[TheBigM5]

Hey guys, possibly a stupid question but i want to make sure, the part circled red-thats the resonator box right? If that part is removed will it through up any error/engine lights on?

Also the mid/centre part circled yellow-what is that? Another silencer?

[Antec800]

Yes resonator and rear silencer

[TheBigM5]

Originally Posted by Antec800

Yes resonator and rear silencer

Thank you! Do you know if i remove them will i get a CEL on the dash?

[pbonsalb]

Is that a Euro midpipe? I don’t think my USA one looks like that. I think mine has the red circled resonator up at the top of the stem of the Y where the OP has separate little cylinder devices.

[Boosted_8]

Item in red is the centre resonator. The OPFs are the round items preceding it. If you delete the center resonator alone there will be a small uplift in sound. If you also delete the chamber between the rear boxes expect raspy frequencies to be noticeable. Delete of either or both won't trigger CEL. Only primary Cats and or OPF removal causes CEL / limp mode.

[pbonsalb]

That explains it — my USA car does not have OPFs and I had not seen a picture of them before.

[onfireX5]

Red is the Resonator, Yellow is the Helmholtz Chamber. Both reduce sound frequency in different ranges without hurting power. It will be louder without them, but you might or might not like “where” the loud is. Keep them in case you do not like the tone so you can put them bac on.

You can cut everything off past the OPF and it will not set a code.

[TheBigM5]

Originally Posted by Boosted_8

Item in red is the centre resonator. The OPFs are the round items preceding it. If you delete the center resonator alone there will be a small uplift in sound. If you also delete the chamber between the rear boxes expect raspy frequencies to be noticeable. Delete of either or both won't trigger CEL. Only primary Cats and or OPF removal causes CEL / limp mode.

Aww thanks man! Exactly what i needed to know thanks!

[pbonsalb]

You can also delete the OPF without triggering a CEL if you buy the lieb engineering delete modules for about 350 euro.

[crypto]

Just because I happened to take a pic when I went to pickup my stock exhaust last week and have it handy posting this to compare what it looks like without OPF. 😀 I never knew what that looked like either.

[onfireX5]

Originally Posted by crypto

Just because I happened to take a pic when I went to pickup my stock exhaust last week and have it handy posting this to compare what it looks like without OPF. �� I never knew what that looked like either.

Excellent picture ! Even though it might not be as loud as some want, (I am guilty ), The OEM exhaust is a very trick piece of engineering. Slightly over 3.00" piping, resonator is a straight through design , the terminal mufflers do not have any baffles except for the electric valve ( I scoped them with my boroscope). It is a straight through system from the cats back with resonance tuning and will compete with any of system on the market for horsepower.

[vanos84]

Interesting... can someone post a sound clip of this mod? I would love to hear a before and after...

[aj_g80]

deleted this same resonator (in post 10) pictured at the top of the photo.

Sound is just a pitch louder, start up louder,and most importantly no drone when cruising, and no cel.. best 175 bucks you can spend on an exhaust.

[TimmyBHGM5]

Originally Posted by crypto

Just because I happened to take a pic when I went to pickup my stock exhaust last week and have it handy posting this to compare what it looks like without OPF. 😀 I never knew what that looked like either.

Just for comparison

[Boosted_8]

Here's what the OPFs look like once chopped out. On the 550i the bends are also squashed and look utterly terrible for flow:

[TheBigM5]

Originally Posted by Boosted_8

Here's what the OPFs look like once chopped out. On the 550i the bends are also squashed and look utterly terrible for flow:

You're right that does look restrictive..good to see whats inside too..i thought it was something else inside

[pbonsalb]

They make the pipe bigger in the filter area to offset the restriction just like with cats, but you are right, there probably still is some restriction even though BMW did not reduce the power rating. The cat pipe expand from about 3” to about 6” but even with the very high flowing (relatively speaking) cats BMW uses on these cars, that pipe ends up flowing about the same as a 2.5” open pipe. A USA member flow benched the cats, but I have not seen a flow bench of the OPF.

[Simon H]

Interesting thread. The USA guys dont know how lucky they are, no OPFs and no pops and bangs mapped out on the engine mapping ?. It really spoilt the car for me, when i bought the LCI, coming from two previous F90 M5s. Sound is a massive emotive part for us petrolheads, thats why electric cars can just .... off,