this set-up.

1. Cost. This isn't a cheap set-up as far as exhaust goes.
2. Space/logistics. You require a second pipe for each pipe you would perform this modification to that is of equal diameter to the main pipe.
3. You would need to confirm if your engine management system would support not having to meter the gasses as they pass through the catalytec convertor (I know the M5 has sensors pre and post convertor that would make this difficult). You 'might' get CEL errors - although this would be no different than removing the cats in their entirety which I know lots of people do and I'm on the brink of performing personally.
4. Performance. This is the end result that you would be doing this all for and has to be seriously considered. What is the gain for the amount of time/money injected. RS6 makes tons of power without this type of a modification. Yes you can get a little more power, but it's not substantial enough to warrant all the headache IMO for what you are suggesting. If you were removing the cats in their entirety I'd say this is a no brainer and money well spent. You don't have this luxury and swapping back and forth isn't all that much fun (unless you own your own shop of course).

Tim

[DuckWingDuck]

Tim, I think myst is just looking for an enhanced sound rather than boost in performance, I could have read his initial post wrong though.

[Bigglezworth]

Tim, I think myst is just looking for an enhanced sound rather than boost in performance, I could have read his initial post wrong though.
I see that now. Well than you certainly could put in a bypass line with valving just for sound. I know it's been done before. In fact it's been done on an NSX by one of the members I chat with on NSX Prime. Here's a couple of pics of the set-up for a mid-engine car.

http://members.shaw.ca/bigglezworth/Car%20Porn/14678i~1.jpg
http://members.shaw.ca/bigglezworth/Car%20Porn/14678i~3.jpg


This system uses an APEXi Dynamic Electronic Control System (DECS). It's an improved version of APEXi’s Exhaust Control Valve (ECV). It allows the user to gain complete control over exhaust decibel levels through a remotely mounted control module. With a touch of a button, the user can electronically modify a spring loaded butterfly fitted into the main piping of an exhaust system. The DECS was created as an alternative to standard silencers and allows the user to fine tune an exhaust system to fit his needs.

http://traffic-shop.com.ua/images/prod/zoom_API432-A002.jpg

[DuckWingDuck]

tim, the nsx is one of the cars that I'm considering, but why are they so expensive?!?!?! Want to sell me yours? Heh.

[Bigglezworth]

tim, the nsx is one of the cars that I'm considering, but why are they so expensive?!?!?! Want to sell me yours? Heh.You're kidding right? They are dirt cheap at less than 30K in many instances. They are an engineering masterpiece, one of the most comfortable rides going, timeless in design for many, and a shear thrill to drive on the track. Also don't forget they are a nominal 95% aluminum (only a few pieces here and there that are HDPE or steel), and hand built. Oh ya, and the most important thing to those that own them is that they are hands off for maintenance. I've beat the crap out of mine on the track for the past 5 years and aside from various modifications I've done to provide that next level of performance or subtle styling cues, have only needed to change oil and plugs..... Can't say that about the RS6 can you. :)