sc4009688

what are the positives/negatives of hollowing out the catalytic converterhaving somebody taking it off and i just hollow everything out so its just there and nothings inside of it. besides that its illegal and it pollutes the air what are the other negatives about it?

5spdSC300

iTrader: (1)

No negatives other than what you already mentioned. With exhaust, i think its safe to say, bigger and/or higher flowing is always better.

vipsoarer

it creates turbulence in the exhaust, which is bad, but more-so for boosted applications. that and for the few horeses you get from it, you wont feel the power but youll be polluting.

xirforever

If your car has 3 cats like mine, id just take the 2 out that connect off the headers and put traight pipes there.

sorry man, but "bigger is better" is not true on N/A motors, you will lose lots of torque if you go too big. Better flowing is always better though u must have forgotten to notice his is a 400 and not turboed like urs

IronCobra

I agree. You need some back pressure. I wouldn't mess with your converters.. Only lead to problems in the future.. Not to mention you may not be able to pass emission testing (if you state has them)

xirforever

Forgot to mention one thing, you could make some of these like i did, then you still have 2 good cats and can put them in if you want again, i donno i just like to have my options open.
https://www.clublexus.com/gallery/da...m/IMAG0020.JPG

JBrady

Excellent advice

Removing the core from a catalyst give you minimal if any gains and in fact as suggested will hurt low end and mid range power and response. Not to mention the terrible sound of the booming walls of the empty cats. Very undesirable.

JspecSC3

iTrader: (4)

Back pressure is very important when it comes to exhausts. I wouldnt gut out my catalytic converters if I were you. It makes your car sound nasty. Like a honda with an open header. What I would suggest is having a Test Pipe made. It is basically a piece of exhaust pipe that is made to replace all the piping attached from the cat to the flange and there you will eliminate the cat as well. If it comes time to smog your car then you just simply bolt your cat back on. Test pipes are Illegal but what isnt? Most muffler shop will tell you they wont make them because it is illegal. But what you have to tell them is that It is only illegal if they put it on. It is NOT illegal if they just make it. For my SC300 I was quoted $85 from a local race shop. You might be able to get one cheaper somewhere else.

But yeah..Test pipes are the way to go if you want to eliminate your cat. Gutting out your cat =

SCV8

The two cats that you want to modify do the least for performance, and the most for pollution.
I would try removing the third cat(if your's is a CA car), or the resonator that takes it's place in the other states instead.

shaman

how about punching your cat? Take a piece of straight pipe, and cram it through the cat. Weld the slightly smaller pipe to the cat, and you won’t have to worry about hollowing anything out, and you can keep the cat on. If you have visual, you still have a cat on the car.

duckworth

it's not even illegal to put one on as far as i know, the epa will own you if they catch you cutting a GOOD cat off a car to replace it with anything other than an equally effective cat......people do it, but my dad chose to never do it because in 5 years we had 2 visits from EPA agents who were undercover......i didn't think they'd have the time to waste on it, but yeah, they did....it was a $10K fine at the time if you were caught.......we have no emissions testing either, and running without a cat isn't illegal, but getting caught cutting one off is, go figure

and most of the time, you'll make a few more peak hp by using a test pipe and lose a couple ft/lbs torque under 3000rpm, but the trade off is worth it as far as performance is concerned.....you can safely run 2.25" pipe on a 2 liter honda engine for optimal performance without losing all your torque, so i'd assume 2.5" at least for a 4 liter v8.........if your v8 can't make low end torque and decent peak hp with a 2.5" system then that v8 is a joke as far as design goes......

most of the time, a high flow cat will actually net you the best of both worlds.....more low end torque compared to no cat at all, more peak hp than the stock setup, and they're legal if you follow their replacement guidelines..........of course they're 10x the cost of a test pipe......as for the environment, it's screwed beyond repair and has been for years, semis pollute 100x more than your average car as well, so sure, keeping a cat is better than not using one but does it really matter in the end? no, maybe the world will blow up in 3 billion years instead of 3.1 billion......we as humans won't make it 1million years so i don't think it matters

duckworth

lol, you've never heard a honda with an open header because there is no possible way any v8 on earth can replicate the eardrum shattering noise that is an uncorked honda..........loud? sure, but that small displacement tone at 8000rpm? no way

Tammy

The Check Engine will be activated on the OBD II. You won't be able to sell as well as register the lexus in MANY states. And they check for a missing or burned out dash bulbs. And replacement costs are huge. The fuel injection is computer adjusted from the O2 sensors, which will fail if the cat is gutted. Not enough gain for the potential loss. Buy a 327 if you want straight pipes..

JBrady

Some good info here Duck but I hope you mean the V8 on a SINGLE 2.5" as dual 2.5" pipes are TOO large. Since the 1UZFE uses twin cats or 3 in the case of California and Canada models... the bypass should be made from 2.25" pipe. I also agree that it is best to keep the cats. Actually headers with high flow cats (preferably metal substrate) followed by a copy of the stock system in 2.25" with a single 2.50" center pipe.

JBrady

I think he means the typical raspy blatty ricer Hondas that are so common on the street creating what is best described as noise pollution. I will add that hollowed out cats on any car including the Lexus V8 qualify for both air and noise pollution.

Regarding the unparalleled sound of an open header Honda turning 8000rpm... I just HAVE to say there are MANY V8 engines that sound much better than the Honda. Not saying a high reving Honda is trash... however a high reving V8 or V12 is superior. NASCAR, Top Fuel, Ferrari F50 (one of may all time personal favorites) and honestly my LS400 with 4 of the 7 muffling devices removed is flat out LOUD. Sounds like a cammed Corvette at idle and intolerable to this old man at any driving throttle position (drove a few miles turned around and put it right back together).