This one is about a subject that I've covered in the past, but we're going to dive deeper into it as it's become a popular discussion since our "Headers vs SPD Y-Pipe" video was released a couple weeks back. Catalytic converters.... and the knowledge that most people are missing that leads to failures.
I'm going to start this by mentioning a post that was made in this group that had to be removed as it was promoting deleting cats, and emissions component, and being that Oz Tuning sponsors this group and we have to abide by EPA regulations. We can't allow those types of posts in our group.
The person that made the post is an Oz Tuning customer and was running a Whipple with Stainless Works headers and the GESI cats offered by Stainless Works. The part number for those cats were GESI HPPL-00080. I reached out to GESI to get more information about those particular cats, and this is the information they shared.
- This part number is a discontinued private label part made specifically for stainless works. Typically, these would be best suited for naturally aspirated/mostly stock applications. Most high HP supercharged/boosted applications require a larger substrate size to adequately manage the increased heat levels in these environments.
- For your customers application we would usually recommend upgrading to a 4.5” body converter such as our PN: 85230 or PN: 85032.
- Managing high horsepower while reducing emissions is what we are all about and we have multiple options to handle 1000+ HP reliably. It is imperative to choose the right size for the application.
So, in this case, the cat was grossly undersized for the application, which lead to the failure.
Many of you guys have likely already heard me say this.... "Boost doesn't kill cats, abuse does."
That is still true, and I wrote this article a while back about how to avoid abusing your cats and it's worth reading at this link Article.
I need to update that article, and this post will be part of that, because people are assuming they can just throw whatever cat they want on the truck and everything will be fine, and that's not the case. The cats need to be large enough to handle the exhaust flow and temperatures that a supercharged engine produces. It’s really no different than sizing your injectors or fuel system to make sure you have adequate fuel flow for the power your engine will produce. You wouldn’t try to make 1000 whp on a stock fuel system, right? So, it also doesn’t make sense to try to double the power of your engine and expect the stock cats to support the required flow indefinitely. I’ll also add that as a general rule of thumb any of the "high-flow" cats that you see offered by header companies aren't going to work well with boost. Header companies typically put the smallest, bare minimum cats into their systems to avoid having the EPA knocking on their doors and in most cases, they are barely adequate for a naturally aspirated engine and definitely will not survive behind a supercharged engine.
If you haven't seen it yet, here is a Video Link to the YouTube video that we made where we tested catless long tube headers versus a catted SPD Performance y-pipe and in that video you will see that the y-pipe made more low-end torque and the same top-end horsepower as the headers. That data shows there is nothing to gain from installing headers on these trucks over a well-designed y-pipe. There is, however, significant performance to be gained from installing a well-designed y-pipe because the stock y-pipe is poorly designed and is the biggest bottleneck in the exhaust system. Replacing it with something like and SPD y-pipe will gain power and the cats that SPD supplies are larger and more robust than stock cats. They also flow significantly better than the stock cats. That means they will handle the abuse of a supercharged engine much better than the OEM cats and they are emissions legal and will pass an emissions inspection. There are a couple different cat options with that y-pipe. I run the standard "Alpha" cats on all three of my F150's and two of them make over 800 whp. I have owned several Coyote powered vehicles over the years, some making over 1000 whp, and they have all had cats and I've never had a failure. That's including making 100's of dyno pulls with those cats, 100's of WOT pulls on the street, and 100's of passes at the track. I've never had a failed cat because I don't abuse them and I follow the tips in article that I linked above. That being said, the Alpha cats are likely at their limit with the power my trucks are making and if I were someone that treats every red light like a drag racing tree, they likely would need to be replaced by now. If you're that type of person, there are two additional cat options available for the SPD Y-pipe. Both are made by GESI, the premier manufacturer of high-performance and emissions legal cats, and there are two options. The 85500 and the 85600. The 85500 is rated for 1000 hp (each cat) and the 85600 is rated for 1200 hp (each cat). They will handle all of the heat and flow your supercharged engine can throw at them, but you still need to be conscious of not abusing them. Here's a link to GESI's site where they list the various cats they offer and their HP ratings, if you're interested go to the link here. Any of these three cat options will pass emissions and which one is right for you depends on the power you want to make and how you drive the truck. If you've got a heavy foot and like to race every muscle car that lines up next to you, you should consider one of the GESI options. If you're a little more of a tame driver, like me, the Alpha cats do an excellent job and have worked well on all of my vehicles.
If you're reading this, you’ll have undoubtedly already read all over the internet that you have to delete the cats. So, I’ll address that as well. Here's the long and the short of it. Can you run catless exhaust? Yes. Will you pass emissions with catless exhaust? No, because it is illegal for us, or any tuning company, to modify any functions related to emissions components in our tunes. That includes disabling check engine lights and especially tampering with OBD test procedures to allow the removal of an emissions component and not causing a fault. The fines for doing something like that start at $35k per offense, and I'm pretty sure you wouldn't be interested in paying that $35k just to not have a check engine light, and we definitely wouldn't be interested in paying it. Tuning companies, and the aftermarket industry in general, have to work in a grey area of the law and any tuning company that plans to stay in business for any length of time isn't going to violate those laws and jeopardize losing everything. I'll also take this further to say that the EPA, in some areas, are even enforcing these fines on individual vehicle owners. It's not common, but it has been reported and the law doesn't specify that only business can be held accountable for violating these regulations.
If you still absolutely want to delete your cats, that's your prerogative and if you're willing to shoulder the potential consequences more power to you. However, if you have emissions inspections that would mean that you would need to reinstall your stock exhaust before every emissions test and drive the vehicle for several drive cycles for the monitors to set before going in for your test. There are guys that do that, but I know I wouldn't want to go through the 10-12 hour job of installing/removing headers every year. Plus, if you've never heard what a Coyote engine with catless headers on it sounds like, it's not a very pleasant exhaust note in my opinion. It's very raspy and tinny sounding and EXTREMELY loud and will have a ton of drone inside the cab, especially at highway speeds. So much so that the vast majority of guys that install catless headers on their trucks end up spending a bunch more time and money installing extra resonators and mufflers to try to tame the exhaust noise and drone, which in-turn restricts exhaust flow and puts them right back where they started. So, if you're someone like me that doesn't like obnoxiously loud exhaust and can't stand cabin drone, you should consider those points before deciding about the exhaust you want to install on your truck.
TLDR - Cats need to be properly sized for the application. Blaming an undersized cat for failing would be the same as running too small of an injector for the power you're making and blaming the injector for blowing up your engine. You can make power, lots of power, with cats and not have an obnoxiously loud, stinky, and technically illegal vehicle so long as you size the cat properly for the application and you don't abuse it. For track use there's nothing in the law that doesn't allow you to temporarily remove the cats and replace them with test-pipes while racing on-track. I've done exactly that on my S550 Mustang that I raced on road courses. Installing v-bands before and after the cats makes it a 10 minute job to swap them out for track use.
Ken Osborne – Owner Oz Tuning, LLC.
