[Former_Boosted_IS]

Well about 2 month ago a discussion began on whether a Cold Air Intake (CAI) would really cool Air Inlet Temperatures (AITs) after the air goes through the hot turbo, then through an intercooler, and finally enters the engine. The discussion went back and forth, but the one thing missing in the conversation was real world hard data. At the time I wasn't sure I wanted to do the extra work for testing, but after thinking about it for a while I thought the time had come to put hard data out there to answer the questions.

Now that I was going to be getting a CAI, I had to decide which one best meets my needs. The project led me to STETT Performance for a couple of reasons:

1. The Charge Pipe / BOV is extremely well made and that gave me confidence in their CAI.
2. Their design looks very good.
3. They have the largest filter of any CAI on the market.
4. Great customer support.
5. Available in black or polished and I love black piping!

Now onto the review!

Shipping

Because I ordered the Stett Performance Charge Pipe / BOV at the same time, I will reiterate the great experience I had here. Chad, from STETT Performance, has been a pleasure to work with from Day 1. STETT has been up front and reliable on the stock of the kit. STETT notified me of shipment and had a tracking number within 24 hours of the purchase. Finally, STETT has been very informative and a huge help in any way I needed. I always got a response within 24 hours of emailing Chad.

The package arrived to my house and everything was boxed, bubble wrapped, and then bubble wrapped again to protect against any shipping bumps. There were no loose items at all.



Kit Contents

Opening the kit up shows just top notch, high quality parts. You get an instruction guide with the kit and the last page has an inventory sheet that is hand checked by STETT before it leaves the shop. STETT is serious about making sure that you get what pay for the first time. The kit includes the following:

1. Intake Y-Pipe.
2. Intake Charge or Down pipe.
3. Stainless Steel Hose Clamps.
4. K&N RU-2820 Filter (It is a large filter).
5. Hoses to relocate brake booster line if you choose to.
6. Power Steering Resevoir bracket & Necessary bolts.
7. STETT Performance decals.

Here is what the kit includes (sorry I am showing the small silicone caps that were for the BOV kit.)



I unwrapped the pipes and there is a huge wow factor! They are incredibly well built and absolutely beautiful!







Installation

Stett includes a detailed instruction guide with your kit, but a few steps lack pictures so I will try to fill in the gaps. They do include good pictures on where to located the filter in the fender area, relocating the power steering reservoir, and one picture identifying the brake booster line.

In your first step, you will be removing the stock air box and brake booster line. This is well covered in many DIYs, so I will defer again to them.

Next, you will need to lift the car and remove the front driver's side wheel. If your wheel sticks a bit, I would suggest lining up a 2x4 on the inside of the wheel and use a rubber mallet to pop it off the hub. Don't forget to use jack stands to support the vehicle while it is on the jack.

This is when you will need to remove the fender liner. There are a number of 8 mm bolts in the liner and under the driver's side bumper that need to be removed. Then, just peel back the liner to expose the fender area. Simple work here.

At this point, STETT Performance suggests you remove the plastic cover between the Brake Air Duct and the Fog lamps. Here is what the plate looks like:



This is where it is located (notice the plastic tabs on the top and bottom that need to be released):



Now it is time to remove the power steering reservoir. It is the reservoir with the green plastic cap. You will need a 10 mm socket to remove it:



Make sure you keep bolts and large washers to re-use later.

Finally you will be removing the brace itself that held the power steering reservoir. Here is a picture of it:



This is a bit tricky because the bolts are under the charge pipe. There is enough play that you can get to the bolts with a little work. A 10" socket extension is extremely useful here.



Notice on the bracket, there are hose clips for the two hoses running under the charge pipe:



Unclip the hoses and pull the clip off the front part of the bracket exposing the bolt. Remove that bolt, then remove the rear bolt (you do not need to pull the back hose clip to do that), then pull the bracket carefully out of the car. I personally took the clip off the bracket and just re-used it to secure the two hoses like this:



Finally remove the two 16 mm bolts holding the short black brace now exposed behind the headlight. At this point you have opened up gap to run the CAI. It should look like this:



Now, onto the installation. Insert the Y-pipe now one leg at a time into the plastic stock intake runners.





Do not tighten the clamps yet because you will still have to fit everything.

Next insert the filter onto the end of the downpipe or charge pipe. Which end? Well, you can use either and decide what side works best for you. The bends are slightly different, so one may work better for you versus the other. Insert the filter only enough to go over the flared portion so you can maximize flow. Don't tighten the clamp yet.

At this point, install the large silicone coupler on the end of the charge pipe. I found it easier to put the coupler on this side first. Leave the clamps loose. Then insert the charge pipe into the opening you created into the engine bay. Twist the pipe to orient it properly and line up with the Y-pipe with the filter sitting just above the fog light. Here is where my filter is located:



Here is what the downpipe or charge pipe looks like passing through into the engine bay:





You can push the fender liner up to make sure it will clear the liner correctly. When you are happy, tighten all the clamps:

1. (1) Intake clamp
2. (2) Silicone coupler clamps between the Y-pipe and charge pipe
3. (2) Y-pipe clamps on front and rear section of the pipe

Now you are almost done. Finally, you will need to relocated your power steering reservoir with the Stett kit. Stett has a great picture and directions here, so I will defer to that.

This is what it will look like when it is all buttoned up (note the power steering reservoir relocated):









At this point, you can relocate the brake booster line with the supplied hoses from STETT. Since this is optional and only cosmetic, I will not get extensively into it. I actually ran out of time and didn't want to hold up my review of the product. I will augment my review by the weekend to address the brake boost line relocation.

You are now finished! Well, after you re-install the fender liner and wheel. Really this is an easy job that should take 2 hours at most for a novice.

I can honestly say this may be one of the highest quality intakes that I have ever seen. The fitment was perfect and required none of the infamous "extra steps". Everything fit like a glove just as it should. I was extremely pleased with the install process.

Performance

So off for a test drive! This intake gives you the spectacular WOOOOSH or "sucking air" sound when you floor the car like the other intakes I have tried. The sound may be a touch more pronounced because it is not within the dampening of the engine compartment. Needless to say it sounds incredible.

The car pulls very hard with this intake too. On a cool car with the JB3 it pulled like a beast. I am very impressed here as well. Nothing but very high marks here. But, how does it compare to the DCIs? Well I will be doing much more extensive testing on that today on a warm car in a variety of conditions.

Conclusion

STETT has outdone themselves on this intake. It is extraordinarily high quality in every way. The parts fit as described and the install is really very simple. The finish on the parts is just perfect! The filter is huge for a CAI and very impressive. Really, STETT gets an A+ on this product and I would recommend it to anyone that would listen to me.

If you are in the market for a CAI, then I cannot imagine a better product. [i]If indeed the CAI does produce lower AITs, then this is the product you need to buy....

So are the AITs really colder?

And that is the correct question. Will this allow us to keep the AITs down at all so we can hold our power longer? Will it keep the AITs cooler when you are in stop and go traffic? When you are at highway speeds, will it hold AITs down more? Under WOT or long runs, will you get lower AITs? These are the questions that will be answered very soon with the detailed AIT analysis I am working on. I have 40,000 data points on the DCIs right now and will do the exact same procedure to test this intake this afternoon. We will know more from the real world today.

[cn555ic]

subscribed

[ragingclue]

Damn dude I want whatever job it is you have....

[gonzo]

Solid read and pics. Should be very helpful for folks.

[ragingclue]

I'm actually waiting on that review to decide between JB3+DCI or LET+STETT

Eagerly awaiting....

[cn555ic]

Originally Posted by ragingclue

I'm actually waiting on that review to decide between JB3+DCI or LET+STETT

Eagerly awaiting....

+1 I am awaiting the results just to see if my UR CAI which is very similar to the Stett CAI, but obviously the STETT uses a bigger filter performs better than the DCI intakes...

[cincy335i]

Great review and great write up as always! Very much appreciated. Looking forward to the results, and hopefully my very own Stett CAI? Thanks again for the great effort and detailed information for the rest of us, without people like you it would be very hard to make informed decisions.

[Panoz]

Reasonably thinking...this should be possibly the best intake solution for 335. A true CAI sucking fresh air straight from the vents. Cant think a better solution than this.

I'm certain that someone else made this question but I will ask again..what happens with the water drain? Its in a dangerous position sucking water

[Former_Boosted_IS]

I will take pictures of the exact height of the filter when I get home Panoz so you can see where exactly how far it sits off the ground. The thing is that you would need to have you entire front end submerged to get water in the intake. At point, the IC would be submerged too.

[sflgator]

Great detailed install guide and write-up! I have a question...exactly how is it sucking in "colder" outside air? From the pics, it seems like the attached large K&N air filter, although just above the fog light, is still sitting around hot engine bay items & lights; or, is it sucking in air from the front spoiler air dam? Sorry if my question seems stupid...just can't tell from the pics.

Either way, we're all looking forward to your detailed AIT tests.

[BMW_TT]

He removed the grill cover so cold air will flow right into the filter.

[Former_Boosted_IS]

Originally Posted by sflgator

Great detailed install guide and write-up! I have a question...exactly how is it sucking in "colder" outside air? From the pics, it seems like the attached large K&N air filter, although just above the fog light, is still sitting around hot engine bay items & lights; or, is it sucking in air from the front spoiler air dam? Sorry if my question seems stupid...just can't tell from the pics.

Either way, we're all looking forward to your detailed AIT tests.

sflgator, the heat generated from:

1) A hot engine in a very tightly sealed compartment.
2) The filters sit on the side of the engine.
3) Convection dictates the heat will rise so it should to the top of any compartment.
4) Conduction is really the other heat transfer method and these are not sitting on the engine.

The STETT CAI draws from a fender well with the only point of heat being the fog lights which many never turn on other than late at night. Second with the plastic cover in the driver's side grill removed, the compartment should filled with ambient air.

That is all great theory, but you, me and everyone else wants facts. I hope I can provide those facts this afternoon. I have timed everything out quite well and hope I can nearly replicate every aspect of the tests.

[sflgator]

Originally Posted by Former_Boosted_IS

sflgator, the heat generated from:

1) A hot engine in a very tightly sealed compartment.
2) The filters sit on the side of the engine.
3) Convection dictates the heat will rise so it should to the top of any compartment.
4) Conduction is really the other heat transfer method and these are not sitting on the engine.

The STETT CAI draws from a fender well with the only point of heat being the fog lights which many never turn on other than late at night. Second with the plastic cover in the driver's side grill removed, the compartment should filled with ambient air.

That is all great theory, but you, me and everyone else wants facts. I hope I can provide those facts this afternoon. I have timed everything out quite well and hope I can nearly replicate every aspect of the tests.

Great...looking forward to your test results! Thanks.

[Panoz]

What kind of HP gains according to STET?

[scottp999]

Excellent review once again. ***Mods need to setup a product review sticky post, and have links to all of your reviews in that post ***

[godot]

Originally Posted by Panoz

I'm certain that someone else made this question but I will ask again..what happens with the water drain? Its in a dangerous position sucking water

Originally Posted by Former_Boosted_IS

I will take pictures of the exact height of the filter when I get home Panoz so you can see where exactly how far it sits off the ground. The thing is that you would need to have you entire front end submerged to get water in the intake. At point, the IC would be submerged too.

I was worried about this too because we get torrential downpours and standing rain in the summertime. I asked the question in another thread, and here is one very encouraging response:

Originally Posted by Azrielsc

I don't have a photo but I hope to describe to you as best as I can.

The filter sits at the same position where the Oil Cooler sits on the other side of the car. (Above the bumper grille and below the headlight.)

In Singapore, it usually pours almost once a week and I never had any problems with the STETT intake since the day I bought it.

Just as recently as this morning, it was raining cats & dogs and there were water ponding everywhere and there isn't any problems at all.

Based on that info, I ordered the STETT, which should arrive tomorrow or Monday!

Thanks for the helpful tips and photos, F_B_IS!!!

[Former_Boosted_IS]

First, thank you for the overwhelming good response guys! I appreciate it very much!

Second, the testing is complete and I am analyzing the data as we speak. There is a ton of data and a lot of graphs to create. I am working on getting everything together on EXCEL and hope to get this up today or tomorrow.

[ragingclue]

Originally Posted by Former_Boosted_IS

First, thank you for the overwhelming good response guys! I appreciate it very much!

Second, the testing is complete and I am analyzing the data as we speak. There is a ton of data and a lot of graphs to create. I am working on getting everything together on EXCEL and hope to get this up today or tomorrow.

No pressure.

Just waiting to make my tuning decisions based on your data.... No hurry....

[Terrance28]

Originally Posted by Panoz

What kind of HP gains according to STET?

I think it was like 22whp or something like that. I am planning on getting in on their group buy of the fmic and the cai.

[ragingclue]

Originally Posted by Terrance28

I think it was like 22whp or something like that. I am planning on getting in on their group buy of the fmic and the cai.

I would be in on that, too, if it didn't look so hopeless that they'll get to 30 any time soon. I'd do it for sure if the CAI was being thrown in for free for sure, but otherwise no...

[Former_Boosted_IS]

The question is...??? Does a Cold Air Intake (CAI) actually reduce Air Inlet Temperatures (AITs) over a Dual Cone Intake (DCI)? Or are intakes simply for getting adequate air flow? This is the question that has been thrown around on the forums a lot and I personally have participated in many of these discussions. The conversations go back and forth with theoretical arguments and no hard facts. What we do know is colder air in the engine equals more oxygen in the combustion process and more power if everything flows the same. Honestly, I wasn't sure I wanted to put in all the hours of work to answer this question. Well, needless to say I decided that I wanted to know the answer, so here we are.

Products Tested

This test was an AIT analysis between the BMS DCI and STETT Performance Cold Air Intake. I want to start by saying both companies have been very, very easy to work with and knowingly participated in the testing. We as a community owe Terry at BMS and Chad at STETT Performance a huge thank you for helping me to make this independent testing happen.

Testing Procedure

Tests were conducted to determine how the STETT Performance CAI and the BMS DCI would perform in multiple situations. I collected nearly 70,000 data points over the last 3 days in a specific testing procedure. Each test was conducted in the following way:

1) JB3 8D4 Rev.4 on map 7 (same as map 6 on 1.2).
2) This is critically important to note... the car has an Active Autowerke Intercooler.
3) Car was warmed up for 18 minutes in identical driving routes, rpms, and speed.
4) Data was logged using Bavarian Technic software and BMS Tuning Tool.
5) Ambients were logged in an attempt to replicate similar conditions.

Four tests were done on each intake using an identical car setup. The tests are:

1) Approximately 10 minute highway runs at 70 mph
2) Approximately 10 minute standing idle
3) Approximately 10 minutes of stop and go driving
4) 3 back to back wide open throttle (WOT) full gear pulls

Ambient Conditions

The BMS DCI was logged under the following conditions:

Temperature of 67 degrees F
Relative Humidity of 54%
Pressure of 30.15" / 1020 mb

The STETT Performance CAI was logged under the following conditions:

Temperature of 70 degrees F
Relative Humidity of 84%
Pressure of 30.09" / 1018 mb

Note the BMS DCI was tested at 3 degrees F colder temperatures and 30% lower relative humidities.

Results

Highway Runs

I am going to start with the highway runs because these we would expect to be identical. These tests were done at 70 mph with about a 2 minute turn around in the middle of the runs. You can see where the AITs rise slightly while waiting at the stop light.

Here is the AIT graph of the BMS DCI



Here is the AIT graph of the STETT Performance CAI



Both showed very consistent results. Around 82 degrees F through the entire highway runs. No difference at all between the BMS DCI and the STETT Performance CAI.

Idle for 10 minutes

This was a simple test. Let the car sit after the highway run for 10 minutes.

Here is the BMS DCI AIT graph:



Here is the STETT Performance CAI AIT graph:



The BMS DCI graph shows the AITs warm up faster in the first 5 minutes or so, then they become very close by the end of the ten minutes. The BMS DCI was at 112 degrees F after 5 minutes while the STETT Performance CAI was at 106 degrees F. The BMS DCI was at 121 degrees F after 10 minutes while the STETT Performance CAI was 119 degrees F after 10 minutes. The STETT Performance CAI definitely performed slightly better here with colder AITs.

Stop and go driving

It is important to note here, there were a few more stops in the testing with the BMS DCI only because I got stuck at more lights.

BMS DCI AIT graph versus RPM:



BMS DCI AIT graph versus speed:



STETT Performance CAI AIT graph versus RPM:



STETT Performance CAI AIT graph versus speed:



I have to say both performed nearly identical to one another. Both hovered from 85 degrees F to 95 degrees F during the entire runs. The single most noticeable thing was that during hard acceleration the STETT Performance did seem to drop AITs faster, but I would not give an advantage to either.

3 wide open throttle long gear pulls

Ok, this is the big daddy and the single most important test I did. There is one piece of bad news. I accidentally cleared the first run off one of my data logs from the Bavarian Technic software, but did log the run using the BMS Tuning tool. The bottom line is the graphs will show run 2 and run 3.

From the BMS Tuning Tool Run 1 on the BMS DCI produced a peak of 109 degrees F and the STETT Performance CAI produced an AIT of 101 degrees F. I apologize for no graphs, but the next two graphs show more than enough.

AIT graph of run 2 and 3 on the BMS DCI:



AIT graph of run 2 and 3 on the STETT Performance CAI:



AIT graph of run 2/3 of the BMS DCI versus the STETT Performance CAI:



The data is very clear here. The BMS DCI had a peak AIT that was 8 degrees hotter on run 1, 10 degrees hotter on run 2, and 8 degrees hotter on run three. This is an average of 8.7 degrees hotter for the BMS DCI over the STETT Performance CAI over the three runs.

The analysis of the graphs clearly shows the entire temperature climb is shifted down by the STETT Performance CAI. There is no exponential difference, but a step difference between the two. You can also see the difference is held through the 1 minute or so it took me to turn around for another run. The data is pretty definitive.

Conclusion

It must be noted that this testing was done with an Active Autowerke Intercooler that has an efficiency of 80%-90% versus the stock intercooler with an efficiency near 50%. The difference in AITs will be magnified if you have a stock intercooler.

Second, the JB3 would lower boost on the high end if the engine was not getting enough flow from the intakes. The boost was logged and identical between the WOT runs.

Despite the STETT Performance CAI being tested in 3 degree warmer weather and 30% higher relative humidity it still out performed the BMS DCI in the WOT long gear runs. Without a doubt, the data proves that a CAI does cool AITs in WOT runs and while idling under 5 minutes. The difference in AIT numbers was nearly 9 degrees F between in the WOT long gear runs.

The question was:
Does a CAI produce colder AITs or is cooling AITs the job of the intercooler?

The answer is:

Yes. The STETT Performance CAI does produce colder AITs then a DCI intake.

[Former_Boosted_IS]

One other thing, to say that the Bavarian Technic software is incredible is an understatement! If you own a BMW you simply must own this software!