[Skyhigh]

As we all know, most cars in the states are with the hot-climate intake, whereas most in Europe are with a cold-climate intake.

One of the differences between the two is the that HC Intake has a spring-loaded safety valve, which opens from the vacuum in the box, in case the intake itself gets clogged. This is a nice safety feature, which I am about to add as part of the CC to HC intake conversion (Thank you BWbimmer for opening my eyes about this one!! Finally acquired!)

Now, with the HC-intake box came a filter I have never seen before:





Apparently the filter for the HC version has an extra piece of (fine-particles?) filter over the flap!!
The engineer in me is struggling to understand the design considerations here!!
- Why would (Plan B) air coming through the valve, hence from the engine bay, need extra filtration!?
- Why would one increase the resistance and decrease the airflow even further in this (Plan B) scenario through an additional filter!?

Thoughts? Those who have converted (BWbimmer - are you using the HC filter or continue to use the CC filter (e.g. Mahle LX3320, which has no extra piece of filter):

[toxik]

i thought one of the big differences between a cold climate car and a hot climate car is the extra air duct behind the kidney grille that is open with a grated plastic, where as a cold climate car has this port completely shut with a solid piece of plastic.



if the question is why would a HC car need extra filtration, this would make sense to me, due to this port being open letting in more particles/debris.

[Skyhigh]

Originally Posted by toxik

i thought one of the big differences between a cold climate car and a hot climate car is the extra air duct behind the kidney grille that is open with a grated plastic, where as a cold climate car has this port completely shut with a solid piece of plastic.

if the question is why would a HC car need extra filtration, this would make sense to me, due to this port being open letting in more particles/debris.

Yes, that is the biggest difference. As for the second part - please read my post again, seems like you haven't grasped the difference in the filter! The extra filtration is ONLY over the back-up valve, which sucks in air from the engine bay (as would the CC intake by default, without extra filtration).

[toxik]

Originally Posted by Skyhigh

Yes, that is the biggest difference. As for the second part - please read my post again, seems like you haven't grasped the difference in the filter! The extra filtration is ONLY over the back-up valve, which sucks in air from the engine bay (as would the CC intake by default).

ah i understand, I didn't realize the filter is where the valve location is.

[QUESTOR]

i manage a ford store parts dept and looks similar (albeit smaller) to the intake pre-filter on some diesels. our techs have always removed them since they cover the entire filter surface and choke the intake to a degree. but bmw smarter than ford so they may actually have a justifiable reasoning behind the engineering/cost of production on the part.

[freakystyly]

If it is what I think it is.. it's emissions related. Fuel rich air from the engine backwashes the intake tract on engine shut down. The charcoal filter is supposed to absorb the fuel vapors. (E90s had a similar but non-replaceable filter throughout the entire span of the filter)

[Skyhigh]

That's a very interesting theory!! I admit I had not thought of that!
It is still questionable why they would think that's sensible, for a secondary inlet... whilst the cold climate intake also sucks in air from the engine bay (true - further to the front, behind the bumper), without extra frustration...

But a very, very interesting theory, which may not be far from the truth!!
Especially assuming it is charcoal (which I have not thought of too).

[QUESTOR]

TRD versions of certain trucks/suvs etc list their pre-filter as a "snow filter" but it wouldnt surprise me if freakystyly is dead on with the raw fuel smell idea. if anyone finds anything solid, id like to hear. cheers.

[Skyhigh]

If it had anything to do with snow, it would have been on the entire surface (but the valve area), since snow is more likely to come from the outside than the super hot engine bay area around the box.

[BaconDouble]

Originally Posted by QUESTOR

TRD versions of certain trucks/suvs etc list their pre-filter as a "snow filter" but it wouldnt surprise me if freakystyly is dead on with the raw fuel smell idea. if anyone finds anything solid, id like to hear. cheers.

I recall seeing this before on other car brands (Audi), and I believe it was also for emissions reasons. The replacement air filters you could get with the extra rectangle or not.

[Billfitz]

Originally Posted by Skyhigh

As we all know, most cars in the states are with the hot-climate intake, whereas most in Europe are with a cold-climate intake.

AFAIK that's not the case. For that matter I believe all US cars are cold climate. My intake is identical to Europe models.

i thought one of the big differences between a cold climate car and a hot climate car is the extra air duct behind the kidney grille that is open with a grated plastic, where as a cold climate car has this port completely shut with a solid piece of plastic.

Mine is cold climate, I have that grate.

[freakystyly]

Originally Posted by toxik

i thought one of the big differences between a cold climate car and a hot climate car is the extra air duct behind the kidney grille that is open with a grated plastic, where as a cold climate car has this port completely shut with a solid piece of plastic.

If this means anything, on my 2 series. I have hot and cold climate (CDN spec) with a cut out at that spot behind the grille and a solid plastic blank on one side, no mesh.

[toxik]

Originally Posted by freakystyly

If this means anything, on my 2 series. I have hot and cold climate (CDN spec) with a cut out at that spot behind the grille and a solid plastic blank, no mesh.

every car has the cut-out but if you have a solid plastic piece that means it’s cold climate spec, getting the grated one would convert it into hot climate spec

based on this thread, i guess there’s other differences too for a hot climate cars, i never knew about this valve and charcoal filter

[Skyhigh]

toxik
Exactly. The cutout is always there.
Blanked - CC.
Open with a grid - HC.

In addition the filter box of the HC has that extra valve and the filter has the extra piece as above. This is a safety feature, as the open inlet of the HC can hypothetically get clogged (by an object, ice build-up, etc). Which is why I also went all the way and am about to replace the box too (too damn cold here right now).

[Skyhigh]

Whilst we are at it:
842 - Cold Climate Version
is the respective configuration code in Europe. It contains more than just the CC intake though.

[Wires]

Originally Posted by Skyhigh

toxik
Exactly. The cutout is always there.
Blanked - CC.
Open with a grid - HC.

In addition the filter box of the HC has that extra valve and the filter has the extra piece as above. This is a safety feature, as the open inlet of the HC can hypothetically get clogged (by an object, ice build-up, etc). Which is why I also went all the way and am about to replace the box too (too damn cold here right now).

Cold climate as a relief valve that pulls open when the air filter gets clogged with snow (not a blank, it's a valve). At least cars shipped to Canada have this.

That felt covers the section where the air flow path pulls into the airbox. Stops bugs and other debris from being sucked directly into the filter fins.

That's the section on my K&N that is plugged with dead insects.

[PeterWT]

Mine has the HC intake. I removed the little box and sealed the spring loaded flap hole and use the CC air filter (w/o small charcoal insert). The chance of the main air intake becoming clogged is negligible, so I don't think the flap is necessary.
https://f30.bimmerpost.com/forums/sh...7&postcount=48

[Skyhigh]

Originally Posted by Wires

Cold climate as a relief valve that pulls open when the air filter gets clogged with snow (not a blank, it's a valve). At least cars shipped to Canada have this.

That felt covers the section where the air flow path pulls into the airbox. Stops bugs and other debris from being sucked directly into the filter fins.

That's the section on my K&N that is plugged with dead insects.

That’s the hot climate intake mate

The cold climate intake has no valves. It cannot get clogged as it is open inside the engine bay.

[Wires]

Originally Posted by Skyhigh

That’s the hot climate intake mate

The cold climate intake has no valves. It cannot get clogged as it is open inside the engine bay.

You sure about that? Canada doesn't have a hot climate, and the valve is needed to prevent choking the engine when the filter fills with snow.

Why would a 'hot climate intake' need to suck hot air off the turbo/exhaust manifold? Trying to see how high you can get the IAT's before the engine grenades? The heat from the manifold melts the snow. I think you got it backwards.....

[Skyhigh]

I am absolutely sure mate I’m not in Canada, but I am in Norway, 842 - Cold Climate Version, no grid, no valve.



The cold climate intake cannot suck in snow as the opening is INSIDE the engine bay, behind the bumper, under the headlight body. It is comprised of 11, 12 and 13 above. The provisional opening behind the kidney is blanked off. Therefore there is no safety feature (valve), as neither snow, ice or large debris can get into the intake, which is well protected from the chassis itself.

The hot climate intake continues from where the CC intake ends (comprised of 11, 12, 14 and 15 above) and is open to the outside world behind the kidney, though the grid (15 above) which comes in place of the blanking plate. It is therefore hypothetically at risk of clogging. Not just by snow, but by road debris, objects, etc. Hence a safety spring-loaded valve in the box which opens once the vacuum is high enough and starts sucking air from the engine bay. This is unfavourable, of course, but a safety feature only! See in red below:



There is no third option.

If your intake is open with a grid behind the front grill —-> Hot Climate intake, incl a valve in the box.

If there is a blanking cover only —-> Cold Climate intake, no safety valve in the box.

If you have a mix between the two - someone modified it off-factory most people who convert to the HC intake don’t know about the safety valve or simply ignore this safety feature as it is relatively expensive to retrofit and has no performance benefits.

[M2C]

Originally Posted by Skyhigh

Hence a safety spring-loaded valve in the box which opens once the vacuum is high enough and starts sucking air from the engine bay. This is unfavourable, of course, but a safety feature only! See in red below:

I not yet understand the function of the vavle. Do you maybe have a proper picture in real of your airbox opened?

Does it mean, if it opens, you would not get fresh air from the front, but hot air from the engine bay? That would not be logical in terms of 'hot climate' option.

[Skyhigh]

Ok... I will try with an example.

First of all, here a photo I found from this forum, someone has been very creative to "modify" (I'd say actually abuse) the box, so please ignore that, focus on the valve compartment:



Now to the function - I am sure you have a vacuum cleaner. What happens if you cover the inlet with your hand or a plastic bag so that it gets blocked? Answer: a small valve opens somewhere else along the way to draw a bit of air into the vacuum cleaner, so that it doesn't overheat/explode from suffocation

This is exactly the same principle! IF (and only IF) the main intake gets blocked by whatever, the vacuum in the the system becomes so strong that it is able to counteract on the "emergency" spring-loaded valve in the box and open it, so that the engine can suck in air from the side of the box / engine bay instead (which is suboptimal, but still much better than suffocation!)! This feature is a safety feature only and not utilised under normal circumstances! Think of a vacuum cleaner! As soon as the primary inlet gets unclogged, the safety valve closes due to spring-force and the engine continues to suck in air from the outside.
More clear now?

And now back to the question why the CC intake doesn't have the valve - because the hazard case does not exist - the intake is well protected as it is not open to the environment as it is in the HC version and cannot get clogged by external events or objects.
Why did BMW not stick to the same box with a valve nevertheless, for commonality and parts portfolio reduction - I don't know.