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      06-25-2015, 02:00 AM   #1
AmmarYasirA
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Muffler Delete Question

I've been searching for a while now and a muffler delete either loses power or gains power. No clear answer, and from my understanding, the weight loss from the stock muffler removed and the slight power decrease from the muffler delete makes it equal to stock, performance wise.

I've been running around without my muffler for a while now and I personally don't see a loss in power. I daily drove the car with the stock exhaust for about 5 months and then when I got a proper daily I took the exhaust off to see what it was like.

I'm in love with the sound but I'd rather get something that benefits me power wise as opposed to dropping $200-$300 on just the sound.

As far as drone is concerned, it's there with the top up, inexistent with the top down so I'm really not bothered by that. I just want it to be faster.

So. With that said, what's the deal? What's the definitive answer? And also, if it loses power, how do the aftermarket applications differ? Wouldn't a less restricted exhaust flow be more beneficial?

I truly apologize if the answer is hidden in the mountain of posts about this question but I just haven't found the clear-cut answer yet.
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      06-25-2015, 05:34 AM   #2
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There is no loss in power. The ones claiming there is truly don't understand backpressure vs. scavenging.
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      06-25-2015, 09:47 AM   #3
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Quote:
Originally Posted by pokeybritches View Post
There is no loss in power. The ones claiming there is truly don't understand backpressure vs. scavenging.
What he said
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      06-25-2015, 11:42 AM   #4
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Agree with Pokey.

If you wanna know the details - http://www.autozine.org/technical_sc...riable-exhaust
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      06-25-2015, 11:55 AM   #5
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Quote:
Originally Posted by UntzUntzUntz
Agree with Pokey.

If you wanna know the details - http://www.autozine.org/technical_sc...riable-exhaust" rel="ugc" target="_blank">http://<a href="http://www.autozine....le-exhaust</a>
That's actually really good info, glad that got cleared up. Thanks for this!



So one more question, is the scavenging effect only useful for low end power? Is it there for a better overall powerband or is there another reason as to why you would want the scavenging effect? (Apart from the ones mentioned in the website)
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      06-26-2015, 09:24 PM   #6
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Quote:
Originally Posted by pokeybritches View Post
There is no loss in power. The ones claiming there is truly don't understand backpressure vs. scavenging.
Whs. Assuming the car has been tuned, there will be an increase. A stock bmw system runs in closed loop till 4000 rpms and then go into open loop where it wont adjust the air. So, commonly making it flow better at wot will make it run slightly leaner than when it was stock, unless the fuel trim has been increased.

My experience from bmw race cars.
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      06-27-2015, 09:01 AM   #7
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Quote:
Originally Posted by AmmarYasirA
Quote:
Originally Posted by UntzUntzUntz
Agree with Pokey.

If you wanna know the details - http://www.autozine.org/technical_sc...riable-exhaust" rel="" target="_blank">http://<a href="http://www.autozine....le-exhaust</a>
That's actually really good info, glad that got cleared up. Thanks for this!



So one more question, is the scavenging effect only useful for low end power? Is it there for a better overall powerband or is there another reason as to why you would want the scavenging effect? (Apart from the ones mentioned in the website)
Scavenging is useful at any rpm or power level. It's a tradeoff though, between scavenging and back pressure. Smaller diameter pipes increase scavenging (torque) at low rpm, but cause more back pressure (torque loss) at high rpm. Large diameter pipes are the opposite.

The myth of back pressure being necessary probably came from some guy thinking bigger was better, so he put a massive fart can on his Honda and noticed a power loss at low rpm. While there was indeed less back pressure, there was also less scavenging, and the power loss was incorrectly blamed on the loss off back pressure.

There is no one size fits all exhaust setup. You choose where you want to maximize efficiency. Stepped headers are a compromise between scavenging and flow, but they are still a compromise.
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      06-28-2015, 05:44 PM   #8
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Quote:
Originally Posted by UntzUntzUntz View Post
Agree with Pokey.

If you wanna know the details - http://www.autozine.org/technical_sc...riable-exhaust
Good read. Thanks for sharing.
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