
Considering that Tetraethyl Orthosilicate has been used on Methalox engines, to reduce the heat flux through the walls of the combustion chamber, what would the maximum specific impulse of an engine that uses Oxygen as oxidizer, and only Tetraethyl Orthosilicate as fuel, be?
I've never heard of it being used with methane, only alcohol. It is used because it forms solid deposits, so I bet it would have very poor performance if used alone (assuming it would burn at all). NASA CEA should be able to give you theoretical performance:
https://cearun.grc.nasa.gov/Edit: CEA apparently doesn't have TEOS
No compounds in the CEA Database contain H, C, O and Si.
Please go back & check your selections.