E39 Cat removal

[aliluya 0]

Hey guys, i'm getting some headers installed later this week and was just curious as to whether there will be any perfomance increase if i removed the cat and installed a straight tru pipe?

Also would it make it much louder or just minimally louder.

Whats the law at in regards to cars with no cat.

And out of interest how much performance would there be if i removed the cat and the second muffler? Would this be much much louder. (Actually, is there a second muffler in the e39 530i?)

Do i need to worry about O2 sensors or any sensors for that matter while removing the cat + muffler.

The car is an E39 530i.

Current mods are just Remus exhaust and Blitz pod filter.

Headers are already on the way so looking forward to fitting and trialing those, from Wayne

(will give you a dyno result as soon as they arrive and we fit them on)

Slotted/Drilled brakes are sitting in teh garage waiting to be installed at the same time also.

Any help would be much much appreciated.

[BM WORLD 1265]

wont change the sound much , change the rear box if you want a better sound otherwise you could just end up with a drone sound.

also if you remove the cats , you might have to get the ecu reprogrammed as if there is no cat there the O2 sensors will make the engine run lean and might burn it out .

[kiwi535 538]

I have heard dont remove the o2 sensors....if you have one AFTER the cats that may make it more complex...Sorry i dont know more

[aliluya 0]

wont change the sound much , change the rear box if you want a better sound otherwise you could just end up with a drone sound.

also if you remove the cats , you might have to get the ecu reprogrammed as if there is no cat there the O2 sensors will make the engine run lean and might burn it out .

I have changed the very last muffler already to an Remus. Thing is i dont want it too noisy becuase i often have my two kids in the car.

Can you comfirm about the ECU thing? Or can some one confirm it.

How about if i just change the mid section muffler to a straight through pipe, will that be substantially louder ? Becuase if it going to be then i won't bother doing it. And will there be any HP gain?

[*Glenn* 854]

A E39 530I should have pre cat and after cat 02 censors (4 in total). You cannot remove that cats in that configuration. It will run too lean and damage the engine. You could however fit larger higher flow aftermarket cats. We have used american made cats fitted by Pit Stop and supplied by Chase Exhaust systems. Once fitted the live data readings from the 02 sensors must be checked. In saying that. Recently we had a problem with an E46 318I where we tried two different cats on the car and were still getting error codes and the rear 02 sensor was unstable with high readings. Reluctantly we had to fit an OEM cat to fix the problem. We are still waiting for the prognosis from the cat supplier. I would suggest that if your cats are OK......leave them. If vehicles only use pre cat 02 sensors then there is no problem with complete removal.

[aliluya 0]

A E39 530I should have pre cat and after cat 02 censors (4 in total). You cannot remove that cats in that configuration. It will run too lean and damage the engine. You could however fit larger higher flow aftermarket cats. We have used american made cats fitted by Pit Stop and supplied by Chase Exhaust systems. Once fitted the live data readings from the 02 sensors must be checked. In saying that. Recently we had a problem with an E46 318I where we tried two different cats on the car and were still getting error codes and the rear 02 sensor was unstable with high readings. Reluctantly we had to fit an OEM cat to fix the problem. We are still waiting for the prognosis from the cat supplier. I would suggest that if your cats are OK......leave them. If vehicles only use pre cat 02 sensors then there is no problem with complete removal.

Thanks for that Glenn, i think my final decision is that i'll leave the cat as is, seems like a lot of hassle with regards to the O2 sensors.

As for the mid muffler can some one shed some information please.

[*Glenn* 854]

Before you do anything.....give me a call Ph. 2722546

[aliluya 0]

I'd like to just thank:

Brent- for the information provided during the weekend - really nice and friendly guy

Gleen - for the advice regarding the E39 - also a really nice guy

Wayne - for the opportunity of testing out the headers, unfortunatly it didn't work out, but we've sorted something out and i'm more than happy atm - maybe in future when i have more $ and more information we could try it again.

Until then thanks for all the input from everyone.