hello,
just got a thought in my head.
I'm researching on doing a catalytic bypass on my 02 p5. it would be a custom exhaust system all the way from a perfomance exhaust manifild to a wider high flow fontpipe all the way to the muffler without a catalytic converter. Now i understand its harmful and also illeagal, but, in Ohio, where state inspections are not done in cars, what difference would it make.
anyone have the thoughts/suggestions on this.

 

exhaust bypasses are VERY effective.....if you can tolerate the noise.

put the bypass right after the header and buy some earplugs....just for fun wait until you're halfway down the track and then open it up mid-run. It'll sound like you blew your muffler off the car!

 

but in a setup like this, wouldn't the muffler operate on its normal specs though??

what i'm trying to ask is, just because the catalytic bypass is done and then a larger diameter pipe running all the way to the muffler, would it actually make the muffler sound louder than it is, and if thats the case, is it possible the eliminate that loud noise while using this setup.. possible? or not??

 

what most people do is insert a "bypass" that is shaped like a Y. the top left and the bottom of the Y are the stock exhaust. The top right of the Y is just left open. When the bypass is closed you would sound just like stock with all emissions. When opened you would basically be running on open header.

That is what MOST people do. You very well could design it to where the top right Y feeds a pipe that blends in to the stock exhaust after the cats but before the resonator....I think this would be minimal gains as you'd be creating more bends, adding more weight and still breathing through your restrictive exhaust.

Just dump it to the atmosphere and invest in some ear plugs.

 

Actually one thing to check on is to see if ohio has a pollution law in effect for cars. I know here in SD and back in TN, there is no law. So I could drop the Cat off the car, and there isn't too much the local PD can do about it. Now here's a question for you.

Do you plan on doing this exhaust work yourself, or having a shop do it?

I know shops around here will NOT take off cats. Because they can get into federal trouble if they do. Another way, is just put on a high flow cat. Expand all the piping to the size of the resonator. And have a muffler put on. That'll get attention going down the road.

 

Maybe this is what you're looking for:
http://www.buickgn.com/electricexhaustcutout.htm



pretty cool...one minute you're stock quiet, flick a switch and you've got a snarling, spitting, howling open exhaust. It would involve some fabrication but nothing a decent muffler shop couldn't do.

 

They showed one of those installed on the TV show Trucks! He took his though and had it run to straight pipes out the side. Word of caution when using those though. Don't run it too long with them open, you'll burn up your valves. Engines need a little back pressure.

 

Running an open exhaust will not "burn up" your valves, and engines do not need "backpressure". They need exhaust velocity, and running a pipe that is too large or completely open can kill the velocity of the gasses exiting the heads. People often see this as needing "backpressure", but its not.

 

Have you ever seen a engine that has run with straight pipes on it?

Cause obvisouly not. It's called back pressure for a reason. Items such as cats and muffler restrict the flow of the gases, causing the pressure to build up. And most stock systems, pressure to keep gases from flowing too quickly by the O2 sensor. Good example, 03 Cavalier, you cannot put a high flowing exhaust on one because the flow is too fast for the O2 sensor. Causing the check engine light to come on, and voiding any warranty along with it.

I know because 5 morons here already did it to their cars. And I've seen the valves of a engine that was run with straight pipes. Not a very pretty sight either.

 

Kcidmil, do you have any professional experience because your reasoning and logic doesn't make any sense??

 

I've been working on cars since I was 16. And currently a mechanic for the military. In fact, this discussion was once brought up at my work. And the explanation that I gave, is the same one that civilians at our work gave. And they have been working on vehicles for decades. Is that enough credit, or do you want the resumes of everyone I work with too.
Exhaust needs to flow, but it needs some restriction. Now that restriction comes from the cat, muffler and the size of the pipe. Why do you think they rebuild the engines of Top Fuelers after every race. They do more than just replace the pistons each time.

 

Well, I'm sorry but your logic is wrong. The reason they rebuild top fuel dragsters after every race is because of the extreme stress a 2600hp engine makes.

I'm an ase certified mechanic and a racer. ENGINES DO NOT NEED BACKPRESSURE...they need VELOCITY. There is a difference. I was being polite and you should probably step back on your tone a little before I get my college physics book out and hand out an intellectual butt-whooping.

I understand that the people at your shop have been around for a while and seen some things....I've worked with guys like that as well. They are the same ones who tell me my 1976 4cyl pinto won't run 11's in the quarter mile. They get proven wrong by me all the time.

I appreciate the fact that you're in the millitary and I appreciate what you're doing. You should, however, realize that the millitary doesn't build top fuel dragsters or performance sport compacts. They have you working on jeeps, hummers, tanks, etc....there are going to be slight differences.

 

Fine you tell the guy to run the car with straight pipes, and just see what happens.

 

I think I did.

p.s. I've run these on several of my cars without ANY adverse affects other than noise.

 

Oh and btw, ase certified here too. And do you think I've worked on Military vehicles my entire career. I built a 90 Nissan D21 up. and raced it. And that was when I was 18.