i read in an old post that the absence of a cat could leave black soot on your bumber. any truth to this?

 

This engine runs kinda rich under normal circumstances. Even with the cat in place, you'll get soot on your back bumper. The visibility of the soot will depend upon the color of the car and the specific richness of any given car. You should already notice that you exhaust tips gets sooty pretty quickly and needs constant cleaning. The cat won't hold that much soot back. If it did, it would clog up very fast.

 

I think I'm going to get a test pipe very soon...I think coupled with the HKS hi power single it will sound great...However I love the sound of it now-very deep and well, I think its the best sounding exhaust you can buy for an s2000...I dont want to install the test pipe and lose that quality sound the HKS provides.

 

You really should run the cat in California, BIG fine if you get caught without it. The cat has very high efficiency. :/soapbox:
I suggest you do before and after dynos to see the change. I initially lost hp when I removed mine.
Weigh the test pipe. They vary from less than 3 lbs titanium to over 10 lbs steel. The cat is only 15 lbs.
The sound will increase. Tone change depends on several factors.

Let us know how it changes your exhaust tone, ride comfort, stereo enjoyment, etc. Also, let us know if you weigh the testpipe or do the dynos.

 

I should've taken a picture of mine... the crap that was on my bumper wasn't just black soot. It had a yellow tinge to it, maybe a bit of sulfur content. Took some elbow grease to get it off, too.

 

What about running a test pipe with a completely stock exhaust. Would it sounds very different? Does it make the car throw CELs?

 

^ No, You wont hear any sound difference....and all most all of the test pipe comes with an 02 bipass module that hooks up to the 02 sensor and tells your ecu everything is hunky doory

 

^Do you think I would see any HP increase? If so this will be a great easy bolt on.

 

^ Yes you will gain a few HP with the stock exhaust...but not near as much as you would if you had an aftermarket one

 

Not quite true for test pipes for the S2000. The owner has to "acquire" his own electronic O2 simulator or make a mechanical O2 simulator.