[nothingman]

Fabspeed argues going catless is not always necessary and you can lose power compared to sport cats on modern platforms such as McLaren, Porsche, Ferrari, etc.

Interesting article I read on B-O-O-S-T-A-D-D-I-C-T.c-o-m. Here's an excerpt from article:

"The conventional thinking is that going catless (ditching your catalytic converters) is best for power. That traditionally was the case but modern motors adjust so many parameters so quickly and are built for such efficiency that you can actually lose power by getting rid of the cats. Frankly, with German HJS 200 CPSI catalytic converters or sport cats you can have 93% of the flow of going catless. That means there is truth to Fabspeed's argument. Fabspeed makes a good argument especially in relation to McLaren platforms:

Originally Posted by Fabspeed
Fabspeed Motorsport has the most long term experience with all these Mclaren models since we were the worlds very 1st company to design, engineer, and incrementally dyno develop exhaust on each and every Mclaren model since the launch of the Mp412C. Our exhaust systems use CAD Designed 3D proof of concept printed and then investment cast lost wax stainless steel inlets and maxflo cast outlets for all our or systems. Nothing is left to chance and our sole mission is "ultimate bespoke quality and maximum power and sports car sound" for all fellow Mclaren enthusiasts worldwide.

Some facts- Mclaren catbypass pipes will give you a Check Engine light P420/P430 code on these cars. Often you can use simulators to keep the light off BUT its not guaranteed. The car runs 100% fine but you get a small light on the dash. Simulators give you a 50% chance of eliminating a CEL light.

Fabspeed Motorsport has awesome record setting safe tunes for all these McLaren cars for stock, with highflow cats and also No Cats RACE system with no CEL Lights 100% guaranteed. All of our tunes are set up safely for 92 to 93 octane pump fuel.

Point of interest- in virtually all of our testing super highflow German imported Extra large diameter HJS 200 cell Catalytic converters make more absolute power and torque all across the RPM band than catbypass pipes. The HJS Catalytic converters FLOW 93% of a straight pipe and the cars don't go into overboost/ spike and the ECU doesn't try to trim and pull everything back as what happens when you install a catbypass pipes.

Fabspeed Motorsport has tunes for all catted or no cat Mclaren cars. Whats interesting is that the power increase/ difference in ONLY +5HP by going tuned and catless. In our years of back to back dyno testing since 2010 with these cars catbypass pipes/competition pipes and with a tune you get only an additional +5HP more than a Mclaren with HJS German sport race cats with a tune on "same day same weather".

So in essence a super premium quality German HJS 200 CPSI catalytic converter will give you all the power the car requires while passing emissions, you will have no Check Engine Lights, full readiness codes and have excellent sports car sound and maximum power all in one. The one and only thing is not all HJS catalytic converters are the same you have to get the largest HJS tri-metallic cores to get the 93% equivalent flow. Some companies offer small HJS cats and these restrict power and can have a CEL light as their is not enough surface area to scrub the exhaust.

We have systems in stock and encourage anyone to come by for a shop tour and see the passion and teamwork that makes our systems world class. Fabspeed Motorsport is the only company to include 2200 degree Thermal military quality blankets on all Mclaren systems to allow for more engine protection, more power and less radiant heat in your engine bay.

Going to sport cats while remaining emissions compliant can be a benefit versus going catless unless you have a tune that will take advantage of being catless. Even then, the percentage gained over modern sport cats is minimal.

The cat bypass pipes made a little more power but less torque and the ECU seemed to struggled a bit down low with the bypass pipes. A CEL (check engine light) without cats is inevitable and at that point you likely are losing power on the factory tune if the car isn't triggering various limp modes.

Ideally, you want a tune to take advantage of the pipes whether running straight pipes or sport cats but the advantage of going catless is not what it once was. You also can lose power if not properly tuned and on the factory tune while triggering a CEL."

[pz619]

Yeah I 100% agree. CEL means the computer thinks something is wrong and thus will attempt to protect itself and change engine parameters. What parameters are changed will vary from car to car. So, if you go catless you definitely want something to fool the ECU into thinking that everything is in place and working properly, thus eliminating the CEL.

Now for the unpopular part which comes from personal experience and admitted bias. I think EVERY car should have a cat and catless shouldn't be an option for street cars. As someone who grew up in LA in the 80s I can definitely see the positive impact of stronger emission laws. Just ask anyone that lived in So Cal for an extended period of time. Furthermore, I had asthma problems especially when growing up, clean air is extremely important to me. I like having the ability to go for a run outside without having to suck down a bunch of exhaust fumes while working out. But, I also value performance as I like to tune my cars. I've always bought high flow cats (had the fabspeed sport cat on previous car) but to me this seems like a good balance between not being too damaging to the environment but also getting to eat my cake too. Hypocritical - yes, but it's a balance that I can live with.

Edit: Worth noting that the Fabspeed sport cat is of extremely high quality. I got pulled over and had to go to CA state referee for inspection. The car passed a rolling CA emission test at 25 and 35mph with the Fabspeed sport cat installed.

[matty_f]

^ agree 100%. I remeber stage 1 smog alerts where we weren’t allowed to play outside. Even staying indoors on those days, my lungs would burn with a deep breath. Seeing the San Gabriel mountains was rare due to the haze. It’s so much better now thanks to modern emissions controls.

I even dislike catless on track cars. I’ve gotten pretty nauseous being stuck behind a row of cars for several laps under caution, while they towed a car off track.

[PAC]

iirc back when I had my old mkiv Jetta in 2005-2006 there were people reporting loss of hp/torque going from stock to 3+in downpipes (with or without cats) due to a loss of back pressure. Even tuned. The sweet spot seemed to be 2.5in downpipes on a stock turbo.

In fact I've read my mkvii Golf R that I commute with gains little to nothing from a downpipe in many cases because the stock system is pretty decent being a performance car. The changes to the downpipe and exhaust are mostly acoustic and weight saving.

I would imagine that the pipe diameters on performance cars these days are close out of the factory. The main difference being a restrictive cat due to regulations : . I can see a similar to stock size and a high flow cat being the best way to go. IMO

[mike@x-ph.com]

Interesting read, its worth noting that not all cats are equal.

A high quality cat will provide the same advantages as the catless without any of its disadvantages

[eatingpizzainthef87rules]

We have seen some cars make more power with a proper HFC than testpipe.