[BWbimmer]

It's called a "Side panel air duct". It's open on the pre LCI Model and it's just optics on the LCI Model. Part number 51747494356

The vents were moved into the bumper, there is an opening besides the fog light the older models don't have, I think.

[kern417]

Originally Posted by Desertnate

They actually plugged it on the LCI? Interesting. I'm surprised they would change the stamping of the fendors for something that minor while continuing to make provisions to attach a piece of trim.

On my pre-LCI M-Sport F32 there is a hole in the front wheel liner on both sides and the vent we're discussing in the back. I don't think there is a lot of air flow going across the brakes, but at least it's something.

Yep, it's the exact same shape and everything just no actual cutout in the boomerang. Like I said, my inner ricer doesn't mind it but I wish it was at least integrated into the body line. It looks more random when mounted so low, and even more random now that there's no cutout. But it does help breakup the long smooth panel.

Originally Posted by BWbimmer

It's called a "Side panel air duct". It's open on the pre LCI Model and it's just optics on the LCI Model. Part number 51747494356

The vents were moved into the bumper, there is an opening besides the fog light the older models don't have, I think.

nope all the vents are consistent, we just lost the side vents (at least the "functionality") on LCI models. But the front brake ducts and air curtains are on pre-LCI models as well.

[BWbimmer]

ok, sorry. I was under the impression this opening is missing on a non LCI

[Oz Striker]

As I understand it, the vent reduces the air pressure under the front wheel arch, reducing lift and increasing front downforce

[smrtypants44]

Originally Posted by BWbimmer

ok, sorry. I was under the impression this opening is missing on a non LCI

That vent exists on my 2017 non-lci also

[BWbimmer]

Originally Posted by kern417

Yep, it's the exact same shape and everything just no actual cutout in the boomerang. Like I said, my inner ricer doesn't mind it but I wish it was at least integrated into the body line. It looks more random when mounted so low, and even more random now that there's no cutout. But it does help breakup the long smooth panel.




nope all the vents are consistent, we just lost the side vents (at least the "functionality") on LCI models. But the front brake ducts and air curtains are on pre-LCI models as well.

Yes, this was already confirmed. Btw, more than a year ago :-)

[visionaut]

To recap and ask a question... (Dead Horse beating or not. ;P)

The original 4-series Aero (M-Sport, pre-LCI) featured 2 different EfficientDynamics techs designed to increase aerodynamic efficiency and reduce drag — that BMW originally invented in 2009, and first delivered into production on the 1M -- called Air Curtains and Air Breathers.

--
The Air Curtains are the far outside, lower front bumper fascia, ~7” tall vertical slit openings, and their supporting ducts that feed the resultant high-pressure/high-speed air out through very small openings in the lower outer lip of the front wheel arch so it exits along the lower outer edge of the front tires, creating a curtain of swifter air flow across the outside of the rolling wheels.

The Air Curtains have nothing to do with lift or downforce - the tech is all about generating high-pressure air they can point into a specific location in front of the front wheels to influence the airflow around the wheel while driving - reducing aerodynamically unwanted turbulence around the rotating wheel, to reduce drag and increase fuel economy.

--
The Air Breathers - aka open Bimmerangs - are the short vertical ducts in the rear facing edge of the front wheel arch which catch and divert some of the air flowing through the wheel arches out through their accompanying open Bimmerang outlets along the sides of the front fenders behind the wheels. They're designed to further reduce body drag and complement the Air Curtains in managing and directing airflow down the body.

--
With the 4-series LCI, it's well known that BMW killed-off the Air Breather tech. They removed the inner wheelwell edge ducting the fed the fender outlets, but retained the Bimmerangs, now sans actual ‘outlets’. There's very likely a different rear-section of the front fender lining without provision for the duct too. It kept the looks (and sheetmetal) but any aero-efficiency was gone.

But did the 4-series LCI also do away with the complete front Air Curtains tech too? I think so.

It's obvious the distinctive Vertical side slits in the outside edges of the lower bumpers are still present. But the photo above of an LCI looking into the front of Air Curtain opening shows it being wide open into the wheelwell at the back. That isn't how it looks on my pre-LCI - it’s missing the essential small port opening at the back needed to generate the “Air Curtain”. The same view from the front on a pre-LCI is about 90% closed off, with the ducting going rearward along the inner fender edge that then dramatically tapering down into a small opening the size of thumb tip. (You can only see tire through that small port at the rear of the duct). Without the properly located small exit port outlet, it would effectively kill most all of the original aero ‘curtain’ efficiency generated by the induced higher-speed air exiting that small port. So if they removed the outlet port they effectively killed-off the Air Curtain too.

If so, then oddly BOTH of these EfficientDynamics aero technologies — Air Breathers and Air Curtains - were dropped for 4-series LCI...


So - what does the forward lower outside edge of the 4-series LCI fender liner look like?

[BWbimmer]

Originally Posted by visionaut

To recap and ask a question... (Dead Horse beating or not. ;P)

The original 4-series Aero (M-Sport, pre-LCI) featured 2 different EfficientDynamics techs designed to increase aerodynamic efficiency and reduce drag — that BMW originally invented in 2009, and first delivered into production on the 1M -- called Air Curtains and Air Breathers.

--
The Air Curtains are the far outside, lower front bumper fascia, ~7” tall vertical slit openings, and their supporting ducts that feed the resultant high-pressure/high-speed air out through very small openings in the lower outer lip of the front wheel arch so it exits along the lower outer edge of the front tires, creating a curtain of swifter air flow across the outside of the rolling wheels.

The Air Curtains have nothing to do with lift or downforce - the tech is all about generating high-pressure air they can point into a specific location in front of the front wheels to influence the airflow around the wheel while driving - reducing aerodynamically unwanted turbulence around the rotating wheel, to reduce drag and increase fuel economy.

--
The Air Breathers - aka open Bimmerangs - are the short vertical ducts in the rear facing edge of the front wheel arch which catch and divert some of the air flowing through the wheel arches out through their accompanying open Bimmerang outlets along the sides of the front fenders behind the wheels. They're designed to further reduce body drag and complement the Air Curtains in managing and directing airflow down the body.

--
With the 4-series LCI, it's well known that BMW killed-off the Air Breather tech. They removed the inner wheelwell edge ducting the fed the fender outlets, but retained the Bimmerangs, now sans actual ‘outlets’. There's very likely a different rear-section of the front fender lining without provision for the duct too. It kept the looks (and sheetmetal) but any aero-efficiency was gone.

But did the 4-series LCI also do away with the complete front Air Curtains tech too? I think so.

It's obvious the distinctive Vertical side slits in the outside edges of the lower bumpers are still present. But the photo above of an LCI looking into the front of Air Curtain opening shows it being wide open into the wheelwell at the back. That isn't how it looks on my pre-LCI - it’s missing the essential small port opening at the back needed to generate the “Air Curtain”. The same view from the front on a pre-LCI is about 90% closed off, with the ducting going rearward along the inner fender edge that then dramatically tapering down into a small opening the size of thumb tip. (You can only see tire through that small port at the rear of the duct). Without the properly located small exit port outlet, it would effectively kill most all of the original aero ‘curtain’ efficiency generated by the induced higher-speed air exiting that small port. So if they removed the outlet port they effectively killed-off the Air Curtain too.

If so, then oddly BOTH of these EfficientDynamics aero technologies — Air Breathers and Air Curtains - were dropped for 4-series LCI...


So - what does the forward lower outside edge of the 4-series LCI fender liner look like?

Here we go:

[Skyhigh]

Another LCI from the front:


I am very curious myself why BMW moved away from the Breathers and modified the Air Curtains. Being an engineer (and also having some knowledge and experience with aerodynamics) and mainly knowing from experience how manufacturers think, there are generally only a few reasons why a manufacturer would introduce post-production design changes (which lead to non-recurring design cost, recurring cofiguration control cost and increased complexity, negatively impacted parts supply and storage, etc.):

1. A design flaw leading to:
A. Safety concerns
B. Undesirable outcome affecting parameters of importance

A. Very unlikely
B. That would be the case here if the features actually turned out to increase drag, and therefore fuel consumption, and therefore CO2.....

2. Appreciable cost saving
Can't see how this could apply in this case, rather the opposite.

3. Obsolescence
Very unlikely

4. Marketing / General "family" improvements
Can't see how this could apply in this case, rather the opposite.

Can't think of other options...

This is not all however - did you know that the Air intake has changed too? As far as I know, pre-LCI had one of the inner openings in the bumper (visible on the right hand side of the picture above) connected directly to the air intake of the engine (piping). In LCI, the air filter inlet is just sucking air from the engine compartment and not connected to the port on the bumper Sounds counter-efficient to me - warmer air, no air pressure. Go figure! One potential problem I can think of with the original design is snow and ice accummulation and in extreme cases - blockage, since the opening is very low...

[Desertnate]

Originally Posted by BWbimmer

Here we go:

After watching this discussion for a while, I thought we are talking about the vent BEHIND the front wheel, i.e. the "boomerang" located in the quarter panel on the F32.

While the vent pictured here does seem to persist across the LCI vehicles, I'm pretty sure the vent just aft of the front wheels is gone on the LCI. I looked at a post-LCI F36 at work the other day and the boomerang is now simply a cosmetic feature with no opening for air flow.

[Skyhigh]

Originally Posted by Desertnate

After watching this discussion for a while, I thought we are talking about the vent BEHIND the front wheel, i.e. the "boomerang" located in the quarter panel on the F32.

While the vent pictured here does seem to persist across the LCI vehicles, I'm pretty sure the vent just aft of the front wheels is gone on the LCI. I looked at a post-LCI F36 at work the other day and the boomerang is now simply a cosmetic feature with no opening for air flow.

Just make an effort and read the previous posts.... you are literally asking what has just been discussed.... If nothing else - read @visionaut's summary. Keyword: Air Breathers

[BWbimmer]

Originally Posted by Skyhigh

Another LCI from the front:


I am very curious myself why BMW moved away from the Breathers and modified the Air Curtains. Being an engineer (and also having some knowledge and experience with aerodynamics) and mainly knowing from experience how manufacturers think, there are generally only a few reasons why a manufacturer would introduce post-production design changes (which lead to non-recurring design cost, recurring cofiguration control cost and increased complexity, negatively impacted parts supply and storage, etc.):

1. A design flaw leading to:
A. Safety concerns
B. Undesirable outcome affecting parameters of importance

A. Very unlikely
B. That would be the case here if the features actually turned out to increase drag, and therefore fuel consumption, and therefore CO2.....

2. Appreciable cost saving
Can't see how this could apply in this case, rather the opposite.

3. Obsolescence
Very unlikely

4. Marketing / General "family" improvements
Can't see how this could apply in this case, rather the opposite.

Can't think of other options...

This is not all however - did you know that the Air intake has changed too? As far as I know, pre-LCI had one of the inner openings in the bumper (visible on the right hand side of the picture above) connected directly to the air intake of the engine (piping). In LCI, the air filter inlet is just sucking air from the engine compartment and not connected to the port on the bumper Sounds counter-efficient to me - warmer air, no air pressure. Go figure! One potential problem I can think of with the original design is snow and ice accummulation and in extreme cases - blockage, since the opening is very low...

I went through the part numbers. Just to have a clear comparision I only looked at the left hand side.
There are 2 Numbers available.
The first on is 51717260729. On a pre LCI model this number is valid for the vehicles without the M Sports package". Cars with the M Sports package required 51717260731.
Later on, on the LCI Models I saw comments that the 51717260731 was meant for cars with "Exhaust emission standards EU6 RDE". But on top that there are differences between rwd and awd. This might be caused by the necessity of additional brake cooling due to the fact that there is an additional drive shaft in the way on an awd vehicles. It's obvioulsy not that easy to understand the choice which liner was picked.
What you described does really make sense but it seems to be more complex on how BMW decided on which liner was used in which situation.
One point we need to take in considration if we look at cars we do not know the history. It is that verious people upgrade to the M bumpers but might not have changed the liners. This might mislead on which combination is correct.

[Skyhigh]

That's the thing. There are many factors indeed.
However, it remains a fact that they moved away from their initial design when they introduced LCI. And xDrive was not introduced at LCI, so that cannot be the factor. Also mine looks just like yours and I have xDrive. And last but not least - none of these features were intended to have a functional purpose, other than improved aerodynamics...

[BWbimmer]

Originally Posted by Skyhigh

That's the thing. There are many factors indeed.
However, it remains a fact that they moved away from their initial design when they introduced LCI. And xDrive was not introduced at LCI, so that cannot be the factor. Also mine looks just like yours and I have xDrive. And last but not least - none of these features were intended to have a functional purpose, other than improved aerodynamics...

I do not entirely agree to your statement that BMW moved away. If you look at a 2018 LCI! XDrive model, there are still both versions in palce. It just seems to depend on the configuration:

https://www.realoem.com/bmw/enUS/sho...diagId=51_8649

I didn't say that the XDrive was introduced with the LCI. I meant the with the LCI model, BMW destinguished between XDrive or not when it comes down to the liner.

And If we take visionaut's car as an examle, he should actually have the liner with the big opening. Maybe his bumper was retrofitted?

https://www.realoem.com/bmw/enUS/sho...diagId=51_8649

[smrtypants44]

My air curtain vent is completely open on my 2017 non-lci 4 series rwd like BWBimmer. My bimmerang is also open.

[visionaut]

Originally Posted by Skyhigh

I am very curious myself why BMW moved away from the Breathers and modified the Air Curtains. Being an engineer (and also having some knowledge and experience with aerodynamics) and mainly knowing from experience how manufacturers think, there are generally only a few reasons why a manufacturer would introduce post-production design changes (which lead to non-recurring design cost, recurring cofiguration control cost and increased complexity, negatively impacted parts supply and storage, etc.):

1. A design flaw leading to:
A. Safety concerns
B. Undesirable outcome affecting parameters of importance

A. Very unlikely
B. That would be the case here if the features actually turned out to increase drag, and therefore fuel consumption, and therefore CO2.....

2. Appreciable cost saving
Can't see how this could apply in this case, rather the opposite.

3. Obsolescence
Very unlikely

4. Marketing / General "family" improvements
Can't see how this could apply in this case, rather the opposite.

Can't think of other options...

Systems engineer with aerospace here - we're thinking alike... And my 2016 435iX M-sport w/THP has an all original body.

My own hunch: It was ultimately a bean-counter thing. A trade-off, where engineering lost to production costs in the LCI refresh.

What's LCI all about? Life Cycle Impulse - they hit the Model mid-cycle with a fresh/update to spur sales. It's typically most noticed in the visual changes - new trim/lighting/etc. That stuff costs money (with a shorter ROI). With LCI what else do they do? - they move a lot of prior 'option' items to 'standard'. But that costs money too. So what else do they do? - they reduce product options and optional parts, or lower-valued added costly parts. They reduce the number of parts, part options, and optimize manufacturing and production costs. That saves money.

(They also might say, change an engine over too at the mid-lifecycle point, but for the 4 series it got the B58 the year before its LCI... So SOME changes to the 4 occurred pre-LCI, due to the B58 change. Like the airbox moving to other side, etc.)

They knew they were giving up these aero advances, but they'd go mostly unnoticed - but save $ on less parts and reduced manufacturing costs to offset the added costs associated with the new LCI parts and the LCI 'standardization' of prior 'options'. (In both situations here, they ended up essentially revising 1 major part, and dropping 1 other. And saved weight over the prior design.)

Yeah, they might've gotten a few customer complaints, mostly for the Air Breathers '"allowing debris to spray on doors". Maybe someone complained the small exit ports in the Air Curtains contributed to possibly "retaining scooped up snow" a bit like you said. But I think that ain't what drove them to dropping these two aero techs...

It's a little funny, because pretty much everyone in auto manufacturing now uses Air Curtains tech to help reduce drag, though some advertise it as their own new innovation (looking at you GM, lol).

--
BTW -- M-Sport models with 'additional cooling stuff' in either/both of their 2 lower outer air scoops (just inboard of the Air Curtains) are the ones that use the different front forward fenders liners (for BOTH pre-LCI and LCI) that have the extra big grid of vents in them. It's not an X-drive thing.

[BWbimmer]

Originally Posted by visionaut

Systems engineer with aerospace here - we're thinking alike... And my 2016 435iX M-sport w/THP has an all original body.


Yeah, they might've gotten a few customer complaints, mostly for the Air Breathers '"allowing debris to spray on doors". Maybe someone complained the small exit ports in the Air Curtains contributed to possibly "retaining scooped up snow" a bit like you said. But I think that ain't what drove them to dropping these two aero techs...

--
BTW -- M-Sport models with 'additional cooling stuff' in either/both of their 2 lower outer air scoops (just inboard of the Air Curtains) are the ones that use the different front forward fenders liners (for BOTH pre-LCI and LCI) that have the extra big grid of vents in them. It's not an X-drive thing.

Again, they might have dropped the Air Breathers but the different liners were still used on the LCI model (part 18):

https://www.realoem.com/bmw/enUS/sho...diagId=51_8649

But going away from the how and when. Are u saying, technology wise your version with the small opening is the better concept? I've got my ducktape ready :-)

[Skyhigh]

Originally Posted by BWbimmer

I do not entirely agree to your statement that BMW moved away. If you look at a 2018 LCI! XDrive model, there are still both versions in palce.

I think we are talking past each other.
What I meant was in general, not particularly about the inner lining/trim. BMW completely moved away from the breathers for example. No variants there post-LCI. Completely closed on all, both sides.

[Skyhigh]

Originally Posted by visionaut

Systems engineer with aerospace here - we're thinking alike... And my 2016 435iX M-sport w/THP has an all original body.

Great, a colleague

My own hunch: It was ultimately a bean-counter thing. A trade-off, where engineering lost to production costs in the LCI refresh.

What's LCI all about? Life Cycle Impulse - they hit the Model mid-cycle with a fresh/update to spur sales. It's typically most noticed in the visual changes - new trim/lighting/etc. That stuff costs money (with a shorter ROI). With LCI what else do they do? - they move a lot of prior 'option' items to 'standard'. But that costs money too. So what else do they do? - they reduce product options and optional parts, or lower-valued added costly parts. They reduce the number of parts, part options, and optimize manufacturing and production costs. That saves money.

So far I fully agree with the logic and approach. LCI is all about:
- refreshing the looks (for marketing purposes),
- using the opportunity to introduce necessary (safety-related or cost-reducing) design changes
- updating some components to the latest standard, mainly multimedia/electronics, etc. or due to obsolescence

As you said as well - LCI is a single, appreciable (in comparison to the minor changes introduced with every modelyear) investment in changes to a model, before it is left to complete its lifecycle naturally. This said, I always prefer buying an LCI /Facelift model, if possible, as it, in reality, is always the best / most modern / bug-free version there will ever be of a certain model. My Audi is also built not long after they introduced the facelift for the model.

(They also might say, change an engine over too at the mid-lifecycle point, but for the 4 series it got the B58 the year before its LCI... So SOME changes to the 4 occurred pre-LCI, due to the B58 change. Like the airbox moving to other side, etc.)

True. To be fair however the list of LCI changes goes beyond those examples. There is the redesigned/improved suspension, updated multimedia and assistance systems, etc., etc.
Actually, having already mentioned my Audi, the F3x LCI changes are appreciably less than what Audi did for the A3 Facelift. The changes there are a bit more extensive, ironically including introduction of new aerodynamic features
But for the sake of this discussion, let's just focus on the external changes and forget the rest. Those I am aware of are:

• New headlights (and options), physically plug&play, no redesign of the front
• New taillights, physically plug&play, no redesign of the rear
• Changes to the air curtain (I call it "changes" conservatively, so that we would not need to argue if it is really disabled or not)
• Dropping of the air breather feature (completely disabled)

Let me know if I missed anything? (again purely on the exterior design - forget interior, engines, multimedia, electronics, drivetrain, etc.)

They knew they were giving up these aero advances, but they'd go mostly unnoticed - but save $ on less parts and reduced manufacturing costs to offset the added costs associated with the new LCI parts and the LCI 'standardization' of prior 'options'. (In both situations here, they ended up essentially revising 1 major part, and dropping 1 other. And saved weight over the prior design.)

This is where the logic fails, IMO, and where I disagree.
Let's take the Air Breather (a.k.a. Boomerang), as this is the more vivid example:
- This feature was never optional, it was standard, no alternatives
- Nothing related to the physical interface of the related components changed at LCI (fenders, etc.)
- Strictly speaking, going over to closed design costs more in production cost, as more material is used to close what used to be open design previously
- Most importantly - introducing yet another 2 components (the inner liner which is now closed and the new, closed boomerang) and also spare parts to the catalogue, costs a lot in terms of configuration control, redesign, manufacturing, stock maintenance, etc.

On top of that, if it does anything for the marketing, it hurts it. The opposite, introducing a new aerodynamic feature could have been a great marketing geek!

The exam question is WHY go through the trouble?
I see zero cost saving, just the opposite, on several fronts. Zero (rather negative) marketing value.
My only possible explanation is that maybe it hurt aerodynamics after all, the way it was designed originally. Which contributed to increased fuel consumption. Which contributed to higher CO2 values. Which contributed to challanges related to the environmental standard and qualification of the new engines, at LCI..... Which is why the design was improved at LCI by removing what turned out to be counter-productive or was simply a marketing feature all along...
Sounds silly, but please give me another possible explanation, given all we have discussed above about production management?

Yeah, they might've gotten a few customer complaints, mostly for the Air Breathers '"allowing debris to spray on doors". Maybe someone complained the small exit ports in the Air Curtains contributed to possibly "retaining scooped up snow" a bit like you said. But I think that ain't what drove them to dropping these two aero techs...

Definitely not! Sadly, manufacturers only care about customer experience if it hurts their economy.
Btw. the snow thing was my theory for another change - the air inlet for the engine (turbo). If you look at your vehicle, you will most likely find that the opening on the right hand side of my photo above (or partially visible at 5 o'clock on my avatar photo, inner side of the bumper) is directly connected to your air filter box. That's no longer the case for LCI.....

It's a little funny, because pretty much everyone in auto manufacturing now uses Air Curtains tech to help reduce drag, though some advertise it as their own new innovation (looking at you GM, lol).

--
BTW -- M-Sport models with 'additional cooling stuff' in either/both of their 2 lower outer air scoops (just inboard of the Air Curtains) are the ones that use the different front forward fenders liners (for BOTH pre-LCI and LCI) that have the extra big grid of vents in them. It's not an X-drive thing.

Depends on what you call "different" front fender liners? You mean where the vents/ports are completely open, as in my case?
If so, than that's not true either.... The additional cooling radiators, as discussed in another thread recently, are a feature of the "Hot climate version" option which appears to be standard in the US, ironically together with the "Cold climate version" option In Europe, those versions are optional. I have the "Cold climate version" option on mine, no extra radiators, closed grids around the fog lights, completely open air curtain ports.....
Go figure

[BWbimmer]

Originally Posted by Skyhigh

I think we are talking past each other.
What I meant was in general, not particularly about the inner lining/trim. BMW completely moved away from the breathers for example. No variants there post-LCI. Completely closed on all, both sides.

I am with you on that.

Still, since you seem to have an idea about aerodynamics. Is there and advantage of the small opening in the liner?

[Skyhigh]

Originally Posted by BWbimmer

I am with you on that.

Still, since you seem to have an idea about aerodynamics. Is there and advantage of the small opening in the liner?

Aerodynamics are often unpredictable, wind channels are the ultimate tool, but from general knowledge - a focused (converging design) airflow can only improve aerodynamics if a higher speed airflow is what is needed to reduce turbulence in a particular direction after the outlet....
Otherwise it actually increases the drag....

[visionaut]

Originally Posted by BWbimmer

Are u saying, technology wise your version with the small opening is the better concept? I've got my ducktape ready :-)

Yes, the small port opening at the back is what makes the Air Breathers work. The inner ducting, which is missing in LCI, routes and compresses the air to exit at higher speed through the directed port that generates the Air Curtain. It is higher drag in the inlet because the back exit is mostly closed off - but that’s more than offset by the reduced drag/turbulence around the wheels, which is much greater.

The open back design produces less drag at the inlet, but more overall drag because it doesn’t generate a hi-speed air curtain past the wheels. The outboard open slots still help some, just not as much.