Ok.. I am running this question off of both the Rotary Engine Newsletter and the FlyRotary groups. This is regarding the 2nd gen 13B turbo we are putting in the Velocity SE/SUV

Background:
I have pretty much settled on having to fabricate my own intake manifold, using a portion of the stock lower (LIM) and stock upper (UIM) intake manifolds and the stock Throttle Body. In between these stock parts I will be welding 4 individual alumninum runners, with an estimated runner length in the neighborhood of twenty inches or so.

The stock LIM provides a mating surface to the block and nearly a 90 degree turn in the intake path. The Intake runners, as fabricated, will make a 90 degree turn over the top of the block and lay across the top of the engine, with the UIM and throttle body on the plug side of the engine. Injectors will be close to the ports/near or in the LIM.

The issue: The stock throttle body and the UIM have a significant amount of mass and if I attach it only at one point to the block (at the LIM end) that is a lot of leverage being placed on welds, giving rise to fatigue of the aluminum runners and welds. So, it would be prudent to secure the entire assembly to prevent excess movement and strain.

Ideas I have so far include using some of the bolt holes in the top of the rotor housings to mount a pedestal for the runners. The stock TB also has a single blind hole in the bottom that appears to be appropriate for tapping/threading and using this to make a single point hold-down for the TB. The plan would be to fab a pedestal out of angle metal/ that would mount on the stock engine mount studs on the plug side of the engine. This pedestal would ensure support of the TB and also not interfere with access to the plugs, as I expect to have to change them every 25-50 hours in a worst case scenario - it would be poor design to have to remove in the intake to reach the plugs.

The REAL issue: The runners are 1 1/2 and 1 3/4 ID 6061 1/8" thick aluminum tubing. I will be getting them bent to desired shape soon. What I am concerned about is deformation and strain on welds and intake parts due to thermal expansion and contraction. If I secure the runners at a midpoint and the TB at the far end, this may not permit an "exit strategy" for expansional forces. I have considered not securing the runners "tightly" and using a slotted bolt hole for the hold-down bolts to be placed through on the hold-down fittings on the TB and UIM. Lightly torqueing, using rubber grommets, a lubricated flange or something to permit the intake parts to slide a fraction of an inch may allow for what I THINK may occur. Safety wire would prevent the bolts from backing out. The goal would be to allow linear excursion of the intake parts without allowing any unnecessary degrees of freedom.

The questions:
1) Is my concern a valid one for the lengths and material I am considering. The stock assembly has enough curves in it to accomodate expansion. Mine may not.

2) Is my potential solution a workable sounding solution? What needs to be tweaked?

3) What may I be missing?

4) What have other people done with similar long runs of tubing?

Dave Staten
eaa12@earthlink.net