This weekend i will be inspecting my catalyctic converter in suspision that it might be clogged or deteriorizing. If i were to find out the car was clogged and i hollow it out, more than likely i will throw a cel correct? But will this put me in limp mode? Also to those of you who have hollowed your cats, what methods did you use?

Im only gonna hollow it out temporary until i get a high-flow after market one, but if the cel is gonna put me in limp mode then ill just say screw it and wait till i get the new one.

 

it will not throw a code, well atleast for 4th gens. I hollowed mine out with a broom stick handle and some big *** pry bars!! It is ghetto, but i got all the stuff out. It will pass visual inspection but will fail on smog.

 

Well i live in florida so smog testing can kiss my ***. My main concern is the cel putting me in limp mode. My car has loss some power because of the clogged cat and i just want to free it up again until i can get a testpipe or high-flow cat in there.

Also, how do testpipes affect the sound of the exaust? Right now i have the GReddy EVO with the AEM CAI conbo and i would hate to ruin nice and deep tone i get with them. Doest the test pipe give you a fart-pipe ricer style sound? Or does it just make it louder?

 

Since you're OBD-II, a gutted cat will throw a CEL. As for limp mode?...probably not. The secondary O2 is mainly emission related, which would read the exhaust gast after the cat to determine if it's working correctly or not. There's a few ways around it though.

1) Buy an O2 simulator. ~$50
2) Convert to OBD-I ($$$)
3) Remove your CEL light behind the dash.

But since you're throwing in a high flow later, just live with the CEL for a few weeks.

 

I gutted mine in my 4th gen and haven't thrown a code. I used a huge steel pipe and smashed the **** out of the honey comb.

 

Yeah i think im gonna go test pipe with an 02 sim. The only fear i got is the way its gonna sound. Anyone have a sound clip of a test pipe on a 5g?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Revi-Ra &raquo;</TD></TR><TR><TD CLASS="quote">Yeah i think im gonna go test pipe with an 02 sim. The only fear i got is the way its gonna sound. Anyone have a sound clip of a test pipe on a 5g?</TD></TR></TABLE>

From what I've seen (and heard), it's going to give your cat a "raspy" but deeper tone. The hollowed out section amplifies the raw exhaust sound, but not usually in a good way either. It really depends on your muffler, piping diameter, and resonator (if your catback has one). A high flow cat will usually sound better since there's "some" catalytic material to absorb "some" of the exhaust noise.

I run a straight test pipe with an O2 sim. I don't care about the environment or how it sounds.

 

the empty chamber also does a good job of messing up the exhaust flow and creating a lot turbulence

 

it will throw a check engine light on a 5th gen but only because the gay obd2 and the fact we have 2 sensors on our cat. i hollowed mine out with a crow bar. it sounds better than any other exhaust i've heard for a 5th gen prelude and it gave me plenty of power. this is with a muffler. do it. it's pretty much a free mod. you may not even want to get the high-flow cat after you do it cuz why high-flow when you can just have no cat at all. by the way i shot flames for a while with no cat when i got on it. and you wont pass inspection. it's well worth it though.

 

shot flames? dizamn sounds sick, i might do it on my 4th gen, im mainly concern about the sound with stock exhaust tho

 

I'm pretty sure you'll be running in limp mode if you hollow your cat on an obd2 system... someone please correct me if i'm wrong.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PhazedSI &raquo;</TD></TR><TR><TD CLASS="quote">I'm pretty sure you'll be running in limp mode if you hollow your cat on an obd2 system... someone please correct me if i'm wrong.</TD></TR></TABLE>
The CEL trouble code for the secondary O2 sensor does not cause the ecu to operate in "limp mode". Primary sensor, yes. Secondary sensor, no.

 

you WILL NOT RUN IN LIMP MODE. you WILL GAIN POWER. it sounds nice with a muffler and you will gain power in a 5th gen. i know because i have mine hollowed out. and it's very easy, just get a crow bar or something and start hitting the **** out of the inside. it's worth it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Revi-Ra &raquo;</TD></TR><TR><TD CLASS="quote">
Also, how do testpipes affect the sound of the exaust? Right now i have the GReddy EVO with the AEM CAI conbo and i would hate to ruin nice and deep tone i get with them. Doest the test pipe give you a fart-pipe ricer style sound? Or does it just make it louder?</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jackedcrew &raquo;</TD></TR><TR><TD CLASS="quote">you WILL NOT RUN IN LIMP MODE. you WILL GAIN POWER. it sounds nice with a muffler and you will gain power in a 5th gen. i know because i have mine hollowed out. and it's very easy, just get a crow bar or something and start hitting the **** out of the inside. it's worth it.</TD></TR></TABLE>
Got dyno?

 

the OEM cats are a bitch, the honey comb is very tough. but hiflow cats like carsounds literally take like 2 hard whacks, and its all out.

Another trick to getting the honey comb out is torching the **** out of it, then dump it in water, makes it crack,

 

Simply put-if you have an O2 sensor on the back end of the CAT you will throw a CEL. ALL OBD-II cars are this way (so far as I know). Will you go into 'limp mode' probably.

 

one thing that no one has mentioned is that your cat should never clog up. if it does you have more problems than that. are you sure that its clogged ( did you check with a heat gun) sounds like you are running really rich. check your fuel and ignition systems to make sure they are working properly. don't have much input on hollowing the cat. i would just wait for the high flow, thats just me tho

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jc836 &raquo;</TD></TR><TR><TD CLASS="quote">Simply put-if you have an O2 sensor on the back end of the CAT you will throw a CEL. ALL OBD-II cars are this way (so far as I know). Will you go into 'limp mode' probably.
</TD></TR></TABLE>
No, the CEL code for the secondary O2 sensor will NOT put the ecu into 'limp mode'.

 

make a test pipe...all it is, is a pipe the same diameter as your exhaust. same lenth as you cat, w/2 flanges welded on. you can get a o2 bung put in for like $10.

hollowing out the cat does NOT do the same. yes it open, but the big open area creates a swirl, and hurts flow. yes its better then the cat itself, but for the 15 dollers and 1 hr worth of work, do it right.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Revi-Ra &raquo;</TD></TR><TR><TD CLASS="quote">

Also, how do testpipes affect the sound of the exaust? Right now i have the GReddy EVO with the AEM CAI conbo and i would hate to ruin nice and deep tone i get with them. Doest the test pipe give you a fart-pipe ricer style sound? Or does it just make it louder?</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Revi-Ra &raquo;</TD></TR><TR><TD CLASS="quote">Also, how do testpipes affect the sound of the exaust? Right now i have the GReddy EVO with the AEM CAI conbo and i would hate to ruin nice and deep tone i get with them. Doest the test pipe give you a fart-pipe ricer style sound? Or does it just make it louder?</TD></TR></TABLE>

No one has yet to answer the sound q. How will it affect the tone of the Greddy EVO/CAI sound? Will it deepen it? Make it louder but deep? Or weed-wacker anoying?

 

it will make it louder in all possible ways...

also, here are 4 pictures of what happens when you run an H22 w/ a straight exhaust:

my friends accord w/ an H22... (stills from a video, sorry about the quality)


my car shot fireballs so big I could see them in the rear view mirror. It was addicting - at night, almost every overpass I drove under, I'd run it up to about 7,000 RPM and time the shift right... POOOOW! A deep explosion sound that you could feel in your chest, and the bridge and road would light up out of the corner of my eye....

On man it was fun. Complete strangers, young, old, would pull up next to me and ask how in the hell that happened...

no cat

 

is throwing flames bad on the motor?

 

the fire itself isn't bad - but you just don't want to run so rich that you fuel-wash the cylinder walls, or foul the plugs.

Although my car was tuned fairly well at high throttle, and at lower RPM, My car ran very very rich at high RPM/ low throttle.

When I lifted the throttle at high RPM, excess gas would fill the cylinder andthe the ehxaust... but the throttle is closed so there wouldn't be nearly enough oxygen to burn, nor much exhaust flow to clear out the gas. When I'd punch it again, (about 0.5-1.5 seconds later) it would force all the fuel vapors out the exhaust, and, provided that the exhaust was hot enough (been driving the car hard for a while), when it came in touch with the Oxygen at the end, then "Houston, we have ignition".

It was quite comical, and amongst the local guys, my car was known more for that then anything else