I just had both pre-cats replaced because over the last week it's been sounding loud "under there". The exhaust place put them in today, and the man said "it'll have more power now", and I thought he was just being funny, but when I drove away I was shocked at the difference. It was like someone gave me back 50hp. Why is that?

 

The old ones were probably clogged and leaky. That would suggest that you lost power to them due to the restriction they caused, and the fresh, nonclogged cats are just freeing up lost power.

 

Shoulda left the pre-cat off and gotten a downpipe. That way you wont lose that power anymore cause theres nothing in there that can get clogged.

 

Yeah, I thought about that, too, but my state is very tough on emissions.

 

The single main cat should be fine for emissions if the air pump is still feeding it.

 

A single cat is all that's needed.
Those precats can't be tested at the places.

I have the Bonez downpipe and high flow cat and had a cone filter and Corksport single exhaust and passed a Dyno Sniffer check here in AZ.

 

word ^

 

Precats are almost useless. They're only good if you need to pass emissions while the car is still warming up :-p

 

You could hollow out your old cats or your new ones ... But you would only pass visual inspection. DOH

 

Hollowed cats sound terrible because the noise bounces around in them.

A silencing unit like a DP should be used.

I had a straight pipe to a shitty cat and it had a high rasp to it.
Once I put the Bonez on it got deeper and growled like a beast.
If I had an NA still I would slap that bad puppy on in a second. No police worries and yet better flow.

To add to the other stuff.
The precats are used for cold emissions and cannot be tested unless you go to the station on a trailor. You'll fail anyways because your main cat hasn't gotten to running temps anyways.

So far The FC is the only car I know with precats. It was a failed attempt at adding high tech crap to our cars(like the cold start assist)

If they look under the car I bet you money they will see the main cat and not realize you should have 2 small bumpy pieces before it.

 

Well said Digi I agree with all that especially the high-tech crap all that failed technology !

 

thats why Montana rules emissions no one even cares about emissions. so many cars and trucks are straight piped, and i've never even tested the emissions on my 7.

 

neither have i

 

FD does too.