Implicit Reimann solvers
 

Hello everyone, I have actually written a code for C-D Nozzle using the Implicit HLL and HLLC reimann solver...
1) The HLL code is working fine but the problem is,it is taking more time to converge compared my explicit code but it is saving on the number of iterations required to converge.
Starting value of CFL=1 and incrementing it by 1.1 times every iteration. My maximum CFL is 10, beyond that its not working.
2) Same problem even with HLLC that implicit is taking more time compared to explicit and also maximum CFL working is only 2.5.

I am using GMRES solver to solve the matrix and the end results seems to be pretty good..can any one explain me why is my implicit taking more time compared to explicit?