Intake manifold construction, intercoolers

Bruce nacelp at bright.net
Tue Dec 4 13:15:34 GMT 2001



Any intercooler that you use in the plenum, would either be too small to be
effective, or need fluids that are really cold.  you'll also be losing the
surface area of the piping for heat transfer.  With the in plenum cooler,
you also be exposing it to the heat of the manifold, thru all it mounts, and
you libel to losing alot  of cooling effect to cooling the manifold.   For a
plenum to be effective the opening intake valve must be able to draw against
the plenum, having the finning in the plenum is going to **straighten** the
air flow, and so the opening valve is going to have to *try* and have this
air change direction, rather then drawing against a rather turbulent chamber
of waves, and air movement.  BTW, this is the same set up as International
Harvester uses on some of it's deisel applications, but they are extremely
low rpm motors.  They also have an area above the I/C that is about equal to
the area below it.  I think you'd have to have a really huge plenum for any
kind of free reving motor to really work,  in the IH version they use
coolant in the I/C so as to just reduce the high peaks of air temp..
  I think it's a stop gap measure, and limited in practical application.
For a diesel tractor working in the fields it's OK.
  I had choices of 2.5 and 3.0" piping for the front mount I/C in my GN ,
and after some investigation think my original thoughts of using the 3" are
best.  Trading a little off idle / low rpm response for cooler ultimate flow
should be worth while.  I'm lucky in so far as mine is an automatic trannied
car, so I can tolerate the lack of really down low torque since converter
slippage with be absorbing that loss anyway, or rather allowing the engine
to rev thru that zone in a lightly loaded state.
  Huge preturbo plumbing, large post turbo, as much I/C as can be fitted,
and calibrate as necessary.   then finalize the hardware to best use the
above.  At least that's the way I'm headed.
Bruce




----- Original Message -----
From: "Rausch, Bernd" <br at rnt.de>
To: "Rausch, Bernd" <br at rnt.de>; <diy_efi at diy-efi.org>
Sent: Tuesday, December 04, 2001 3:04 AM
Subject: Intake manifold construction, intercoolers


> Thanks for the responses I got, I have some additional questions:
>
> At the moment, I have an air/air intercooler per side (twinturbo V
> engine). I have per side: three 90deg bends, about 2m piping, two
> intercooler mandifolds with 90deg bends and four silicone hoses.
>
> I am thinking of welding an air/liquid intercooler core from Spearco
> directly in the intake plenum. The throttle body will be upstream of the
> intercooler. With this construction I can exit the turbo in a straigt
> line, with an expanding pipe of about 0.4m to the throttle body. I will
> only need one hose (turbo has a flange at the outlet). This setup will
> save me five 90deg bends, 1.6m piping, three silicone hoses and two
> manifolds at the intercooler per side.
>
>       TB   IC     intake runners
>        |---------|------------|
>        |   ||    |------------|
> -------|   ||    |
>  ->    /   ||    |------------|
> -------|   ||    |------------|
>        |   ||    |
>        |   ||    |------------|
>        |---------|------------|
>
> -Is there any downside of this setup ?
> -How do I calculate intake plenum volume ? Only the volume on the
> downstream side of the intercooler or the complete plenum including
> intercooler ?
>
>
> Any help would be appreciated.
> Bernd
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