Is there a way to safely bypass cats?

[panic]

Is there a way to bypass E92 M3 cats without mod the electronis? or a safe way to mod its electronics without starting an electrical nightmare?

BTW, how many and where are cats located in the new M3?

Thanks/Giu

[E30M3SE]

Manifolds



CATS & Centre silencer



Rear Box

[panic]

Thanks, very usefull...

[dadofbud]

panic said:

Is there a way to bypass E92 M3 cats without mod the electronis? or a safe way to mod its electronics without starting an electrical nightmare?

BTW, how many and where are cats located in the new M3?

Thanks/Giu

No and No, if you want to get some extra peformance ? get less restrictive cats, if you remove the cat where are the O2 sensors going go, just a whole can of problems.

Look at Milltek site they will have replacement Hi-Flow cats, 100cel ?

Bob

[E30M3SE]

dadofbud said:

panic said:

Is there a way to bypass E92 M3 cats without mod the electronis? or a safe way to mod its electronics without starting an electrical nightmare?

BTW, how many and where are cats located in the new M3?

Thanks/Giu

No and No, if you want to get some extra peformance ? get less restrictive cats, if you remove the cat where are the O2 sensors going go, just a whole can of problems.

Look at Milltek site they will have replacement Hi-Flow cats, 100cel ?

Bob

You can get bungs welded into the decat pipe and fit the O2 sensors in those bung....... no can of problems.

[panic]

E30M3SE said:

dadofbud said:

panic said:

Is there a way to bypass E92 M3 cats without mod the electronis? or a safe way to mod its electronics without starting an electrical nightmare?

BTW, how many and where are cats located in the new M3?

Thanks/Giu

No and No, if you want to get some extra peformance ? get less restrictive cats, if you remove the cat where are the O2 sensors going go, just a whole can of problems.

Look at Milltek site they will have replacement Hi-Flow cats, 100cel ?

Bob

You can get bungs welded into the decat pipe and fit the O2 sensors in those bung....... no can of problems.

Sorry, i dont get what you mean...

[E30M3SE]

If your going to remove the cats then they will need to be replaced with a de-cat pipe. So on this de-cat pipe a hole is cut, or two in the case of your car, and a threaded recepticle is welded into that hole and the lambda/O2 prode is then fitted to the de-cat pipe, one at one end one at the other. result, no cat but lambda/O2 probes still taking the necessary readings of spend gases.

Although removing of cats on a car manufactured/registered after 01/01/1993 does technically make it illegal to use on public UK and European roads, but you know that, don't you?
So the 100 cell cat is the legal way to go.

[panic]

E30M3SE said:

If your going to remove the cats then they will need to be replaced with a de-cat pipe. So on this de-cat pipe a hole is cut, or two in the case of your car, and a threaded recepticle is welded into that hole and the lambda/O2 prode is then fitted to the de-cat pipe, one at one end one at the other. result, no cat but lambda/O2 probes still taking the necessary readings of spend gases.

Although removing of cats on a car manufactured/registered after 01/01/1993 does technically make it illegal to use on public UK and European roads, but you know that, don't you?
So the 100 cell cat is the legal way to go.

...arent the lambda sensors reading wrong or would send a wrong input to the ecu?
Who's selling for the new M3 these sport cats?

Sorry to bother you with all these wquestions.
Thanks/Giu

[houlbt]

I don't think it is this simple... don't really know the details but I am pretty certain the ecu reads lambda results before and after the cats and if you just cut them out it does indeed register as an error and the car goes all screwy.

This was a problem with decatting the E46 CSL - which I wanted to do but after numerous discussions it appeared it just wasn't worth the hassle of trying to get around the ECU and also ultimately cheaper to buy race cats. Plus power gains race cats vs no cats were not believed to be significant.

[E30M3SE]

houlbt said:

I don't think it is this simple... don't really know the details but I am pretty certain the ecu reads lambda results before and after the cats and if you just cut them out it does indeed register as an error and the car goes all screwy.

This was a problem with decatting the E46 CSL - which I wanted to do but after numerous discussions it appeared it just wasn't worth the hassle of trying to get around the ECU and also ultimately cheaper to buy race cats. Plus power gains race cats vs no cats were not believed to be significant.

Your probably right, my answer was a reply to the question of where to put the O2 sensors, as sensor before and after cat registering the same would probably register a cat fault as the reading would be the same.

[mrmr96]

Just for the record, it's NOT illegal to remove the cat. The rules basically say that any new car sold after (think it's 2001) must be fitted with a cat when it is sold as new, and that car's must pass an emissions test at any time.

So there's no law against removing the cat, nor against buying or selling a 2nd hand car which has been decatted. The only requirement for 2nd hand cars is that they can pass the emissions test.

A lot of cars will fail the emissions test, by not having a cat. But the point is that it's the failing of the test that's the problem, not the decat. As such if you can find a way for the car to be able to pass the emissions test without the cat, then you're fine. Some people have achieved this via fuel additives or a change to the ECU mapping prior to the MOT test. Other people have achieved this via a 'sympathetic' MOT tester.

Edited by mrmr96 on Friday 2nd May 10:50

[houlbt]

E30M3SE said:

houlbt said:

I don't think it is this simple... don't really know the details but I am pretty certain the ecu reads lambda results before and after the cats and if you just cut them out it does indeed register as an error and the car goes all screwy.

This was a problem with decatting the E46 CSL - which I wanted to do but after numerous discussions it appeared it just wasn't worth the hassle of trying to get around the ECU and also ultimately cheaper to buy race cats. Plus power gains race cats vs no cats were not believed to be significant.

Your probably right, my answer was a reply to the question of where to put the O2 sensors, as sensor before and after cat registering the same would probably register a cat fault as the reading would be the same.

y, fair point

[panic]

I believe it's a better solution to buy racing cats thus the next (and final) question: what's the best cats available for an M3 and who sells them?

[dadofbud]

E30M3SE said:

houlbt said:

Your probably right, my answer was a reply to the question of where to put the O2 sensors, as sensor before and after cat registering the same would probably register a cat fault as the reading would be the same.

Sorry, that was a rhetorical question,and it's clearly promlematic and not worth while.

OP Speak to Milltek for their Hi-Flow cats and get someone like Thorney to fit it for you as they will be able to address any subsequent fault codes for you there and then, and remember to keep the oem cats.

Edited by dadofbud on Saturday 3rd May 16:50