Ok so I apologize if this is a long post. I just need a really solid answer before I do this. I've been wanting to do this for a long time, but never really had a defining answer, and I didn't want to do it in case I failed emissions.

Anyways I have a 2001 F150 and have 4 cats. I obviously cannot get hi flow cats. My truck has about 127k miles on it, and I'm pretty sure the 4 cats I have on it now are getting plugged up. They've been on since the truck was built.

I have an exhaust guy who said he could do this job. I was wondering if I could hollow out the 2 pre cats, but leave them there visually. So the 2 pre cats closest to the headers. As for the rear 2 cats I'd have them replaced with Magnaflow CA approved cats for my truck. Now I'm curious does anyone have experience doing this, and will they pass CA emissions with just the 2 rear cats? Will I gain a tiny bit of power and sound getting rid of the 2 pre cats, and getting new 2 rear cats?


Thanks everyone. Sorry for the long post. I just need as much info as possible about doing this before I pull the trigger. Cause we all know how strict CA is about emissions.

 

With the C.A.R.B cats you will be fine, but hollowing out the front cats I am not too sure of. If he will do it then it is certainly worth a try.

 

Are the front cats the cats that everyone hollows out the most? And do you think I'd still be able to pass CA emissions with just 2 C.A.R.B cats instead of the 4 I have now?

 

Yes the fronts usually are on your generation truck. As for the emissions, the sniffer test yes it should, however if they know it visually came OEM with 4 they could fail you if you only have the two C.A.R.B. cats inplace.

 

Well the 2 front cats I'd just hollow out and leave in place, plus I don't worry about visual since my smog guy is a family friend.

If I can pass the sniffer test with only the rear 2 C.A.R.B cats then that's awesome.

Darren, I was looking on Magnaflow's website and saw tons of options for CA cats. Could you help me out and point me to the right ones? I checked my EIN on the inside of my hood and found it to be 1FMXT05.4RF8

I found this cat on Magnaflow's website. It's for the 5.4 4x4 Driver or passenger side rear. http://www.magnaflow.com/02catalytic...iversal=447206
It also matches the EIN.

I'm assuming that's the cat I need to replace my 2 rear cats on my truck?

Thanks for all the help

 

Yes that appears to be the proper cat for your rear converter replacement following C.A.R.B regulations. I would check your stock cats though and make sure it isn't the version that has them mounted in the middle. I believe it was LEV models that had the sensor inside the cat, and non LEV ones had the O2 after the rear cat.

 

What do you mean mounted in the middle? Also if I remember right I'll have to check again, but the o2 sensor was mounted before the rear cat.

Also with the hollowing of my pre cats will that affect my computer in any way? Throw any C.E.Ls?

 

And just to confirm hollow out the 2 front/pre cats and replace the rears with C.A.R.B cats

OR

replace the 2 front/pre cats with C.A.R.B cats and hollow out the rear 2?

which will setup will pass California SMOG, and not throw up any codes?

 

Hmm, I have not yet seen any '97 - '03 with the rear O2s in the middle of both cats. If this truely is how your cat setup is, then your front cats contain the filtering catalyst. So clearing them out and replacing them empty will aid in a CEL. The way to get around it is the O2s need to be mounted AFTER the new cats so get a fully filtered reading. But, I am almost sure your front cats are only sound resonating cats and your rears are the main filtration. Patman gutted his '03s pre-cats years ago and it gained him the sound, without an engine light. I am quite sure if you gut the fronts, get the Cali converters installed inplace of rears, and your O2 sensors are after the new cats, there will not be a CEL, and it should pass the sniffer.


Option 1. Explanation is in my comment above this quote.

 

Darren, thanks for all the help. I just crawled under and checked and I have 2 o2 sensors before the pre cats and 2 more o2 sensors behind the rear cats. So after reading what you said I'm assuming the 2 o2 sensors in front of the pre cats are reading whats coming out of the engine so nothing to do with the pre cats.

So its set I will be gutting the pre cats, and replacing the 2 rears.

thanks for the help it has been much appreciated.

 

Those sensors in front of the pre-cats are your air/fuel O2 sensors which do not need touched. The second set behind the rear cats are what give you the filtered cat reading and those will be the ones that need mounted after the new cats, just as they are now for your current rear cats. Should be a direct change out for you

 

I have some news that may make all of us CA people happy.

As far as my reading has gone, starting January 1, 2013, smog tests will be done using ONLY OBDII readings. They are not going to do visual or sniffer tests anymore because sniffer tests pollute the air (irony?). Therefore, if a shop will install high flows and remove pre cats, and one ran either custom tunes or O2 sensor mod, no codes would show up, allowing us to pass the test!

As soon as I can confirm this I'm throwing on high flows with the custom tunes.

 

If the cell is turned off system is not ready and you fail. However some tuners have a way to make the vehicle pass by the way it runs at startup or something like that.

 

The Cel doesnt need to be turned off if one runs an O2 sensor mod. Heres a link with some info: http://www.smogtips.com/new-smog-law-AB-2289.cfm
It looks like they still may do visual inspection, but a lot of smog guys will let that go if theyre good friends. It also is MY2000 trucks, which screws me unless I can say I hae a MY2000 when my truck was built in 6/1999.

 

Thats pretty interesting...I live in a Smog Check II area, so they run the smog check on a dyno under load...

I believe I have one cat going...over $ 2k to replace, so I am waiting to fix it...

Regards!