Quartus eliminates intermediate signal causing an overflow.

When inputs are hardcoded some additional optimizations may occur which is why I was asking. Typically when I need to worry about this sort of thing I carry out the operations as sequential assignments. So something like this:

input signed [13:0] b;

input signed [13:0] c;

input signed [13:0] d;

output signed [13:0] e;

wire signed [27:0] g;

wire signed [27:0] f;

assign g = b * c;

assign f = g / d;

assign e = f[13:0];

Have you tried doing the same and if so does the same behavior occur? Also to prevent optimizations from happening you can use the (* keep *) keyword. So when you declare 'f' you would do it like this:

(* keep *) wire signed [27:0] f;