density altitude per hundredth

[leeseracing]

I know this is an old topic - but it piqued my interest. I'm wondering why a smaller displacement engine would be more affected by weather change. If I understand DA correctly, the concern is that the effect of pressure and humidity in the air take the place of where there could be more oxygen (which is good for combustion). When DA is a high number, that means that the air is crappy - could be a low barometer, but it also could be high humidity (again, high DA = low oxygen) If that is the case, wouldn't smaller engines feel an equal effect as the large engines - because they both are working with an equal percentage of oxygen in the air? If anything I would think that a larger displacement motor would be able to do MORE with the increase in oxygen in "better" air - because it can pull more into the chamber on the intake stroke (although, again, it would be the same percentage as the smaller motor, so how would smaller be more affected?)

I'm curious - I'm tracking DA for myself but we haven't changed motor size in 20 years so I've never really been exposed to how smaller/larger displacement reacts to changes in DA. Thanks for any responses!

[SuperCompDiv3]

Smaller engines are much more sensitive especially when barometer is added into the equation.

The only correct way to figure ratios is like Don Higgins said:
Same day, same lane. 60 foot must be within .01. That is the only way to verify ratios of air quality to ET differences.

I see many stockers that are 50 - 80 feet per .01 on the Crew Chief Software. While guys with 632 inch motors can be upwards of 400 feet per .01. The reason I have been told is the carburetor size. Smaller carbs bottle up the efficiency and are more sensitive.