Stock Catalytic Converter vs. No Cat vs. High Flow Cat

[RedRyder]

^Should have just gone with 2.25" or 2.5" piping, really don't need 3" w/o FI.

 

[G'sAccord01]

^^That was the plan but I didn't realize I was going to run into as many problems as I did with the swap. But I have been looking into going down to 2.5" haven't really thought of going 2.25". A few people have told me 2.25 would be to small (working on gathering parts for a J36 build)

 

[RedRyder]

2.25” isn’t too small, that’s what you get with Magnaflow catbacks, etc. That’s what I’m running now, but I think if I did it over again I wouldn’t mind having less back pressure. Though the car is loud enough at 2.25”, it may be too loud with 2.5”.

 

[G'sAccord01]

Don't you have dual though? I thought magnaflow used 2.5" but looking at it now it does say 2.25". hmmm something else to think of then I guess

 

[Gman86]

99' CG5 LX 4Cyl Just got a "CEL" yesterday P0420 67 Catalyst System Efficiency Below Threshold and have been told a new cat/02 sensor is the right fix.

With that being said im a "Test-Pipe" guy...ran em on all my obd1 hondas. Locally we have no emissions testing at all in metro Jacksonville, FL.

I am looking at the "Megan Racing" Test-Pipe (on ebay) to swap out my Cat with....im going to buy a new O2 sensor as well from "Rock Auto".

I read the below post and was a litttle skeptical of buying a test-pipe, because im trying to remove my "CEL"....this individual claims to still have a "CEL" after installation.

Just buy a cheap catalytic converter. I had the Megan Racing test pipe with O2 sensor bung which still trigger the check engine light. There are more negative effects than benefits. You will lose noticeable torque and gain unnoticeable horsepower, probably gain real 2hp at redline. Your mpg will go down significantly by 30%, its like throwing money down the drain for some noise. If you want to experiment with it that is fine. I just got tired of getting 20mpg and no value in any power gain.

Has anyone had this same issue with "test-pipes"?

 

[agginline86]

Has anyone had this same issue with "test-pipes"?

I have the megan test pipe installed since I'm waiting on my high flow cat
It makes the exhaust louder and a tad bit raspy (hardly noticeable)
as far as throttle response or performance it does absolutely nothing, definitely no negative effects. Even with the O2 sensor I still throw codes though

 

[Gman86]

Even with the O2 sensor I still throw codes though

That sucks...never had that problem on obd1 accords. The truth is Catalytic Converters are very restrictive, but it seems a necessary evil to combat "CELs".

Ive heard talk of "high flow cats" but im even wondering at this extent if they are worth it in the end. Rockauto.com has OE replacements and "hi-flow" cats for cheap. just thinking about that "magnaflow" cat stated above and whether it throws "CELs".

 

[RedRyder]

^The Magnaflow high flow cat will not cause a CEL.

 

[trvllogy]

I just installed a Megan test pipe on my 99 DX manual(the bottom of the totem pole haha)
I race my girlfriend in her V6 Chrysler allll the time and I would always get some pull on her around 3rd gear. Well since i installed the test pipe and got a tune, thanks to my dad being the UPS guy and knowing some shop owners, i let her get the jump on every race since then and still get past her in mid 2nd gear. So going from stock cat to test pipe+ a tune, can show some improvements. Not major to where i'm getting wheel spin in 3rd gear, but enough to get some more "pull" out of your car.