Does any one ever done a twin quad exhaust on a 08, 528i?
It sounds crazy but I love the look of the twin quad exhaust and want to know if any one here in the forum knows of a place near Riverside CA, that can do it with out having future engine cell coming up or problems to pass smog test?
Thaks in advance.

 

Wow, twin quad, that's a new one. I would first double check if they make a diffuser for 8 exhaust tips

 

On a 528i, i wouldn't do it. I believe you will have back pressure problems.

 

Thanks for a quick response, I was afraid your guys where going to tell me this answer.
So now I can get it out of my mind and start saving to buy me an used M5.

 

I see people mention "back pressure issues" with exhausts on this forum all the time and I've never seen it anywhere else.

A reduction in backpressure (higher flowing exhaust) will generally add a few peak HP and move the power band up in the RPM range. You won't see a drastic reduction in power but you might see a loss in lower end power but unless you're really changing the size of the exhaust a lot you're not going to make any appreciable gain.

Unless a cutback is a restriction, changing them doesn't tend to have a drastic effect on power, especially with a lower hp car like a 528. Exhaust gasses have cool and velocity has slowed by the time it hits the cutback so on a 528 you're really not going to see anything plus or minus. I just put a quad on my 535 and I'm 400+ WHP and I noticed zero change in performance. If there's a car you'd notice it on it would be a higher power car like mine. You'll never notice it on a 528. Don't let something this trivial stop you.

 

i know. it's ridiculous. it's mostly on this forum though which, well, given the heavy focus on aesthetic mods sorta makes sense. nobody gets away with this 'back pressure" crap in the FI section of bimmerforums.

 

we recommend not to put a quad setup on the non-M E60s. typically a quad setup will result in a loss in power. best exhaust setup with dyno-proven power would be the RPI exhaust if interested.

 

what do you mean by 'typically'? these setups have worked well for many.

 

i actually believed this nonsense about quad setups loosing power at first. the design goals of my 550i build don't care much about how many pipes stick out of the rear bumper or what it looks/sounds like.. all that mattered to us is how a free flow exhaust would impact performance and if we could uncork more power out of this small v8. we threw a considerable amount of time and money at the exhaust on my 550i and took many dyno samples along the way. at no point during our investigation did we uncover any data that supported quad setups losing power. quite the contrary. we observed gains with the dual (quad setup if that's what you want to call it) exhaust. simple.

 

So just to be sure about what you really mean - a "quad" is 4 and "twin" is 2 therefore 2 x 4 = 8 pipes.

Or do you really mean a "dual" twin i.e. 2 x 2 = 4 pipes?