4.8 Restricted Exhaust

dadysev · 10-10-2019, 02:43 PM

Been having this issue for a long time. I thought maybe the cats but this thing will sound like a normal 4.8 with growl and power sometimes, and usually when its cold it sounds quiet like there is something holding it back. My friend just left with his 4.8 same year, identical to mine (2007) and when he revved his exhaust its like a jet at the back. you can feel the pressure 5 feet back.
Questions:

Did they have different exhaust options for these 4.8's?

Is there some sort of flap like on my F10 550 ?

Can cats open up with full flow when hot if they are going bad?

Thecastle · 10-18-2019, 05:04 AM

I had a 4.8i and it’s a nice sounding engine. In fact the startup sound is what sold it for me. One of bmws best sounding engines...

To my knowledge there was only the standard exhaust and no optional exhausts from the factory.

According to real oem, there is no exhaust flap

A cat being hot or cold won’t change its flow when it’s physically obstructed

Are you smoking? Oil will plug cats

10-10-2019, 02:43 PM	#1
dadysev Captain 169 Rep 687 Posts Drives: Man Join Date: Jul 2013 Location: Toronto, Canada iTrader: (0)	4.8 Restricted Exhaust Been having this issue for a long time. I thought maybe the cats but this thing will sound like a normal 4.8 with growl and power sometimes, and usually when its cold it sounds quiet like there is something holding it back. My friend just left with his 4.8 same year, identical to mine (2007) and when he revved his exhaust its like a jet at the back. you can feel the pressure 5 feet back. Questions: Did they have different exhaust options for these 4.8's? Is there some sort of flap like on my F10 550 ? Can cats open up with full flow when hot if they are going bad?
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10-18-2019, 05:04 AM	#2
Thecastle Major 307 Rep 1,146 Posts Drives: F10 550i Join Date: Apr 2015 Location: Houston, TX iTrader: (0) Garage List 2020 BMW M340i [0.00] 2019 RAM 3500 [0.00] 2020 BMW X3 [0.00] 2016 BMW 550i [0.00] 2000 Ford F450 7.3l ... [0.00]	I had a 4.8i and it’s a nice sounding engine. In fact the startup sound is what sold it for me. One of bmws best sounding engines... To my knowledge there was only the standard exhaust and no optional exhausts from the factory. According to real oem, there is no exhaust flap A cat being hot or cold won’t change its flow when it’s physically obstructed Are you smoking? Oil will plug cats
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