Second air filter in air filter box

[schwalmy]

Hey guys
i remember a while back there was a post re the second air filter in the air box (white one) if i remember it was used to help trad esacping gas vapous?
what were the thoughs on it being taken out ?
is it even worth thinking about?
any one have problems or gains from it
thanx
schwalmy

 

[greasefingers]

In order to meet higher emission standards, a second black carbon filter is installed in the air-box. After you shut the engine off, any vapors in the intake manifold travel backwards towards the inlet of the air-box and get absorbed by the carbon. Then when you start the engine they get desorbed and burnt.

 

[jeober]

Thanks grease, I've wondered about this...

Has anyone had a problem with restriction over time with this? I'm guessing that this part would be covered by an emissions warranty - 100,000 mile??

I wonder what the pressure drop is across this element at max HP?

 

[duck95]

I hope it doesn't make you fail emisssions! I took mine out, and it doesn't unbolt or anything like that, so in other words I snapped it out. But, it is highly restricitive for air flow. I can feel the power just by removing it! Maybe.....

 

[greasefingers]

I have a scanner that graphs sensors on my Laptop. I will do some tests with and without the carbon filter and measure the MAF. My first guess is that it does not restrict the air flow. This was the case for the paper air filter.

 

[duck95]

I've got say that it does. Mine is off an '06 V6. If you blow through it, barely feel any air pressure. That plus the 1st air filter is creating twice resistance of air flow. Just my observation.

 

[jeober]

As stated the activated carbon adsorbs unburned [evaporative] hydrocarbons from the intake system. This is different than tailpipe emissions. Toyota certifies to an EPA evaporative emission standard by using a sealed housing [known as a SHED test] around the complete vehicle under going diurnal temperature cycles. All the hydrocarbons coming off the vehicle are measured.

Removing this filter may slightly increase evap emissions -- of course neither legal nor green but in the grand scheme of vehicle emissions a relatively minor event with no other downside.

Grease, you mention a MAF [mass air flow] sensor. Can you also access a MAP [manifold absolute pressure] sensor? Absolute pressure at WOT might be a better measurement changing as a restriction drop across the intake system [vs. flow is ideal if you can get both sets of data together and x y plot].

 

[greasefingers]

I am having problems with the software that ProScan provided me with. I can plot real-time graphs. The problem is storing the data. It does not store the values correctly for exporting to Excel.

I can tell you that the stock paper element offers zero resistance at idle speed. This is measured in grams/second.

At 706 rpms and a engine coolant temperature at 187 C

 

[greasefingers]

Monitoring sensors and using higher tech trouble-shouting tools is something that I am very interested in. If anyone has the same passion, then please share some of your experiences or comments.

On my Triumph TR6 & my MGB I use to use a match-book cover to set the point gap
:cheers:

 

[Kmvreter]

I did not realize that the T4R has a manifold absolute pressure sensor. I will look for this. I thought that vehicles with a MAF did not need a MAP sensor?

The one thing that showed much improvement was cleaning the MAF. I measured a 9 % decrease in flow after cleaning the MAF. This indicates that the MAF gets thermally insulated with hydrocarbon residue. Due to this I am now cleaning the MAF every 30 k miles. All it takes is the removal of two screws and some aerosol spray injector cleaner.

Nothing in the wiring diagrams about a MAP, just a MAF.

Can you elaborate on the MAF cleaning? I didn't realize this could be a maintenance item. Does a more accurate flow lead to better mileage or performance? I could find it and remove it but I don't want to screw it up by using the wrong thing to clean it. Can you be more specific on the cleaning? Is it obvious by looking at the part? Pics would help.
Thanks in advance.

 

[jeober]

grease:

you may be right about the MAP. I looked for the service part and couldn't find it. I saw a sensor in the manifold having removed the top cover on the v-6 and thought it was a pressure sensor.

Aiir flow at idle is very low. So there won't be air induction pressure drops except of course across the throttle plate. Also if you restricted air flow at idle, the idle air control, which is now apart of the ETC [electronic throttle control], would just open up to compensate and maintain idle rpm. You could drop a hell of lot of pressure across your restriction and the engine control would trade the pressure drop from throttle plate to your restriction at idle.

You'll need to measure at WOT. Hopefully the ETC will give you WOT when you are at WOT - there's no guarantee of this anymore!

 

[greasefingers]

Yes I plan to do more useful testing of this. I just need to find the time!

I use a product called Electrical Cleaner from a company called CRC. 4x4-wire talks about cleaning the MAF. It is an important sensor that is part of the air-to-ratio calculation. Many times, when you see your fuel mileage drop, the oxygen sensor and MAF are the culprits. The link below describes who to clean the MAF sensor. I got this from 4x4-Wire in the Toyota Section

http://www.4x4wire.com/toyota/maintenance/tacoma_4runner_30k/maintenancep5.html

 

[Kmvreter]

Yes I plan to do more useful testing of this. I just need to find the time!

I use a product called Electrical Cleaner from a company called CRC. 4x4-wire talks about cleaning the MAF. It is an important sensor that is part of the air-to-ratio calculation. Many times, when you see your fuel mileage drop, the oxygen sensor and MAF are the culprits. The link below describes who to clean the MAF sensor. I got this from 4x4-Wire in the Toyota Section

http://www.4x4wire.com/toyota/maintenance/tacoma_4runner_30k/maintenancep5.html

Thanks for the info and link. Nice simple addition to the maintenance schedule.