Catalytic converter question

[birdman941]

Does anyone know which converters are more restrictive on an 04 Mach 1?
The light-offs or the rear cats?
Remember on the 04's the rears are dual brick.
I am trying to decide which 2 stock cats to have installed on "R".

[wutang61]

the 2 front ones are "pre-cats" and then the dual bricks are the actual cats

so the rears would be more restrictive.

[mach1 03]

the 2 front ones are "pre-cats" and then the dual bricks are the actual cats

so the rears would be more restrictive.

i agree i put the two bricks on my x pipe so i could pass emissions and it was not much louder than the stock with all four.

[birdman941]

On an 04, the way the O2's are positioned,
the "green" O2's are before the lightoffs, and the 2nd O2's are directly after them.
This makes me think that the PCM only "cares" about the lightoffs.
In theory, (since I have never done it) removing only the second set
should not activate the SES light.
What I am thinking here, is if the second set is less restrictive,
I can use them instead of the lightoffs,having the O2's before and after them.
This is assuming that the second set being used as lightoffs will
clean it up enough to avoid the SES.
I was originally going to use aftermarket cats on "R",
but I have a near brand new catted H pipe here I can use.
Feedback on this wacky theory is welcome.

[wutang61]

well if you have a new catted h pipe then just use that lol
do you have emission testing there or do you just not want a SES light? cause if you don't have testing i'd go catless and get mil eliminators. the 2nd set of cat's (the ones after the rear O2 sensors on 04') are the most restrictive part of the midpipe. but if you have a new catted midpipe there gonna flow alot better then the stock cats anyway (just enough to past emissions testing) if i was you id go catless...no reason to hold back the ol' 5.4 :23:

[SHAKEN]

I made my M.I.L. eliminators. From info on this site. http://paladinmicro.com/PalMFrame00.htm?wks= which cost about 5 or 6 bucks. I could have turn them off with my tuner but couldnt see ruining them by shutting them off if I ever needed to have warranty work since I have extended warranty. I also found the pig tails at a junkyard to make my M.I.L. eliminators modular as the ones you buy added cost 20 bucks. As far as your theory Bird cant help you I have a 03 sorry not trying to jack your thread just couldn't see spending 60 to 80 bucks for M.I.L. eliminators.

[birdman941]

I would prefer to have cats if possible.
I will need to have it tuned (obviously), but I am trying to make it emissions legal.
I am running EGR also.
Just want to see if it is possible so others can follow.

[wutang61]

I would prefer to have cats if possible.
I will need to have it tuned (obviously), but I am trying to make it emissions legal.
I am running EGR also.
Just want to see if it is possible so others can follow.

well get some mangaflow hi-flow cats for project "R" there emissions legal and very low loss

[birdman941]

Thanks, I'll check it out.

[Marks04DSG]

Thanks, I'll check it out.

Yea the part no. is 91406 just did them on mine awhile back