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Following on from a previous topic of some years back on flow simulation through SU carbies has any one done on on PI manifolds?

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Might be something on here somewhere.

 

Think it's fair to say that the PI manifolds (especially the early ones) will flow more than the head, even a well-modded head.  What can have a positive effect is changing the effective length of the inlet tracts by adding trumpets or even suitably sized, smooth bore hose.  There are folks on here who have tried it and reporting that long is good with space/packaging being the limitation.  Some have also moved the injector locations back from the head which is supposed to help power at big throttle openings.

 

What do you have and what are you aiming for?

 

Nick

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I am looking at the interface between the inlet port and the manifold as I have  a cylinder head incorrectly ported so that the inlet port dia is nearly 3 mm larger than the manifold dia. I want to see if it is worth opening up the manifold back to the butterfly's or leave as is.

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2L or 2.5L?  Ports are too big for the 2L as  standard and arguably for the 2.5 too.

 

The PI manifolds have a taper to them - ports are something like 30mm ID (if the the earlier round type) and the butterflies about 46mm (too big!!), so you could open them out (if there's enough material wall thickness to stand it) without loosing all the taper.

 

I'd probably leave them as they are though - the step is the right way for flow and the section change just might help increase the pressure at the back of the valve......  Plus if you open out the PI manifolds they'll be useless for any other head.

 

Nick

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I know that CW recommends leaving a step between inlet and head ports, i.e. manifold smaller than head as it helps prevent reversion in the port at lower and medium rpms on carb based systems. Do I? No.

 

Alan 

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