Quad exhaust - Decat - or not

B

BDswarveP

Member
Alright,

Just wanting to pick some peoples brains re getting an exhaust system done on a 3.0si

im not after something stupidly loud but would like it louder than standard, so it sounds powerful.

is it worth removing the secondary cats and gutting the precats?

will it give any BHP increases? is that likely to be a large trade off and make the car stupidly loud?

would like to think i could get some slight perfomance gains even if slight, but id like it to sound fairly sensible. I want it louder, with burbles and pops but i dont want to be setting car alarms off and waking the neighbors 5 streets over up. Or end up making it sound like a long fart when accelerating
 
Removing the cats will give you minimum, if any increase in noise, as the rear silencer will still be doing it's job...

There are, however ways of making it sound MUCH better.. Read this thread - http://www.z4-forum.com/forum/viewtopic.php?f=2&t=89154

Mike
 
Ducklakeview said:
Removing the cats will give you minimum, if any increase in noise, as the rear silencer will still be doing it's job...

There are, however ways of making it sound MUCH better.. Read this thread - http://www.z4-forum.com/forum/viewtopic.php?f=2&t=89154

Mike
Click to expand...

Cheers for the response. But im going to have a stainless system put on with quad pipes.

Will have a 3.0si backbox spare afterwards mind.....
 
BDswarveP said:
Ducklakeview said:
Removing the cats will give you minimum, if any increase in noise, as the rear silencer will still be doing it's job...

There are, however ways of making it sound MUCH better.. Read this thread - http://www.z4-forum.com/forum/viewtopic.php?f=2&t=89154

Mike
Click to expand...

Cheers for the response. But im going to have a stainless system put on with quad pipes.

Will have a 3.0si backbox spare afterwards mind.....
Click to expand...


how much does this cost mate? and I'm guessing you have to get a z4m bumper?
 
You will get a noise increase if you remove the first set of silencers. I am just building a new system for my car with these removed. I am also going from 2 2" pipes into 1 21/2" or 3" pipe straight after the headers. And then either 1 center exit or keep the quads.

Are you going to tee off and have 2 silencers or are you taking 2 outlets out of one silencer?
 
Not entirely sure atm.

I'm planning on leaving the battery where it is, so not a z4m style T, but if I can get them to put two smaller sports back box's in place of the current one?

Really don't know tbh. I've only had a brief convo and quote, will see what they cam do on the day.

I was fancying getting a valvetronic system put on till I saw the price. (button to bypass baffles)

Whatever I do, I want it to have some sound sensible but louder and some performance gains if possible
 
your not going to get any noticeable performance gains from an exhaust really. If you reworked intake and map maybe a touch but nothing major. If you do the exhaust its really only for looks and sound.
 
Zero4 said:
your not going to get any noticeable performance gains from an exhaust really. If you reworked intake and map maybe a touch but nothing major. If you do the exhaust its really only for looks and sound.
Click to expand...

Agreed and I'd go as far as to say that most folks (and I include typical exhausts shops) end up reducing power output due to not understanding the real importance of how the system is tuned to the engine (reducing back pressure but keeping exhaust velocity up for scavenging) Also deciding where you want the power, torque etc..

Most folks just fit bigger pipes, less restriction and due to the noise are happy, but the real result is no better, so all depends on what you want to achieve
 
It's performance I want to focus on. As I say I'd like it louder aswell but not too loud.

So I was after some advice from people about exhaust design. I'M getting powerflow in Doncaster to do the exhaust and I know they will just build whatever I ask for.

So could anyone give me some info on optimum pipe bore, any runs which can be straightened out, how best to get the second tail pipe across while maintaining flow.

Obviously when I say performance gains I'm not expecting the world, im just meaning an improvement on standard, if that's only likely to be 2bhp and the car feeling more responsive, happy times. I just don't want a noisey exhaust that's actually reducing the power.

Cheers
 
What's the point of doing it for 2bhp. If you get slimmer pipes I doubt you would loose more than 2-3 bhp anyway
 
You'll not feel 2bhp at all and even then you'll not even know any power gains unless prep and post dyne and who the hell wants to spend that kinda money when you know it'll be 0-2 bhp gains anyway.

Reality is there's only 1 reason to do it, looks and sound ( unless as part of a larger tuning pack ) so if you keep the boxes on the back it won't be so loud but will sound nicer.

I took my box off the back and added pipes. relatively inexpensive, no power loss as i can feel at all and damn!! it sounds amazing.
 
I'm full aware I won't feel 2bhp (me saying 2bhp was an example btw). Any torque difference may be felt though. I am planning on further performance mods, that's why I'm wanting to make sure the exhaust system gIves some positive increases no matter how small.

I think I'm just going to have to trust to folk at powerflow to do the job.
 
I have pawn sacrifices old car and it has an Eissenmann quad and if you look on here and you tube can see how he did it, modified the rear bumper
 
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