I doubt that the second sentence translates to “faster”, because “as fast as I can” means at my maximum speed. The first sentence uses the word twice, as pointed out by Colin Fine, so it is also a “Comparative of Equality” as you call it, but it compares the original size to double the size. So actually the first translation is also not accurate:
a = 2b does not mean the same thing as
a > b
In other words: a sentence with the structure
A is as B as C
always means: B is equal for A and C
But beware of optional modifiers like twice, half, n times. These can be between is and as, like for example:
A is 7.3 times as rich as C
which means exactly this:
The wealth (richness) of A is exactly 7.3 times the wealth of C.
Edit: I've thought of more modifiers: "at least", "at most", "nearly", "hardly", "likely", "certainly", “not” and I'm sure many adverbs would be able to fill this spot depending on context. Example:
A is at least as good as B for the job.
Meaning A is equally good or better, compared to B, analogous to ≥
Not all of these have obvious counterparts in mathematical notation, I wouldn’t know how to write “nearly”, but the starting point is always equality.