Custom R36 Cold Air RAM intake - Almost $0 DIY or small fee to get it done

[Elmura]

Hi R36 and Passat CC V6 fans.

I wanted to share with you a DIY mod that improves performance of your R36 that only costs time, patience and the right tools.

I inspected and reviewed a few intakes for the R36 / CC V6. The Evoms produces a nice sound but ultimately has a couple flaws. First, it lets underbonnet hot air in near the exhaust manifold. This is a big No-No for performance and economy. Secondly, the filter is smaller in surface area than the original filter, which would outweigh any restriction improvement.


The net result is loss of performance and a waste of money (excluding the improvement to sound). The Gruppe unit is quite expensive & hard to find. I haven’t seen the filter nor the inner design to assess it.


So, I had a good look at the factory setup. It's pretty good mostly. I started by removing the AF sensor, then removed the metal screen behind the plastic grille. The metal screen serves to protect the AF sensor from stones etc but I will never have the Air Filter removed while the engine runs. It creates unnecessary turbulence and in one test I saw on Autospeed, they found an airflow improvement when removed. I then used electrical cleaner spray over the sensor electronics inside before reinstall.
I didn't remove the plastic grille as this controls the airflow over the sensor at lower RPM and would disrupt the performance.

The pipes leading to the airbox inlet over the radiator is made up of a few pieces. It’s an odd design, likely for Europe where snow / sleet and sub-zero temperatures. This part is not great for performance as it sucks both hot air and cold air. Also, the cold air path has to do a loop and so is not ideal. With my son, we had a look at how we can improve it. We came up with a great solution that has three benefits:

1. No more hot air induction
2. Ram Air at speed – The possibility of slight supercharging effect
3. When installed with cover, it looks completely original.

Benefit – More torque, more power, less fuel consumption due to needing less revs for the same amount of acceleration.

How it works- The hot air intake is sealed off, whilst the cold air airflow is straightened and opened for less restriction. Now the engine only sucks cold air from the front of the car - and at speed, this is slightly forced in (Ram Air). It’s a Win-Win.

HOW TO: (PS – Very hard to describe)

1. Unclip and remove the top cover of the inlet pipe
2. Unclip and remove the inlet pipe that fits between the air box inlet and the front ‘scoop’. It has a multi-inlet design
3. Cut (with a hack-saw / dremel / small grinder) along the edges where the cold air blade of the inlet points up. The idea is to enable the cold-air ‘blade’ to flex.
4. With a heat gun, protective gloves, patience, and good air-flow (toxic fumes), you heat up the ‘blade’ and apply pressure to make the blade fully flex down to the front inlet, whilst reshaping the outlet pipe back to original shape as the pressure causes it to deform.
5. Clamp with a vice (or grips) the blade to the inlet and fill all small gaps with a sealant (exterior grade silicone or similar) whilst using it to fasten the blade to the inlet. Images: https://dl.dropboxusercontent.com/u/...2012.10.52.jpg and https://dl.dropboxusercontent.com/u/...2012.10.38.jpg
6. The big gap created needs a different approach – I used expanding foam then cut it back once cured. I think heat resistant tape may be suitable as well.
7. Leave it for a day to cure. You can still drive your R36, it will be sucking hot air so performance will drop slightly.
8. Refit. https://dl.dropboxusercontent.com/u/...2009.36.12.jpg Then fit cover

I’d be willing to do this for owners for $80. Just mail the part to me and I’ll mail it back. You can still drive ur R36 while u wait - No harm. PM me if you’d like me to do this for you. Otherwise, if you have the right tools and skills, DIY.

Bonus tweaks – Overcome the overkill designed for non-enthusiasts

1. Use the same sealant to block a small hole at the bottom rear of the airbox. I believe it’s a secondary drain hole.
2. Improve the airflow through the ‘scoop’ in your grille. This has two parts, on top of the grille, and between the grille fins. Using fine side-cutters, cut off all the scoops’ grille to reduce turbulence and restriction for an enhanced RAM Air Effect. These are designed to minimise large foreign materials (leaves, sticks, stones) entering you airbox, but most manufacturers don’t have them. The airbox will hold this rubbish fine, just clean out every service with a vacuum. IMAGES: from top https://dl.dropboxusercontent.com/u/...2016.58.47.jpg AND from front https://dl.dropboxusercontent.com/u/...2016.59.27.jpg

[snerlo]

Hmmm,
Bit hard to follow without actually doing it mate, but good right up all the same. I have bought a cheap BMC filter which I am waiting to install when I get a chance so I might have a look at this while I have it apart and see what's going on. Hopefully it makes a lot more sense when you see things in real life. Good effort mate.

[Elmura]

I've just installed the app Torque for Android and bought a Bluetooth OBD2 adapter from a Ebay (Awesome). Anyways, on this cold Sydney night the app was displaying Ambient at 18-deg C. When the car was sitting idling for several minutes, you could see heat soak on the Intake temperature climb to over 50-degrees. Start driving and this temperature varied between 28-deg to 30-deg depending on throttle opening and speed (only tested to 60kph in local streets).

I pulled over, removed the intake pipe cover, and drove the same lap. This time I was getting 31-32 deg. So, even on this cold night, my cold-air-ram intake mod was benefiting on average 3 to 4 deg C. On a hot day, the difference should be significantly more. Note that I wasn't comparing original to modified (not possible) but something half-way between.

If any interested parties want to do a direct comparison, you can arrange a time to bring ur R36 and we can do a swap from ur stock to my modified version. I'm in the Liverpool-Fairfield region of Sydney. I reckon we could do a test at speed (100kph on the M5). PM me.

[gldgti]

A note on maf grilles -
Yes, they cause a restriction. No, its not there to protect the sensor from stones! Mafs have a mesh grille not to cause turbulence but to eliminate it. In order to be able to calibrate a hotwire maf over a large flow range, eliminating reducing turbulence in the pipe at the sensor improves the accuracy (a lot!)
By removing the grid you will decreasing the accuracy of the air mass flow measurement, at least at some flow rates. The consequences will vary, but on principal, feeding your ECU incorrect data should be avoided unless you can predict the error and account for it. FYI

[Elmura]

To be sure. Are you correcting me? If so, my post did not state that the grille was there to protect MAF sensor from stones; and I did state that removing it would not be wise for reasons of controlling airflow over the sensor.

I stated that the fine metal screen (behind the plastic grille) unnecessarily adds turbulence, and is likely there to protect the MAF sensor.

[Elmura]

In my post, I've shown a link to the plastic grill being kept

[gldgti]

Not so much correcting you as being pedantic. The grid doesn't increase turbulence,it actually is there to make the flow laminar. Your advice about what to do was sound, I just wanted to clear up the reasoning. Turbulent and laminar flow are specific fluid dynamics terms and the engineer in me likes to see them used correctly, that's all

[Elmura]

It's an interesting perspective - I'm an engineer myself. I can understand how the plastic grille would make the flow laminar (straighten the airflow for non-engineers) hence why it's being kept, but the metal screen is similar to flyscreen. If it would make the flow more laminar, why not just make the plastic grille with a finer grid? Hence channelling the air more finely? Think about how the air would flow through that screen.
At higher airflows the screen is a restriction - that's a given (and proven).

Hence, I am convinced the screen is there for protection of the electronics and engine from worst case scenarios. When you design a product that has to cater for all possible scenarios (damaged or worn air fliter, no air filter, incorrectly sealed air box etc) you have to over engineer.

Just like the cold air intake scoop grille, water drainage points, shape of the intake pipes - they're designed for worst case scenarios. If you were engineering an intake for a Pagani - you have different constraints - Formula 1 - different again.

[gldgti]

My allroads maf only has the metal grid, and no plastic one... But I have seen both too. I agree it looks like a fly screen. Perhaps some further investigation is in order!
Consider though, that the plastic screens I've seen look like they would do a better job of stopping rock than the metal one...

[gldgti]

So after a bit of reading, it seems there is good evidence that flow through a wire screen will indeed serve to change the velocity distribution through the pipe, making it more constant from the middle out towards the wall (e.g before the screen it will be slow at the wall, fast in the middle, after the screen the difference in velocity will be less).
If you google " airflow through a screen" you will come up with quite a few papers on it, some of which explain. Unfortunately I'm without internet other than ony phone at the moment, so posting links is beyond me