I recently traded for a '96 D1, but didn't crawl under (I know, I know!) and now see that from the manifolds back is completely bubba'd. No cats, homemade Y-pipe, etc. There are O2 sensors. It seems to run okay, and sounds alright. Do I need to be aware of any potential problems? No emission inspections where I live. I crawled under to look, only because the po has the exhaust exiting under the driver's side rear passenger's door, and I want to take it back to the rear.

 

curious, how does it sound?

 

Pretty good, actually! I just don't like the exhaust exiting near the windows. I'm sure it will not be pleasant at a stop with the back window open.

 

with the set up that you have and with out the worry of emissions, I would pipe it where ever I wanted. that would be behind driver's rear tire, for me.

 

Ya Dusty1, that's my thought... I was just curious with the computers and stuff on vehicles now if not having the cats would create any problems with the running. It seems to run fine as is, but don't want to find any hidden problems.

 

I assume people delete cats after they are out, so as not to pay for new ones. I have not heard of any gain in performance or mileage. I think the the computer gets fooled with spacing or something like that, not sure.
found=https://landroverforums.com/forum/of...ll-work-28993/

 

Could be true. I have heard many people, though, claim better performance after removing the cats, which are more restrictive than a system without them. How much gain? I can't say I've ever seen dyno results. It does make since though. Unrestricted flow in and out results in hp gain, which is why there are aftermarket intake and exhaust systems. I don't know, though, how much gain you would get by only adding a high flow airfilter and removing the cats.

 

Coming from someone who's done a lot of exhaust work, here's experience speaking:

High flow catalytic converters or no catalytic converters will help very marginally. A straight through muffler design like a Borla or Glasspack (NOT THE LOUVERED KIND) will help marginally. With that said, it is barely noticeable, and the gains are in the top end. You will actually lose some bottom end. Well, atleast until you add a K&N or Green Pod filter and a custom smoother intake. I used a couple of 3.25" turbocharger couplings and a 9" length of 3.25" aluminum pipe for mine. That's where the bolt on change is noticed. I have not tried the intake without the exhaust changes, but I doubt it would help as much. I am currently having a port and polish done and that should show even more increases.

So, in short, exhaust alone helps virtually none. You will also need intake work to have a noticeable difference.

PS: If you make a custom intake, you will have to make the MAF wires longer.

 

Alex,
is correct; you do sacrifice low end torque for high end hp gains.
most manufactures these days rely on the back pressure from the exhaust system to help in scavenging exhaust gas out of the system.

 

I hollowed out my cats on my 95 RRC 4.2

Left the O2's in. I can agree on the loss of low end torque and the higher rpm hp gains.

I'm also running other mods, but I can push higher RPM's thus giving me the power. But I've got a list of engine mods, so the lack of cats helps me.