I am about to order an electronic exhaust cutout and I am wondering if I should put in front or behind the cat. I'm thinking it might sound better in front of the cat, but at the same time I think there is a sensor there by the cat? Will this reak havoc of any kind if there is no exhaust getting to the cat? Will there be a CEL and will that CEL hurt my horsepower? I am doing the cutout for the sound alone, so lets not turn this into another thread about the benfits or lack thereof of backpressure. I never get my questions answered when that happens.

 

I have no way to respond to your post without saying WTF so I'll say nothing.

 

You will have a CEL. Because you are bypassing the convertor.

Your car will be exceptionally loud as well. It may burn the exhaust valve seats due to not using an exhaust system, and you also may set fire to anything you drive over or the car itself.

Still sound like a good idea?

 

So would it be alright behind the cat? Will you explain to me what exactly happens to make it burn the valve seats? I don't get that. Would the exhaust gases get pulled back that far some how?

 

 

I ran a QTEC exhaust cutout before the cat on my 02 Neon ACR. Never had a CEL come on. I think it is because although you are bypassing the rest of the exhaust system, there is still enough gasses being passed through the converter to make it happy. The sensor only measures AFR, not volume. I picked up 6 whp peak with it. That was on my Neon though. YRMV on an S2000.

As far as burning exhaust valve seats because of no "exhaust system", how many race cars are burning exhaust seats? Your exhaust valve seats will be fine unless you start running very lean.

Slows2k is quite right about it being very loud though, although I never remember setting fire to anything with the car. Made the tires smoke plenty of times, even if they were the wrong ones.

 

Running too lean will burn your valves or seats. Backpressure (or lack thereof) has nothing to do with it.

Having an exhaust cutout will make you run a bit leaner, if nothing else is changed, but it should not move you more then half a point at most.

I havn't had my S2000 on a dyno yet to check it's AFR, but knowing factory tunes, it probably runs rich enough at WOT that it will help you to lean it out a hair.

If you are cruising around then the O2 sensor will take care of the AFR, but if you are crusing around with the cutout open you are doing everyone around you quite the disservice.

 

It won't cause any problems.

 

While I have a couple people's attention, one more thing: what is the little pipe that comes off at a perpendicular angle behind the cat, and then stops?

 

That's a Heimholtz resonator...it keeps the exhaust from droning and/or buzzing (or so I've read here on this site)