So, I got a deal on an intake tube (thanks Miles7), and I have decided to share my process with everyone!

This is a DIY project, again using cheap materials from home improvement stores and such.

if anyone sees room for improvement, or has suggestions for build ideas, or has knowledge to assist me when i run into a snag, please feel free to chime in!

So, as some of you may know, the Mini intake tube, (from TB to SC) is quite a strange character, consisting of strange twists and crimps. To me, it looks like someone squished the tube as they put it in, and then made a mold out of it :p

In order to keep this piece as "stock" as possible, with respects to having it just drop in, I had to build a Jig to hold the end pieces in place.

 

Here are the replacement pieces I plan to use. Somehow, i have to securely attach these to the end pieces of the stock tube, while maintaining its original "shape" within the jig.

 

Here are some pictures of the Insides of the tube. You can see the strange restrictions and bends i was talking about.

I am hoping to alleviate all of that using this electrical conduit i found.

I ended up cutting out the entire middle of the tube, in order to replace it with the non-restrictive conduit piping. I found a neat little side piece that should work for the BPV connection (above picture).

 

Here are a couple of pics of the mock up for replacing that tubes guts. As you can see, the bend of the pipe is almost the same as the stock tube! good thing for me. the opening that connects to the Throttle Body is nice and Round, i should not have too much issue making that connection. However, the connection for the SC is another story. This is the part where I could use some suggestions!

*(i have included a pic that shows both the SC connection, and another portion of the main tube, which further shows its strange morphs and bends)

 

wow this is pretty crazy! i like it tho! is the whole point of doing this to get better air flow? for the supercharger side why dont you use the piece off the oem part that you cut off and some how mold it to your new pipe. maybe build up the sides with some type of adhesive and connect them. maybe heat it up and form fit it to your new pipe and use some kind of rubber coupler to seal the two sides....idk.... just promise me you wont use any duck tape haha i wonder if this will make the whine in your supercharger much louder? cool idea tho!

 

Any new work done? Or pics?

 

not as of yet. i was looking for a replacement throttle body adapter plate, but they dont make them in 2.5 inch sizes :( so, im back to cutting the original. I have to cut the plastic off the original, leaving enough to bolt a silicone hose onto. Then, I have to measure, and order said hose off ebay. I suspect i will have to use a 2.75" to 2.5" reducer coupler, as the conduit is quite thick. that will take care of the TB side...

still contemplating the SC connection. This will be quite difficult, as it is an odd shape...

 

In any system, the most restrective spot is what holds the whole thing back...
On the gen1 s, a few places sold a boared out enlarged throttlebody.....folks installing it found no change...it was simple not the restrection. Since the throttle body is SMALLER THAN THUBE LEADING TO IT, i suspect that while the tube is not the best flowing part, it is still better than the TB, leading me to say it may be a fun project, but the challange in making a 100% airtight and HEAT RESISTANT tube is a challenge.....while the pvc conduit is of a similar shape, anf you might be able to shape it with a heat gun, this PROPERTY IS IT DRAWBACK...DEFORMATION FROM HEAT.......
Interesting idea, but i think you may be stuck using metal tubes and silocone couples/connectors like on a custom intake. Good thinking...brainstorming is great!!

 

well, that PVC conduit is fairly heady duty stuff. Im not sure if its made of the same material as standard plumbing pvc, as i imagine it would have to have some sort of fire and weather rating. Plus, its really quite thick, i dont imagine it will deform easily with heat... and itd have to be a LOT of heat.... I think id have better luck forming / deforming the TB tube before that conduit piece.

im much more concerned with its connection to the SC portion than anything, again because that is an odd shape: its oval, not round. and, they dont exactly make "oval" silicone couplers... do they?

as further heat protection, i have some insulative wrap for piping and such, i planned on wrapping the entire pipe, both for protection, and to keep heat soak down.

 

Silcone couplers go over any regular shape....heck they are used as sc replacent couolers...just tge matter of finding the right one the fits both end, and clamps to hold it....the clamp may need a bit of a backer to round out the shape, but if you toy around with it, ibet it could be done.
The idea of using a non heat resistant polly in an engine bay makes a shudder a bit...
Sure i bet it has flame retardants added to prevent burning for the short term, but different plastics have differing properties/costs....vinyl under the hood just is not used for some reason...i bet it has to do with heat/flambility in more than just the near term.
One thing to consider...any chance the tube was computer moddled for hours and hours and test to flow from the round to the odd intake shape?! Not much on a car is done without lots of research .....

 

good point on the silicone coupler. Id like to use one, on the SC side of the tube. i will need help / ideas for the clamp, as you said, and i figd thatd be the spot that would be hardest to clamp... guess they dont make oval clamps!... or do they?! lol

as for the computer modeling, Yes, the spent hours on it, but, did they make it the best shape for performance? im willing to bet NO. i think they made it easy to install, but did less in the way of performance..

 

UPDATE!

after another hour or so working on this project, I have run into another snag :(
Turns out, as Zippy foretold, the electrical conduit looks like it will NOT hold up to the heat extremes of the engine bay.

the conduit itself gives me its exact specs: 90 deg C

after using my heat gun to try to adjust the shape of a piece of conduit, i found out that it does indeed get quite soft when hot. its almost as soft as play-dough :(
i could spray it with high temp paint, then wrap it in insulative pipe wrap, but i fear for doing this as prolonged heat would eventually seep through this armor, causing the entire structure to most likely collapse, and surely deform.

another issue I am running into is the connection from the TB on. That "port" is not round, FYI, and is actually fairly small and restricted. After I managed to cut away more of the stock tube, there is not enough room left on the original "flat piece" to give a good grip for a silicone tube and clamp (unless i shave down the bumps holding on the bolts).

I have decided to port out the TB side, and I was in the process of making the conduit fit INSIDE of that, so that I could secure it with a silicone hose, but alas, I ran into the temp issue of the material itself.

I am at this point tempted to try and go full Metal with this, making connections with silicone tubing, where applicable.... My other thought, was to make the ENTIRE TUBE out of silicone. This could solve my temp issues, and even my connection issues, but I have never made a silicone hose before, and im sure its not super cheap.

if anyone knows of 1. some good heat resistant plastic tubing (abs?) or 2. has a good instructable on making silicone tubes, or 3. has a whole new concept all together, im all ears

*p.s. will post pics later, i still have to clean up from my mess yesterday :P

 

i was hoping ultimately to use one of these:

http://www.ebay.com/itm/84-91-BMW-E3...ab62e2&vxp=mtr

and just ditch the factory connection from the TB to the SC tube. This would give me the perfect area to attach a silicone or other tube. But alas, they dont directly make 2.5" TB adapters (apparently every other car in the world uses either a 3" or 4"!). i would like to try this one in particular, as it appears to be closest in size (stock piece measures 3.25" across, each side, and actually has varying inlet sizes from just Under 2.5" to just Over 2.5"...) but i dont really wanna keep throwing $10 out the window for adapters that probably wont work.

so, if anyone Finds this elusive (and prolly non-existent) 2.5" TB / MAF adapter, pls post a product link!

 

Plastic just wont work. There is not enough materials available for this project in the plastic section of any home improvement store. So, after an hour? of perusing HD, I finally found something that should work!

"Bendable" metal Duct Work! This is a 3" diameter metal duct work piece, and a 4" to 3" reducer. The reducer will be used to clamp around the SC connection, while the other end will be clamped / bolted to the TB side.

I was able to find a piece just like the plastic one that was to be used for the BPV. I also found some locking bushings to use with it to hold in place proper.

The plan is to shape the end pieces so they fit their respective connections, and shape the tube to something that will obviously fit the 2 original pieces, resembling the stock tube. After final fitment, and all connections are made and again finalized, I will have to seal the joints to prevent leakage. Planned on using RTV or liquid gasket for this step, as that product is both heat resistant, sealing, easy to work with, readily available, and cheap.

Ultimately I would like to Heat Wrap this tube, sealing that with high temp silicone heat wrap spray. This will provide "insurance" for the RTV, as well as keep down on heat soak, and protect the metal itself from rust and deformation, all while adding to its strength.

Still debating on how to actually attach this to the stock plastic pieces. I was considering rivets, bolts, silicone tubing, RTV, clamps, or some multitude of what i just listed.

I feel the hardest part of this may be the actual BPV tube placement, as this will be difficult without taking half the car apart to properly fit it...