E46 330i Decat

[Bavs108]

Bavs, tbh the process you used is not exactly my cuppa tea esp when considering the m54 and the way it sounds out the factory, my ex 330i went to a work colleague and I see it everyday... I promise you hearing that car starting up in a underground parking lot will make many hairs stand on edge,

I chose to use the 328 catless manifolds as swop outs over the stock manifolds and replace the centre cat with a resonator. The car had a deep idle, punchy tone mid rpm and at the top you could hear the engine wail..

Diff strokes I guess...

Thanks Kish. Definitely going to explore those avenues as well. As I said this was just to see how the car performs and sounds and adjust accordingly. Will be monitoring it over the next few weeks and see how she runs then take it from there:rollsmile:

Hi,

I have seen quite a few posts about de-catting, is there anyone who de-catted a 2002 E46? Will the 2002 need cat foolers? Does removing the cats worsen fuel consumption? Will the car need to be chip tuned after removing the cats? How much performance do cats rob the car of? I have heard that up to 10kw is lost due to catalytic convertors, is this true?

Thank you in advance.

I have not seen an e46 that needs cat foolers yet dont think we got post cat sensors in SA

fuel consumption and power get better with Decat

Strangely enough I went to a couple of exhaust places some time back and they all said that I need to replace my cats with cat foolers:fishwack: Either they don't know what they're talking about or they try to make some extra money off unsuspecting customers:flyfun:

 

[Philip Foglar]

Great info here!! :thumbs:

 

[LPM320]

The main issue I had with the 328i manifolds is the fact that they were designed to work on a 2.8 142kw motor. And I suppose that with the extra stroke of the 330i motor, the volume of air being pushed out would be slightly different to that of the 328i, hence pipe size might hamper efficiency, although the performance will improve naturally due the restrictive cats being removed. I think the best option here will be a set of quality aftermarket headers. Theoretically, replacing with pipe would also be good option, but you also worry about the actual angle,size and flow dynamics of the pipes being fitted on in relation to the original pipes, etc. Then there is the issue of actually getting the work done at a reasonable price, then aftermarket headers just seems like a better option.I know Moranor has Viper headers at an excellent price. Hollowing out of the cats is the easiest and cheapest, but not the most efficient option.

My current 330i has a full decat with hollowed out cats (done by previous owner) and an aftermarket back box, and it sounds like the car has a full aftermarket exhaust, complete with crackling and popping on the overrun. It sounds amazing. I think the aftermarket back box cuts out the rasp caused by hollowing out the cats completely.

I have been told that the standard e46 6cyl xpipe is in the centre muffler, but I have not confirmed this. So atleast by keeping the stock system you benefit from the factory x pipe. In addition to this the stock pipes are 50mm, so they are not exactly undersized to begin with.

 

[speeddemon]

The main issue I had with the 328i manifolds is the fact that they were designed to work on a 2.8 142kw motor. And I suppose that with the extra stroke of the 330i motor, the volume of air being pushed out would be slightly different to that of the 328i, hence pipe size might hamper efficiency, although the performance will improve naturally due the restrictive cats being removed. I think the best option here will be a set of quality aftermarket headers. Theoretically, replacing with pipe would also be good option, but you also worry about the actual angle,size and flow dynamics of the pipes being fitted on in relation to the original pipes, etc. Then there is the issue of actually getting the work done at a reasonable price, then aftermarket headers just seems like a better option.I know Moranor has Viper headers at an excellent price. Hollowing out of the cats is the easiest and cheapest, but not the most efficient option.

My current 330i has a full decat with hollowed out cats (done by previous owner) and an aftermarket back box, and it sounds like the car has a full aftermarket exhaust, complete with crackling and popping on the overrun. It sounds amazing. I think the aftermarket back box cuts out the rasp caused by hollowing out the cats completely.

I have been told that the standard e46 6cyl xpipe is in the centre muffler, but I have not confirmed this. So atleast by keeping the stock system you benefit from the factory x pipe. In addition to this the stock pipes are 50mm, so they are not exactly undersized to begin with.

This is what i tried saying earlier and the performance is def noticable...no other 330 in Cape town has even sat close to me with this mod.....that's a fact that was proven...

 

[Bavs108]

This has turned into a very informative thread:thumbs: thanks to everyone for your inputs:thumbs:

With regards to consumption. I just filled up today and got about 700km off a tank with some conservative driving in the week and some spirited driving over the weekend. So it's a bit better than before under the same conditions. I would say about 50-100km more on a tank. I think with conservative driving I should be able to get about 800km on a tank. In the week my obc was showing a tank range of 900km which I only ever got on long distance trips.

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This was in the week.

And this was when I filled up today after a weekend of spirited driving:rollsmile:

 

[Philip Foglar]

Very good fuel consumption there!! :thumbs:

 

[Gizmo]

Now chip it and get even better fuel economy.

 

[Bavs108]

Now chip it and get even better fuel economy.

One step at a time:rollsmile: I'm taking baby steps:rollsmile:

 

[LPM320]

Bavs, if you hollowed your middle (lower) cats, you might want to reconsider just replacing with either resonators or piece of straight pipe. Normally guys just hollow out the manifold cats because of the amount of work needed with the other manifold options. But the middle cats are easier to work with. You must be getting quite some raspiness with that set up?

 

[Gizmo]

Now chip it and get even better fuel economy.

One step at a time:rollsmile: I'm taking baby steps:rollsmile:

The sooner you do it the sooner you start saving...The wife will approve.

 

[Bavs108]

Bavs, if you hollowed your middle (lower) cats, you might want to reconsider just replacing with either resonators or piece of straight pipe. Normally guys just hollow out the manifold cats because of the amount of work needed with the other manifold options. But the middle cats are easier to work with. You must be getting quite some raspiness with that set up?

It actually sounds quite nice outside the car, it's just in the cabin with the windows down that it sounds a bit weird almost like a toy car. I actually spoke to a guy at powerflow last week. He said putting straight pipes in will not make any difference to the way the car sounds. I think a resonator is the only way to reduce the raspiness.

 

[GPGrobler]

This might sound crazy, but is it possible to weld a straight pipe inside the hollowed-out cat to improve the flow dynamics of the exhaust?

 

[moranor@axis]

This might sound crazy, but is it possible to weld a straight pipe inside the hollowed-out cat to improve the flow dynamics of the exhaust?

the issue on the branch is having to take it out for cutting... then re installing for tacking... then taking it out again for full welding... then final install... this is ball ache and why its easier just to hollow out...

If it were my shop I would install an after market branch or cut away sections of the cat case to allow the pipe to go in and get tacked (using the case remains as a 'brace') before the full case is cut away for final weld... this would solve the problem of alignment without having the install the branch multiple times...

 

[JENICH]

On my E90 320d,

I had a full decat, with down pipe. Removed 1 box and it sounds awesome

Done by Xcede in Randburg
Best move ever

 

[LPM320]

Bavs, if you hollowed your middle (lower) cats, you might want to reconsider just replacing with either resonators or piece of straight pipe. Normally guys just hollow out the manifold cats because of the amount of work needed with the other manifold options. But the middle cats are easier to work with. You must be getting quite some raspiness with that set up?

It actually sounds quite nice outside the car, it's just in the cabin with the windows down that it sounds a bit weird almost like a toy car. I actually spoke to a guy at powerflow last week. He said putting straight pipes in will not make any difference to the way the car sounds. I think a resonator is the only way to reduce the raspiness.

The sound is one part of it, but the main disadvantage of hollowed out middle cats vs straight pipe/resonator is a reduction in gas velocity as the gases tumble over themselves due to the large vacant cavity left behind in cat casings instead of being forced out under a pressurised controlled manner that you would get with straight pipes or resonators.

 

[GPGrobler]

@ Moranor, do you have branches (headers) that are a straight bolt-on replacement for the manifolds and cats on the 320i E46? After this morning I want to rip the things out and drive over them!

 

[moranor@axis]

@ Moranor, do you have branches (headers) that are a straight bolt-on replacement for the manifolds and cats on the 320i E46? After this morning I want to rip the things out and drive over them!

Viper branch bolts onto head and comes with flanges... they are longer though so you need to cut the stock system a little and weld the new flanges on...

other option is to fit the Viper branch with two new pipes till after the secondary cats...

I also have a custom resonator box to replace the cats with a built in X pipe

 

[GPGrobler]

@ Moranor, do you have branches (headers) that are a straight bolt-on replacement for the manifolds and cats on the 320i E46? After this morning I want to rip the things out and drive over them!

Viper branch bolts onto head and comes with flanges... they are longer though so you need to cut the stock system a little and weld the new flanges on...

other option is to fit the Viper branch with two new pipes till after the secondary cats...

I also have a custom resonator box to replace the cats with a built in X pipe

So someone who is handy with a TIG welder and an angle grinder will be able to fit the Viper branch? Will he then only have to cut out the secondary cats and fit straight pipes?

 

[moranor@axis]

@ Moranor, do you have branches (headers) that are a straight bolt-on replacement for the manifolds and cats on the 320i E46? After this morning I want to rip the things out and drive over them!

Viper branch bolts onto head and comes with flanges... they are longer though so you need to cut the stock system a little and weld the new flanges on...

other option is to fit the Viper branch with two new pipes till after the secondary cats...

I also have a custom resonator box to replace the cats with a built in X pipe

So someone who is handy with a TIG welder and an angle grinder will be able to fit the Viper branch? Will he then only have to cut out the secondary cats and fit straight pipes?

correct

If you such a person I can also provide you with Mandrel bends and pipe to increase the front section Demeter :rollsmile:

 

[GPGrobler]

The strange thing is that a supposedly reputable company like Van Der Linde did the exactly same thing on the mainfold cats like Bavs car on Sankukuers 330.

it is the easy way to make sure pipes are not miss aligned this is the only possible reason why they would do it this way...
ask any engineer if this void would be good for flow and he will tell you no...

reason why the diameter is so big around the cat is to compensate for the volume taken up by the cat with it removed it is too big...

Something else I thought about, those "oil drums" in the engine bay, hollowed out or not, must be generating (and storing) some extreme unneeded heat under the hood of the car?

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@ Moranor, do you have branches (headers) that are a straight bolt-on replacement for the manifolds and cats on the 320i E46? After this morning I want to rip the things out and drive over them!

Viper branch bolts onto head and comes with flanges... they are longer though so you need to cut the stock system a little and weld the new flanges on...

other option is to fit the Viper branch with two new pipes till after the secondary cats...

I also have a custom resonator box to replace the cats with a built in X pipe

So someone who is handy with a TIG welder and an angle grinder will be able to fit the Viper branch? Will he then only have to cut out the secondary cats and fit straight pipes?

correct

If you such a person I can also provide you with Mandrel bends and pipe to increase the front section Demeter :rollsmile:

Nope, I am talking about an oldish man here in town, who I am always taking my cars to, who really knows his way around exhausts, he will most probably know how to install the pipes.