Catted vs. catless?
 

Hello peeps,
I’m running a catless uel header. Unfortunately, to pass emissions (every 2 years) I have to swap back to stock catted header. Not a difficult task when I have the time and the weather’s ok- no garage.
Anyways, if I got a catted uel header, what kind of gains will I loose?

If it's just a visual inspection you just need a pipe with a bump in it...

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Welcome to our happy group, there, BleachBlanket - :clap:

You wouldn't notice the difference, as long as you stay out of the timing traps at the drag strips and stay off the dynos - :D

:popcorn:


humfrz

Cats have come a long way since the 70's and unless you're also running boost of some sort, you probably aren't seeing any significant HP gains by removing yours.

If you weed out the usual internet hearsay, people that have dynoed before and after show very little loss, to even a slight gain [ame="https://www.youtube.com/watch?v=OSMcHg_7eo4"]slight gain[/ame] with cats installed.

To put it in even better perspective, here's a post someone did where they dynoed 15 86's the same day, with a mix of OEM, tuned, catted, non-catted and so on. The numbers support the cats don't make a huge difference. In fact, there's a tuned 86 with no-cat, UEL headers on 93 gas and it only makes 3 more HP than a plain-jane factory 86. Heck, an otherwise stock 86 with the OFT E85 tune makes 9 more HP than the non-catted car.

So, while it's only two every two years, you're making more work for yourself, and spitting more crud into the air for a potential gain that you could also see if you just took a good dump before hitting the track day. :D

Or they can see his front pipe if it's stock

Oh we don't have rules like that in CT just need to have a cat (bump in pipe) and no CEL with sensors readied.

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In MD, you have a bored state-employed "technician" (probably making minimum wage) plug the computer in to take a reading and print a piece of paper.

Like so many "power increasing" mods they can work wonders on some cars and mean almost nothing on another but everybody just looks at the gains from the first group and thinks they apply to all cars.


Take a 1993 Civic DX replace the 1 1/4" exhaust with a 2" non catted system, swap a header for the exhaust manifold, change out the hot engine bay sucking intake for a real cold air snorkel and even without a tune it will make a huge difference. Swapping out those same parts with very similar aftermarket ones on a Twin is not going to gain you much if anything.


It is the simple difference of turning a "normal" car into a performance one vs trying to improve a car that was designed for performance from the start. They can of course be improved but it isn't near as easy as turning your mom's old Civic sedan into a sleeper.

Just shed some weight bro, those are the best gains. You or the car.

https://media.giphy.com/media/Tlg08MWwaDaJa/giphy.gif

This whole catless things is so annoying. I guess if you don't remember what it was like to be in the big cities and not be able to see across the river or sometimes even 10 blocks back in the late 60's and early 70's.

From my experience
You do see a nice power gain from removing OEM cats, after tuning of course.

Alot of high flow aftermarket cats (100-200 cell) though will not pass your cars emmisions sniffer test requirements, even some 400 cell cats won't pass.

And sometimes, even when your highflow cat doesn't trigger a CEL code, you will fail a sniffer test.

In the end, if your not chasing that tenth of a second you are better off having a decent OEM cat/s and the car tuned to comply.

Or, risk it for the biscuit

I'd be surprised if they were inspecting the header cat. I think they are looking for the one on the FP.

But thats just based on what they do here in Australia.

It is very nostalgic in a horrible sort of way when I am behind or beside an uncatted car. The annual car show I attend with 300 or so classic cars stinks the main street up when the parade passes by. God I do not miss that smell!

Carbon monoxide has a 230x greater affinity for binding to hemoglobin than oxygen. With a concentration of 12,800ppm in the air, someone would go unconscious after 2-3 breaths and would be dead in less than three minutes. A catless exhaust produces between 30,000-100,000ppm of CO versus 1000ppm, so don't go sniffing very close to your catless tail pipes or running your car in a closed garage or in poorly ventilated spaces long.

https://www.abe.iastate.edu/extensio...icles-aen-208/

https://en.wikipedia.org/wiki/Carbon_monoxide#Toxicity

Some say, well, it is just the precat. The precat warms up faster than the main cat and reduces emissions until the main cat heats up, and it helps to warm the main cat. Even then, the emissions from the first 30 seconds can be equivalent to driving a car for 100-300 miles. Without the precat, the main cat may take longer to warm like over five minutes and potentially as long as 10-15 minutes. I only have a five to ten minute drive to work or the gym, so doing such a modification could make my car equivalent to a catless car in emissions.

Seems like an electronically heated catalytic converter system for a main cat with no precat should be better in every way.