How many Catalytic converters?

[Joebaurer]

Have a 91 Explorer 4.0 Eddie Bauer and I need a new catalytic converter. When i look underneath I see the section of the exhaust which has two oem converters. My question is to replace the cataloytic converter section im planning on buying the universals made by magnaflow or flowmaster, do i need to replace with 2 converters or can 1 converter with a 10"-12" extention of exhaust pipe work? As far as performance will there be gain/loss in performance? is replacing with one do any harm or for the 4.0 motor does the engine need 2 catalytic converters to replace the oem 2 converter section of exhaust? An OEM cat can run upwards from $240-$290 and the universal is anywhere from $85-$110 i guess x2 if i would need 2. Now lets say there wouldnt be no harm in haing only one, does that effect the emissions test on passing? And would the performance be better with half the restriction visa versa? Please let me know what you think and what would be my best way to replace the cat. I want the truck to pass smog, still sound good, and have the power it use to have before the cat became clogged or if not more after the replaced cat is in. Let me know your thoughts please.
Thank you joey
91 explorer 4.0L eddie baure

 

[Centaurious]

I think if Ford could have used just one and passed emissions they would have. Therefore you need two and you get what you pay for. If it is cheap the platinum is thin and wears away faster.

 

[MrQ]

Have a 91 Explorer 4.0 Eddie Bauer and I need a new catalytic converter. When i look underneath I see the section of the exhaust which has two oem converters. My question is to replace the cataloytic converter section im planning on buying the universals made by magnaflow or flowmaster, do i need to replace with 2 converters or can 1 converter with a 10"-12" extention of exhaust pipe work? As far as performance will there be gain/loss in performance? is replacing with one do any harm or for the 4.0 motor does the engine need 2 catalytic converters to replace the oem 2 converter section of exhaust? An OEM cat can run upwards from $240-$290 and the universal is anywhere from $85-$110 i guess x2 if i would need 2. Now lets say there wouldnt be no harm in haing only one, does that effect the emissions test on passing? And would the performance be better with half the restriction visa versa? Please let me know what you think and what would be my best way to replace the cat. I want the truck to pass smog, still sound good, and have the power it use to have before the cat became clogged or if not more after the replaced cat is in. Let me know your thoughts please.
Thank you joey
91 explorer 4.0L eddie baure

If the vehicle came with 2 cats then two are required, plain and simple.

We do not suggest or endorse modifying or removing emissions systems on this forum for both legal and safety reasons.

 

[masospaghetti]

Ford may have used 2 converters to place them closer to the engine - this helps them "light off" faster and reduce startup emissions.

You might be able to pass smog with 1 new converter but you will be polluting more on startup. This may be illegal, I am not sure. I doubt you will notice any performance difference.

 

[BKennedy]

When I replaced my transmission with a GM 700R4, the two OEM cats would not fit next to the wider transmission. The two cats were replaced with one high-flow performance Magnaflow cat. That was over a decade ago and it has passed smog every other year since, in California. Its cleaner now than with the two OEM cats. If your state doesn't require two OEM cats, it should pass smog fine. Check Nevada law and report back. This is no longer legal in California, but it is grandfathered in as its over ten years old.