Does it make sense to remove the centre catalytic converter in our exhaust system?

[aoch88]

As the topic says, I notice there's a centre catalytic converter in the middle of our exhaust system. Does it make sense to remove it (de-cat) and replace it with a resonator so that it won't be so noisy? Any bros out here that has done it before or not recommended to do so?

 

[B33mEr]

As the topic says, I notice there's a centre catalytic converter in the middle of our exhaust system. Does it make sense to remove it (de-cat) and replace it with a resonator so that it won't be so noisy? Any bros out here that has done it before or not recommended to do so?

What model is your car? For E46 the catalytic converter is on the exhaust manifold while the two tubes you see in the middle of the exhaust system is a resonator (with a bit of catalytic). After that is the middle and rear muffler.

 

[astroboy]

I know of 2 E90s, both 6-potter refab exhaust from manifold onward, delete everything that's on the way.. :4: loud, but not to my liking. I suspect performance drop due to lack of back pressure.

U want to play with noisy exhaust, just get an after market rear box. The BMW Performance rear box is nice, about RM4k and they even have 1 for 4-potter, which comes with twin tail pipe. Nice! at about half the 6-potter price.. :wink:

 

[aoch88]

Thanks guys and I'm on a E60 LCI. Actually I dislike loud exhaust but would like to free some bhp trapped inside the catalytic converter. Since emission isn't really a big thing in boleh-land, I was wondering if it helps to remove those centre cats? True enough that we will lose back pressure and from my previous experience removing the cat on a Honda, it actually made the car worse I don't dare to simply do it on the E60 so would you guys recommend that I just get a quad exhaust like Remus?

 

[desbimmer]

Yes, if you are going to do something just spend the $ and get a proper system meant for the car. I remember removing mine in my last ride and it made a difference for a while but after a few weeks...it felt like a redundant exercise

 

[turbology]

There is no such thing as "you need a little back pressure".
All "backpressure" is evil, like Dark Vader.

http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm
Dark vader: www.starwars.com/characters/darth_vader/

In more technically correct terms: Removing CAT will affect your Engine's volumetric efficiency. Is more notice-able in Auto Transmission car.
It depend on the Mechanic's skill & knowledge (in bolehland is experience), a wrong exhuast mod will likely make your car feels... laggy.
Instead of using the term "backpressure", I would use to 2 very important V-words to explain how exhaust work : Volume & Velocity

For exhaust that is too big : great in volume but poor in velocity.
For exhaust that is too small : excellent velocity, but bad in volume

Just like intake system, for low rpm (which create torque), you want more volume.
For high rpm(for hp), you want more velocity.

Hope these help

 

[stig]

volume = (exhaust cross-sectional area) x velocity x time

If you want to increase volume for low end torque, you can also increase velocity :elefant:

Ok things are getting a bit more confusing...

 

[turbology]

stig : that is different kind of formula

Increasing the diameter of the piping will also increase the average path/cross-sectional area that the air can pass with a minute decrease in velocity. If the diameter (and hence cross-sectional area) of the pipe is increased too much, the velocity of the air flow will decrease more than the area increases, so flow would be adversely affected and power would be lost.

- copy from http://www.quickhonda.net/exhaust.htm

 

[aoch88]

Thanks to turbology and stig for the information. To be honest, this sounds very complex and I am utterly confused, haha. My instinct is telling me to just leave it alone (untouched) I think I might as well get a proper quad exhaust done instead of removing any of these cat-con. Btw just to share, the other day I went to Super Circuit in Sunway and as usual their prices are extremely over-priced (costs even more compared to JFA). They claim that changing rear muffler does not increase power and recommended me to change from extractor all the way to the end. I wasn't very convinced obviously but recently I bought a Hypertune magazine and there's a E92 335i which had it's exhaust done in Super Circuit. In the mod, no cat-con was removed and they basically changed only the piping and made it a quad exhaust setup. After a few rounds of dyno, the increase is only 5bhp, lol.

I think for the price we're paying to Super Circuit especially a car like 335i with only a 5bhp increase, it's just not worth it IMHO

 

[turbology]

5bhp dyno increase on wheel, that is actually pretty impressive.
Which another word, the stock exhaust system is very efficient too.

SuperCircuit is somehow accurate on the claim : change rear muffler don't usually increase horsepower.

 

[aoch88]

5bhp dyno increase on wheel, that is actually pretty impressive.
Which another word, the stock exhaust system is very efficient too.

SuperCircuit is somehow accurate on the claim : change rear muffler don't usually increase horsepower.

5bhp for a car originally with such high horsepower is considered impressive? I thought it should be more than that because even a simple air filter intake mod would get us a few bhp

 

[Iylia H]

have you tried going to everco in sunway? the corner lot shop at the end of the road near esso. Price is cheaper there. They have wider range of products. If you're going for quad pipe set up for e60... make sure that both look similar. as what I usually see in the e60, left side got back box, right sex don't have back box (as the right side is just an extension of the real muffler at the left hand side). It will not look neat.

 

[aoch88]

I've never tried Everco yet but I've heard of them before I thought of getting Remus brand or those original quad exhaust setup which is plug and play. Most of them don't have the box on the right side (even Eisenmann). They normally branch the right side out from the left side and not from the centre. I think it's because our exhaust is hot and having a box there just below the battery would affect it and bushes around the area?

 

[Iylia H]

I've never tried Everco yet but I've heard of them before I thought of getting Remus brand or those original quad exhaust setup which is plug and play. Most of them don't have the box on the right side (even Eisenmann). They normally branch the right side out from the left side and not from the centre. I think it's because our exhaust is hot and having a box there just below the battery would affect it and bushes around the area?

the box is there to filter out the sound.. the reason why there's no back box on the right, as there is actually no use to have it there, as before the exhaust branched, it has already been filtered by the left back box..you could ask the exhaust man to custom make a steel plate to resemble a back box for the right hand side.. so it won't look awkward if viewed from the back.

 

[9der]

Cintailah lapisan ozon kita hehehe..