Losses During Overlap

[Indycars]

Is there any information on the importance of the ridge that runs between the intake and exhaust valves???

On one hand the higher this ridge the more it restricts flow, but on the other hand it would stop some of the intake flow from going straight across and out the exhaust during overlap. Maybe there is some level of overlap where it starts to make sense to keep some height above the valves to stop overlap losses.?

 

[grumpyvette]

Id be far more concerned with the heat and wear on the exhaust valve seat causing seat erosion, and the limited mass of metal in the hardened exhaust valve seat than any slight fuel/air mix bleed over during overlap, theres always some scavenging losses and bleed over during the overlap, but any wasted fuel/air mix burned in the exhaust is more a minimal mileage loss than a problem with function or power produced.
guys forget that it only takes about 40hp to cruise at a steady 60 mph, and if your producing peak power your spinning most sbc engines up in the 6000rpm range, at 6000rpm theres about 50 intake strokes PER SECOND and the overlap might be 1/6Th of even that time frame, so theres not a great deal of overlap flow going out the exhaust simply because it takes time for air flow to over come and reverse the inertia, in the direction of initial flow

due to the limited time and inertia of the air/fuel mix theres usually minimal flow loss due to overlap

Good atomization is a big part of the picture – but it is far from all of the picture