GT3_ISH

That is simply not all true. There are plenty of gains to be had by removing the cat on just about every car if tuned properly. It's an emissions product at the end of day plain and simple. It wont make the fuel mix any harder to manage at all, it will indeed be different, but no harder or easier than fuel management already is.

Engines across the board in any form of racing do NOT use cats, NA or Turbo. Well, thats for now anyways until someone makes them in the sake of saving the earth.

mcfisticuffs

Bad.

It sounds bad.

Tried Fabspeed catless race-headers on my 2009 C2S with and without Sharkwerks center bypass... in both scenarios it did not sound pleasant. Loud, yes, certainly. But not good.

rootwyrm

Except re-tuning for catless is not "blah blah fuel map blah blah flash." You have to re-flow the whole thing. Removing the cat from a modern engine does not magically make power. Period. This ain't the 70's and 80's where they just clogged flow till it passed. The catalytic converter and it's resultant backpressure is part of the design, which has gone through thousands of hours of CFD work. If you suddenly jack post-valve exhaust velocity 15%, that's not a "just chip it" change. You have to change the base map and the fuel trim algorithms. And putting an O2 simulator - which is fixed value returns - does in fact make fuel management more difficult. Just because I haven't done Porsche engines doesn't change the physics and code. I'd have the same problem on GM, same problem on Chrysler, same problem on MoTec. When STFT/LTFT is algorithmic by Lambda, you need valid Lambda.

This is completely false. The 997 GT3 Cup is catalyst equipped. So's the 991. (So much for the 'blah blah tree huggers' complaining, huh?) Quoth the 991 Cup specs: "Race exhaust system with regulated race catalytic converter". GT3 R has a cat. GT3 RSR has a cat. Because, gasp, most sanctioning bodies have been requiring catalytic converters for 10+ years. Because, shocker, when you HAVE to install something on every car for 40 years, you invest a whole lot of time and money to make it suck less. The idea that modern catalytic converters are 'power robbing cans that do nothing but choke the engine' is as much a myth as Japanese car reliability or bigfoot. Just the horsepower numbers on anything out there proves what a fallacy it is.

A modern, properly designed, properly selected catalytic converter is no worse than bolting up a muffler. And in many cases, less restrictive than the muffler. (See also: the 997. If it wasn't true, why would just the center pipe give more power? Duh.) And as previously stated: removing the catalytic converters is illegal period. The EPA exercises enforcement and rule-making discretion when it comes to modifying cars exclusively for non-highway use. Doesn't matter if it's not registered. By the letter of the law, it's illegal. It continues to be a whole thing. You can act like it's some "hippie crap" and throw all the "and I want leaded gas at the pump like in the 50's" tantrums you like.

Law's the law, facts are facts, data is data, and the proof's in the pudding. Porsche won LeMans with a catalytic converter. Deal with it.

GT3_ISH

Did I say that simply removing the cat from a "modern" car would make power? No I certainly did not.

I don't come from the land of "chip it", I never used that term, so I'm not sure why you even have it in quotes. You'd be changing more than fuel trims, all of these would inevitably lead to....more power. Any good tuning software would allow to simply disable the secondary o2, which is used to monitor what we're hypothetically removing here and has no bearing on fuel at all. Are you sure you arent meaning the primary o2?

I dont think anyone mentioned bigfoot, and I dont think anyone is going to argue that cars with cats make power. What you will get a strong argument for is that cars are capable of making more power with said cats removed and a proper tune to coincide.

Again, the o2 sim typically goes to the secondary o2, which isnt going to suddenly kill any sort of lambda value from the primary o2. So your statement makes no sense there either.

The GT3 Cup has a cat, yes. If you don't understand why, then I'm not sure I should even keep typing. The IMSA rules do not specify any exhaust restrictions and certainly dont mention the use of a cat for GTLM where the RSR is raced. Porsche won Le Mans with a cat? You'd better head over to the FIA website and check out the 2018 regulations where it clearly states that "silencer/converter for exhaust" is "free design" meaning no restriction. What sanctioning bodies are requiring cats for the TOP level classes in their sport? Show me. I'll wait.

I'm not trying to rub you the wrong way man, but do some fact checking.

platinum997

Thanks..

I haven't heard the sport cats either but assuming those sound much better.

jlert

I think the exhaust would be way louder, and probably drone like mad. If noise level isn't a concern, but the quality of the sound is important, just google Helmholtz chamber to help cancel out a wide range of unwanted frequencies. Or a 1/4 wave resonator to heavily cancel a narrow range of unwanted frequencies.

fabcar996

A catcon is always restrictive compare to a straight pipe.



"Needing" some sort of backpressure is a myth on naturally aspirated engines. NA engines are much more sensitive to header design changes. On boosted cars, you want the least back pressure.