ok i hve decided to just go with one muffler for this upgrade, i am going to use 2.5 inch exhaust piping and one muffler (obx 9) my ? is if i go straight from the cat back or even remove one cat will the check engine light come on? i was reading up on the pipe sizing and from the search i did, 2.25 and 2.5 on a N/a is a good size to use. i went with the 2.5 only cause it the inlet size of the OBX and wanted to keep it the same.i was going to take all the cats out but the little metal tubing ggoin into the downpipe from the engine, that i cant replicate. i cant weld. the exhaust piping i have has ends that are a bit bigger so the pieces slide in each other. so no welding required.

just wanted to make sure that i wont be having
check engine light problems and engine failure prob due to the increase of exhaust.

let me know please
thanks
andy

 

I've never had a problem with the check engine light coming on after gutting an exhaust. As long as the O2 sensor is still there, the ECU aint gonna know the difference

 

That little metal tube actuate your aux ports also called 5th and 6th ports, I saw in your profile its an s4 so that means on your car exhaust backpressure goes up that tube and once enough pressure is built up the ports open, if you do remove your cats, or free up your exhaust enough you will have to find an alternative method to open the ports. I hooked mine up to the stock air pump, there are other methods of activating them using an aux air pupm and an rpm activated switch PM me and I can direct you towards some more info on this, but if you want to save the hassle keep the cats but they do give you alot of power when you lose em.

 

unless this process is easy i think ill just keep the cats on there for right now. i should still notice a bit difference i assume by putting on 2.5 instead of 1.75 and getting a straight through flow muffler. anymore info on this ?

thanks
andy

if the ports dont open, how will i know when im driving ? is it a big difference ?
thanks

 

You should start to see a moderate to strong hesitation at about 3500-3800 RPM.

I would recommend hooking it up to your airpump. This is what is done on my car. Have not had any ill effects. They open up at about 3k rpms now, and yes the car will run slightly rich from 3K to 3.5K or so... but I have a s-afcII to compensate for that

I don't know anything about his RPM activated switch... but I'm going to look into it now, and if it looks like its worth it.. I'm going to try it .

 

exactly how do i hook it up the air pump and how do i know the air pump is working.

if its what im thinking of then,

when i first got the car it would rev up to whats it soppose to because of the blower type of device which i think is the air pump your are revering too . not it only cmes on for a sec and the rpms drop down to regular idle. but everyone on here says thats fine it wont hurt the car. so i guess im asking how do you install the set up you have and ,
is that the same item im talking about cause if so i dont believe it would work in my case.
thanks again
andy

 

anyone else? still waiting for someone of you to pm me back to the info on how to do the above mods for the system to work incase i wanted to gut the cats.
thanks in the long run
andy

 

You need better thread titles.

And 2.5 is a good size, no check engine light for you.

 

anyone know of how to do the above? please let me know.
thanks a lot

anyone have a idea of how much increase the exhaust will porvide ?

how much louder will it be?

thanks again
andy