Installing a High Flow Cat

Kellen Hileman

Active Member
6
2
Vehicle Model
Civic Si
Body Style
Coupe
I'm interested in installing a high flow cat, but most downpipes with them pre installed seem to be around $500. My question is: is it possible to just get a muffler shop to weld in a high flow cat onto a catless downpipe or could i swap my existing cat for a high flow? I don't know if either of these options are even plausible but i wanted to ask. If this would be possible, which option would be least expensive and produce best results?

Thanks
 
Whoops-- hit reply before I was done. I meant to mention that I see why the Hi-Flows are so much-- it seems like they all come with an aftermarket exhaust manifold attached to them. This kind of complicates things-- Even if a muffler shop welded a new cat into a downpipe for you, I'm curious about if it'll bolt up afterward. I'm always a proponent for custom stuff though-- don't know if it'll be cheaper, however.
 
Whoops-- hit reply before I was done. I meant to mention that I see why the Hi-Flows are so much-- it seems like they all come with an aftermarket exhaust manifold attached to them. This kind of complicates things-- Even if a muffler shop welded a new cat into a downpipe for you, I'm curious about if it'll bolt up afterward.
Ah i see. Maybe i should call a muffler shop and ask them?
 
Ah i see. Maybe i should call a muffler shop and ask them?

I'd ask them just to make sure, because it looks like-- at least the Magnaflow that I saw-- would require you to get the Manifold and Cat combo no matter what. Magnaflow's high-flows look like they don't necessarily bolt right up to the OEM manifold-- so they sell you theirs as a package deal.
 
Looks nice I might buy one but I am waiting till I get my inspection sticker, don't for get you must tune the car when using the pipe.
 
this seems crazy to me. The amount of money you'd spend buying the downpipe, a high flow cat, and then hoping the shop can weld it in perfect for spacing without fitment issues....? You'll spend more than just buying a proper downpipe with a high flow cat. Also, you will need hondata flashpro or ktuner with a custom tune to get the car to drive properly after installing a downpipe. If you don't already have that, I wouldn't waste my time looking at making some type of custom downpipe. Get the proper tuning device, and get in touch with a tuner who will get you scheduled for e-tuning or dyno tuning. If you want to potentially go turbo down the road, go with flashpro as it offers more customization/options.

https://www.hondata.com/flashpro-civic-si-2012-2015-us
https://ktuner.com/12civicsi/
 
I think you should look for bolt on downpipe and manifold-I believe they are separate parts? I would not weld anything at a muffler shop because it may not match up correctly and it would also cost money to weld it up and may not last as long either and may not fit as well. You want everything to just bolt up, no welding and everything made out of the same material like the 304 SS! I am interested in your project because I want to do the same thing except that all the pipes and exhaust should be a full 3" for max power and gas mileage and also tuned correctly or just don't bother.:eyebrows:.
 
You open up the flow of the cat, you will need FlashPro and a tune.
 
I've got Ktuner. But thanls for the advice. Definitely seems like a bolt on downpipe with a cat would be overall less expensive than trying to piece one together. Thanks everyone!
 
I would never use anything the muffler shop has for piping it all most all ways low quality especially for area's with salt. 304 SS has lasted 5yrs in salt and shows just normal wear. I like cheap speed tricks.:flame:
 
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