Fox Does a Cat Really Need Air?

[Black1987]

Borderline Tech...but maybe opinionated...so

Do the new Catted X and H pipes from LMR/AM still require smog? Or does it cause the cats to prematurely fail without it?

Looking at all the kits with the exception of the weld in SVE w/Flowmasters high flow cats , all have the provision for it.

I recall reading @MFE92 used magnaflow magnetic spun high flows, but didn’t see any others except yeah you can but no comment on the smell.

Second question, someone mentioned just venting the air provision to atmosphere via a check valve would help the longdvity of cats? ( This seems counterintuitive to me I don’t know why).

Lastly can you just run the air pump striaght to the provision port without the TAD/TAB stuff (mine was lost in the fire) and it moreless do the same job? Pretty in this scenario its all or nothing.

Trying to make my Foxbody smell a little better. In the process of getting a new shifter (old one is torn), Charcoal Canister and purge solenoid.

Started to look at my old pipes/ turn downs and figured it may be time to change up things.

 

[Mustang5L5]

Yes, you need the pump.

Reason being that even though the new cats are more efficient, the 5.0 engine in general is not and is still a rather dirty engine. If you stuck a coyote in your car, you wouldn't need the pump because those engines run much cleaner. But the good ole Windsor still needs the pump.

With regards to the 2-cat setup, you can generally eliminate the piping to the heads. Basically you just route the air hose to the bypass valve, and keep the solenoid intact that actuates it. You can then route the hose to the mid-pipe. That wasy you eliminate the diverter and the yellow tube in the above graphic since there are no pre-cats to worry about. You can even route the air line through the fender down to the h-pipe to clean up the bay a bit. I wish I had the original of the above graphic to modify it to reflect my proposed routing with a 2-cat pipe.

Unsure how the above would affect codes generated by the car. I'm sure you might get a code 44/94 but you'll know why since the tube to the heads is MIA.

I plan on doing the above to my car. Bassani catted X-pipe is just too expensive to risk not running a pump with. I'm going to route the air line into the fender and mount the bypass valve there. Other than the pump in the bay, that side of the engine will be cleaned up.

 

[Black1987]

Yes, you need the pump.

Reason being that even though the new cats are more efficient, the 5.0 engine in general is not and is still a rather dirty engine. If you stuck a coyote in your car, you wouldn't need the pump because those engines run much cleaner. But the good ole Windsor still needs the pump.

With regards to the 2-cat setup, you can generally eliminate the piping to the heads. Basically you just route the air hose to the bypass valve, and keep the solenoid intact that actuates it. You can then route the hose to the mid-pipe. That wasy you eliminate the diverter and the yellow tube in the above graphic since there are no pre-cats to worry about. You can even route the air line through the fender down to the h-pipe to clean up the bay a bit. I wish I had the original of the above graphic to modify it to reflect my proposed routing with a 2-cat pipe.

Unsure how the above would affect codes generated by the car. I'm sure you might get a code 44/94 but you'll know why since the tube to the heads is MIA.

I plan on doing the above to my car. Bassani catted X-pipe is just too expensive to risk not running a pump with. I'm going to route the air line into the fender and mount the bypass valve there. Other than the pump in the bay, that side of the engine will be cleaned up.

That prompts a follow up question / or (s)
The only thing I have currently is the air pump ...no TAB/TAD, bypass, nor diverter valve. All that got roasted and few and far between in the JY.

Any issues running straight air pump no solenoid/bypass?

Bassani was the one I was leaning towards. Seems similar quality as my Corsa on S550 (Sold it btw). Have done any research on no drone mufflers for when you do yours?

Kind disappointed Corsa doesn’t make a kit for our cars, even thought about modifying the S550 kit for a fox, but it is now funding new mods for the fox.

 

[Mustang5L5]

I believe the only time the bypass valve opens up is during WOT. It's goal is to relieve strain on the air pump by dumping the air straight back to atmosphere, freeing up a few HP. I guess the only consequence of not having the bypass is you have additional load at WOT.

I haven't installed the Bassani yet. Figure I lump that into this coming winter's modifications. Unfortunately I need to run it with my flowmaster cat-back as that setup will clear my panhard bar. Later on, i'll revisit and probably weld in some different mufflers, but the car is a weekend cruiser and I actually like drone.

 

[LX Dave]

With regards to the 2-cat setup, you can generally eliminate the piping to the heads. Basically you just route the air hose to the bypass valve, and keep the solenoid intact that actuates it. You can then route the hose to the mid-pipe. That wasy you eliminate the diverter and the yellow tube in the above graphic since there are no pre-cats to worry about. You can even route the air line through the fender down to the h-pipe to clean up the bay a bit. I wish I had the original of the above graphic to modify it to reflect my proposed routing with a 2-cat pipe.

Unsure how the above would affect codes generated by the car. I'm sure you might get a code 44/94 but you'll know why since the tube to the heads is MIA.

My car is set up as you described and I'm getting no codes. I don't think the computer knows if the tube and diverter valve for the air injection going to the heads is there or not (yellow tube in pic) since they are strictly vacuum operated. I do have the TAD valve plugged in just in case it's being monitored by the computer.

 

[Mustang5L5]

My car is set up as you described and I'm getting no codes. I don't think the computer knows if the tube and diverter valve for the air injection going to the heads is there or not (yellow tube in pic) since they are strictly vacuum operated. I do have the TAD valve plugged in just in case it's being monitored by the computer.

I think the ECU looks at O2 sensor changes when It diverts the air to the heads or pipe to see if they entire pathway is clear. That's why you have both code 44 and 94 which is side specific. . But i'm not quite sure.

Either way, I don't think it affects how the car runs at all.

 

[Steel1]

When my car was still going to the sniffer every other year, I ran a Pypes high flow catted x without smog pump. Just plugged the tube on the cat.
Always passed smog without issue but then again I only drive it a few hundred miles a year.

 

[NIKwoaC]

I've always been curious about this myself. As I understand it, the cats are in place as a heated element to help burn off unburnt hydrocarbons leftover from the imperfect combustion process. Typically to burn something, you need an oxygen source. However, outside of WOT, and maybe some compression braking scenarios, engines typically operate near stoichiometric, so in theory you started with enough air to burn off all the fuel you squirted in the cylinder. Obviously the air pump existed in the first place to guarantee enough air was getting pushed back there, but it seems to me modern cats could still maintain some amount of efficiency without it.

 

[Chuckman]

Really depends on the cat, or really the chemistry inside the cat. New stuff doesn't have air (smog) pumps like the old stuff used to use. Whether or not a bolt-on h/x has the cats that's need it.....probably need to call the manufacturer.

 

[Dan02gt]

Doesn't the air connect to the secondary cats only? I'm guessing part of that is due to them being so far downstream that they don't get hot enough to work properly. Seems like a modern cat installed as close to the engine as possible might work pretty good.

 

[Mustang5L5]

Doesn't the air connect to the secondary cats only? I'm guessing part of that is due to them being so far downstream that they don't get hot enough to work properly. Seems like a modern cat installed as close to the engine as possible might work pretty good.

It's splits. The tube goes to the secondary cats, but the pipe to the back of the heads feeds air to the exhaust ports in the heads in order to mix with the purposely rich fuel mixture and feed the pre-cats during the warmup stage getting the cats heated up quickly.

The reason new cars don't use o2 pumps is simply because the newer engine runs cleaner and hotter than older engines like our 5.0's. The amount of extra hydrocarbons is reduced, so the cats really don't need to work as hard. Our engines are just not as efficient, and spew a lot higher level of hydrocarbons into the exhaust. If the converters cannot oxidize these HC's, it builds up on the surface of the cat.

It really has less to do with the type of cats on the car, and more tied into the state of tune of the engine. Modern coyote engine..i wouldn't run one.

 

[jrichker]

Yes, you need the pump.

Reason being that even though the new cats are more efficient, the 5.0 engine in general is not and is still a rather dirty engine. If you stuck a coyote in your car, you wouldn't need the pump because those engines run much cleaner. But the good ole Windsor still needs the pump.

With regards to the 2-cat setup, you can generally eliminate the piping to the heads. Basically you just route the air hose to the bypass valve, and keep the solenoid intact that actuates it. You can then route the hose to the mid-pipe. That wasy you eliminate the diverter and the yellow tube in the above graphic since there are no pre-cats to worry about. You can even route the air line through the fender down to the h-pipe to clean up the bay a bit. I wish I had the original of the above graphic to modify it to reflect my proposed routing with a 2-cat pipe.

Unsure how the above would affect codes generated by the car. I'm sure you might get a code 44/94 but you'll know why since the tube to the heads is MIA.

I plan on doing the above to my car. Bassani catted X-pipe is just too expensive to risk not running a pump with. I'm going to route the air line into the fender and mount the bypass valve there. Other than the pump in the bay, that side of the engine will be cleaned up.

If you have Visio or access to a Visio compatible software package, I can probably sent you the original Visio drawing.

 

[Steel1]

Not sure of the scientific reasoning for why it worked without the air pump but always made sure I drove around a little to heat the cats up
before I went to the sniffer.
I did have a function EGR though, glad I don't have to deal with that anymore !

 

[Mustang5L5]

Not sure of the scientific reasoning for why it worked without the air pump but always made sure I drove around a little to heat the cats up
before I went to the sniffer.
I did have a function EGR though, glad I don't have to deal with that anymore !

I guess it ultimately depends on your tune

 

[Mustang5L5]

If you have Visio or access to a Visio compatible software package, I can probably sent you the original Visio drawing.

I do have Visio.

If you want, you can send it to [email protected] and I'll modify it to my proposed two cat setup.

Stil on the fence as to if it's proper. My understanding is initial cold start is rich and the o2 pumped into the heads aids in burning off that fuel. Unsure if that needs to be done at the heads, or if it can be done downstream and still be effective. The unburned fuel is what ruins the cats

 

[MFE92]

Cats work on a lot more than just heat burning off excess hydrocarbons. They're catalytic converters, meaning they change the chemistry of the gases based on exposure to a catalyst. They oxidize CO into CO2, they oxidize hydrocarbons into CO2 and H2O, and they reduce NOx's into N2.

The air injection inserts oxygen to maximize the oxidation stages of the catalyst, and in some cases, to offset an overall rich mixture. It's there for a reason.

But...do you NEED it? Other than from an equipment-mandate standpoint, I land on "no", because most cats in most circumstances will run a long, healthy and test-passing life without it.

 

[lizzard]

I'd like to know when exactly the diverter valve lets the air through to the heads and when to the cats.
because I have new heads (FR X307) without the provisions. now I have a setup which directs the air after the bypass-valve directly to the check valve and then to the cats (I took the diverter valve away). But I have also the stock pre-cats and if you're right (the ones who say that the pump is mandatory) then it's only a matter of time when they will fail.

 

[Noobz347]

Whether or not cats need additional air depends on the makeup of the cat. Two-way catalytic converters require additional air in order 'burn' correctly and get to and remain at operating temperature. The diverter opens when the motor is cold and at other times based upon sensor input. Air is directed at the first set of converters in a two-way converter.

Three-way converters do no require the additional air or diverter valve.

 

[lizzard]

I'm confused: do we have stock 2- or 3-way-cats?

 

[Noobz347]

I'm confused: do we have stock 2- or 3-way-cats?

Cars with 4 cats from the factory are two-way. The pre-cat gets the air from the diverter valve.