[TDIwyse]

Not sure if anyone else has put a filter minder on their 335d airbox, but I wanted to do this after seeing DWR's pressure drop readings and also after reading this great analysis of air filter restriction affects on mpg's and power for a Cummins, TDI and the 335d.

https://www.fueleconomy.gov/feg/pdfs..._AirFilter.pdf

There's many ways one could tackle this, but here's what I did.

Bought this filter minder as it appeared to have a range that should work for this application (based on the pdf and DWR's measurements): http://www.amazon.com/gp/product/B00...ilpage_o04_s00

Also got a couple 1/8 NPT adapters and drilled/taped the airbox as shown. Got it installed this afternoon and then did a test run tonight.

I'm completely saturating the MAF sensor and it pegs at 44.09 lb/min using Torque and DWR's custom 335 PIDs. This relatively new filter pulls a vacuum of 20 inh2o, or 5 kPa (units used in the pdf), or 0.72 psi. That's more pressure drop than I was hoping for.

Couple weeks ago I did some water column testing on the stock airbox and the AEM cone filter I had been using the past couple years, using the shop vac to create the airflow. The AEM cone filter produced a lower vacuum measurement than the OEM setup, however, it messes up the MAF reading due to changing the air flow pattern across the MAF (this is a common problem others have discovered as well). From my measurements the reported airflow with the AEM is about 13-14% lower than with the OEM airbox. Multiple used oil analysis showed the AEM dryflow filter doing a good job of filtering, but I didn't like the MAF reading issue. However, after seeing the magnitude of the pressure drop with the OEM setup I'm considering going back to the AEM...

[Gearhead51]

Wow. I had no idea it was pulling that hard on the filter.

[brando1985]

Tdiwyse-

Very interesting! Thanks for all you do for this community. Would you mind snapping a few pictures of your AEM filter setup and/or providing part numbers? I've been considering the addition of a cone filter, and would entertain using what you've used in the past so I know it works properly.

Thanks,
Brandon

[Mik325tds]

Indeed, very interesting. I didn't know that those filter minders even existed. I just installed a new K&N air filter and saved my old paper air filter. Would be interesting to get comparison measurements.

On a side note - I went to Grattan raceway the other day and was rolling coal quite a bit on the long straight (with the new air filter). Looking at Torque, the air/fuel ratio dropped to low 14 during full fueling. I'm now wondering if it was insufficient airflow on the intake, an aging MAF or the SCR restricting airflow in the exhaust that caused the more than expected smoke. I'm running Jarek's state 1 tune with Jess' downpipe.

[Thecastle]

I'd be interested in seeing if there is any performance gain by swapping filters, I'm generally skeptical on these.

Though I suspect that a lower pressure drop filter will allow the turbos to operate more in their efficiency range pumping less heat into the intake, which has its benefits... Rather than any substantial increase in air flow, since the turbos are making requested flow correct? Probably would need a tune that can adapt to more flow, or request more flow.

I'd be interested to see if this would make any measurable gains.... Damn I want a bigger turbo for these cars.

My last experience I had a carbon fiber cold air intake for my MK6 GTI with both a K04 and 2867GTX turbo, and other than more noise and sound of cooing pigeons when I'd let of the gas they didn't make much difference, expect a little more flow at peak HP.

[TDIwyse]

Originally Posted by Thecastle

I'd be interested in seeing if there is any performance gain by swapping filters, I'm generally skeptical on these.

Though I suspect that a lower pressure drop filter will allow the turbos to operate more in their efficiency range pumping less heat into the intake, which has its benefits... Rather than any substantial increase in air flow, since the turbos are making requested flow correct? Probably would need a tune that can adapt to more flow, or request more flow.

I'd be interested to see if this would make any measurable gains.... Damn I want a bigger turbo for these cars.

My last experience I had a carbon fiber cold air intake for my MK6 GTI with both a K04 and 2867GTX turbo, and other than more noise and sound of cooing pigeons when I'd let of the gas they didn't make much difference, expect a little more flow at peak HP.

I agree on being skeptical. Most impartial comparisons I've seen/read show the aftermarket filters can reduce power. This kind of made sense to me after seeing what it did to my MAF readings (if fueling is based on MAF, then a lower MAF reading would correspond to lower fuel injection and confusing AFR values....).

The SAE paper I linked in the first post did power/acceleration comparisons of 3 levels of filter restriction on the TDI and 335d. Both cars showed decreasing performance with restriction. The BMW lost ~2% with a "clogged" filter and 6.7% with a "severely clogged" filter. And this was on a stock vehicle...

[TDIwyse]

Originally Posted by Mik325tds

... Looking at Torque, the air/fuel ratio dropped to low 14 during full fueling...

Below ~15:1 is where I start to see some smoke on this platform, so that seems to align with what you're seeing.

[TDIwyse]

So this might be interesting for some of you who are sucking in A LOT of air...

I didn't like how much pressure drop was occurring in the intake pre-turbo. After looking at an older air filter and the way the intake box is configured, it was obvious the entire filter surface is not being utilized. There's a section of the box that's isolated from the main intake path. This appears to be some type of "safety" area, where if the main path becomes restricted this back section will open up a small pressure relief path and suck in hot air from the turbo area, and perhaps the MAF intake temp reading would change enough that the DDE could tell there's a need to change the filter? This is just on a guess on my part...

However, it's obvious that there's a lot of surface area not being used. See attached for the visual of the loading of the surface.

So I cut out that portion of the OEM box and did some pressure drop testing. Sure enough, there was a slight improvement in the max vacuum pulled in the intake box (dropped from ~20 inHg in post #1 to just under ~18 inHg in the attached pic below the filter loading example). Based on the increased filter surface area, I was expecting a bit more drop.

Then I hypothesized the restriction might actually be from the OEM "cold air" path. So I thought I'd cut some extra openings into the bottom of the air box to test that. First, however, I did some measurements of air temps in the area behind the passenger headlight in front of air box where I was thinking of cutting. It was just a couple degrees above ambient. So I went ahead and cut openings in the box bottom.

This morning I went out and did a full fueling pull and ... the filter minder didn't budge at all (see bottom filter minder pic).

[Gearhead51]

Thanks, TDI.

I want to send you a $20 or a case of suds of your choice for doing the hard research and taking a saw to parts of your car so we don't have to.

[shnaggs]

Great find TDI! I'm overly impressed at your constant tinkering and data logging. Keep up the good work!

[Poosik]

TDI- thanks for another insightful post.

How large are the holes you created? Mind sharing a pic?

Aside from creating a low vacum state, are there a quantifiable improvements in fuel consuption/power??

[TDIwyse]

Happy to help guys. As far as online communities go, this is a good one with lots of helpful people sharing ideas and experiences and data.

Originally Posted by Poosik

...
How large are the holes you created? Mind sharing a pic?

Aside from creating a low vacum state, are there a quantifiable improvements in fuel consuption/power??

I'm embarrassed to say I didn't take pictures... had a short window of opportunity to fit this in and was in a bit of a rush.

I did find a useful picture to work with, however. It's from FormerRotor in this thread: http://www.e90post.com/forums/showthread.php?t=797822

I copied his picture and added some comments and approximate places where the cuts were made. This is not necessarily the best way to do it, but it seems to have produced good results on reducing pressure drop before the turbo intake. I'd estimate this modification easily more than doubles the air intake area.

If you do this, make sure you don't cut too high on what's labeled as "Cut 2", as you don't want to bypass the filter (due to the picture angle, the vertical length on Cut 2 doesn't appear as big as it actually is, and due to the shape of the box the cut down by the OEM air entrance is longer than the cut on the left side).

From the data provided in the SAE pdf in the first post, you won't see any mpg benefit from this. Depending on how hard one is pushing their turbo, you may see a hp benefit. I have not quantified that yet. However, if you take away pressure drop before the turbo intake, then for the same turbo pressure ratio you'll gain more psi at the compressor output. Which "can" give you more power. And is exactly what the SAE paper showed for a clean versus "clogged" air filter performance in the stock 335d example.

[DWR]

Now, if you can plumb back up to the front end and have sufficient flow area, you'll get a small ram air effect. The stock system does this well at highway speeds and low load. With your 1/4 mile trap speed that would be ~ 2% increase.

[DWR]

Originally Posted by TDIwyse

... if you take away pressure drop before the turbo intake, then for the same turbo pressure ratio you'll gain more psi at the compressor output. Which "can" give you more power.

According to BorgWarner MatchBot, this mod would gain you about 2.25 psi boost in your rig. Add in 0.25 psi at the compressor inlet, if you can get back the ram air effect. Whopping total of 3.1 psi gain in boost, for the same turbine shaft work, compressor outlet temperature, pressure ratio, etc. If you can add the fuel, that's worth over 25Hp at the top end. If not, it is still worth something because of the improved AFR.

Getting into hybrid turbo territory. Now, if you want to talk about wet compression, maybe trade off some pumping work for more margin on the compressor choke line.

[TDIwyse]

Originally Posted by DWR

According to BorgWarner MatchBot, this mod would gain you about 2.25 psi boost in your rig. Add in 0.25 psi at the compressor inlet, if you can get back the ram air effect. Whopping total of 3.1 psi gain in boost, for the same turbine shaft work, compressor outlet temperature, pressure ratio, etc. If you can add the fuel, that's worth over 25Hp at the top end. If not, it is still worth something because of the improved AFR.

Getting into hybrid turbo territory. Now, if you want to talk about wet compression, maybe trade off some pumping work for more margin on the compressor choke line.

Something like this STI mod? I had wondered why there were some cars with removed headlights at the dragstrip. It makes sense now. Although wouldn't want that on my daily driver...

Haven't had the chance to do any good logs on this new mod, except the quick 3rd gear uphill test that showed no movement on the filter minder. That log looked promising, but I really need a 4th gear pull to tell.

The wet compression is something that does interest me. And it's something that could be used in a daily driven car. We've talked a little about this in the past, and I appreciated the thoughts and insights you shared. I also like this idea more than NOS because it's something that can be used on a daily driver configured car that has more than "seconds" of additional output. But that's just a personal hangup I have ...

[Gearhead51]

In the RX7 world, there are people that run h2o nozzles pre turbo to make the turbo act larger. http://www.riceracing.com.au/water-injection.htm
From what I recall, his systems are super simple using an air cap similar to an hvlp paint gun to atomize the water directly in front of the compressor. The air pressure to siphon the water and for atomization comes from the intercooler piping. The most obvious concern pre turbo is compressor wheel erosion, but I don't know that it has ever been proven. In that world turbos meet their demise due to poor or no filtration etc. in pursuit of 600+ hp from 80 cu in.

[TDIwyse]

Originally Posted by DWR

... if you can get back the ram air effect. ...

Maybe something like this? His thread has some good pics in there...

http://www.e90post.com/forums/showthread.php?t=183780

[TDIwyse]

Well, I opened it up again to look around for easy ways to bring in a connection that allow some "ram air" affects for the alternate openings. As with nearly all things in the engine bay, it looks tight. It might almost be easier to route something around the back of the box and come in through the area where the spring loaded secondary input is...

Took some pics of the OEM intake and the places that appear to be the smallest area. This seems to be the snorkel entry into the box and perhaps the "pass through" above the radiator.

Also took some pics of the cuts I made in my airbox. Although their kind of dark and may not be easy to see...

[Poosik]

Nice. I'm wondering if the "ram air" effect will be negated by the filter acting as a dam. Also, since you have already reached a "0" vacuum state with the air box holes are we assuming a "positive" pre turbo pressure is beneficial?

[TDIwyse]

Originally Posted by Poosik

Nice. I'm wondering if the "ram air" effect will be negated by the filter acting as a dam. Also, since you have already reached a "0" vacuum state with the air box holes are we assuming a "positive" pre turbo pressure is beneficial?

Well, I don't have enough resolution to say it's at a 0 vacuum (the gauge is on the clean side of the airbox, not in the area where the holes are). The filter minders lowest reading is ~12 inh2o. So it's somewhere lower than 12 inh2o. I may order another filter minder with a lower range now that I've got the losses reduced.

A positive pressure pre-turbo would help, per DWR's explanation above. It would have a compounding affect.

[Chief Orman]

Originally Posted by Poosik

Nice. I'm wondering if the "ram air" effect will be negated by the filter acting as a dam. Also, since you have already reached a "0" vacuum state with the air box holes are we assuming a "positive" pre turbo pressure is beneficial?

Over the past couple of years I have also noticed the weird filter/dirt pattern in the airbox. However I have noticed a variety of aftermarket airbox replacements. Has anyone out there used one of these? I personally am not a fan of K&N filters given the amount of mist/soot thrown off by our engines.

[Poosik]

I see thanks. Really looking forward to read your interpretation of baseline log runs (pre air box cut outs) vs. current airbox configuration.