CAT-less disco ?

[johnjcoyle]

Hello chaps,

Just a quick thought, ,,,,

That was quick, no seriously,

I live in the wonderfull province of Quebec in Canada

Over here you only do a vehicle check up when you sell the car to someone else. I aint sellin my Disco.

I was wondering if it was possible to completly remove my cat converters and replace them with just straight pipe ?

I would like to know if anyone has done this ? where the or what the hell to do with the o2 sensors.

Seems like a goer for me;

Any input as per normal is gratefully recieved;

[roverX]

The problem is that you will change the back pressure on the engine would could cause damage over time.

[me.guevara]

Many of us have what's called the "Australian package" Disco, which comes without the cats and carbon canister (among other differences). Without the cats, you only need two O2 sensors.

Don't ask me what happens with the "spare" wire harness from the other two - for all I know all the Discos have the wires for 4 sensors, but only use 2 when the cats aren't there.

From what I've read, there's a resistor that changes in the ECU when you add or remove the cats (I imagine it's to deal with the backpressure issue that X mentions).

I believe that there are a couple of LRO members who just removed their cats and haven't had any problems - I'm sure that they'll pipe up about it (there was recently a string about this that you could probably find with the search engine).

Good luck!

[johnjcoyle]

thanks for the responses,

If anyone can point me in the right direction for the last thread on this topic, or to someone who has removed his cats I would be real gratefull.

Cheers

[roverX]

Considering you might have to mess with the ECU...it might be cheaper to run a high flow cat with a cherry bomb (glass pack) which is essentially a straight thru system.

I think it might be Steve at DAP that knows about the high flow cats... I can't remember exactly who...

[johnjcoyle]

Thanks X,

I'll contact steve for the info.

[roverX]

Originally Posted by johnjcoyle

Thanks X,

I'll contact steve for the info.

OK but I "THINK" it's Steve! If it's not him, he might know which one to get and where to get it from.

[Muddy Oval]

My ears were burnin...

I'd run cats- hell, do it so you at least pretend to care about the environment.

Changing the backpressure a little won't hurt it at all, only if you were running a huge diameter straight pipe w/o muffler or cats etc. There are some good high flow cats from Flowmaster and several other brands- I've even used cheapo Catco ones from Summit Racing with success. There are modern cats that are much less restrictive than the older ones, but I think a lot of people think they are more restrictive than they really are...

[DiscoTex]

Originally Posted by Muddy Oval

My ears were burnin...

I'd run cats- hell, do it so you at least pretend to care about the environment.

Changing the backpressure a little won't hurt it at all, only if you were running a huge diameter straight pipe w/o muffler or cats etc. There are some good high flow cats from Flowmaster and several other brands- I've even used cheapo Catco ones from Summit Racing with success. There are modern cats that are much less restrictive than the older ones, but I think a lot of people think they are more restrictive than they really are...

+1

What little tech that I can add to the board:

Car Craft ran a test a couple of years ago on exhaust systems. Basically: cat v. non-cat and cat +/- mufflers v. no cats and muffles or no mufflers.

Bottom line: You loose power running straight pipes (no cats, no mufflers, and peak power IIRC), and whatever power was gain/lost with and w/o the cats was negligible. I'm talking about 1-5 hp difference, and not even peak hp. What DID make a big difference was the mufflers, and the use of h or x-pipes. Running WITH mufflers gave more power as opposed to running straight pipes (something about the back pressure).

So I'd go with Steve's route: Just get some catco's, and swap them in. Hell, I think they're currently around 50 bucks at Summit.

Just to play devil's advocate: The 94-95 trucks: those only come with 2 O2 sensors, right? So would it affect the computer at all if you removed the cats?

[me.guevara]

Originally Posted by DiscoTex

Just to play devil's advocate: The 94-95 trucks: those only come with 2 O2 sensors, right? So would it affect the computer at all if you removed the cats?

You devil, you!

I don't know much about my own truck (I do know that it has no cats and only 2 O2 sensors), but even less about other folk's trucks and absolutely nothing about other model years...

I imagine that the answer to your question would depend on if the two O2 sensors are located before or after the cats, eh?

Cheers,

[johnjcoyle]

It seem like I opened a can of worms in this subject.

I have recieved some great info from you all and I think I will end up buying some new cats, (the cheapo ones) and some new o2 sensors.

I just need to get this dreadfull gas situation sorted out and I think the o2 sensors could be part of the problem;

Think I'll start a new thread on gas economy, or how to get it; I am currently running at approx 20 ltrs to 100 kms......

Thanks to all for your responses.

[Craig]

Getting rid of the fumes as fast as poss and back pressure,,,, well, the cats will give you back pressure and lack of power because the engine carnt breath correctly. This is a four stroke not 2 stroke!!!!!!!!!!!!!!!!!!!!! As for 02 sensors, I replaced my cats with straight pipe and a BMW system, got heaps more take off power and from the performance garage that checked it I gained 16hp instantly..... Rest my case...........

[roverX]

Originally Posted by Craig

Getting rid of the fumes as fast as poss and back pressure,,,, well, the cats will give you back pressure and lack of power because the engine carnt breath correctly. This is a four stroke not 2 stroke!!!!!!!!!!!!!!!!!!!!! As for 02 sensors, I replaced my cats with straight pipe and a BMW system, got heaps more take off power and from the performance garage that checked it I gained 16hp instantly..... Rest my case...........

Details my man..details!!!!

[Craig]

Hey RoverX, I had a 325i "M Sport" type system fitted (NEW) from the front joining section of the headers. BMW's are designed straight through type and only have small lugs inside to kill the high end noise. The sound this thig gives out is fantastic and actually not too loud when town running, but hit the gas and WOW, what a neat sound it makes When first fitted it was infact a tad too loud so a cherry bomb unit was fitted at the rear and the tip was reformed to shoot out to the side by a couple of degrees, all good now

[Adam in NYC USA]

Originally Posted by me.guevara

Many of us have what's called the "Australian package" Disco, which comes without the cats and carbon canister (among other differences). Without the cats, you only need two O2 sensors.

Don't ask me what happens with the "spare" wire harness from the other two - for all I know all the Discos have the wires for 4 sensors, but only use 2 when the cats aren't there.

There are kits available that mimic working o2 sensors. They also have them on some after-market racing exhausts.

You would have to buy the dual sensor box and then the stock ECU would be fooled in seeing four o2 sensors when in fact there are two working.

You would probably fool an inspection station until you put the car on the exhaust machine.

Adam in NYC