[chenry]

What is this for - and why is it positioned so close to the exhaust/turbo (I think) / and is there any benefit in keeping it open all the time (it seems to be vacuum actuated - I may be wrong)

[kbsilver]

Somewhat of a guess but it may be a water bypass hose. If a lot of water enters the main air intake because of extreme spashing or high water this secondary air path prevents a high vacuum from being created that could cause the engine to pull the water up into the air filter causing water to be injested, which usually will destroy the engine.

[Timujin]

I was just looking at this today. My first though was VTA blow off valve, but no.

[Merv]

I was wondering about this too. I blocked it with my hand while idling and there's a vacuum. The engine didn't seem to mind me blocking it.

[Puerto Rican 335d]

I had replaced my intake and put the AMSOIL filter and saw this , if you dismatle the BOX you will see an actuautor valve inside the filter BOX, I beleive it regulates the heat and Air mixture to the intake, thats my 2 cents on this!!

[Timujin]

On the highway WOT it has to suck air.

[chenry]

Originally Posted by Timujin

On the highway WOT it has to suck air.

I thought the same but just can't figure out why with all the options available they would put the intake for the darn thing only inches away from the turbo and exhaust - I guess the heat doesnt impact things all that much

[NRG]

That is a weird design in E90, don't have anything like it in my E70 diesel, took apart the air box. I'm running K&N so that helps a little.

[Vreimann]

Originally Posted by chenry

What is this for - and why is it positioned so close to the exhaust/turbo (I think) / and is there any benefit in keeping it open all the time (it seems to be vacuum actuated - I may be wrong)

It's main use is to provide warm air. It's a very similar looking setup to my previous VR6. Helps alot in warming up the vehicle in cold weather. For the warm weather folks it probably doesn't get used to much.\

Once the weather cools down, I'll try and get some readings to see how fast a diesel can warm up in -30 weather.

[DieselDiner]

Originally Posted by Vreimann

It's main use is to provide warm air. It's a very similar looking setup to my previous VR6. Helps alot in warming up the vehicle in cold weather. For the warm weather folks it probably doesn't get used to much.\

x2

This makes the most sense, as diesels are slower to warm than gas engines.

I tried to find this hose on realoem, but haven't had success yet.

[dubulup]

the air box will be [somewhat] saturated with fresh air while moving; turbo's will suck what they want. I'd imagine excess air leaves via that hose and passes fresh air over the extremely hot turbine housings.


I can't see that hose providing much inlet air while fresh air from the front of the car is being rammed into the box.


standing still...sure ambient and hot will enter the box.

[chenry]

**UPDATE**
OK so took a look at the air box again and realized that I could just pop the snorkel tube along with the "valve" out of the air box with relative ease...so of course I did. I took a look at the valve and it is regulated by a spring and it's normal state is in a closed position...as the engine demands more air and the vacuum inside the box increases the spring is pulled in thus allowing access to more air for the motor (albeit very hot air given its position as discussed before) so that ends the debate over a cold air start or a cooler for the turbos etc...

But here's the interesting thing...before I put the valve tube back into the box I buttoned up the airbox closed the hood (bonnet for those of you across the pond) and took the car for a spin around the block....I hit 75% throttle and BAM limp mode...took the car home reinstalled snorkel and thought I would need to use my reset tool but before doing so I simply restarted the car (no limp) and took it for a hot lap and no problems....so obviously my car likes this little thing just where it is - that said Im scratching my head why my car threw an error with this minor change while others are running open element filters with no problem / oh well maybe my jbd has something to do with it but that said note that I did not touch the JBD during this whole process

So you now have my 2-cents on the matter

[Timujin]

Great research chenry thanks.

[cssnms]

Originally Posted by chenry

**UPDATE**
OK so took a look at the air box again and realized that I could just pop the snorkel tube along with the "valve" out of the air box with relative ease...so of course I did. I took a look at the valve and it is regulated by a spring and it's normal state is in a closed position...as the engine demands more air and the vacuum inside the box increases the spring is pulled in thus allowing access to more air for the motor (albeit very hot air given its position as discussed before) so that ends the debate over a cold air start or a cooler for the turbos etc...

But here's the interesting thing...before I put the valve tube back into the box I buttoned up the airbox closed the hood (bonnet for those of you across the pond) and took the car for a spin around the block....I hit 75% throttle and BAM limp mode...took the car home reinstalled snorkel and thought I would need to use my reset tool but before doing so I simply restarted the car (no limp) and took it for a hot lap and no problems....so obviously my car likes this little thing just where it is - that said Im scratching my head why my car threw an error with this minor change while others are running open element filters with no problem / oh well maybe my jbd has something to do with it but that said note that I did not touch the JBD during this whole process

So you now have my 2-cents on the matter

Just a guess, but if the actuator opens to allow more air in while under load and you closed it up, you effectively restricted the airflow, which probably triggered the limp mode. With a cone filter, the box is removed so there is no restriction at this point - granted your engine is sucking in more hot air this way; it would kind of be like leaving the actuator open all of the time.

Question: what is at the end of the snorkle? Is there a filter or is it just an open tube?

[chenry]

Originally Posted by cssnms

Just a guess, but if the actuator opens to allow more air in while under load and you closed it up, you effectively restricted the airflow, which probably triggered the limp mode. With a cone filter, the box is removed so there is no restriction at this point - granted your engine is sucking in more hot air this way; it would kind of be like leaving the actuator open all of the time.

Question: what is at the end of the snorkle? Is there a filter or is it just an open tube?

i didnt close it I removed the whole darn thing leaving a 2" (guessing) opening in the airbox (under the filter mind you - meaning no unfiltered air to the engine) - i allowed the air box to breath more / an there is nothing at the end of the snorkel its where the snorkel runs into the airbox that you will find the "valve" (for lack of a better term)

[Concentric190]

you unplugged it, that probably threw a code. I'm sure the reason it's there is for cold start ups.

[cssnms]

Originally Posted by chenry

i didnt close it I removed the whole darn thing leaving a 2" (guessing) opening in the airbox (under the filter mind you - meaning no unfiltered air to the engine) - i allowed the air box to breath more / an there is nothing at the end of the snorkel its where the snorkel runs into the airbox that you will find the "valve" (for lack of a better term)

In that case i can only guess the MAF meter was not happy with the volume and or quality (turbulant) of air it was seeing.

[chenry]

Originally Posted by Concentric190

you unplugged it, that probably threw a code. I'm sure the reason it's there is for cold start ups.

Its not plugged into anything electrical - it is simply a closed valve held closed by the pressure of a spring, its that simple- by removing the valve its simply like putting a 2" hole in the side of your air box (under the filter)

[chenry]

Originally Posted by cssnms

In that case i can only guess the MAF meter was not happy with the volume and or quality (turbulant) of air it was seeing.

yup thats the only thing that makes sense to me too

[Vreimann]

Originally Posted by chenry

What is this for - and why is it positioned so close to the exhaust/turbo (I think) / and is there any benefit in keeping it open all the time (it seems to be vacuum actuated - I may be wrong)

Ok, so a guy I work with whom use to design components for BMW through a third party German company has a different answer about the purpose for this snorkel.

What he says is that at WOT and heavy use of the accelerator, the vacuum will allow the intake to open and pull hot air from around the turbo to help draw in cooler air to keep that area under the hood from getting too hot and to provide some general cooling.

[Julesandtrish]

Interesting. Thanks.

[EPOS]

Originally Posted by Vreimann

Ok, so a guy I work with whom use to design components for BMW through a third party German company has a different answer about the purpose for this snorkel.

What he says is that at WOT and heavy use of the accelerator, the vacuum will allow the intake to open and pull hot air from around the turbo to help draw in cooler air to keep that area under the hood from getting too hot and to provide some general cooling.

Sorry, but that's just flat out wrong.

1. diesel engines have higher thermal efficiency compared to gas engines
2. has nothing to do with cooling

It is a dual stage intake, essentially there are 2 chambers to control the air velocity. I know it's hard to believe, but it is to improve torque at low RPM and help with higher RPM power as well, that's when that valve opens up and air is now being sucked in through that snorkel and into the secondary chamber, combining the 2 to make one big intake box.

Motorcycles incorporate intakes like this all the time and same goes for most race cars. The IS-F uses a dual stage intake box and I believe the NSX did as well.