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 aluminum 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 torquing, 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 accommodate
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

Hard to say. A trick Tracy uses is to put your hand on the assemble
when the engine is running full chat on the ground and see if anything
is vibrating.

Paul Lamar

Dave,
The mistral set-up has flexible hose joints, to my mind this is simple and
allows for some movement between bottom, tube and TB. I doubt the tubes
weigh much and the bottom( of the manifold) is secured to the engine - you
would need to secure the TB and Plenum independently and let the tubes float
between the two.
MO- FWIW.
George ( down under)

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