bye bye rattle!!! but.......?

[integralover]

since i had a high flow cat(actually a resonator) on i kept getting this exhaust rattle. so i went to the junk yard today and got one for $20. used of course. put it on and no more rattle. and yes i checked to see if it sould be the heat shield or something else. i figured that since it was a straight flow through exhaust that the sound waves were were not traveling right and causing a vibrating sound. got to be very annoying.

now my question. i took the cat back off and i'm thinking of putting some holes through the honeycomb in the cat. is this ok if i only put like two?

[DjMasaker]

It depends on the state that you live in, any modification to the cat is gonna cause extra "bad" gases to be sent through the exhaust. But if the state is anywhere but Cali, you should pass the emissions test without a problem.

[integralover]

well i live in florida where there is no emissions at all. but it seems to be more of a factor of back pressure. trying to find out how much exhaust i can let through before it starts that rattling sound again.

[DjMasaker]

I'm not 100 percent sure on that then, but it shouldn't rattle at all, its not like your just pulling a flap down. Your just drilling, it's goona be a perfect circle, so there shouldn't be a rattle. But like i said, I'm not 100 percent on it.

[integrawhat]

since when is back pressure a good thing i keep reading on hear about people complaining about not enough back pressure. can someone tell me if a lack of back pressure aka a free flowing exaust is a bad thing why have we all paid so much for i/h/e and hi flow cats that add power by letting gases out without restrictions.

[Igovert500]

Because a little backpressure is needed for a naturally aspired car...if you do a search you can find alot more info, but I'll try and explain the basics.

It is physics..which isn't my strong point, but here goes. Pressure creates velocity in the flow of the exhaust gases. Freeing up your exhaust too much relieves too much back pressure and it actually has a negative effect on the flow of your exhaust.

Turbo cars are completely different and backpressure is a bad thing for them...as the turbos themselves already create enough of a restriction. But NA cars rely on some backpressure.
This is why a turbo car can go with 3 or 4 inch exhausts, or no exhausts at all, but common NA cars, such as an N/A integra shouldn't go bigger than a 2.5" catback.

Any aftermarket highflowing exhaust on an N/A car is going to reduce backpressure...therefore you sacrifice a bit of low-end torque for the higher rpm hp that you gain...

It is all physics.