Wednesday, 5 January 2011

Single Plane Manifold

A new year and a new set of results...

As with the dual plane manifold, I have created a CAD model that lets me simulate and analyse the air flow down individual runners of the single plane manifold:

The model was run under the same conditions as the dual plane manifold i.e. each inlet valve is opened in sequence and a pressure drop applied to approximate the piston velocity. The simulation is then interrogated for the mass flow into each cylinder. The mass flow variation against the average for each cylinder is shown below:

The average mass flow was 18% higher in the single plane manifold when compared to the dual plane design indicating that the engine would be able to breathe more easily and hence produce more power with this type of manifold (unfortunately it does not represent an 18% gain in power due to the complex flow conditions present when the engine is drawing air in sequence with the firing order, not the simple steady state conditions of the simulation). However, it can be seen that the cylinder-to-cylinder variation is still in the order of the dual plane design (-20% / +10% variation) indicating that this manifold is also not ideal for a port fuel injection application. Either manifold is suited to a carburettor or throttle body injection since the air-fuel ratio is established at the throttle plate rather than the valve.

Given the above information and a distinct lack of a readily available stock port fuel injected manifolds on this side of the pond (I didn't like the look of it much anyway!), I have decided to look at the possibility of fabricating my own. The CAD work I have done to date suggests a twin-plenum design would be the best for packaging around the known hard points. Watch this space...