Hollowing main cat and replacing dummy cat

[The Stig]

On an S14 KA, is there any issues hollowing the main cat if the dummy cat is replaced with a real one? When I bought my car the previous owner had that setup, presumably the main cat has gone bad.

[240sxScores]

Dont hollow out your cat, or push a straight pipe through. When you open all the inside area you'll just create turbulence in the exhaust flow trying to exit lose power.

[projectRDM]

Dont hollow out your cat, or push a straight pipe through. When you open all the inside area you'll just create turbulence in the exhaust flow trying to exit lose power.

Horrible. Loosing power by creating turbulence is the stupidest thing ever written on here.


Stig - Yes. Plenty of people run an aftermarket converter in place of the resonator on S14s, especially those that run a header and delete the converter in the downpipe. It works fine. Only issue you may have (to keep the CEL out) is to extend the rear O2 harness and weld a bung in for the sensor on the rear section of the converter.

[S14DB]

Horrible. Loosing power by creating turbulence is the stupidest thing ever written on here.

No it's not. Any time you increase then decrease the piping size you create back back pressure by stalling out the flow.

[Bigsyke]

Heres my take on it. A " down pipe that connects the upper part of the manifold that includes a flex pipe will properly eliminate the primary cat.

Or you can get a cheap header (Xtune, but it was 100% perfect fitment) I got mine for 150 shipped.

How can you punch out the catalyst material when the pipe is curved? if you have ever holled out a 92-00 civic cat its not that easy, since the combs break off in chunks.

On the flip side there was a pipe insert that was sold on summit racing that fit inside your exhaust pipe to "swirl" the air thus lowering the dBrating of the noise by 10dB's with 0 loss in power. However durring a "bend" in the exhaust I would rather have it be smooth.

Get a proper header, then get a carsound cat. Use the 14mm to 18mm spark plug fouler adaptor and call it a day. No need to extend the wiring.

[MrChow]

I have a S14 with my stock Cat and I replaced the hollowed cat with a hi-flow cat. My car runs fine. I track my car every month.
And like Bigskye later down the road I'll replace the downpipe.

[Bigsyke]

I have a S14 with my stock Cat and I replaced the hollowed cat with a hi-flow cat. My car runs fine. I track my car every month.
And like Bigskye later down the road I'll replace the downpipe.


IMO I would just replace the whole exhaust manifold assembly. The KA OE exhaust manifold is heavy, and doesnt line up well to most 3" downpipes.

Ill stand by and say im very happy with the Xtune header I got for the S14, even with a snapped stud the manifold is very healthy. I plugged the lower O2 port with an M18x1.5 Oil drain plug I found at o'reillys. The xtune header was about 1/4th the weight of the OE manifold assmbly.

However next time I do it, im going to have a flex pipe welded in on the collector side, and replace the 2bolt flange with a larger faced flange, that doesnt have the slotted bolt holes.

[Tenchuu]

i would just replace the whole car.


i replaced headers and had a resonated test pipe when i had a KA in my car for a while. worked fine, lost a bit of gas mileage, but that was because it had more throttle response so i put my foot into it more. whenever i gingered it on ice goin about 50 for 3 hours i got well over 30 MPG.

[MrChow]

IMO I would just replace the whole exhaust manifold assembly. The KA OE exhaust manifold is heavy, and doesnt line up well to most 3" downpipes.

Ill stand by and say im very happy with the Xtune header I got for the S14, even with a snapped stud the manifold is very healthy. I plugged the lower O2 port with an M18x1.5 Oil drain plug I found at o'reillys. The xtune header was about 1/4th the weight of the OE manifold assmbly.

However next time I do it, im going to have a flex pipe welded in on the collector side, and replace the 2bolt flange with a larger faced flange, that doesnt have the slotted bolt holes.
Yeah I've taken out and had a meagan header thing on for a bit. Hated it put the old one back one for now till I get my turbo stuff.
2 of my stud snapped too... D=
Either my whole exhaust system is being redo or my body damage. I think it's my body first... Anyways.

Well I had to weld my flanges to my cat. So I have a 2.5" going in and 3" going out so it fits perfectly.