true duals question

[FX4OffRoad1992]

What kind of inspection do you have. One where a guy looks over your vehicle to check for stuff? Is it an actual emissions test with an exhaust sniffer while driving on rollers.
In WI it's a half-assed emissions test. Only vehicles 96+ (OBDII) required to do it. Basically they just hook a scanner up to the OBD-II DLC, if you don't have any active or pending trouble codes, and your gascap passes the pressure test (they might not even test the gascap anymore) you pass.

My Grand Marquis had 4 cats (1st O2 sensors, cat, 2nd O2 sensors, cat, y-pipe). I cut out the last set of cats. I pass the "emissions" test. It passes. It definitely wouldn't pass a exhaust gas analyzer/sniffer.

around here they just look around the truck checking lights and blinkers.. and then hook it up and if it doesnt throw any codes your fine.. im pretty sure they don't do the whole exhaust gas sniffer thing.. so im not sure if i would be okay without the last cat or not..

 

[JohnnyO]

The first two smaller cats are called Pre-cats. Because they are smaller they light off quicker so the truck is emissions-legal when cold. The next item down the pipe is indeed a full-size cat. For true duals you would need at least one more OE cat or a pair of aftermarket ones, but that isn't the main problem with putting on true duals. The main problem will be the gas tank. So run the pipes down the right side? Well, then you've got to get one of them over the axle and around the spare tire. I'm not saying it can't be done but it will be difficult.
Simple fact is that a 4.0 doesn't flow enough air that true duals will make any difference. Gibson makes a single system (that I have on my Sport Trac) and a single-in dual-out system. Their data shows the single system makes more hp and torque than the dual.

 

[85_Ranger4x4]

The first two smaller cats are called Pre-cats. Because they are smaller they light off quicker so the truck is emissions-legal when cold. The next item down the pipe is indeed a full-size cat. For true duals you would need at least one more OE cat or a pair of aftermarket ones, but that isn't the main problem with putting on true duals. The main problem will be the gas tank. So run the pipes down the right side? Well, then you've got to get one of them over the axle and around the spare tire. I'm not saying it can't be done but it will be difficult.
Simple fact is that a 4.0 doesn't flow enough air that true duals will make any difference. Gibson makes a single system (that I have on my Sport Trac) and a single-in dual-out system. Their data shows the single system makes more hp and torque than the dual.

You also run into the problem that each bank of your 4.0 may not produce enough volume to keep a cat designed for both banks effective.

Most aftermarket ones have both stages in one can, so you need to trash the pre-cats too.

Duals on a Ford with a inboard fuel tank has been delt with many times. When they put my true duals on they just got a dual kit (fake Y-pipe setup) and just used the over the axle part of the kit and credited me for what they didn't need. The SI/DO setup probably isn't as effective as a true dual setup since it has to split the exhaust... and IMO if they make any noise at all they sound like crap. A V6 needs all the help it can get in that department, but it will make a V8 sound stupid too.

 

[Strieg]

Wish I could mod my truck more... Stupid California....: but yes that is absolutely a cat.

 

[BlueChariot]

The first two smaller cats are called Pre-cats. Because they are smaller they light off quicker so the truck is emissions-legal when cold. The next item down the pipe is indeed a full-size cat. For true duals you would need at least one more OE cat or a pair of aftermarket ones, but that isn't the main problem with putting on true duals. The main problem will be the gas tank. So run the pipes down the right side? Well, then you've got to get one of them over the axle and around the spare tire. I'm not saying it can't be done but it will be difficult.
Simple fact is that a 4.0 doesn't flow enough air that true duals will make any difference. Gibson makes a single system (that I have on my Sport Trac) and a single-in dual-out system. Their data shows the single system makes more hp and torque than the dual.

I was going to make the point of "there isn't much space", but you've explained that. It did give me the idea of putting a large fuel cell in the bed though, more for weight distribution than freeing up space tho because as you said, true duals wouldn't do much good. Would free up valuable room if one were to do a V8 swap though.