I have a 2000 expo with the 5.4 that i am looking to upgrade the exhaust on. If i were to run something that doesnt have cat's what would my ecm think about the o2 readings? I dont mind putting some high flows on but i just want to make sure the computer will adjust or do i need to get a chip for it? Thanks
Removing the O2's would require a custom tune ($$$), as the engine computer uses the sensors to make sure the engine is operating at the proper AF ratio (approx 14.7:1). That's also providing it's legal with your local emission laws. Otherwise you might have to keep the sensors. I gather that as you mentioned you want to replace the cat, you want to do an ENTIRE exhaust change out, including headers to the tail pipe?? I'd go with Gibson, they're a reputable name. There are other options out there. To give you some ideas, put in your truck info here Performance Parts Online for Cars and Trucks - Performance Center
what if i just removed the Cats and left the o2 sensors in on my new system? i dont necessarily want to switch out the entire system if its not required i just figured i would get better performance if i went front to back, do you agree? looking at the gibson's they look real nice $574 for the low end on these guys, is that normal for the expo? Guess i will have to get used to that, headers on my old chevy were $150 lol
Thanks for the comments, that site is extremely helpful as well.
You'll get better flow/performance by removing the cats and putting in a straight pipe. Do be cautious however, as there are ways around the cats and O2 sensors, but it'll set you back a lot of $. Generally a cat back will provide the best performance to dollar ratio, while keeping emissions in tact and working properly. If you remove the cat and leave the sensors, the sensors will throw a code, as the particulate matter will be the same from the first sensor, downstream to the next. The downstream sensor should read cleaner than the upstream as it tells the PCM that the cat is working properly.
I wouldn't worry about the do-not-tow recommendation. If you add on too many performance parts, you can change the peak HP and torque specs on the engine. As the 5.4 makes peak torque as early as 2500rpm, the added performance mods might alter that to 3500rpm (as example) which won't be noticeable as you drive as the extra HP and torque the mods will provide will offset the stock low range torque. For optimum performance if you plan to add other mods, do it soon and get a custom tune done to better calibrate the computer to work as efficiently as possible.
It'll pair just fine with Superchips. After you add the mods, be sure to disconnect the neg battery cable for half hour or so. This will allow the PCM to reset itself and 'learn' the new mods faster than if you decide not to reset. If I were you, I'd add a cold air intake to take full advantage of the exhaust. Taking in more air and having the ability to push it out just as fast will fair well in the mid to high rpms. Superchips also has a 'towing performance' setting, that alters some of the parameters to give you more low end torque. Enjoy!
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