in-cabin air filter

Anyone have the specs for it? Just saw a Lexus commercial bragging about their air filtration system and wondered how good BMW's system is. The auto-recirc ext odor detection sucks since I smell diesel exhaust and other various smells come in through the vents.

Is your recirculation setting on automatic? If it's not then maybe you're not hitting the recirculation button when pollutants arrise that should stay out. Also maybe your filter needs to be replaced. Personally I'm biased towards BMW, but for me, the auto button has worked just fine- and that includes driving past multiple cow farms on I-5 and diesels in the mountains.

~Jon

It is on auto mode. Not sure if replacing the filter will work since it never seem to work right from day one.

I have the same experience as BMWer. It always seems to let smells etc get past it when it is on AUTO. The Lexus has a nifty little light that comes on that shows when the auto recirc feature kicks on and off. I've never had any problems with foul smells in my fathers LS430 from outside the car. My E46 (2004) seems to take a minute for it to 'recognize' these things.

Johnny

Mine seems to take a few seconds before it seems to kick in. I don't have any experience with Lexus but I know it def makes a difference than a car w/o one.

Anyone know what the specs are for the filter? HEPA?(I doubt it, otherwise it will be all over the brochure) How many microns does it filter down to?

I always manually turn on full recirculation when driving on the NJ Turnpike through Kearny/Bayonne/Newark... if I don't, the pollution smell is like a frying pan to the face. The auto mode doesn't seem to realize it smells like burning rotten ass out there.

I haven't been impressed with the auto recirc feature, either. I just had new filters put in with my service and still get blasted with diesel exhaust if I don't manually switch out of auto.

Its far from HEPA, take a look its only held in by two or three thumb screws at the base of the windshield under the hood. Its about as high end as a 3 dollar furnace filter, better than nothing but hardly a serious filter.

Originally Posted by FalconGuy

Its far from HEPA, take a look its only held in by two or three thumb screws at the base of the windshield under the hood. Its about as high end as a 3 dollar furnace filter, better than nothing but hardly a serious filter.

I believe the filter you are describing is the intake filter for when the car is on normal (i.e. outside) air.

When recirculating there is an interior filter that is used - mine is at the top of the inside of the passenger's side footwell (E46) It's a black rectangle that can be slid downwards to be changed out.

SealBeemer, you might have a leaky seal around the aforementioned in-hood filter or maybe you've got a leaky exhaust that is getting fumes in there.

Originally Posted by SealBeemer

I haven't been impressed with the auto recirc feature, either. I just had new filters put in with my service and still get blasted with diesel exhaust if I don't manually switch out of auto.

I typically just leave it on recirculate and rarely if ever use auto-recirc. The system takes too long to detect outside 'odors' then cut off the 'fresh air intake'.

What I don't understand is, that according to the Bentley manual, the sensor for the auto-recirculation is mounted on the radiator fan shroud... wouldn't it work better if it was mounted right at the A/C air intake?

Originally Posted by BMWer

Anyone have the specs for it? Just saw a Lexus commercial bragging about their air filtration system and wondered how good BMW's system is. The auto-recirc ext odor detection sucks since I smell diesel exhaust and other various smells come in through the vents.

A friend of mine has a 2003 Lexus SUV (470) and it lets in fumes from outside the car even when recirculate is on. I don't know if this one has the air filtration system in the commercial or not but it doesn't work that great. I am somwhat sensitive to car fumes and am shopping for a new car with air quality being one of my criteria and from what I can tell BMW has very good air quality when recirculate is on. I haven't driven the Lexus in the commercial, maybe I should go test out their "great" air quality system, get behind some stinky truck and see if it works, I have my doubts. Some cars have poor air quality even when recirculate is on as they let some outside air in even when recircuulate is on and apparently don't have good filtering systems.

From what I've been told by some auto service advisors and mechanics there is some sort of federal requirement (I haven't been able to find it) to allow a certain amount of outside air into the cabin of vehicles even when recirculate is on so that the cabin oxygen does not get depleted. However if the car does not filter the outside air well this can be a problem when in traffic or when the outside air is poor for whatever reason.

I don't know if BMW just doesn't allow any outside air in when recirculate is on or if it really has a good filtering system. I suspect it may not be letting any outside air in when recirculate is on because it has the auto function that they probably think it can detect "stale" cabin air and turn on and off recirculate automatically as needed. However if auto is forced off and recirculate forced on all the time and there is no outside air coming in then replenishing the cabin oxygen can be a problem. There is also a risk of mold getting into the air system if no fresh air is ever let in so recirculate should be turned off from time to time when there's no traffic and when the car is parked. By the way there are some filters and ionzizers for cabin air that plug into a cars cigarette ligher that are being sold on the internet and other places, I'm not sure if these things work though.

Originally Posted by pjsatz

I don't know if BMW just doesn't allow any outside air in when recirculate is on or if it really has a good filtering system. I suspect it may not be letting any outside air in when recirculate is on because it has the auto function that they probably think it can detect "stale" cabin air and turn on and off recirculate automatically as needed. However if auto is forced off and recirculate forced on all the time and there is no outside air coming in then replenishing the cabin oxygen can be a problem. There is also a risk of mold getting into the air system if no fresh air is ever let in so recirculate should be turned off from time to time when there's no traffic and when the car is parked. By the way there are some filters and ionzizers for cabin air that plug into a cars cigarette ligher that are being sold on the internet and other places, I'm not sure if these things work though.

If you turn recirculation on in the E46, it will cycle the system and let in fresh air every 15 minutes. If it is in auto mode, fresh air will be let in unless the system detects bad air and turn on recirculation. As for the Lexus, was the air directed at the windshield? Most new cars will automatically turn off recirculation in this situation to reduce the likelihood of fogging.

Originally Posted by Dirtboy

What I don't understand is, that according to the Bentley manual, the sensor for the auto-recirculation is mounted on the radiator fan shroud... wouldn't it work better if it was mounted right at the A/C air intake?

Logic would dictate that if the sensor is located further away from the intake, it would give it just that much more time to detect the 'odor' then have the system do its thing.

Originally Posted by AG

If you turn recirculation on in the E46, it will cycle the system and let in fresh air every 15 minutes. If it is in auto mode, fresh air will be let in unless the system detects bad air and turn on recirculation. As for the Lexus, was the air directed at the windshield? Most new cars will automatically turn off recirculation in this situation to reduce the likelihood of fogging.

The air on the Lexus was directed at the passengers, with recirculate on and the auto function off.