Turbo manifold design.

[justin ivan]

If you are insistent on running a single flange then you should enlarge the 
hole and use a washer as it was suggested.


>From: Jörgen Karlsson <jurg at pp.sbbs.se>
>Reply-To: diy_efi at diy-efi.org
>To: <diy_efi at diy-efi.org>
>Subject: RE: Turbo manifold design.
>Date: Wed, 10 Jan 2001 17:38:21 +0100
>
>Justin Ivan wrote:
>
> > Not sure if I agree with everyting that you are saying. When the
> > flange is a
> > single piece, essential all (really just a large portion) of the
> > expansion
> > takes place at the ends of the flange, the material in between 
>constrains
> > the flange from expanding towards the center. When the flange is
> > separated,
> > each port can expand in 2 directions, therefore has more flexibility.
> > If someone can debunk this please do.
>
>If the manifold had looked like an ordinary V8 header I wouldn't have
>anything against using separate flanges, it would be far better then using
>one large flange. An ordinary header usually has pretty long runners in 
>thin
>material that are pretty flexible.
>
>In my case the distance between the ports are 86mm and the runners are
>routed the shortest possible way to the runner next to it, turbo exhaust
>manifolds must also be made from a bit heavier tubes then ordinary headers.
>To prevent cracking I used high quality tube bends and welded it with
>electrodes made for the specific material.
>
>This makes my manifold very strong, to make the ends of it flex 2mm 
>requires
>a lot of force. A lot more force then I would trust the manifold studs 
>with.
>
>When we use separate flanges the temperature of the tubes in the exhaust
>manifold decides how long the manifold will be. From room temperature to
>700ºC the manifold will grow 4mm.
>
>If we use one long flange that is bolted to the head, the temperature of 
>the
>flange will decide the length of the manifold. Since one side of this 
>flange
>is bolted to the engine that I guess are 200ºC around the ports, one side
>are welded to the runners and 80% of its surface are exposed to the air I
>would guess that it will have a temperature somewhere in the middle of the
>200º engine and the 700ºrunners. Hopefully closer to the engine 
>temperature.
>I think that the flange temperature will be around 250-350ºC. Since the 
>1/2"
>thick flange will be a lot stronger then the red hot runners of the 
>manifold
>it will not be affected much by the runners will to grow 4mm when the 
>flange
>only has grown 1-2mm, the runners will hopefully take the beating without
>cracking to often.
>
>Since the cylinderhead will grow with temperature too the flange and the
>head will hopefully grow about the same amount.
>
>
>Jörgen
>
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