Snorkel Pre-Cleaner Efficiency and Restriction Data

You are welcome! It’s hard when most info out there is objective. Mine is a bit objective as well though.

Good thought! The ARB inlet just makes it easier to fit snorkel heads without adapters. But the actual size of the snorkel is larger in volume. So between the intake size and volume chamber it is bigger compared to the Dobinsons. It actually sticks out from the fender further. Just don’t have measurements to say how much more though. Also the template for the ARB is spot on. While the Dobinsons I had to re-do the holes on the template. I also think the ARB has slightly better fit and finish. Performance wise I don’t see it being a massive difference though.

Hope that helps clear up some of your thoughts as well!

 

Yes a little! That “build quality” and “fit & finish” plus the hole alignment is somethings I’ve heard before. And a bit disconcerting. But…considering you can buy almost two Dobinson’s for the price of one ARB.

 

You hit my dilemma right on the head haha If money is tight a Dobinsons will get the job done well and they are still a reputable company.

 

I got an update from USPS and the delivery will be a day early. So tonight I cleaned up the air box and sealed up the last drain hole I had open. The photos below are after two months with the open ram head. I was actually quite surprised how clean the air box was. Those two months were about 2,000 miles of driving.

 

Here is the after photo. All before and after photos were taken on October 13, 2025. Air filter is still fine so I will be keeping that as is until the filter minder says different. Also forgot to attach mileage of cleaning, 141,787.

 

I received and Installed the filter minder. It did not come with the grommet so I had to get one separately. I removed the downstream (top) half of the air box completely before drilling, to facilitate making sure no bits of plastic were left inside.

 

Woah! It does say TRD!! Also nice clean install!

 

Thanks. I just copied yours.

 

Okay Sy-Klone 9001 has been fitted to the Dobinsons snorkel! Date: October 14th,2025 Miles: 141,805

Came with a rubber adapter to get it from a 4” to a 3.5” inlet. Then I tried using their tape that was sent to fill in the extra space. It was too soft and didn’t give me confidence. So I had some 3M body tape laying around that is a little more dense. Now it holds much better. Also it doesn’t sit all the way down since my a-pillar is in the way. I thought I would have clearance but I was wrong. Still fits on the snorkel inlet enough to get proper grip on the snorkel. Also make sure the ejection port is at the 8 o’clock position so it helps with the ejection efficiency. Creates a Venturi at the opening and helps pull debris out due to the pressure difference between the fast moving (low pressure) air and slower moving (high pressure) air.

Did a test drive and throttle response seems the same. Also did a highway on ramp run to get it up to about 4,300 rpm under some load. The filter minder ended up showing 8 Inches of H2O restriction. Not surprised since they did say it would be 5.88 Inches of H2O restriction at 275 CFM. My chart says at about 4,300 RPM I would pull 270-290 CFM. So I reset it and did some normal driving and it didn’t trigger the filter minder. So far very impressed with the build quality. Now excited for the long term study and fuel economy.

 

This system looks serious, sir! Well done.

 

I wasn’t expecting it to be that serious looking in person. But it is! Thank you!

 

I added a Filter Minder to my wife’s 2022 Subaru Outback Wilderness (2.4L Turbo). Did a highway on ramp run and got it up to 4,500 RPM. Air filter was changed about 5,000 miles ago. Pulled 11 Inches of H2O of restriction. So cool to see how two different engines perform and what a baseline should be for each vehicle.

 

In the previous pictures you probably saw how close I put the pre-cleaner to the a-pillar. Well I learned today that it thermally expands quite a bit. I had about an 1/8” gap at ambient (60°F) and then when in the sun I measured the pre-cleaner temp. It was at 137°F when ambient outside was 71°F. So I had to move the pre-cleaner up to get about a 3/8”-1/2” gap. Now we are all good! So keep that in mind when installing the 9001!

 

I pulled the tape off since I didn’t like the tape job I did originally. Also I put never seize on the threads of the clamp since stainless on stainless galls extremely easily. I drew up a template and cut out the 3M VHB. Wrapped it around the top of the snorkel and then pealed up one corner. Cleaned up the reducer and slipped it on so it was pretty flush. Ensure the backing you peeled off is accessible after sliding the reducer on. Then pull the red backing off and grip the reducer to help adhere the pieces together. I then reinstalled the 9001 and clocked the ejection port to 8 o’clock again. Now we are good to go and I can sleep at night knowing my tape job is better. Even though no one will see it haha.

 

Any flow/ restriction data for the TJM snorkel? Been on the fence about it for a long time honestly.



I like how low profile this particular snorkel is compared to the Dobinsons or ARB option

 

I do not have any data on that snorkel unfortunately. But I must agree it is a great looking snorkel!

 

https://youtu.be/0flEIBOTYrE?si=-xDiKpHShoiF4MFN

A great video that just came out a few days ago! Wanted to share this here because it is along the lines of what we have been talking about.

 

Compiling some data that I posted on here a while ago on another post. It is about the engine air filters and the two different styles you can get from Toyota. I also reached out to Denso to see what their ISO 5011 test results are. Napa has that information posted for their two filters, Napa Gold (FIL9350) 99% and Napa PROFORMER (SFI 29350) 98%. So if you went with a Napa Gold, which is cheaper, it actually has better filtration haha.

Okay, I got a reply from Denso...They unfortunately cannot publish their efficiency data and I spoke with their senior technical product support. So I said, since you cannot give me the exact data how does the OEM Denso filter perform compared to aftermarket filters? He said he would run the 17801-38051 because it is better than others on the market. I even received what sounded like a side remark that it is better to get the Toyota Denso than the regular Denso.

---Bumping this thread and created an account finally. Called three local dealers here in Denver. Two of them do not sell the

$29 Genuine Toyota - FJ CRUISER AIR FILTER NEW - 17801-38051

17801-38051 and will only sell the 17801-YZZ13. Luckily the third one either had back stock or still gets them in. Parts guy said, “You can get any part in the YZZ budget but we can also source true factory parts.” So that was reassuring that Toyota still has them out there. Just have to find a place that does that. I picked up 2 today just in case they do not stock in the future. Also to note the YZZ13 is $1 cheaper haha.

Since I had a YZZ13 in my air box I figured I would do some measuring to figure out if more pleats = more surface area. While doing this I was surprised and what else I found.

17801-YZZ13: USA Denso
- pleats: 131
- pleat dimensions: w- 8.6563” h- 1.0938”
- Filter surface area formula (SA=(w*h)*(pleats*2)) pleat count is each tip. Air is sucked through both faces of pleat hence why pleat number is multiplied by 2.
- Filter surface area: 2,480.557 in^2

Things I noticed about this filter are:
- gasket has a lot of porosity and seems to be a softer durometer.
- very flexible filter (torsional rigidity)
- air box clips, clip on loosely
- Gasket thickness (0.427”)
- Filter media seems to be the same as OEM Factory filter. No way for me to actually test it.


17801-38051: Japan Denso Factory Filter
- pleats: 107
- pleat dimensions: w- 8.6563” h- 1.875”
- Filter surface area formula (SA=(w*h)*(pleats*2)) pleat count is each tip. Air is sucked through both faces of pleat hence why pleat number is multiplied by 2.
- Filter surface area: 3,473.320 in^2

Things I noticed about this filter are:
- gasket has no porosity and is very smooth. Also seems to be a harder durometer.
- very stiff filter (torsional rigidity)
- air box clips, clip on very tight
- Gasket thickness (0.427”)
- Filter media seems to be the same as OEM USA filter. No way for me to actually test it.

 

Griz-

I’ve thoroughly enjoyed this thread. Thanks again for all your efforts in this! The Dobinson snorkel priority is inching up the list of things to do!

 

You are quite welcome! Whenever you do get the snorkel and have any snags on installation just hit me up on here.

 

Today Mother Nature did not disappoint. It was extremely windy out here in Denver. Which kicked up a lot of dust, but that wasn’t all. It was whipping the tall grasses so much the fuzzy seeds were flying through the air and I was driving through sheets of that. Well here is the air box! Some sand in the bottom and I saw one seed make its way into the filter element. Also saw a few of those seeds fling out of the ejection port. For driving through a wall of this crap today I’m pretty impressed, especially with wind speeds up to the upper 40 MPH. Driving both into and against the wind.

 

Thanks Griz. I’ve been researching for a few and finally put an offer on a generic Dobinson. I’ll keep you posted.

 

Hey Griz,

I’m just double checking as I couldn’t see it in your photo, but did you plug your airbox holes when you installed the snorkel? Kind of going down a rabbit hole with “do/don’t on the Internet.

And if you did, do you think the after market filter minder could present an issue with water intrusion?

Wanted to get another opinion, before the project begins.

-Trail Safe

 

So when I had just the ram head on my snorkel I plugged the upper hole that is on the front of the airbox. I did keep the bottom hole open at that time.

After I installed the Sy-Klone I did plug the bottom hole, so now both holes have been plugged. I used silicone because if I need to drain it, which I hope is never the case, I can just poke the hole and let it drain out. Not imagining any moisture will get past this pre-filter that will cause the airbox to get flooded.

The Filter Minder has two ribs that press out very hard on the rubber grommet and acts like a labyrinth seal. I have not tested it personally but having it on the upper lid on the back side it should be pretty well protected from water. If I have water up that high I would be very concerned about a lot of other things haha. But again I have not tested how well it seals, I did take it apart the other day to see if dust made it to the second rib and there was not dust present there or even on the first rib. Here is a screen shot of what the ribs look like. Just make sure you drill the hole to the correct size in their instructions so it puts the correct load on the grommet and filter minder ribs.

 

Excellent. And YES, if water has reached the hood…

Thank you.

 

So I went off roading last weekend on a dusty trail. Buddy was up front and sent plenty of dust my way. When I got back home I wanted to see how well the pre-cleaner worked and if there was any dusting on the clean side of the air filter. To my surprise I did find some dust on the clean side of the filter and some dust on the MAF. The air box on the dirty side looked great for how much dust we were driving through so the pre-cleaner definitely did its job. The dust on the clean side of the filter was from a tiny corner that didn’t seal well. So I purchased some K&N air filter sealing grease (doesn’t contain any silicon). Testing it out now to see how it holds up and will report back on Saturday if it dries up after 5 days or if it is still grease like. Below are the pictures of what I found and after cleaning the MAF.

 

Say Griz,

Nice update. I am about to install my snorkel this weekend. I’m not going to get the pre-cleaner just yet. Did you ever try/test a snorkel sock? That’s the route. I’m probably going initially before spending money on a pre-cleaner.

Trail safe!

 

Nice!!

I did run a snorkel sock. Since I’m a dork I custom made them out of bulk Black Uni Filter Foam. Price came out a tad cheaper than ordering pre made ones. I sprayed them with PJ1 Foam Filter Oil. Did a few tests with this filter including dusty trails. Big stuff didn’t get in which was nice. But still a decent amount of dust went through. Less dust than if it was not on there though!

 

Done.

Wasn’t too bad. Measured about 100x and still had to drill a couple of holes bigger and back the bolts out a bit on others. Fit is good. I used the supplied gasket so it’s not flush to the rig. All in all… I’m satisfied. Now for all the nerd airflow data to begin!

Sidebar- accidentally fired up rig with MAF sensor unplugged… threw a few codes I cleared up with my diagnostic tool. But apparently they are still in there…

 

Wow! Nice work! Looks absolutely great!