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I stumbled into this research paper yesterday from the National Renewable Energy Laboratory from 2016. Basically it goes into their current level of understanding of where vapor lock occurs in a fuel system and how it is tied to the fuel blend and it's volatility. It covers current fuel blends, up to and beyond E85, and driveabilty problems associated with vapor lock even in current cars with EFI and Direct Injection. It does not cover or mention older fuel blends, I wish it did.
It does however make a few mentions of how older carbureted cars are even more sensitive to this issue. It does mention Aeromotive and how they believe the suction side of a pump is a strong area of concern for vapor lock.
Very technical reading, but exactly on-target for us. Here is the original graph, and my doctored up graph for us carburetor lovers. Also attached is the original 23 page research article and my 1 page "cliffs notes" with extracted comments.
Original graph
With my carburetor edits added
If the Vapor Pressure of the Fuel (at temp) exceeds the Normal pressure of the atmosphere (or the fuel line pressure) it will "boil" Even when it gets close it makes a lot more vapor than normal.
Last edited by leigh1322; Mar 17, 2020 at 11:01 AM.
Fuel Volatility and Vapor Lock
