Fender air box feed

[importfighter01]

Hi 5gers! About 2 mos ago I decided to setup a second air feed for the factory airbox. I have my reasons for doing so, but I have no dyno numbers (data) regarding this mod so no reason to extrapolate as I know I will be challenged on “Your reasons and research suck, etc”. Thus this thread is simply to show the final product and what’s possible vs debate the mod.

All that being said I will provide my qualitative review that I noticed an immediate difference in throttle response and accompanying spool as well as top end pull at WOT. Again not making claims, just sharing my observations. Onto pics and descriptions...

I used this velocity stack on the inside of the fender:

https://www.summitracing.com/parts/...qz6i0bxkV6_tSr76S1XLz_Y6fJaCgHIxoCzdcQAvD_BwE

Installing it was accomplished by partially detaching the fender liner after drilling a 3in hole in the sheet metal separating the engine bay from the fender airspace using this:

https://www.homedepot.com/p/Milwauk...5MhSKJwG1mKhgpmsOSxoC_nIQAvD_BwE&gclsrc=aw.ds

With the airbox removed I held the velocity stack tight against the inner fender wall and from the engine bay side I slipped this silicone coupler onto the straight section of the velocity stack:

https://www.amazon.com/Straight-Sil...uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl

With the velocity stack held in place flush with the fender wall via friction fit with the coupler slipped on, I secured the coupler onto the velocity stack with a 3in hose clamp. I then installed the bottom of the air box, slipping the other end of the coupler into a properly aligned 3in hole in the air box bottom. I then trimmed the coupler back to be more flush with the inner wall of the air box bottom.

In order to ensure the fender feed does not ingest warm air from the engine bay, I sealed off all air gaps where the fender bolts to the body and covered many small holes with white duct tape (cause my truck is white).

As far as where this fender feed draws air from, it comes from 2 places. The first is where the front of the fender liner opens up into the front bumper area (cold air area) and the second is from the fender vent by the door (I have the Ford Performance mesh fender vents, so another cold air area).

All in all not a hard or expensive mod to double the amount of air feeding the factory air box, just measure and remeasure to make sure your holes will line up correctly. As seen in photos you can’t even see the fender feed unless looking for it.

Thanks for reading 5g friends!

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[RangerFitz]

Looks good! Thanks for the idea might try myself!

 

[importfighter01]

Looks good! Thanks for the idea might try myself!

One thing I forgot to mention is when drilling the hole into the sheet metal be aware that the rubber hose for windshield washer fluid is on the other side. It’s a loose fit in there so when pulling down the front of the fender liner for inner fender access just unclip the hose from the inner fender wall so you don’t cut the hose with the hole saw.

 

[txquailguy]

Just out of curiosity....how do you think this will help with performance?

 

[importfighter01]

Just out of curiosity....how do you think this will help with performance?

Happy to share. It’s gonna be a lengthy post, so I’ll reply throughly this evening.

 

[importfighter01]

Happy to share. It’s gonna be a lengthy post, so I’ll reply throughly this evening.

@txquailguy - Here goes...you’ve been warned lol.

———

Intake design research:

All of this began as I (like others) searched for “the best” intake. I’ll start with intake design and what I learned along the way.

First up is the aFe Rapid Induction Cold Air Intake. Design is a cone filter with the lower air box still in place, along with a hard intake pipe replacing the factory accordion pipe. According to the dyno chart (which the dyno descriptions show the truck even has an supporting mods like an upgraded cat-back and intercooler pipes on a stock tune), the gains across the powerband are almost non-existent. Lesson learned: a clean paper filter and factory accordion intake pipe are not significant restrictions to power.

Next up is the Mishimoto intake. Design is a cone filter and hard intake pipe replacing the factory accordion pipe like the aFe (which the prior aFe dyno test showed were not significant restrictions to power even with supporting mods in place), however Mishimoto does not use the lower half of the factory air box, but a different air box design altogether.

In these dyno graphs we can see that there are more gains across the powerband vs the aFe, both with a stock and aftermarket tune (interesting that a tune with higher boost levels does not show an exponential benefit over the stock tune dyno graph). In this case since we know from the aFE dyno that a different filter media and hard intake pipe don’t really make a difference, we must therefore deduce that the airbox design was the difference.

In regards to air box design, the Mishimoto box is superior to the stock air box due to a much larger and efficient air box inlet snorkel. You can see in the circled portion in the image below that where the snorkel is molded into into the air box is much bigger than the 2.5x3in rectangle opening where the factory snorkel enters into the lower half of the factory air box. Also the inlet size of the Mishimoto air box snorkel where it ingests air from the radiator cowl area is larger than the factory snorkel. Lesson learned: the factory snorkel size and the actual opening in the lower factory air box where the factory snorkel mates up to it are restrictors.

To further flesh out the deduction that a both a larger snorkel and air box to snorkel opening size improve power, enter the Airaid and K&N intakes. As seen in the images below, they appear to have even larger snorkel to air box openings and also have larger than factory snorkel inlets on the radiator cowl side of things too. So like Mishimoto but bigger. The dyno charts seem to correlate that bigger is better as the Airaid design seems larger than Mishimoto and makes a lil more power across the power band.

The K&N snorkel and snorkel to air box opening design is even larger than the Airaid design and thus makes more power too (regarding the lower stock base line on the K&N dyno, it looks like the truck might have had the A/C on as I’ve seen other non-Ranger dynos where the A/C compressor robs 10-12hp easy, but who knows). Lesson learned: Bigger is better in snorkel and snorkel to air box design. This motor wants as much air as it can get.

The final info I found on intake design that further validated my findings on access to airflow being more important than filter media or post-airbox tubing design was the now discontinued Injen short ram intake. While no dyno sheets were published, Injen claimed their intake made 14hp in their testing. As seen in the pics, it was the least restrictive option of all with no snorkel or airbox design to restrict any airflow. So if we have learned from the aFe dyno that filter media and smooth hard piping are not contributors to power, why the significant power increase? It’s because the motor could ingest as much air as it wanted with nothing limiting the amount of air getting to the filter. This again further validates that access to airflow is where power can be found with intake design on these trucks, which Mishimoto / Airaid / K&N all help for accomplish.

———

A real problem:

So now that we have established that airflow quantities from snorkel inlet and snorkel to air box inlet are what makes a difference (or have the greatest impact on power of if you will), why not just buy a K&N intake and call it a day? Because something that Gale Banks of Banks Power pointed out in one of his dyno videos...when everyone dynos their vehicles they do so with the hood open! On our Rangers, THIS is a real problem. Why? Because when the hood closes the clearance between the hood and radiator cowl (through which the snorkel draws air) narrows down at some points to only a 0.5in x 7in slit! Here’s some math for you. We have discussed that the data shows that the 2.5x3in snorkel to lower factory inbox inlet is restrictive. The area of that opening is 7.5in. The area of a 0.5 x 7in slit is only 3.5in!! That means that sucking air from the radiator cowl area is 2x more restrictive than the already restrictive lower factory air box inlet which dynos show restricts power.

Using the rubber hood bumper as a point of reference, you can do the math to determine how narrow the air pathways are within the radiator cowl area. I even removed my cowl at one point and held it up to the underside of the hood to verify as well. All this to say, no matter how good your aftermarket air box is at making power vs the stock setup, all current intake designs have the same restriction stifling them when the hood is closed. The only design that overcame this was the Injen, but it was crappy as it was ingesting hot engine bay air.

Nothing out there today addresses the issue of the restriction to increased airflow the radiator cowl causes. You can’t cut it open anywhere between the stock fresh air feed hole in the cowl and the snorkel either because doing so will allow the snorkel inlet to ingest warm air from the engine bay (area under the cowl is not sealed off from the engine bay by any means and doing so would take a ton of work like sealing around the intercooler piping). I also looked into running a 3in hose from a new hole in the cowl right in front of the snorkel inlet, but doing so would add several feet to the intake airflow tract, creating a different type of restriction due to excessive length.

All this being said, I recognize that the factory design was not done to make a Ranger a street rod. It was done to a. ingest cold air (which it does) and b. make water very difficult to make it to the airbox for those who off-road (which it seems to be a good design for). However for those who want to go as fast as possible, it’s a real issue.

The Velossatech ram air scoop helps because it is forcing air through the slits in the cowl area to the snorkel, but even then if you look at the hood design and it’s accompanying rubber seals it’s a Swiss cheese design that opens into the hot air of the engine bay, thus the air the Velossatech is delivering is not forced towards the snorkel inlet, reducing its efficiency (you can see how I overcame this with white duct tape and redoing the rubber intake tract seals on my hood below).

———

My solution:

After reviewing all of this for over 2 months, I determined to do what should have been done from the factory (because it has been and is still done today in other vehicles), but prob couldn’t be done due to crash testing, was to create a second air feed for the factory air box by creating a fender feed as seen in my original post. In doing so I’ve created more cold airflow volume than any current intake design will allow in the shortest path possible, regardless of hood being open or closed. It’s similar to having the benefits of a short ram setup, but no hot air ingestion issues. Like I mentioned in original post I observed immediate positive results and am very pleased.

———

Again, sorry for the length but hope this provides the context you were looking for!

 

[txquailguy]

I really like your train of thought on all of this. Let me do a little peer review but I'll be gentle....lol. I'm not sure if you know what I'm running for the CAI. I did what I call a home made setup with the stock air box, an aFe power scoop, and a K&N filter. I believe that gives me at least 50% more intake air flow than the factory setup. I went this route instead of an aftermarket CAI for one reason....when I do get off-road, I don't want my wonderful 2.3 sucking in dirt!!! Those high flow conical filters with the baffle will let too many dirt particles fly on through....IMHO.
Ok, now, lets talk about your side vent air flow. I do not see how you will capture any ram air from the side vent configuration on our trucks....only static air pressure. I'm not sure how that would affect flow. Maybe you are thinking that opening up another hole in the box will increase flow but I'm not sure if that is correct. Could a vacuum form with the static pressure from the second vent? I'm just thinking out loud and surely not being critical only practical in an engineering sense. I applaud your thought and effort and you may be on to something really cool! If only there was a way to easily measure the air flow dynamics of your setup. I am very intrigued..... but need more data before I cut any holes in my truck.....lol.

 

[viperwolf]

I was installing some lights on my nephews Mazda 3 hatchback, noticed it had two intakes. One was high and one was low. The lower intake was static as far as I could tell.

 

[Rinn69]

It comes down to air volume. If you were to take a paper towel cardboard tube, tape off one end and cut a 1/4" hole in the side and try inhaling through the open end. It will allow a little air to flow, but not enough, no matter how much you try to inhale. Now, cut an additional 1/2" hole on the opposite side from the 1/4" hole and try to breath through it again. The OP concluded that the single and restrictive inlet on the stock air box is it's Achilles heel since it restricts the volume of air it allows to enter, which is evident from the dyno sheets. Adding the 3" tube that "inhales" from the cool fender space may not be rammed, but it does allow for more volume, which turbo engines need and the engine doesn't care where it comes from. Rammed air would be a little better, but unless we start cutting and fabbing up scoops, this seems to me to be a very simple and a low cost and effective mod IMHO.

 

[viperwolf]

How fast do we have to go to call an intake ram air? Still, the only air going to the engine will be what it needs, the rest is dumped right? If you er at lower speeds where air is not pushed into the air box, it seems the extra would benefit bc then it would not have to work as hard to get its required mixture. I guess it would just be more efficient, although I doubt they are starving for air anyway.
Modding is not always about HP gains All companies get choked down by EPA laws, its our job to find the loops holes for efficiency and sometimes HP.

OP Im assuming the fender liners are keeping splash and debris from entering?

 

[importfighter01]

I really like your train of thought on all of this. Let me do a little peer review but I'll be gentle....lol. I'm not sure if you know what I'm running for the CAI. I did what I call a home made setup with the stock air box, an aFe power scoop, and a K&N filter. I believe that gives me at least 50% more intake air flow than the factory setup. I went this route instead of an aftermarket CAI for one reason....when I do get off-road, I don't want my wonderful 2.3 sucking in dirt!!! Those high flow conical filters with the baffle will let too many dirt particles fly on through....IMHO.
Ok, now, lets talk about your side vent air flow. I do not see how you will capture any ram air from the side vent configuration on our trucks....only static air pressure. I'm not sure how that would affect flow. Maybe you are thinking that opening up another hole in the box will increase flow but I'm not sure if that is correct. Could a vacuum form with the static pressure from the second vent? I'm just thinking out loud and surely not being critical only practical in an engineering sense. I applaud your thought and effort and you may be on to something really cool! If only there was a way to easily measure the air flow dynamics of your setup. I am very intrigued..... but need more data before I cut any holes in my truck.....lol.

Haha I appreciate the kind feedback. Here are my thoughts. The aFe scoop is less restrictive vs the factory scoop but with the issue that it is still restricted on the opposite end where it mates to the factory air box, still only the 2.5x3in opening. So while the aFe scoop solves the issue on the radiator cowl inlet side, it cannot address the restriction on the other side at air box entry (think of it like the factory 2.5 in exh getting restricted down to 1.5 in the factory muffler). The aftermarket air box products solve for that side too.

All that being said, regardless of how awesome and freer flowing an aFe scoop or aftermarket air box is, it does not address the stiflingly effect of air being drawn into the scoop from the radiator cowl area when the hood is closed. All intakes are pulling in air through the same restrictive “straw”. The mod is meant to overcome this as air (like water) will take the path of least resistance, and under WOT the fender airspace is way, way less restrictive than the radiator cowl area, so under WOT the engine can draw from both feeds at once if needed, providing airflow the path of least resistance to enter the engine.

In regards to the fender feed, it is meant to be static just like the factory setup. No ram air intended. The fender liner opens up into the front bumper area and on the backside can draw from a fender vent if you have them installed like I do. This is also why I installed a 6” velocity stack on the inner fender side, so airflow can be pulled from any direction.

As far as data goes, should be able to test easily with $100 of dyno time (1hr worth) and stuffing a 3 in pvc cap into the air box inlet side of the fender feed, closing the hood, then doing a run with the cap in and one with the cap out to see effects. Now to find $100 my wife will let me have freely is another story lol...

 

[importfighter01]

How fast do we have to go to call an intake ram air? Still, the only air going to the engine will be what it needs, the rest is dumped right? If you er at lower speeds where air is not pushed into the air box, it seems the extra would benefit bc then it would not have to work as hard to get its required mixture. I guess it would just be more efficient, although I doubt they are starving for air anyway.
Modding is not always about HP gains All companies get choked down by EPA laws, its our job to find the loops holes for efficiency and sometimes HP.

OP Im assuming the fender liners are keeping splash and debris from entering?

Correct, fender feed is located near the top of the fender arch and very well protected by the fender liner. Thankfully the Ranger fender is bulbous in nature, providing a nice airspace even high up.

 

[txquailguy]

Haha I appreciate the kind feedback. Here are my thoughts. The aFe scoop is less restrictive vs the factory scoop but with the issue that it is still restricted on the opposite end where it mates to the factory air box, still only the 2.5x3in opening. So while the aFe scoop solves the issue on the radiator cowl inlet side, it cannot address the restriction on the other side at air box entry (think of it like the factory 2.5 in exh getting restricted down to 1.5 in the factory muffler). The aftermarket air box products solve for that side too.

All that being said, regardless of how awesome and freer flowing an aFe scoop or aftermarket air box is, it does not address the stiflingly effect of air being drawn into the scoop from the radiator cowl area when the hood is closed. All intakes are pulling in air through the same restrictive “straw”. The mod is meant to overcome this as air (like water) will take the path of least resistance, and under WOT the fender airspace is way, way less restrictive than the radiator cowl area, so under WOT the engine can draw from both feeds at once if needed, providing airflow the path of least resistance to enter the engine.

In regards to the fender feed, it is meant to be static just like the factory setup. No ram air intended. The fender liner opens up into the front bumper area and on the backside can draw from a fender vent if you have them installed like I do. This is also why I installed a 6” velocity stack on the inner fender side, so airflow can be pulled from any direction.

As far as data goes, should be able to test easily with $100 of dyno time (1hr worth) and stuffing a 3 in pvc cap into the air box inlet side of the fender feed, closing the hood, then doing a run with the cap in and one with the cap out to see effects. Now to find $100 my wife will let me have freely is another story lol...

Interestingly, I just hyper dipped my side vents last weekend. That was the first time I’ve had them off and was able to see inside the fender. You are correct that our Ranger fenders lend themselves well for air flow. I’m very interested in your dyno data when you get the mrs go on that.
I need to make the trip to the dyno I had scheduled recently but ended up canceling due to sudden climate control service work that popped up.
Your mod is easy and unobtrusive so if you pull some measurable data that shows promise, I might be willing to give it a go too. I’m a biologist so I tend to go where the data leads me...lol
If you prove it, people will do it...

 

[onobeka]

Correct, fender feed is located near the top of the fender arch and very well protected by the fender liner. Thankfully the Ranger fender is bulbous in nature, providing a nice airspace even high up.

Congratulations on your mod! The european models (diesels) have this done by factory, they are sucking air from the fender, similarly as you've did, that's why attaching an offroad snorkel is such an easy mod for diesel rangers. I do not like the look of a snorkel, does not go with a clean design, however I was thinking of creating a hidden snorkel up to the plastic cover near the mirror, the one with the engine indication or model version. It will raise a bit the water depth level (not much) breathe better and for sure create a bit of intake sound closer to the cabin.

Of course the plastic cover of the fender needs some modifications (drilling,cutting) to allow air to enter. In addition that should be a high pressure area given the mirror vicinity. So, it should in principle act also as a sort of ram air.

More info on the diesel airbox here, it also shows the plug in play (no cutting) snorkel version install:

 

[importfighter01]

Congratulations on your mod! The european models (diesels) have this done by factory, they are sucking air from the fender, similarly as you've did, that's why attaching an offroad snorkel is such an easy mod for diesel rangers. I do not like the look of a snorkel, does not go with a clean design, however I was thinking of creating a hidden snorkel up to the plastic cover near the mirror, the one with the engine indication or model version. It will raise a bit the water depth level (not much) breathe better and for sure create a bit of intake sound closer to the cabin.

Of course the plastic cover of the fender needs some modifications (drilling,cutting) to allow air to enter. In addition that should be a high pressure area given the mirror vicinity. So, it should in principle act also as a sort of ram air.

More info on the diesel airbox here, it also shows the plug in play (no cutting) snorkel version install:

watched video, super cool euro diesel rangers have a fender feed stock. Gonna start calling this mod the “Euro fender feed mod” Fancy that way lol

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