Silicone Elbow Workshop
Courtesy of: Mance Etheredge

 

OK, a quick down-n-dirty mini silicone elbow workshop...


I'm getting too many emails to answer so I'm gonna post this here. The pic below is of the 3" silicone elbow used in the S3 hose kits of yore. It has been cut down to clear the A4/B5 and C4 cars between throttle body and firewall. This is the max that can be cut from the sleeve and still manage to get them clamped on to the throttle body flange securely. If you have 3.10" between the outer rim of your throttle body and firewall this will work for you.

This also shows why I don't like the short silicone elbows with the "bumps" near their inside radius. If that bump is there when you cut your elbows down you cannot get the clamps to tighten on the bumps without them "squishing" the elbow out & away from the throttle body flange seat, pushing it away from the flange seat and nearer (or into) the firewall.

TB= Throttle Body
TBF= Throttle Body Flange width
RS= Recovery sleeve

Pardon the text in this pic as it was all done in " MS paint" (ick!).


 
Spend MORE time making your elbow flow than on the entire installation...


of all the other parts of your hose kit. It's altogether common for me to spend 3 hours just making an elbow flow.

Short, tight-radius elbows are almost impossible to wrap smoothly for much the same reasons you cant get 2" wide tape to conform and lay flat on a baseball. It's called "compound curvature" and it's a necessary evil when dealing with tight radii.

A peek inside the short elbows will reveal something that looks like the pic below. That just cannot be allowed to remain and live there if "flow" is on the menu.

There's only one way to do this and thats by sanding with a drum (dremel) or flap wheels (die grinder or Foredom type) as you cannot cut this stuff easily with an X-acto knife or razor blade. And yes, it matters! That single ridge in this pic was costing me just under 42CFM of air (between both elbows). It's a dramatic flow impediment! And remember you have TWO silicone elbows to do this on!

Same elbow after sanding/smoothing...