Finally got these aftermarket headers installed and wow. I just wanted to share my impression after a week of driving.
Header: looks like stock design minus the cat. It is ceramic coated made of steel? Piping size measured OD 1 3/4" x 2" x 2 1/2.
Installation: The not so fun part. The oem Header is located on the backside of the engine next to the firewall. It's a pita to remove. There is physically no room to remove the stock header d/t the build in cat. I wrestled with it for quite some time, even had to partially drop the subframe and still no way. Eventually got fed up and chopped it in half with a zawsaw
as I needed my car for work. the aftermarket header itself is easy to slide in. 7/10 difficulty.
Sound: loud on cold start up but mellows out once car is warm. I'm running tanabe axle back exhaust and k&n drop in filter. the primary cat still retained. While coasting it's barely noticeable. However with full throttle the car no longer sounds like a 4 banger. It has a nice deep sound with no drone at all. Not extremely loud like cars with deleted cat. Love the way it sounds now.
Impression: The difference is literally night and day. The car feels like a different animal. In its original state the car is slow af. Mazda locked up all its power. For me 2nd and 3rd gear was by far the worse. The wife's 16' cx-5 feels so much more responsive and torque-kier probably a different tune file. Note: I have an ATX tranny as well. GT model.
I did several pulls since the install both in auto and manual shift mode. I'm very impressed with the throttle response. Once I blip the throttle I can instantly feel the torque and the car doesn't struggle to take off. Before there was always a delay around 2-3k rpm then more delay towards the end of the gear. which was very annoying imo. Initially 2nd gear pull still felt a tad bit underwhelming but once the header settled, its starting to feel like real nice constant pull. 3rd gear is where I notice the most torque kick. It literally has me at the edge of my seat. Reaching 80mph feels so much faster I have to check myself sometimes to make sure I'm not speeding.The car is actually fun to drive now. At the time of testing I was running on 87 octane in California heat wave. With A proper tune I can see major gains.
CEL threw code p0421 cat malfunction. I already ordered a non-fouler for the 02 sensor. Will see if it helps. For now I have to clear the code during cold start.