Will I regret this?

moosetang408w · May 2, 2010

I am finishing off my exhaust system here just an H-pipe to weld in between. I have been getting alot of heat about running Catalytic Converters. The thing is I actually want to try to be nicer to the environment. I have taken combustion courses and know how good cats can be but I wondering how it is going to hold up as time goes. I am not running leaded gas but I will be running richer than stoichiometric in my fuel maps under full load at higher rpms.

What is your opions guys? Should I leave the cats? Cut them off? Wait to see what happens?

I can probably use the back pressure anyway.

Here is a pic of the exhaust so far. This is being fed from BBK Long tub headers and the exhaust is 3". The mufflers are Mac Pro Dumps

This is the power plant that is feeding this system

Cheers

fastfox90 · May 2, 2010

Im all for saving the environment, the new hi flow cats are supposed to be great. But the way I see it all the semi trucks, not to mention all the souped up diesel pickups running around belching black smoke everywhere are far worse than our Mustangs that are only driven in good weather. But thats just my take on it, Im sure others would dissagree. Plus I like the sound of mine without the cats!

Cobra4075 · May 2, 2010

Another thing to consider is the mpg savings that you immediately notice once you take them off. I've had three mustangs and all saw 20+ miles to the tank during hwy use when i deleted the cats.

Uber88GT · May 2, 2010

Ditch the cats if you don't need them for any inspections, then you can get rid of the smog pump too.

Mustang5L5 · May 2, 2010

Leave the cats...unless they are cheap catco cats which tend to fall apart

moosetang408w · May 2, 2010

For sound I think I will like the cats because it will make it a lower tone. The fuel mileage is something I haven't really considered, but I think I need the back pressure because it is N/A. At least that is what I have been told. I don't think they are cheap cats either. I bought them at our local performance shop. They are 3" magnaflow cats so I hope they are okay.

There is no smog pump on this setup.

I am starting to lean towards leaving them for now just out of interest what will happen. How it will sound, last, mileage, and performance. I think I will keep an eye on these and if the cats have to be replaced I will just weld in straight pipe. See what changes. I am up in Alberta, Canada and we luckly have nothing requiring emission testing..yet.

Thanks for the feedback my mustang friends!

Mustang5L5 · May 2, 2010

Well, unless those are the new magna flow spun metallic cats, you will need the smog pump.

Keep in mind having the cats tends to shift the torque curve lower, while no cats tends to shift it to the upper rpm range.

Also, you car won't smell like a refinery when you drive around which was the make or break point in my decision to run cats

TheUser · May 2, 2010

Yeah, I was gonna say you'll need the smog pump unless they're the new cats that don't need them. Both of mine have cats deleted and I've sometimes wished I had cats because of the smell. It sounds badass without them, but the smell is sometimes rediculous...and I'd like to not hurt the environment anymore than necessary.

As far as the semi's go...two wrongs don't make a right

moosetang408w · May 2, 2010

Mustang5L5 said:
Well, unless those are the new magna flow spun metallic cats, you will need the smog pump.

Keep in mind having the cats tends to shift the torque curve lower, while no cats tends to shift it to the upper rpm range.

Also, you car won't smell like a refinery when you drive around which was the make or break point in my decision to run cats

I was aware of the torque curve being lowered which is perfectly fine with me as this is a street minded car. I don't know why I "need" a smog pump. I don't plan on adding anything to my accessory belt...unless it is forcing air into my intake. But seriously, I was under the understanding that a smog pump just pumps air into exhaust for emission reasons.

moosetang408w · May 2, 2010

these are the cats I put on

MagnaFlow 94009 - MagnaFlow Universal Catalytic Converters - Overview - SummitRacing.com

BigmacK192 · May 2, 2010

If the smog pump is gone, you're going to shorten the life of your cats considerably. They're designed to be run at a certain temperature to filter properly. If you don't have a smog pump installed, the exhaust you're throwing from the engine isn't going to be at the temperature that your cats will need. Thermacore secondary air systems help get exhaust temps up when the engine is cold and get them down when the engine is hot. The catalysts in the cats are designed to operate at a standard temperature, depending on the compound.

So as noted before, unless you get the special ones with the specific compound rated to work at different temperatures, you'll want to leave them off or throw the smog pump back on. I hear what you say about being a little more environmentally friendly, but when it comes down to it, if you run them without the pump in that stout of a set up, they'll clog, you'll lose performance, and sooner or later, you'll be spending more money/time to swap them out and pop some new ones in.

I run without them. And I recycle.

Shaolin Crane · May 2, 2010

fastfox90 said:
Im all for saving the environment, the new hi flow cats are supposed to be great. But the way I see it all the semi trucks, not to mention all the souped up diesel pickups running around belching black smoke everywhere are far worse than our Mustangs that are only driven in good weather. But thats just my take on it, Im sure others would dissagree. Plus I like the sound of mine without the cats!

Uhm just cause its black doesnt mean its more pollutive, its known gas fumes have more hydrocarbons than diesel does, just a word of thought

stang&2Birds · May 2, 2010

If you're making less than 500RHWP, leave them on. With a good high-quailty high-flow cat, you'll see very little (if any at all) power loss. In fact, for the DOHC 4.6 crowd, they see a LOSS without cats.

My guess is that the same will be true with the new 5.0's.

There have been tons of tests with and without cats. You have to be careful though of which cats/h-pipes people/companies used. Yea, a 20 year old 200K cat is going to result in power loss. Especially since Ford recalled many of their cats from the 80's! I know, my '86 Stang(5.0) and '86 T-bird(3.8) both had recalls for their cats.

Also, IMHO, with a 3" exhaust, you'll want to run cats! You'll get very little scavenging from your 3" exhaust. So, the cats will raise the temps of the exhaust gases, and that helps with scavenging. Scavenging reduces the "stale" (oxygen depleted) air in the cylinders, and promotes filling the cylinders with new fresher air/mixture.

Good Luck!

moosetang408w · May 2, 2010

Well I am not putting a smog pump in so since these are already welded on I will run them for the season hopefully then get rid of them once I get my nitrous on in the fall. At least I can say I concidered it. I better start recycling a bit more

stang&2Birds · May 2, 2010

moosetang408w said:
I am not running leaded gas but I will be running richer than stoichiometric in my fuel maps under full load at higher rpms

This is the power plant that is feeding this system

So, are you running a TBI?
If you are, just wondering, is it a Holley or Ford?

moosetang408w · May 2, 2010

It is going to be on the edge. I am hoping for 500 flywheel horse power but it will be alot higher once I get my nitrous installed. It is going to be interesting. I guess will just have to keep an eye on them. As for my setup it isn't TBI it is multi port. When I built I wanted to give it an old school look so I hid as much as I could. here is a pic of the engine from a while ago with no air cleaner on.

Mustang5L5 · May 2, 2010

moosetang408w said:
But seriously, I was under the understanding that a smog pump just pumps air into exhaust for emission reasons.

Yes and no. Cats require o2 to function properly. On the mustang this is supplied via the smog pump.

Without it, the cats are not efficient and can clog. I have an catted hpipe which was run without the smog pump causing them to clog as verified by a vacuum test....so it's not an old wives tale

stang&2Birds · May 2, 2010

moosetang408w said:
It is going to be on the edge. I am hoping for 500 flywheel horse power but it will be alot higher once I get my nitrous installed. It is going to be interesting. I guess will just have to keep an eye on them. As for my setup it isn't TBI it is multi port. When I built I wanted to give it an old school look so I hid as much as I could. here is a pic of the engine from a while ago with no air cleaner on.

Nice! I like it!
As long as you realize that you'll lose some low-end, and high-end without going to a tuned port input. IMHO, I think that you'll still have plenty HP, and on the quarter mile track, hooking fully/properly up will be more of a limiting factor until you get that all dialed in.

Also, that means that you're running either a Mass-Air setup with the MAF disabled, or an SD setup. People have had success with both at that HP.

Good Luck!

stang&2Birds · May 2, 2010

Mustang5L5 said:
Yes and no. Cats require o2 to function properly. On the mustang this is supplied via the smog pump.

Without it, the cats are not efficient and can clog. I have an catted hpipe which was run without the smog pump causing them to clog as verified by a vacuum test....so it's not an old wives tale

If he has a 3-way cat (as he should for a 5.0 to pass smog), I agree.
However, many 2-way cats don't need the extra oxygen.

I agree that for 3-way cats, you really really want a working smog pump setup for a 5.0!

If passing smog isn't an issue, then I'd suggest using high performance, hi-flow 2 way cats, and ditch all of the smog pump setup (that seem to last only ~30K-50K miles on occasional use Stangs).

Just an FYI on some tech stuff: Also, without pre-cats (the smaller cats up front), the car will pollute more on start-up until it's fully warmed up. However, I don't see the OP's car as a full year short trip "grocery getter".

My Stang isn't either. For short trips to the grocery store, I'll take my Olds. I don't want some **** leaving a carriage loose, and then have it bang into my car. Come on, how *** hard it it to put carriages in their little corral in the summer when there's no snow to have to push the carriage through?

The pre-cats are important for smog since for big cities, startup emissions account for ~20%-40% of the pollution from cars. That's way many States now do "cat counts" for smog checks. And, why someone at CARB was either on crack or paid off when they approved some two-cat systems for Stangs (the CARB numbers have since been removed).

BTW: It was Calf that was very instrumental in determining, verifying, and limiting start-up pollution from cars. So, it's not like CARB (Calf Air Res Board) didn't know about the issues of start-up pollution.

For me, I'll keep my 3-ways and smog pump. I now replace the smog pump at the first sign of any noise.

Good Luck to the OP!

moosetang408w · May 3, 2010

I don't know what you mean by three way cat. The engine is a stroked 351w and I have a stand alone ECU for accurate closed loop control. So if I warm the engine up properly with low loads to keep the combustion around stoichiometric until it warms up the cats should survive. Also to answer a past question that you had the load is based off of a MAP sensor.

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