I have a 2004 monte carlo n/a 3800. I removed the resonator and put two flowmasters on. Needless to say, it isn't loud enough for me. I want to remove the converter and u-bend. I would like to put in a straight piece and weld a bung in for the o2 sensor. If anyone has done this or can tell me if it will affect how it runs or if it will trip a check engine light, I would appreciate it. I am considering a reprogrammed pcm as well. If the pcm will keep the light off I might do that. Please let me know. Thank you.

 

https://www.zzperformance.com/grand_...=551&catid=110

done.

Will trip a code P0420 because you don't have a Cat, just program that code out of your PCM

 

um yes it will turn a light on...ull be missing the correct o2 input to the pcm. it will also dump more hydrocarbons, nox and CO into the atmosphere. the reprogram could(if done right) take care of ur cel but it would still set the code jsut not turn on the light (ud fail emissions) finally u could get a o2 sensor simulator but im not exactly sure how that works

 

Is there a programmer you recommend, and what about a emulator, do they work on 04+?

 

I recommend getting someone who knows how to tune a 3800 to tune the car, but you could just get a ZZP PCM, or another canned tune by another company...

ZZP, Overkill, etc.

 

Is the zzp pcm easy to install, and easy to relearn the security process?

 

install is a breeze, security re-learn isn't always necessary.

Can't give you an exact because I have a custom tune.

 

Thank you for all the help. I have msd ignition, pace setter headers, and kn filter, any other reasonably priced mods I can do for my n/a motor, that will give good gains?

 

i would get a 2.5" downpipe, and just keep the cat to stay legal. going catless won't make it much louder or gain hp anyways. what you could do is get a magnaflow hi-flow cat.

the downpipe eliminates the ubend automatically, and you can buy them with the hi-flow cats too. the pipe will throw a code, but at least you will be legal.

 

Have you thought about doing an electric cutout (like a Qtec or DMH)? You could just have a dump welded to the bottom of your downpipe at the base of the firewall, and bolt the cutout on. That way you could get the loudest possible sound when you want, go back to how it is now when you want (ie if police are behind you or you're in a neighborhood)- or anywhere in between. They run under $200.

A cat delete isn't going to have a major difference in sound volume- the mufflers do the bulk of the sound reduction. It will be a little louder and raspier without it, but its not going to be a massive difference.

I also reccomend just doing a downpipe if you want to do this, its easier and will get rid of some of the restriction up top too.

It will trip a light without the cat, a tuned pcm can delete it- just make sure you tell them to turn that code off.

Not true at all. In the tuning software (DHP at least) there are 2 different sections for the SES codes. One controls whether it trips the light or not (ie you can make it still set the code, just not turn the light on). The other one controls whether the code is reported at all (turn the code 'off' and it will never set).

I passed emissions with my 99 GTP with no cat or EGR (and the occasional minor EVAP leak code)- I just set all the codes to 'not reporting' in the pcm tune, and it passed with flying colors in the OBD plug in test.

IMO the MSD is a waste of money- do you have the MSD coilpacks or a DIS 4? Either way, you could've saved some money there.

As for the pacesetters (don't they come with any sort of downpipe?)- I think they're a bad choice for an NA vehicle. They have 1.75" primaries with a 3" downpipe outlet which is huge for a nearly stock NA engine. For comparison purposes the S&S headers were designed for the NA 3800s and have 1.5" primaries and a 2.5" downpipe outlet.

Outside of a top swap, the only other cheap mod with decent power gains would be some ER rockers.