Another Exhaust Question

[DerekS]

"EXHAUST PIPE AND BIG IMPROVMENT" I read this post and I found the rerouting of the exhaust most informative, but I have a Q for test purposes only on a strictly offroad vehicle regaurding the O2 sensors on my 6/92 fj80. Is there a way around the removal of the O2 sensors without screwing up the computer system. Exhaust should be replaced from the exhaust manifold all the way back. Seriously thinking about removing 2 cats for a highflow single as to tuck up under the rig more. Looking for improved performance and ground clearance. I live in Southern NH and am out in the hills w/ rocks;mud; and just all around fun. Any input would be greatly appreciated.


Derek

 

[motorsargeT]

You can't get rid of the O2 sensors. They are what the computer uses in closed loop operation to adjust the amount of fuel the motor needs. Just replace the exhaust and have a shop weld the bungs on the exhaust you build.

 

[alkaline747trio]

There are "dummy O2 sensors" out, but most I have found are for OBD2. Do as motorsarge said and get the shop to weld bungs onto your exhaust.

 

[jamisobe]

I have known folks who have scrapped the cat and used dummy sensors (I think they may have only used a dummy in the rear position) for more power.

 

[DerekS]

Thanks

Thank you for your input. I recieved some shocking news at a local exhaust place and they said that they could install everything for $700.00. I think I have decided that I will purchase the pipe from summit racing and mock it up and then have a local place bend it for $3.00 and bend, and save myself so serious cash. The guy That looked at it said he wouldn't put anything on larger than 2". I personally want 2.5". So thanks again for the info on the O2 sensor.

 

[alkaline747trio]

Go 2.5 from the cats back. It is what I have and I have plenty of power (had, before my cats started to go out).

 

[Bearcat80]

Yes, you could blame a lack of 3FE power on plugged cats.....LOL

 

[Bambusiero]

DerekS,

Check out this posting for cat options (nice and small, easy to tuck up tight).
https://forum.ih8mud.com/showthread.php?t=122613

 

[Walking Eagle]

i used the manaflow cat
https://forum.ih8mud.com/showthread.php?t=121618

 

[jamisobe]

Thank you for your input. I recieved some shocking news at a local exhaust place and they said that they could install everything for $700.00. I think I have decided that I will purchase the pipe from summit racing and mock it up and then have a local place bend it for $3.00 and bend, and save myself so serious cash. The guy That looked at it said he wouldn't put anything on larger than 2". I personally want 2.5". So thanks again for the info on the O2 sensor.

2.25 might be a good diameter for that application if you keep the cats and don't make any other mods.

 

[Walking Eagle]

2.25 might be a good diameter for that application if you keep the cats and don't make any other mods.

Don't know about the fj, but the FZJ is 2.5 to the cats, 2.25 after. I've also read where contrary to popular myth, once you're past the manifold / header, you can't go too big.

 

[DerekS]

Thanks Guys

Thank you for the input. I am changing out the double cat for a single and tuck it up for clearance, anyone know if a Y pipe going into the cat will work with the two O2 sensors, or any other option that they have heard of. Thanks again.

Derek

 

[jamisobe]

Try this exhaust thread out...

 

[Bambusiero]

Yeah, Heath, I saw your post with the spun Magnaflow cat. Yours is the 1st one I've seen in use. Gives me lots of ideas!

 

[OGBeno]

2.25 might be a good diameter for that application if you keep the cats and don't make any other mods.

Why?

 

[jamisobe]

2.5" is a big jump from 2" without other mods. IMO the stock 3fe with stock manifolds and a cat wouldn't provide enough exhaust velocity or heat for 2.5" pipe (I could be wrong-there is no magic fomrula). If the exhaust cools too much before it exits the tail pipe exhaust scavenging will be reduced or eliminated. You could actually end up with less power than stock.

On the other hand, eliminating cats, mufflers, employing headers, and reducing bends would work better with larger pipe. Scavenging and power would likely benefit from larger pipe if the flow was increased.