S/C'd 37VHR vs. 35HR?

phunk

VHR vs HR with the same supercharger... interesting conversation.

Think of PSI as your measurement of how much your engine is restricting the air leaving the supercharger. Take everything identical (piping, IC, pulley ratio, temps), so that precisely the same amount of air is entering both HR and VHR throttles. How much "boost" each generates indicates how well that engine flows. The lower the boost, the better the engine is naturally flowing.

There is reason to assume the VHR will flow better than the HR. With about 4.5mm greater stroke, the cylinders will be attempting to draw in 5-6% more air. Assuming the cylinder heads allow it, or at least some of it, evacuating the air backed up in the intake manifold more quickly into each cylinder's intake stroke will generate a lower boost pressure for the VHR engine. If the VHR cylinder heads (valves, lift and timing profile, as a package) were extremely restrictive, its possible to hurt airflow to levels lower than the HR despite the increase in displacement. This is unlikely, based on the type of power output we are seeing between the 2 engines comparatively.

The VHR engine has a higher static compression ratio. This means that, all other things alike, it will more effectively create power from the fuel/air mixture it is burning. So, at the same airflow from the supercharger, you will make more power through increased volumetric efficiency, despite the lower "boost" in the manifold.

So to answer your question, yes, if everything else is indentical, a HR will require more boost to generate the power a VHR does.

If NA vs NA one engine makes more power, the same one will pretty much always make more power boosted too.

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