I really hope that's sarcasm. If not, 525ienjoy googled it for you.

Yeah cause that's a good reason to spend another $20k on an already depreciating vehicle especially when a custom quad exhaust setup is similarly priced as your exhaust systems. I doubt you tell your customers who buy your exhaust systems to buy an M5 if they want more hp...

 

True, a quad exhaust can be made to produce power however I strongly believe one could achieve stock power if not better from a custom quad setup for the same price as what RPI produces. Point being that you don't have to spend a ton of money to get a power producing quad exhaust so long as you use the correct specifications to keep backpressure within moderation. Obviously, an exhaust system with endless hours of R&D and dyno tests will more than likely produce more hp but the point of this thread is to simply guide members in the direction where their quad setups will not lose hp at a reasonable cost.

 

You know I can't remember if they really were resonators or not. You should have them double check as there are pre-cats coming off the back of the headers, and then those those were main cats on the M5 and I could have sworn they were on the 545i as well. Could be wrong tho, it's been over a year since we developed out the 545i.

Our final #s were something like +10hp / +8-10tq. The first version lost a lot of power and it was basically a straight pipe after the x-pipe with a magnaflow muffler. The second version gained torque by adding a 3" resonator into the system but still lost power and the third made a lot more power and that was after we added a high-flow cat. Pissy car. Wish I could find the pics.

 

If you mean the exhaust in the link in your sig, you do know that is not a quad exhaust right?

 

Quad or single doesn't matter. I could add another muffler to system and reverse y out the back of the 3" single and it wont change the dyno results. If you keep a high-flow cat and resonator in line you should be fine. We removed the muffler on our 4th dyno - just straight pipe, and it didn't change the power output as the back pressure needed was already generated ahead of the muffler.

 

crmb,
Kudos on the M5board exhaust build thread! I have been watching that thread always waiting for more pics

Would you mind describing in more detail how you would personally setup a quad exhaust for the 545i?

 

edit - nvm

 

I can only recommend based upon our testing, but if you reverse merge the streams down to a 3" before the cat/resonator cans (to be determined) and run a 3" high-flow metal catalytic converter (magnaflow, etc) and a 3" ID, x 4" or 5" case resonator ~18" body length, that will generate enough back pressure to negate the effects of what muffler you choose (atleast from our dyno results). At that point you could run straight pipes out the back single or dual. Now if they removed the pre-catalytic converters off the header, all bets are off.

 

What does that do to noise level? These are not track cars, they need to be driven on the street, so my question would be is there a quad setup I can install that will add power comparable to the RPI exhaust but with noise levels about the same as the RPI as well (meaning wife/kid friendly)?
This thread is getting interesting - good one socale39

 

this is also a big concern for me.
something about putting the muffler right under the cabin leads me to believe the sounds are gonna be loud in an annoying way.