Fox HAD ENOUGH OF EXHAUST FUMES!!!

[PonyGTrider]

Hello gentlemen,
I have a question for ya’ll
I think I had enough of those pesky exhaust fumes after years running without the air pump and the entire anti smog system. Besides that I removed the secondary cat converters, at one point I removed the upstream cats and it was horrible so I put them back on.

My question is can I run all four cats without the air pump? Or, if I decide to have all the cats can I run continue air flow to the downstream cats? That is installing the air pump running a straight hose to the pipe that goes to the H pipe having a constant air flow.

I’m just trying to remove that bad smell out of the tail pipes…

I read that those secondary cats will get clogged if no fresh air comes from the air pump. What about running fresh air constantly?

Could anyone help with this issue?

 

[Noobz347]

If you put the OEM style cats back on then you should use an air pump.

The alternative would be to run 3-Way catalytic converters. They are meant to run on their own with no pre-cats.

 

[PonyGTrider]

If you put the OEM style cats back on then you should use an air pump.

The alternative would be to run 3-Way catalytic converters. They are meant to run on their own with no pre-cats.

I heared what you say, I was reading about the 3 way cats and it says those cats are for OBD II and require two downstream O2 sensors. Will it become a problem, or it will work correctly?

 

[Noobz347]

What sensors do you have left, now?

 

[AeroCoupe]

I ran them with no air pump and passed emissions in Houston. No gas smell after they heated up.

 

[JMG9350]

Downstream oxygen sensors are only there to monitor catalyst efficiency. They are not needed for the converters to function properly. Modern catalytic converters are also far more efficient and you can get rid of the secondary converters, as well as eliminate the smog pump.

 

[PonyGTrider]

What sensors do you have left, now?

Well Foxes only have two O2 sensors and I still have those. '95's have four sensors, and learned that when the downstream O2 sensors see a rich condition after the upstream cats didn't burn fumes at that stage then the ECU reduces the injectors pulses for less fuel, that's whay I asked if there any issues running those 3 way cats with OBD I system.

 

[PonyGTrider]

I ran them with no air pump and passed emissions in Houston. No gas smell after they heated up.

That sounds very good, so no clogging or anything like that? I will focus on finding those cats.

 

[PonyGTrider]

Downstream oxygen sensors are only there to monitor catalyst efficiency. They are not needed for the converters to function properly. Modern catalytic converters are also far more efficient and you can get rid of the secondary converters, as well as eliminate the smog pump.

So I should run those 3 way cats on a fox without any issues? No issues on the cats life expectancy? then I will do that.
I removed the whole alternator/air pump/belt tensioner bracket and didn't want to put it back on to install the air pump. I kind of like my engine to be more compact (Narrower) with a manual belt tensioner, and for that I build my own alternator bracket and like it better that way.

 

[PonyGTrider]

I ran them with no air pump and passed emissions in Houston. No gas smell after they heated up.

Do you happen to remember what brand did you use then? Maybe it will be a good idea for me to run them I'm really tired of that damn smell.

 

[Noobz347]

Well Foxes only have two O2 sensors and I still have those. '95's have four sensors, and learned that when the downstream O2 sensors see a rich condition after the upstream cats didn't burn fumes at that stage then the ECU reduces the injectors pulses for less fuel, that's whay I asked if there any issues running those 3 way cats with OBD I system.

You can make it work either way. Like mentioned above, you really only [need] the pre-cat sensors so that the EEC knows what's going on with combustion [before] the cats.

How is the condition of the rest of your exhaust?

 

[PonyGTrider]

You can make it work either way. Like mentioned above, you really only [need] the pre-cat sensors so that the EEC knows what's going on with combustion [before] the cats.

How is the condition of the rest of your exhaust?

Sounds good. The rest of the exhaust is in really good shape, it is just I got tired of that darn smell.
Thanks man

 

[AeroCoupe]

87-93 Mustangs only have one set of O2 sensors so no "pre" and not "post". The O2 sensors are installed just before the first set of cats in a factory H-Pipe.

I ran Walker universal 2.5" high flow cats in a BBK offroad X-Pipe. Don't run them anymore as there is no testing where I live and I don't drive the car everyday either. Ran them in the car for five years and they are still good to go based on visual inspection in that there is not clogging. The tune on the car has always been really good so it doesn't dump a lot of fuel. I just had to have them to get it over the hump and pass the under the car visual as they did not pop the hood in Texas.

 

[Noobz347]

The O2 sensors are installed just before the first set of cats in a factory H-Pipe.

Those, are pre.

And just to add some detail that may not be required:

Pre Cat sensors are so that the EEC can taste the exhaust stream and make fuel adjustments to combustion.

Post Cats are for the converters themselves to determine if they are functioning (not required, in other words).

 

[AeroCoupe]

Well if they are the only ones installed then they are just "the O2 sensors". No sense in adding fancy words and churching things up brother Noobz.

 

[Noobz347]

Well if they are the only ones installed then they are just "the O2 sensors". No sense in adding fancy words and churching things up brother Noobz.

You say that but how many hacked up nightmares have we come across in this forum?

 

[Mustang5L5]

You can get away with no smog pump provided your car is in a good state of tune and not running rich. It would also be more ideal if the car was driving in situations that allow it to get hot, shich as a nice summer cruise on an 80 degree day, vs a quick drive to the corner store on a 45 degree fall day to get milk.

But with the stock 4-cat h-pipe, you should try to put the air pump setup back on. the plumbing can be modified as well based on each individual user's needs as well.

For instance, you don't really need the diverter in the mix to send air to the heads during startup, and then to the main cats once driving. This may be for emmissions, but in terms of cat longevity it won't matter. Once your engine gets hot, those two pre-cats will be toasty enough to burn off excess fuel on their own without the supplied air, which is why ford doesn't send air there after the engine warms up.

The TAB (bypass) is for WOT to lessen load on the air pump at WOT. When you go hammer down, the air from the pump just gets dumped.

You can run the hose direct to the h-pipe without any bypass either and have it pump 24/7. You just lose the bypass function so you are going to lose 1HP.

You can also run no air pump if you are sure you aren't running rich as hell and will be getting the car (and exhaust) plenty toasty on your drives.


Downstream O2's are not needed for Fox cars as the ecu has no way to monitor downstream cat efficiency. Wasn't even a thing yet. That came about when OBD2 was phased, in, although some manufacturers started a little earlier.

 

[PonyGTrider]

87-93 Mustangs only have one set of O2 sensors so no "pre" and not "post". The O2 sensors are installed just before the first set of cats in a factory H-Pipe.

I ran Walker universal 2.5" high flow cats in a BBK offroad X-Pipe. Don't run them anymore as there is no testing where I live and I don't drive the car everyday either. Ran them in the car for five years and they are still good to go based on visual inspection in that there is not clogging. The tune on the car has always been really good so it doesn't dump a lot of fuel. I just had to have them to get it over the hump and pass the under the car visual as they did not pop the hood in Texas

Excelente! I’ll try to find those or whatever I find should work fine.
Thanks man

 

[PonyGTrider]

Those, are pre.

And just to add some detail that may not be required:

Pre Cat sensors are so that the EEC can taste the exhaust stream and make fuel adjustments to combustion.

Post Cats are for the converters themselves to determine if they are functioning (not required, in other words).

It’s all right, I can sort out all the information and suggestions