ive been wanting to put true duals on my f150 but all the local muffler shops wont cause they say its ilegal. but ive been looking around and as long as i have a cat and a muffler on each pipe i should be set. or am i missing something?

 

Yeah you should be set. The only thing that I can say is that there might only be one O2 sensor in the pipe after the y pipe collects both headers. If you lose the collector of the two pipes then there isn't computer control of the second pipe. This might be what the exhaust shops are talking about. I'm really not sure.

 

maybe they didnt say.



oh and these is for a 92 f150 with a 5.0L

 

I think, legally your not allowed to remove a CAT that is still functional. So, unless it has a hole in it, or is rusted out or you can prove chunks of it are coming out, they won't touch it. The fine is just too great to chance. . .$15,000+ fine or turn down a $350 exhuast job Not a hard choice for the shop owner.

Now, CAT backs are fine becuase it has nothing to do with emissions. . .

Just what I know, take it with however much salt is needed

 

Thats not entirely true. Legally you cannot remove the factory cat while it is still under the factory warranty (Doing so will also void the factory warranty). Since they won't let you do true duals, go for a 3" single exhaust, much cheaper. If you want duals, go with a nice cat-back kit that has a dual outlet muffler and the dual tailpipes. They are available in side by side duals or you can split them to each side, or you can bring them alongside the hitch right out the back.
I have previously expressed my opinion of true duals versus single/false dual exhausts. I feel the single exhaust or false dual will make a more consistent output and the power curve will be less "peaky" (is that even a word?)

 

tomorrow im goin to buy a cherry bomb extreme muffler and have a cat back installed. so i think thats the way im going to go.

also would having longer tips make a effect on any thing?

 

Huh, the muffler shop here said he would put true duals on for me for $175. Then again he's pretty cool and told me if I didn't want to, I didn't have to put cats on it.

 

Well, your truck is not OBD-II, and may have grandfather status. Also in the US you cannot eliminate the cats legally, regardless of your local emission laws. But by all means, if you want to eliminate them, I'm sure you will. Converter manufacturers make better money restoring catless systems back to what they should be, since more parts are required, and often is is more cost effective to replace the entire Y-pipe system than the weld in universals.

 

Even with OBD II, you can get O2 replicators and hack out the cats.

 

Well, the muffler shop just told me that if I needed to pass inspection, alls I would have to do is put my cats back in, and he said it would be legal. What do you mean grandfather status?

 

grandfather status is if something outadates a law that has since been placed on newer models.
ie cars manufactured before 1964 dont have to have seatbelts (as long as they didnt have them when made)
same principle with emmisions systems, if your truck didnt have any when it was built, they cant make you add one later, but a 1987 still would have had cats and PCV, as well as O2 sensors


I had never heard that, i thought if you lived in a no emmissions zone you could do whatever with the cats. where i live tires and exhaust ar ethe first 2 changes when you get a new truck, and just about everyone i know ditches the cats when they get the new exhaust.

 

There are FEDERAL emissions laws, not just local. If your area has no emissions laws, you still have the Feds to deal with.

 

Yes, you can get O2 eliminators, but they do cause some issues of their own. They are giving the computer a false signal. The rears sensors on an OBD-II system are mostly for catalyst monitoring. But they do play a role in fine tuning and minor timing adjustments. When the catalyst is working efficiently, the then the fuel trim is ideal. The computer will make minor adjustments to determine if catalyst is as efficient as it can be. If an O2 eliminators is always telling the computer that the catalyst is working just fine, then the computer cannot fine tune the system, and depending upon the accuracy of the front sensor, could result in a change of as much as 1.5 MPG loss.

IMHO a well designed single exhaust is just as good if not better than duals because of the improved velocity of a single exhaust, which results in better scavenging. If your vehicle has a single rear O2 sensor, just stick with a single exhaust, or do false duals (dual outlets on the muffler.) If you have a rears sensor off each bank, then there are no laws that I am aware of that would prevent you from going with a dual setup. For the record, what year and motor is your F-150.

 

Its a 92 f150 with a 5.0L

 

In some states and localities true duals are illegal unless the vehicle was equipped with them from the factory.

I know for a fact in massachusetts an exhaust shop can only install what came on your vehicle from the factory.

And yes, if you get caught with a vehicle that should have a cat that doesn't, it's about a $2500 fine. For the most part if you aren't doing stupid stuff you won't get caught, but i've seen a Missouri state trooper pull over a Camaro with a loud exhaust and pull out a mirror on a stick to make sure he had converters.



Then a 2.25" Y into a single 3" will support more power than a full dual 2.25.
While the cross sectional area of two 2.25" pipes is the same as a single 3" pipe, the dual 2.25's have more contact area between the exhaust gasses and the pipe creating more friction which leads to a velocity loss and decreased scavenging efficiencies.

So while a dual 2.25 system and a single 3" system have the same area, a single 3" will flow without causing as much of a velocity loss as dual 2.25's.

So while they flow the same amount, a 3" pipe will flow at a greater velocity increasing scavenging efficiencies. It's what I'm getting put on my 390 tomorrow.

Justin