[ucsbwsr]

I wanted to share a recent project on my X5D.

Disclaimer: This isn't a step by step guide however for those inclined DIYers all the critical information is covered and the process is outlined, there should be adequate information to build your own replica if you fancy. Follow at your own risk, do your own research, and take responsibility for your work. No that this is done....

The goals:
- Improve turbo response by shortening intake length and increasing air flow potential
- Retain "cold" air source
- Simplify system to make engine access easier
- Clean OEM+ aesthetics

I have yet to confirm the performance gains of the system but once I get my X5 tuned I plan to get some back to back dyno runs comparing the custom inlet vs stock airbox. I would love to find a race shop that can bench dyno the CFM too. This system was "engineered with common sense" so it would be nice too see some data to confirm the increase in performance
....or show that I wasted my time Hopefully #CommonSenseEngineering prevails.

Here is the parts list, if they were modded those details are below:

- K&N RC-5000 Filter
- K&N RC-70031DK Dry-Charger
- 3.5" 45 Elbow
- 3.5" 90 Elbow (4" legs recommended)
- 3.5"-3" Reducer (3" length)
- 3.5" Aluminum Joiner
- HPS SSWC-59-83 x1
- HPS SSWC-84-108 x4
- Pro Fabrication 3.5" Oval 90 Pipe
https://www.profabrication.com/3-5-x...l-bend-ms.html

Parts ran me ~$300

Here was when the idea was conceived. Happy to say this state-of-the-art scribble turned out to be fairly accurate.


The star or this inlet system is the 3.5" 90 degree oval piping as retains the 3.5" diameter while clearing the hood once it's shut. Originally I was looking at a 3.5" oval pipe from CX Racing that was aluminum but I went this Pro Fab pipe because it has a tighter 4" radius, I called CX Racing and asked them for the specs but they didn't know (must be lost in China somewhere, lol). If I had to guess the CX piping is 4.5-5" radius, either way the 4" of the Pro Fab is extremely helpful.

*This Pro Fab pipe is mild steel and starts to rust if you look at it wrong so plan to seal/protect it somehow.

Here is the original pipe being test fit


In an ideal world I would maximize the amount of metal and minimize the amount of silicone used to construct the inlet but the direct routing to the turbo meant form will follow function. Here is what I was eyeing up.


The oval pipe fit snugly into the oem hole in the shroud but the pipe needed to sit lower for hood clearance. This is without trimming, notice the height relative to OEM.


If you look closely at the edge of the green tape you can see there was a circular cutout in the radiator shroud so I trimmed the plastic on top and did my best to make a clean cut.


I did an initial trim of the oval pipe.


With the oval pipe and the radiator shroud trimmed fitment was much better, notice how low the pipe sits now, very similar to the stock snorkel.


I had to take some more length off the oval pipe to help straighten the routing. Here is after final trimming. I don't have the exact measurements but there is about 1" of leg (past radius bend) that goes towards the filter, the other end which runs to the turbo is slightly longer with ~2" of leg.


Here is the OEM turbo inlet removed from the X5


We won't be needed the top part and thankfully the PCV connection is built into the lower pipe. With the upper portion removed I noticed there was a large flange, this isn't ideal.



Using a sanding wheel I removed the outer lip and bored out the inside to make a nice smooth transition.



For good measure I bored out the MAF as well.


This is the 3.5" joiner I use between the silicone 90 and 45. It has a bead as it's intended to be used as charge piping.


That bead will only disrupt air flow so I trimmed off each bead to keep things smooth. Not pictured but you can notice this when observing the final product but I stuck this 3.5" pipe in my bench vise and made it oval to help keep continuity in the shape of the piping.


If you look closely you can see the oval piping is slightly concave on the long sides, this is a byproduct of the bending process.


To alleviate this I used some JB Weld to fill in the small dips on all 4 sides.



After the JB cured over night it was time to sand, clean, prep, prime, and paint. I used some high temp stable engine paint and added further protection with a top layer of ceramic coating. Hopefully this resists paint chips when I inevitably remove the inlet for more wrenching.




Once I got the general routing of the system down my attention focused on filter location. I was adamant about the filter being vertical and NOT contacting the shroud or radiator, or poking through towards the kidney grills so aligned the filter where I wanted it and worked backwards aligning and trimming if needed.

After achieving ideal filter location and confirming there would be no contact with the hood shut I looked into ways to secure the system. I was thinking about L-brackets and all kinds of serviceable mounting solutions but once I had the system mocked up I realized the system was fairly rigid. The silicone does offer some flex but considering the short length of the system overall and the M57 doesn't seem to move much underload, the intake wasn't flopping around, it was barely moving at all. My solution was using a small rubber disc I had laying around, I attached some 3M VHB, and use this is a locating /buffer for the hose clamp. After some test drives and manyu WOT pulls I confirm this works like charm. The only contact points for this whole system are this and where the OEM turbo inlet bolts to the turbo. Very happy about this.



*Depending on what length 45 degree silicone elbow you buy your trimming may differ but I took about 1" off each end of mine. Also the 90 degree silicone elbow w/ 4" legs was also trimmed, I took about 1" off the end that connects to the MAF.

*Also not pictured but the opening of the K&N filter is larger than the 3.5" oval piping. The trick is to take one of your 1" silicone trimmings and use that as a spacer. -Slide the 1" long ring of silicone onto the forward edge of the oval pipe and then install your filter, works like a charm and you can recycle! Look closely at the pics below and you can see the silicone sticking out where the filter mounts.

For added security you can add a K&N Dry-Charger which is a hydrophobic filter guard, great for dust and water.



Let's first take a look at the stock intake system



...and a peak inside, notice the entire filter is not utilized



Now the final product





Installed

[335dlci]

Nice write up sir

[RL18]

Looks awesome! Glad you took it on. Looks a whole lot better in there lol.

So uh... how much for you to make me one?

[robnitro]

Good idea for 335d, not for x5d:

Nice craftsmanship but I hate to say it but our stock filter is huge and not a restriction. Even with it dirty, I reach at most 1-2 in h2o on my restriction gauge. Max 30 psi and all the way to redline (max mass flow is at high rpm and high boost). We have more of an issue with exhaust manifold pressure as tuning goes up.
If you take that k+n and unwrap the filter element and measure surface area vs the stock panel filter it will be close. My money is on the stock filter having more surface area. This would be a great mod on the 335d where they have an overly restrictive filter.

The piping is not a restriction at all. It's bigger all over cross section area wise than what the turbo inlet takes in.

[lnxguy]

Before and after dynos are needed. Great fab work!

[ucsbwsr]

Originally Posted by 335dlci

Nice write up sir

Thank you

Originally Posted by RL18

Looks awesome! Glad you took it on. Looks a whole lot better in there lol.

So uh... how much for you to make me one?

No plans on selling them. This guide should offer plenty of info you you want to copy it.

Originally Posted by lnxguy

Before and after dynos are needed. Great fab work!

Agreed, can't wait.

[RL18]

Originally Posted by ucsbwsr

No plans on selling them. This guide should offer plenty of info you you want to copy it.

Joking man. I'll probably do this now I have something to go off of. Keep us updated on how it does long term. I'd only be nervous running this in the winter with all the road salt and shit hitting this. You think the filter cover would need to be cleaned often?

[ucsbwsr]

Originally Posted by RL18

I'd only be nervous running this in the winter with all the road salt and shit hitting this. You think the filter cover would need to be cleaned often?

I have no idea and won't be able to test that, my winters are usually 70 and sunny. You might have better luck finding people who run the dry chargers on other vehicles in similar conditions. I know they are used for off-roading and extreme conditions like that but not sure what the service interval is like?

[CMichael]

Originally Posted by robnitro

Good idea for 335d, not for x5d:

Nice craftsmanship but I hate to say it but our stock filter is huge and not a restriction. Even with it dirty, I reach at most 1-2 in h2o on my restriction gauge. Max 30 psi and all the way to redline (max mass flow is at high rpm and high boost). We have more of an issue with exhaust manifold pressure as tuning goes up.
If you take that k+n and unwrap the filter element and measure surface area vs the stock panel filter it will be close. My money is on the stock filter having more surface area. This would be a great mod on the 335d where they have an overly restrictive filter.

The piping is not a restriction at all. It's bigger all over cross section area wise than what the turbo inlet takes in.

During my testing, I've shown 36 inches H2O restriction for the stock intake system when running a tune, and that's with a brand new filter. The vast majority of that is the convoluted intake ducting, which I'm sure works great when the car is stock, but not so much when tuned. I agree that the stock filter is not a major restriction, though it's unfortunately connected to a lot of other items which are.

[NoGuru]

Very nice! I love this custom stuff.

[robnitro]

Originally Posted by CMichael

During my testing, I've shown 36 inches H2O restriction for the stock intake system when running a tune, and that's with a brand new filter. The vast majority of that is the convoluted intake ducting, which I'm sure works great when the car is stock, but not so much when tuned. I agree that the stock filter is not a major restriction, though it's unfortunately connected to a lot of other items which are.

36 in h2o is 1.2 psi. I don't know how? I never got that high. I'm tuned but only to 30 psi max.
How much boost are you running and what kind of gauge do you use? My filter minder which is used on industrial generators and trucks only goes to 15 iirc.

My restriction gauge is right after the filter, before the maf. Though, I did mod the airbox to remove the segmented hump, near the section next to the springs. That flap stays closed until you suck in something big enough to basically clog the inlet anyway but I wanted to use more of the filter as the one I was replacing was cleaner at that area, making me wonder if that section was being unused.

Anyone else take readings and get this high restriction?

Looking forward to the dyno results.

[Jpm57tt]

Originally Posted by robnitro

36 in h2o is 1.2 psi. I don't know how? I never got that high. I'm tuned but only to 30 psi max.
How much boost are you running and what kind of gauge do you use? My filter minder which is used on industrial generators and trucks only goes to 15 iirc.

My restriction gauge is right after the filter, before the maf. Though, I did mod the airbox to remove the segmented hump, near the section next to the springs. That flap stays closed until you suck in something big enough to basically clog the inlet anyway but I wanted to use more of the filter as the one I was replacing was cleaner at that area, making me wonder if that section was being unused.

Anyone else take readings and get this high restriction?

Looking forward to the dyno results.

I have but in a 335d with dp and software its 38-40 on a complete stock box filter.
I think this intake will have great improvement on a tuned -dp car.

[robnitro]

Yes stock 335d has a small filter. My vw TDI had a bigger one and it was only 2L engine!

The x5d is another story... Very big filter..