Front bumper side grills on 35i vs 50i !!

[Singh97]

Hi, I know that on a 35i side grills under the fog lights are not vented/meshed like 50i but are only designed to like a perforated one. So my question is has anybody swapped them and also is there a reason other than looks to weather this should be done or not. Please share all pros and cons you can think of. Pictures are welcomed if you have done this mod.

Another forum member @Neon01 asked me this question.

[Chio]

I have the m sport and I changed the solid ones to mess! The only reason the 50 has them open is because of the intercoolers !

[edennelson]

I believe mpg will suffer.

[Singh97]

Did u noticed some extra dirt accumulating inside the bumper or any other difference?

Originally Posted by Chio

I have the m sport and I changed the solid ones to mess! The only reason the 50 has them open is because of the intercoolers !

[Singh97]

can u please expand on that ?

QUOTE=edennelson;14896554]I believe mpg will suffer.[/QUOTE]

[edennelson]

Originally Posted by Singh97

can u please expand on that ?

By drawing air into the front of the vehicle you increase the drag coefficient.

[///SAL]

Originally Posted by Singh97

Did u noticed some extra dirt accumulating inside the bumper or any other difference?

Nah no dirt theres a slot under the intercoolers that goes out under the car so basically its just a vent but no dirt stays behind. Only problem i have is the leafs going into the center mesh of the bumper And have to stick a vacum hose thur the hood where the kidneys go to vac.

[Singh97]

Thanks. But I was more concerned about the after affects of changing the grills to open meshed once on a 35i. As you said 50i have inter-coolers so there is no much open space there.

Originally Posted by 1FASTX5

Nah no dirt theres a slot under the intercoolers that goes out under the car so basically its just a vent but no dirt stays behind. Only problem i have is the leafs going into the center mesh of the bumper And have to stick a vacum hose thur the hood where the kidneys go to vac.

[Singh97]

Will it add even more air from the side grills even after having that big center grill and big kidneys?

Originally Posted by edennelson

By drawing air into the front of the vehicle you increase the drag coefficient.

[///SAL]

Originally Posted by Singh97

Thanks. But I was more concerned about the after affects of changing the grills to open meshed once on a 35i. As you said 50i have inter-coolers so there is no much open space there.

Since we have the intercoolers, whats behind yours have u checked. Take a look before buying them to see whats gonna be exposed. Sometimes you might see something that dont look good being exposed

[edennelson]

Originally Posted by Singh97

Will it add even more air from the side grills even after having that big center grill and big kidneys?

Yes it will reduce mpg. I can't say by how much, it's defiantly not huge.
It's probably similar to having a dirty air filter, or a couple PSI low in your tires.

[Chio]

It will not do anything to mpg! When they were blocked it was like hitting a wall! Now they are open and the air can flow threw !

[Chio]

The air will just go in then down and out! I have been getting same mpg since I have done this both city and hwy

[edennelson]

Originally Posted by Chio

It will not do anything to mpg! When they were blocked it was like hitting a wall! Now they are open and the air can flow threw !

People think removing the tail gate from their pickup allows air to flow threw...
It in fact creates a low pressure area behind the cab and causes mpg to suffer.

The OP asked for downside. The downside is a small decrease in mpg.

[MonacoJoe]

agree the sealed mesh looks terrible. though adding vents with no intercoolers seems korny to me. no way that would impact MPG...thats retarded.

[Singh97]

Thank you for the pictures Chio.

Originally Posted by Chio

The air will just go in then down and out! I have been getting same mpg since I have done this both city and hwy

[Neon01]

Originally Posted by edennelson

People think removing the tail gate from their pickup allows air to flow threw...
It in fact creates a low pressure area behind the cab and causes mpg to suffer.

The OP asked for downside. The downside is a small decrease in mpg.

As an aerospace engineer I understand what you're trying to post, however, what's uncertain in this case is whether or not the volume of space behind those grilles is sealed or vented. If it _does_ vent to somewhere, it's unlikely that this will significantly impact the overall drag of the vehicle.

I think you would have a stronger case if the closed grilles were a part of some laminar or turbulent low pressure region (such as in your pickup truck analogy) that would be disturbed if they were gone. As it is, they are completely within the free stream airflow, and probably creating a high pressure region (due to being almost completely oblique to the vehicle velocity vector) anyway, so I'm not sure if creating a hole there will really change the flow over the vehicle much. It will divert less flow over the rest of the front of the vehicle. If that is beneficial or not is unknown.

One thing is certain - unless the x50i has these regions ducted somehow and the x35i does not, it will certainly create a situation no worse than the one on the x50i. Though there are heat exchangers in those locations on the x50i, the air still flows over those and has to go somewhere.

When I asked Singh, part of what I was inquiring if anyone had actually done it before since I simply don't know what's behind there. If there are large chunks of white styrofoam supporting that region of the bumper, for example, I certainly wouldn't want that visible. Also, whether those areas on the x35i or x50i are actually ducted or vented somehow.

[BIG CRAIG 203]

Originally Posted by Neon01

As an aerospace engineer I understand what you're trying to post, however, what's uncertain in this case is whether or not the volume of space behind those grilles is sealed or vented. If it _does_ vent to somewhere, it's unlikely that this will significantly impact the overall drag of the vehicle.

I think you would have a stronger case if the closed grilles were a part of some laminar or turbulent low pressure region (such as in your pickup truck analogy) that would be disturbed if they were gone. As it is, they are completely within the free stream airflow, and probably creating a high pressure region (due to being almost completely oblique to the vehicle velocity vector) anyway, so I'm not sure if creating a hole there will really change the flow over the vehicle much. It will divert less flow over the rest of the front of the vehicle. If that is beneficial or not is unknown.

One thing is certain - unless the x50i has these regions ducted somehow and the x35i does not, it will certainly create a situation no worse than the one on the x50i. Though there are heat exchangers in those locations on the x50i, the air still flows over those and has to go somewhere.

When I asked Singh, part of what I was inquiring if anyone had actually done it before since I simply don't know what's behind there. If there are large chunks of white styrofoam supporting that region of the bumper, for example, I certainly wouldn't want that visible. Also, whether those areas on the x35i or x50i are actually ducted or vented somehow.

I believe that on my 50i it vents the breaks

[wyatth]

Sorry to bump this but I couldn't find any more info on this after extensive searching. Have any others swapped these grills? Is there anything to cool on a 35i? Not worried about mileage, more curious if there is anything ugly exposed on a 35i or if there are any mechanics that could be cooled by the vented 50i grills.
Cheers -

[lanbrown]

The 50i vents the hot intercooler air out through the wheel well. There are slots there so the air has a place to escape. See part number 14:
http://www.realoem.com/bmw/enUS/show...diagId=51_7518

[larryv]

I put the 50i vents on my 35ii and they look better in my opinion. When the stock vents are removed there is nothing but black plastic behind them. Just pull the vent out and take a look, they just snap in.

[Singh97]

Originally Posted by larryv

I put the 50i vents on my 35ii and they look better in my opinion. When the stock vents are removed there is nothing but black plastic behind them. Just pull the vent out and take a look, they just snap in.

Double that

I have swapped them on my 35i and it looks much better.