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Loses, and manual cad systems
Mark Allanson - 14/10/08 at 08:03 PM

It seems that making exhaust manifolds is hampered by having to use expensive mandrel benders or buying expensive preformed bends.

The most used word seems to be 'expensive'!

I had a wandering thought today about making square sectioned bends using sections of big 'washers' and flat strap. What would the losses be in efficiency bearing in mind a square section tube has a significantly higher cross sectional area than round?

I think you could make up a 4:2:1 manifold in a day for little more than pennies

any thoughts? Rescued attachment Manifold 2.GIF
Rescued attachment Manifold 2.GIF

Thinking about it - 14/10/08 at 08:13 PM

How will you bend the square tube?

hellbent345 - 14/10/08 at 08:15 PM

can you explain exactly how you were thinking of bending the tube? i know from reading the above that you werent hinking of bending it persay, i think, but dont know exactly what you were thinking? it seems an interesting idea if it can be done

Mark Allanson - 14/10/08 at 08:32 PM

I wasn't thinking of bending it at all, but fabricating it from cut curved parts for the sides and flat strap for the tops and bottoms.

The curved sides could be cut from large 'washers' if such a thing is available, or cut out of plate (more time consuming).

mr henderson - 14/10/08 at 08:41 PM

I think it's a very interesting and novel idea. I guess the change in cross section isn't ideal, but so what, at least the pipe is gwtting bigger rather than smaller.

How do you see the pipes coming together?

John

Mark Allanson - 14/10/08 at 08:56 PM

I think using 1.5" primaries running into a 3" square ERW tube and the converting to round with a little mild planishing then exiting the lower engine bay in a conventional manner.

The square section tube is undoubtedly less efficient than round for the same given sectional area, but the increased size may well counter any losses.

Does anyone use/make/sell large 'washers' 4"-6" with a 2.5"-4.5" hole in 1.6-2mm mild?

turboben - 14/10/08 at 08:58 PM

I made my (turbo) manifold from weldable handrail sections. It was very cheap - do a search for weld sections /handrail.

Ben

Mr Whippy - 15/10/08 at 07:26 AM

quote:
Originally posted by turboben
I made my (turbo) manifold from weldable handrail sections. It was very cheap - do a search for weld sections /handrail.

Ben


good idea

nick205 - 15/10/08 at 10:51 AM

It's an interesting idea, but I think you'd have to weigh it up against using the OEM cast iron manifold linked to a tubular down pipe a la tin top install.

From what you describe, I can't see it being any better or worse in terms of performance or ease of fitting than the OEM manifold.