Cowl induction snorkel

I know there is another thread here: https://www.tacomaworld.com/threads/different-approach-to-a-snorkel.266449/ . Thanks to all who contributed!

I've made a few refinements to this, so I thought I'd start a new thread. That way it doesn't get lost in 15 pages.

First, here are the parts I used:

https://www.ebay.com/itm/Black-76-102-mm-90-Degree-Reducer-3-To-4-Silicone-Hose-Pipe-Coupler-Turbo/263148614826?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

https://www.ebay.com/itm/1pc-108mm-116mm-Stainless-Steel-T-Bolt-Clamp-for-ID-4-inch-102mm-Silicone-Hose/131825291718?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

https://www.ebay.com/itm/1pc-83mm-91mm-Stainless-Steel-T-Bolt-Clamp-for-ID-3-inch-76mm-Silicone-Hose/131825295753?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

https://www.ebay.com/itm/3-OD-X-063-X-12-ALUMINUM-ROUND-TUBE-6061-T6-BEST-PRICE-BEST-RATED-SELLER/201570212167?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

Special tools required: You will need a 3-1/4" bimetal hole saw, and either 2" or 2-1/4 bimetal hole saw. Get these before you start. Everything else is just common hand tools.

When I evaluated the feasibility of doing this mod, several things became apparent. First, the cowling itself is plenty large enough to move sufficient air for both the HVAC system and the snorkel, but the inlets into the cowling are questionable. There is a top vent on the drivers side, and there are two openings from the cowl into the fender wells on each side. If all of these openings are unobstructed, then there may be enough area to meet demand, but what about when that top vent is covered in snow? The places where air gets into the cowling on the sides are not large enough to flow that much air. The 4.0 flows roughly 72 CFM for every 1000 RPM. I haven't corrected for volumetric efficiency in that calculation, but for our purposes, that is close enough. At 3000 rpm, that would be 216 CFM, 288 CFM at 4,000 rpm, and 360 CFM at 5,000 RPM. At redline of 5500, it hits 396 CFM! That is one hell of a shop vac pulling through the cowl. Then add in whatever the fresh air system is demanding. That is a LOT of air trying to find it's way through the relatively small openings into the cowling area. The cowling system was only designed to handle the relatively low flow of the HVAC system. There have been many references to issues with decreased flow through the HVAC after this mod. I believe it is caused by the engine pulling vacuum on the cowl and actually pulling air from the cab of the truck.

My fix for this is shown here:


This is a picture of the end of the cowling on the passenger side. The 2.25" round hole is one that I cut. I put one on the drivers side too, and it almost doubles the supply area into the cowl. I covered both ends in screen because rodents will get in here! They can get into your HVAC system if not covered, and they can get into your new intake tube. With these holes added, there is no issue with air supply.

Some people who have done this opted to use a 4" tube into the cowl, but I chose 3" instead. There are two reasons for this. First, a 3" tube can supply all the air flow needed for the 4.0L. The design of this system is very laminar. One tip here: only push the aluminum tube into the silicone elbow about an inch. This will give the smoothest air transmission through the system and prevent eddies at the aluminum to silicone transition. Secondly, it is important that the tube enter the cowl as high as possible, so that the gutter beneath the intake tube is large enough to channel water away in the event that the cowl becomes flooded. If the tube is 4", or cut lower into the cowl, the likelihood of water getting into the intake is greatly increased. Here is a pic showing the placement of my intake hole:

You can see that the gutter under the hole is preserved. The tube comes in at the same level as the HVAC intake. The HVAC is also elevated for the same reason. Here is a pic from the engine side with the cables relocated below hole:

Here is the tube installed. I cut the tube at an angle to provide as much shielding as possible to water splashing underneath, without restricting air flow into the tube. I also have an aluminum shield separating the engine intake from the HVAC intake. The aluminum is covered by an insulating layer to lessen sound transmission into the cab through the HVAC opening:



The finished system. The intake tube is also insulated to prevent the cold air from being warmed by the intake tube.


I have found that this system does a great job of protecting the intake from water, if you don't want a full external snorkel. Water washing over the hood has no effect, and is easily channeled away. There is no worry that water surging into the wheel well will drown you. With the added inlet holes cut, and the shielding over the HVAC, air flow into the cab is completely normal.
The sound level is interesting. At cruise and lower engine demand, I cannot tell any difference at all. At WOT, there is a low but distinct intake sound, that I really like!
The mod opens up a ton of room under the hood for any number of items.

I never felt I needed a full snorkel, and I didn't want the air restriction. Aside from that, a snorkel is just begging to get torn off in the woods. This mod does not provide the same water protection, but is way better than stock. Short of a full submersion, I feel pretty secure. I have also noticed that my intake air temp is a couple of degrees cooler. Not enough to care about, but at least moved in a positive direction.

Hope this sheds some light on this mod for anyone interested.

 

Very cool, but wouldn’t you want the angled tube to be 180 degrees the other way to prevent water ?

 

No, because the top of the cowl is completely covered. The only threat of water is from below if water is forced in and sloshing side to side. Bear in mind that this mod will not work for water levels above the hood! It can handle a ton of water washing over the hood, as often happens during a water crossing. This mod is for moderate water levels that are too deep for stock intakes, but not a full snorkel crossing. I don't want to giv a depth number because there are many variables.

 

Nice take on it, I like this version

Gotta ask... is that a tea/coffee dipper hanging off your ABS mod?

 

My intake works great. No issues at all, and even when the cowl is totally plugged with snow, I get plenty of airflow. Yes, the tea ball was to hold moth balls to keep rats out. Now I have sonic deterrents, so I don't have to deal with the odor.

The additional holes that I opened up at the ends of the cowl help evacuate water quickly, in the event the cowl gets gets flooded by a surge of water over the hood. This is important! There have been reports of some people getting a little water in the intake with this mod. It is because they came into the cowl too low and didn't open these holes. Done right, this mod is an awesome stealth snorkel.

One more comment. I have steered away from traditional snorkels partly because I wouldn't be on the trail 30 minutes before the cap would be torn off. That hood would catch everything.

 

I like this a lot. Thinking about putting glass fenders on my truck. If I do, I’m ditching the snorkel and doing this.

I wonder if there’s enough air flow for the Supercharger with 2.55” pulley with the added holes in the sides.

 

Yes, the holes provide more than enough airflow. I'm considering a supercharger myself. I've got a lot of trail time on this mod and still no issues.

 

For anyone looking to do this. Amazon got the 90angle pipe for $7.51 and free shipping!

 

I have stolen this idea from the previous and now in the process of slight modifications given the lack of space on Sport TRD with the ABS lines and offset of the S/C intake ever so slightly. I am chasing down one last vibrations, but it is extremely tight at the 90 degree into the air filter. I stayed 4" across the board, but will have to drop down to 3" now. More to follow with pics. All similar Amazon parts being utilized.

 

Will this pass California?

 

Project complete!

 

finished mine a little while back

If i have water rushing over my hood into my cowl, wiper area.....I got waaaay more problems than a real norkel will take care of......

 

While you're in there why not use the AC to cool the intake air.

 

sub for future reference. going to be cutting up my fenders for 34/35s and will have to loose my fender liners. Not sure if i want a snorkel and like this option.

@bagleboy per your comment above, how so?

 

By mounting an AC evaporator in the wheel well inside a chamber and passing snorkeled air through it. Would need a chamber large enough to space the fins generously and avoid restricting air flow but the space is big enough for it.

 

It’ll fail visual for smog. Save the stock intake for when you need a smog check.

 

Right on. Do you happen to have links for the reflective, insulating materials used for the pipe and air damn?

 

@ovrlndkull

 

This will pass smog no problem. This used the stock intake box

 

nope

100%

been there, done that