AW: Intake manifold construction, intercoolers

[Bernd Felsche]

Rausch, Bernd tapped away at the keyboard with:

> the complete intake manifold with plenum and intake runners will
> be custom fabricated. So I am open for various suggestions.

In that case, having separate throttles is even more attractive.

> I do not understand why integrating the IC in the plenum hurts
> throttle response. In a "classic" setup I have the IC before the
> throttle body, with extra piping and manifolds on the IC, so
> throttle response should become even better.

The plenum volume; that between the throttle valve and the intake
valve determines how quickly a pressure change can occur to change
airflow.

> I thought individual throttle-bodies are normally used for engines
> with long duration cams to avoid cross-flow and get better
> idle/part throttle response ? I want to avoid the extra work (and
> money) integrating 6 TB´s and linkage.

Individual throttles are used where throttle response is required or
where there's no common plenum.

I envisage a common throttle plate with separate butterflies on a
common shaft (per side in a Vee engine). It's simple machining to
bore some suitable holes through a sandwich of two long aluminium
plates, machine a shaft and to make some butterflies. The throttle
cable enters what is the post-IC distribution box and pulls on a
lever attached to the butterfly shaft. A spring counters the cable
to close the butterflies.

If the runners leave at opposite sides of the air distribution box,
then a relay link can mirror the motion for an identical setup of
throttles on the opposite side. There are only two throttle bodies;
each with 3 butterflies on a common shaft.

A competent machinist can probably make all the throttle parts in
less than a day using a lathe and bench drill in addition to some
hand tools. A milling machine would be useful but not essential.
Especially useful for creating the lip against which the butterflies
close on each half of the throttle plate sandwich, and for chasing a
groove for the butterfly shaft and its bushes. (Don't skimp on the
bushes - the shaft has to be quite thin in places and could be bent
by a backfire, causing it to stick subsequently.)

Each throttle plate sandwich, complete with butterflies and spring
can be held together with screws through one plate tapped into the
other.

Don't let the price of commercial units fool you into thinking the
parts are hard to make.

If you want to, you can attach the spigots for the inlet runners
directly to the throttle plates and use the plates as a side of the
distribution box.

-- 
Bernd Felsche - Innovative Reckoning, Perth, Western Australia
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