OK13B

iTrader: (3)

i was told that if i hollow out my cats that i wont have enough back persure and will lose power. what do you all think?

Hades12

That you should stop talking to that person.


welcome to the forum.


.

rOtAryIsbEttEr

get urself a long scredriver and a sledge, have fun and tell your friend that its an rx7 and not an escort and u dont need any more backpressure.

jfachner72

If you do it make sure you are outside and do not breathe any of the dust.

The dust is a carcinogen and can cause cancer.

I used an impact hammer and wore a respirator.

Also be careful with the clean-up. make sure you get it all cause it could kill an animal if it was to be eaten.

Jay

OK13B

iTrader: (3)

thank for the info and thanks for the welcome.

Siraniko

iTrader: (13)

Just remove the cat and drive it with an open exhaust to the nearest muffler shop so they can make a straight pipe.

rolfs_7

whoops i hallowed mine out inside my shop lol o well! i just a pipe and a hammer ! not hard at all except it looked like some had started 2 melt and got harder when it was melted.

Rx-7Doctor

iTrader: (13)

Guy's your slipping. He has a GSl-Se. Hollowing out the cats will stop the 6 ports from opening. If he is going to do this then he need to wire them open.

Rx-7Doctor

iTrader: (13)

Guy's your slipping. He has a GSl-Se. Hollowing out the cats will stop the 6 ports from opening. If he is going to do this then he needs to wire them open.

rolfs_7

rx7docter does it really hurt 2 wire them open?? i have heard from many people to not wire them open. I know you can hook them up 2 a small air pump but how do you go about getting them 2 open at just the right rpm?

Rx-7Doctor

iTrader: (13)

Wiring them open will affect some of the bottom end response. Hooking them up to the smog pump via a t fitting can open them but may not at the correct itme but will still be effective.
You can get really complicated and hook them up to a RPM switch that opens vacuum at the correct RPM but that's not worth the effort.

PT Ray

Not to hijack but I just hollowed out my after market cat on my SE this weekend and noticed no loss in performance, stock engine with a RB header and muffler. The substrate was loose and making an awful clang, could not take it anymore. Dropped the cat and knocked out the substrate with a broom handle.

rolfs_7

pt ray its probly ur 5th and 6ths not working i can tell when mine dont and dont work. doc i have them on my smog pump but they dont open at the right time and stay up for a while after the gas is released so it sucks. hmm well i got another idea how about putting the redline light/buzzer down and disabling the buzzer and hooking it up to somthing else...but again thats probly not worth it...how bad does it affect my low end if i wire them open?

PT Ray

Someone needs to explain to me how a presilencer offers the back pressure to open the ports while a gutted cat does not. Both are straight through, the presilencer is just insulated to absorb noise.

rolfs_7

i dunno?? it might not be ur prob it was just a suggestion.

PT Ray

I hear you. Rx7docter just made the post that hollowing the cats on an SE would not open the 6 ports, I do not see the reason for this or noticed any indication there of when I hollowed my cat.

BigJeff

Alright, now this has me curious. A carbed system I can pretty much understand how it works, but my knowledge of EFI systems is severely lacking.

How does port opening get timed by the exhaust backpressure and why does it even need to be set up that way? Apparently this only happens with two of the ports, which I can kinda halfway come up with a guess as to why that would be, but anybody want to expound on this?