[GA/\/\/\/\A_CT]

Are there any gains to be made by using a full turbo-back system as compared to a downpipe only, both setups catted?

I see Active sells a catted downpipe and catback, and wondering about a mid-pipe.

Is there much difference for a ‘16 340xi with BM3 stage 1?

Thanks

[Logicoeur]

There is no power gained from anything behind the downpipe.

[GA/\/\/\/\A_CT]

I have heard the same; but am looking at active’s website and they say 10-15hp for cat back??

[G.Newt]

I was FBO (CG DS-1 catted DP, BMS intake, and AWE catback) but untuned. My 2 SAE dyno runs:
333hp / 375 lb-ft
344hp / 355 lb-ft

These definitely seem like slightly above stock numbers. Probably 10-25whp worth.

[GA/\/\/\/\A_CT]

Originally Posted by G.Newt

I was FBO (CG DS-1 catted DP, BMS intake, and AWE catback) but untuned. My 2 SAE dyno runs:
333hp / 375 lb-ft
344hp / 355 lb-ft

These definitely seem like slightly above stock numbers. Probably 10-25whp worth.

Thanks G.Newt, you always give good info. Did you add a tune after? Any idea how much extra with the tune plus all your FBO compared to an otherwise standard tuned car?

[Juice247]

The stock exhaust is not very restrictive, but it's more restrictive than aftermarket pipes. The stock intake is not very restrictive, but it's more restrictive than aftermarket intakes. When people say they make no difference I don't know where they get that information. Whether you believe 10-15hp to be significant or not doesn't mean it's nothing. Also as you do more upgrades, the increased airflow only bolsters those gains. Whether you do it for the power, the sound, or both, there are changes that come along with revised intake and exhaust. They are not as significant as changing the cat, but they are still there.

[eluded]

Originally Posted by Logicoeur

There is no power gained from anything behind the downpipe.

^^^^ this

[Logicoeur]

Originally Posted by G.Newt

I was FBO (CG DS-1 catted DP, BMS intake, and AWE catback) but untuned. My 2 SAE dyno runs:
333hp / 375 lb-ft
344hp / 355 lb-ft

These definitely seem like slightly above stock numbers. Probably 10-25whp worth.

Originally Posted by GA/\/\/\/\A_CT

I have heard the same; but am looking at active's website and they say 10-15hp for cat back??

Marketing speak

Originally Posted by G.Newt

I was FBO (CG DS-1 catted DP, BMS intake, and AWE catback) but untuned. My 2 SAE dyno runs:
333hp / 375 lb-ft
344hp / 355 lb-ft

These definitely seem like slightly above stock numbers. Probably 10-25whp worth.

This delta was before and after what mod?

[mike@x-ph.com]

You get more power with the correct catback but it's not worth it for the price.

[G.Newt]

Originally Posted by GA/\/\/\/\A_CT

Thanks G.Newt, you always give good info. Did you add a tune after? Any idea how much extra with the tune plus all your FBO compared to an otherwise standard tuned car?

Check my signature. I basically gained 100whp and 150 lb-ft from a tune alone.

Originally Posted by Logicoeur

Marketing speak

This delta was before and after what mod?

I didn't get a chance to dyno it before I was FBO. I agree that almost ALL of the gains are from the downpipe (and probably only 10-20whp MAX). The intake and exhaust gains are negligible.

I'm going to re-dyno on the same one I used for my untuned FBO run, now that I have my TU pump installed for the Stage 2+ E30 map. My Mustang dyno was a different one although they used the same SAE standard (And Mustang dynos read lower than dynojet), it's not the exact same dyno. And that's really the only/best way to get true deltas. Stay posted boys.

[Skyhigh]

Originally Posted by mike@x-ph.com

You get more power with the correct catback but it's not worth it for the price.

That is the most accurate answer here so far.

The exhaust system is called a "system" for a reason. The downpipe is by far the most restrictive component in the system so you gain most by making changes there. This however does not mean you would not gain anything by changes elsewhere in the system. The resistance (a.k.a. back-pressure) of the exhaust system is a property of the entire system, not a single component.

Changes downstream from the DP bring limited power gains and therefore have a low value-for-money ratio when it comes to power. They do however have a high-value-for-money ratio in terms of sound A less-restrictive cat-back exhaust is also advantageous for the turbo.

Example: There is a reason why the MPPSK cat-back exhaust has larger diameter than the stock. If the design-goal was just better sound, there would have been no need for that.

[G.Newt]

Originally Posted by Skyhigh

That is the most accurate answer here so far.

The exhaust system is called a "system" for a reason. The downpipe is by far the most restrictive component in the system so you gain most by making changes there. This however does not mean you would not gain anything by changes elsewhere in the system. The resistance (a.k.a. back-pressure) of the exhaust system is a property of the entire system, not a single component.

Changes downstream from the DP bring limited power gains and therefore have a low value-for-money ratio when it comes to power. They do however have a high-value-for-money ratio in terms of sound A less-restrictive cat-back exhaust is also advantageous for the turbo.

Example: There is a reason why the MPPSK cat-back exhaust has larger diameter than the stock. If the design-goal was just better sound, there would have been no need for that.

I was with you until your example. MHD, BM3, MG, etc., offer Stage 1 maps intended for completely stock hardware that pushes more power than MPPSK. Let's just face it: that's marketing BS so they can sell you a $3k (at the time of release) OEM upgrade. Not saying it's not a nice combo when paired together. But the tune doesn't need the exhaust.

[Skyhigh]

Originally Posted by G.Newt

I was with you until your example. MHD, BM3, MG, etc., offer Stage 1 maps intended for completely stock hardware that pushes more power then MPPSK. Let's just face it: that's marketing BS so they can sell you a $3k (at the time of release) OEM upgrade. Not saying it's not a nice combo when paired together. But the tune doesn't need the exhaust.

You either misunderstood or chose to I never said any tune needs an exhaust.

I don't need proper clothing for jogging and I can run just fine with jeans and shirt on, but it is so much more comfortable (and healthy!) to do so in sport clothes!

A sport-cat without any tune (stock SW) brings a noticeable power increase. What does that tell you? Does that mean that the stock software needs a sport cat? No it doesn't, the same way a Stage 1, and even a Stage 2 for that matter does not need it. It means however that there is an extra gain for having it. Same for a cat-back exhaust, just on a much lower scale.

Hope it's more clear now.
It is not just marketing. In reality BMW don't even advertise with the fact that the MPPSK exhaust is larger. It is a purely engineering decision and a very good one.
You certainly don't need it, but unlike the red Start-Stop button - it actually does something for you if you have it.

[Juice247]

Originally Posted by G.Newt

I was with you until your example. MHD, BM3, MG, etc., offer Stage 1 maps intended for completely stock hardware that pushes more power then MPPSK. Let's just face it: that's marketing BS so they can sell you a $3k (at the time of release) OEM upgrade. Not saying it's not a nice combo when paired together. But the tune doesn't need the exhaust.

It's MPPSK. M Performance Power and Sound. It provides power with the tune and sound with the exhaust.

Sound is every bit as much of the experience. Adding a wing and a carbon fiber diffuser is a complete waste of money if all you care about is performance. Give me the power, yes, but in the dying age of ICE engines PLEASE GIVE ME THE SOUND TOO!!!!