I'm considering making my Disco offroad only...if I do this..there would be no need to have cats on the exhaust. Does anyone sell catless y pipe?

 

Just have your muffler shop cut them out and weld straight pipe back in. It will run like crap and you will get like 6 mpg, literaly 6 mpg. Not to mention the plug fouling.

 

hmmm..thats not good. I was able to delete them from my Mustangs with a little improvement in performance.

 

These trks are not like other cars. They need there backpressure. And you will know when your O2's go bad, because you will get like 6mpg.
There are little to no mods to get more power out of these engines. Just full synthetic motor oil, Iridium plugs and Magnacor wires. Even K&N air filters dont work.
If you want more ft. lbs. you will need to change the gearing. But I will tell you that these trks dont need mods to off road. They are just about perfect the way that they are.

 

In my opinion an engine as small as the one in the disco coupled with the low power output does not push enough gas around to need to remove the cats. The only thing that i can see hapening is as posted before, poor performance. When you lessen back pressure you also have to be aware that if the velocity of the gas is not kept fast enough that you will cause a carbon buildup on your valves. Plus with a cat-less Y it would get anoying....
Just my .02

 

The backpressure requirement on engines is a myth. The only negative to removing flow obstacles/ going with a 5' pipe is that the exhaust will loose velocity through the pipes, and become stagnant in the pipes resisting flow.

You can also get offroading only dummy sensors to put in place of the O2 sensors that supply the ECU with the desired reading so that your MPG stay the same. Check with your local offroading shop.

 

Yeah, it's not the removing of the cats these engines are run in all kinds of older vehicles without them, it's the ECU that's the problem. If you did a carb conversion you'd be fine, but that's a lot of work. You're probably better off doing something like a Megasqurt injector control module then you can dyno-tune the engine. Going with some proper headers and wide bore pipe into some good flow but still not open mufflers would probably give you the best results.

Then again, why not just bore it out to 4.8 and put on a performance head to get the extra 50hp.

 

I have a usedY pipe I got from someone on Craigslist for cheap and they cut out the cats. My plan is to use it as a doner Y-pipe tohave some hi-flow cats welded in place. But I was thinking of putting the cat-less pipe before I did thaton and driving it around on my friends land to test out how it runs like that? But I might be too lazy to want to put on a Y pipe just to drive around for a hour or two.

 

You are all forgetting one thing, the 02 sensors, without them you will have a for s--t running engine cause you will always be in open loop running way to rich.
Just leave the truck alone and go play.

 

I agree 100%. Gut your own cats, or even go with 200 cell cats,it is not hard at all. I have done it on three different vehicles.

As for the o2's. They can easily be relocated or use dummy sensors. Either option will trick the ECU and you will not through codes.

One of the hardest cars to work on was my Audi S4, but gutting the cats and pre-cats resulted in 28 extra whp. This is dyno proven on my car. As far as back pressure my Audi is a 2.7 liter twin turbo 6 cylinder and it requires more back pressure than most cars on the market due to the turbos needing the exhaust pressure to spin.

Back pressure is not anissue with a normally aspirated motor. Gut the cuts, and relocate the bung holes for the o2's further down the pipe. You'll be fine. I highly doubt you'll notice any performance enhancements, but the exhaust tone will definitely be louder ;-)

The dyno plot is after my car had stage III completed, I will find the one for just Stage II + (downpipe, gutted cats, staright through exhaust from turbos back,ASP ECU set at 19psi rev limiter removed, and RS4 intercoolers)