# How to gut catalytic converter without o2 sensor misreading



## SentraThis96 (Nov 14, 2009)

So I'm looking to increase the performance in my 96 Sentra any way possible. Would it be worth gutting the cat and having to bypass the o2 sensors to get better performance? If so what would be the best way to do this?


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## jdg (Aug 27, 2009)

SentraThis96 said:


> So I'm looking to increase the performance in my 96 Sentra any way possible. Would it be worth gutting the cat and having to bypass the o2 sensors to get better performance? If so what would be the best way to do this?


Only if the cat itself was hindering good flow...
With a stock 1.6, probably not going to happen unless the cat was hosed in the first place. And by stock I mean no major engine mods. A cold air intake and a fart-can muffler don't count...
Bypass the upstream O2 sensor, and you can kiss any decent gas mileage goodbye.
Bypass the downstream sensor, won't have any effect on performance (all other things being equal), and you get to look at a constant Check Engine light.


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## SentraThis96 (Nov 14, 2009)

jdgrotte said:


> Only if the cat itself was hindering good flow...
> With a stock 1.6, probably not going to happen unless the cat was hosed in the first place. And by stock I mean no major engine mods. A cold air intake and a fart-can muffler don't count...
> Bypass the upstream O2 sensor, and you can kiss any decent gas mileage goodbye.
> Bypass the downstream sensor, won't have any effect on performance (all other things being equal), and you get to look at a constant Check Engine light.


So Basically its not worth it at all... I just put a quad unifilter on the intake which replaced the stock air filter box. My mpg's are in the mid 40's now. I really want to replace the stock muffler what do you suggest the best way to go about this is?


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## Dark_angel (Jul 13, 2009)

Im running a 3in straight pipe on my 99 sentra 1.6 and Im still getting 33mpg


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## SentraThis96 (Nov 14, 2009)

Dark_angel said:


> Im running a 3in straight pipe on my 99 sentra 1.6 and Im still getting 33mpg


Isn't 3" for a 4 banger 1.6 a little much? I have been doing a little bit of research and have found that 2" is the best size for optimal performance although a catback, glasspack or whatever aftermarket exhaust you put on isn't going to add that much performance


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## Dark_angel (Jul 13, 2009)

this is what im running http://www.nissanforums.com/b14-95-99-chassis/157072-wanting-know-what-else-i-can.html


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## mudpaws (Feb 25, 2009)

No need for that big diameter pipe, so much resonance, that it builds too much back pressure. For V8s 350-400 HP I use max of 2.5", so for 4s forget it! 2 to 2.25" with a high-flow cat, and a good muffler...


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## nova73guy (Mar 30, 2004)

Depending on the emissions laws where you live, it probably isn't worth it. If your car gets emissions test every year it will fail without a cat, and it'll fail for a check engine light. Best thing if you REALLY want more flow is get a high-flow cat. However, without increasing the amount of air going in (through turbo or whatever) you're really not going to see much if any improvement over stock exhaust. If you're looking to up your game have a turbo installed along with slightly larger exhaust and high-flow cat. OR do the famous SR20DE swap and have fun!

Bottom line, high-flow exhaust isn't really all it's cracked up to be on a stock engine. If you increase the flow out, you gotta increase the flow in and vice versa.


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## Asleep (Jan 19, 2003)

mudpaws said:


> No need for that big diameter pipe, so much resonance, that it builds too much back pressure. For V8s 350-400 HP I use max of 2.5", so for 4s forget it! 2 to 2.25" with a high-flow cat, and a good muffler...


depends on the size of the engine, whether its a 4 banger or an 8. 
it also depends on where you want your power. my 240 with 3" exhaust, when it was n/a would match my altima - gear for gear. my altima only had 2.25". it wouldnt do that with the stock exhaust. there are also many altimas and 240's with 3" exhaust that have experienced very nice gains. granted, these are 2.4 liter engines, so the same wont go for a 1.6, but you get the idea.
Which Size


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## mudpaws (Feb 25, 2009)

and no freakin way a Sentra gets 45 mpgs...Unless you're driving around at idle speed everywhere....Stick shift or not..Check your math again..:wtf:


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## SentraThis96 (Nov 14, 2009)

mudpaws said:


> and no freakin way a Sentra gets 45 mpgs...Unless you're driving around at idle speed everywhere....Stick shift or not..Check your math again..:wtf:


Umm whether you believe it or not I average 38-41 mpg city. I'm rated for 35 city and 40 mpg look at the owners brochure for it online. I took my stock intake off and put a cheesy little unifilter on for now til i get my CAI in which helped a little but this thing is insane on gas mileage. I went 85 miles on 2 gallons of gas so wait let me go back to my 3rd grade math... isn't 85 divided by 2 over 40mpg's?


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