[BoogieMan2]

So I bought a M5 Comp exhaust off a forum member here. Just the Mufflers really. Had it put on today and I slightly feel like I might have actually lost HP. Also the vaccum hose thats in the rear do I need that connected to the muffler for back pressure or can I just plug it. Its currently plugged and I feel like that might be part of the issue. Any answers would be great. I wanna get this fixed ASAP last thing I want is to break my new toy

[BlackWidow]

Yes I had comp mufflers on, and it feels like you lose low end torque. But it's nothing major.

As for the vacuum hose, you don't need it plugged together, just plug up both ends and tuck them away. All it does it control the valves for noise control.

[BoogieMan2]

Ok so I'm not crazy about the torque loss. Any way to fix that or did I go down the rabbit hole and need a tune to fix it

[Zer0Cool92]

Originally Posted by BoogieMan2

So I bought a M5 Comp exhaust off a forum member here. Just the Mufflers really. Had it put on today and I slightly feel like I might have actually lost HP. Also the vaccum hose thats in the rear do I need that connected to the muffler for back pressure or can I just plug it. Its currently plugged and I feel like that might be part of the issue. Any answers would be great. I wanna get this fixed ASAP last thing I want is to break my new toy

What do you mean by low end torque loss? Does it feel like it's choking a little around 1500 rpm ? Mainly in higher gears

[BlackWidow]

There isn't any "choking" that's not the same as low end torque loss

Torque loss feels like there's less 'punch' during spirited drives off the line. I have slight choking on idle and when climbing to 1500 when running 91 Octane. But with 95 octane the choking is almost nonexistent but that's not related to the comp mufflers because I have my stock back on now and it's the same thing. From what I've read on the forums, it's a known problem with the N63 and CCP doesn't fix it.

[ezaircon4jc]

Originally Posted by BlackWidow

There isn't any "choking" that's not the same as low end torque loss

Torque loss feels like there's less 'punch' during spirited drives off the line. I have slight choking on idle and when climbing to 1500 when running 91 Octane. But with 95 octane the choking is almost nonexistent but that's not related to the comp mufflers because I have my stock back on now and it's the same thing. From what I've read on the forums, it's a known problem with the N63 and CCP doesn't fix it.

Where do you get 95 octane? I haven't seen any higher than 91 for almost 15 years!

[BoogieMan2]

CCP? Is there any way to fix this at all. There's gotta be something. You would assume opening up from 2.75 inch pipes to 3.25 would give you a gain not loss

[BlackWidow]

Originally Posted by BoogieMan2

CCP? Is there any way to fix this at all. There's gotta be something. You would assume opening up from 2.75 inch pipes to 3.25 would give you a gain not loss

BMS Stage 1 or 2.

I use Stage 2.

I cut the comp mufflers off of my full comp exhaust and did a muffler delete. And I gained my torque back. Don't understand that at all. People will tell you that it's a placebo effect, but it's a very noticeable torque loss. I even test drove a stock 550 at the dealer after I installed my exhaust just to make sure I wasn't crazy and you can tell difference in torque.

But when I had the full exhaust, I increased the boost with BMS and I didn't even notice it unless I really tried to fee for it.

[BlackWidow]

Originally Posted by ezaircon4jc

Where do you get 95 octane? I haven't seen any higher than 91 for almost 15 years!

I mix my gas. 10 gallons 91 octane + 8 gallons 101 octane and I'm between 95-96 octane on a full tank.

[ezaircon4jc]

Originally Posted by BlackWidow

I mix my gas. 10 gallons 91 octane + 8 gallons 101 octane and I'm between 95-96 octane on a full tank.

OK.... Where do you score the 101??? Race gas?

[BlackWidow]

Originally Posted by ezaircon4jc

OK.... Where do you score the 101??? Race gas?

E85

[xxpanipuri]

So the 550i has the mufflers and the resonator. did u keep the stock resonator?

I'm getting ready to do this swap. However i'm going to replace the 550i exhaust form the OEM cats back. (even though i have the high flow cats from the m5 competition package).

So just wondering if you did mufflers only or removed the oem resonator as well.

muffler replacement in general shouldn't cause any torque loss (doesn't seem to make sense)

also aren't the vacuum lines for the valves on the exhaust? it opens the valves past 2500/3000 rpm for a louder sound and more airflow.

[ezaircon4jc]

Originally Posted by BlackWidow

E85

E85 is verboten per the OM...... Maybe it's OK in a blend...

[BoogieMan2]

Originally Posted by BlackWidow

E85

When you had the comp exhuast on did you tac the valves wide open AND plug the hole? Im thinking this all could be from having the resonators open all the time. Maybe a lack in back pressure is throwing the computer off alittle bit?

Let me know Ill close the valves to check and reconnect the hoses and see what it all renders.

[BlackWidow]

I always had valves wide open with the valve mod and the hose only controls the sound of the exhaust, that's it. Back pressure claims are debatable, on top of that, there are a lot of myths about back pressure and turbo engines. But that's a whole different topic.

Also, the comp exhaust doesn't have resonators. They look like twin resonators but they are straight through pipes

[BoogieMan2]

I have a reversable valve mod maybe if I take off the tacs and have them operate normally it will reverse it. Looking at my stock exhaust they have a valve system too from what it looks like. Seeing as the low end torque loss is from 0-3000 rpm and thats when the valves open on an M5 and if what I saw is a valve in the factory exhaust this might explain why its acting this way

[dadysev]

Hmmm, is the comp M5 mufflers different from the regular M5 mufflers? I did the regulars and felt no difference on my 550. I modded my own remote switch from amazon to mod the exhaust vacuum solenoid in the trunk (cost me 12$ ) and feel no difference open or close, but like you say its only sound anyway.
Curious about this one.

[BlackWidow]

Originally Posted by BoogieMan2

I have a reversable valve mod maybe if I take off the tacs and have them operate normally it will reverse it. Looking at my stock exhaust they have a valve system too from what it looks like. Seeing as the low end torque loss is from 0-3000 rpm and thats when the valves open on an M5 and if what I saw is a valve in the factory exhaust this might explain why its acting this way

I have a muffler delete with the hose still plugged and I gained torque.

The vacuum hose does nothing for performance.

[BlackWidow]

Originally Posted by dadysev

Hmmm, is the comp M5 mufflers different from the regular M5 mufflers? I did the regulars and felt no difference on my 550. I modded my own remote switch from amazon to mod the exhaust vacuum solenoid in the trunk (cost me 12$ ) and feel no difference open or close, but like you say its only sound anyway.
Curious about this one.

The whole comp exhaust is different than the stock m5 exhaust. No resonators, and the mufflers are different on the comp exhaust. I believe the baffles are removed.