Question about cats

[Nixthebomb]

I have a total of 4 cats, two in the y-pipe off the headers but they are after the 02 sensors, then the y-pipe goes into 2 more cats then another 02 sensor, then muffler.

If I were to remove the cats in the y-pipe would I throw a CEL?

if it matters its a 99 sport 4.0 OHV

 

[Anime]

It might not throw a CEL initially, but it could throw one once the last sensor gets all gunked up with stuff, or when the 2nd set of cats overheats or gets clogged up from the first set not being there to do any conversion.

2-cat systems are designed to work so the upstream cats, which heat up quick because of their location, do one part of the conversion process, with the downstream cats taking care of the rest once that part of the exhaust gets up to operating temp. Removing either set of cats results in messing up the entire system.

The only proper way to go about it would be removing all 4 factory cats, and replacing them with either a pair or a single 3-way converter. Changing up the factory setup so the Y-pipes go into a single pipe, then into a single cat, and a single-in muffler might be easiest, and save the headaches associated with the multiple-cat setup, though it does work ok with dual cats and a dual-in muffler.

You'd also run into legal issues removing part or all of the system without a fully functional replacement for a street driven, registered vehicle. To the tune of a $5,000 fine and/or 5 years in jail.

 

[2000StreetRod]

thanks for explanation

Anime, thank you for that informative explanation. I've wondered why some OHV V6 Sports have 4 cats and my SOHC V6 Sport only has two. I didn't realize that some OHVs did not utilize 3 way converters.

 

[Nixthebomb]

thanks for the info, guess when i move onto the cats, ill get the bolt on 3rd and 4th cat, and have the local shop weld on two new ones in he primary

 

[ranger7ltr]

Looking at my FSM...

Ford claims the convertors on the OHV 4 liter are 3 way... It also doesn't mention the front 2 cats at all...It even shows the headpipe y pipe as having no cats installed in it...

 

[Anime]

Ford has used several converter configurations for the 4.0L OHV, not just on different model year Explorers but on Rangers, Aerostars, and more. I don't think one of them uses a single 3-way conveter, Ford engineers seem to use 2-cat systems for the larger motors, even to the point of dual 2-cat systems on the '98-99 and newer models.

You can of course replace them with much less expensive aftermarket 3-ways, and fill in the Y-pipe gaps with pipe. I'm pretty sure you could have 2 aftermarket 3-ways installed right after the Y-pipe on each outlet (or one really big 3" single cat), and they'd heat up properly in that location, plus you'd avoid the expense of buying 4 new ones. There are probably some emission advantages to 2-cat systems, and Ford's use of dual 2-cat systems probably has more to do with reducing emissions (over the old single dual cat systems) than necessity. If you get a good brand name (Carsound by Magnaflow, Walker, etc.) they will probably do as well emissions wise but flow slightly better.

If you do have the stock cats removed, be sure to sell them off for the precious metals. They can be worth quite a bit.