Remove set_time_limit() call. CodeIgniter should respect php.ini setting.
diff --git a/system/core/CodeIgniter.php b/system/core/CodeIgniter.php
index 00db6e1..e1892ee 100755
--- a/system/core/CodeIgniter.php
+++ b/system/core/CodeIgniter.php
@@ -101,17 +101,6 @@
 
 /*
  * ------------------------------------------------------
- *  Set a liberal script execution time limit
- * ------------------------------------------------------
- */
-	if (function_exists('set_time_limit') && @ini_get('safe_mode') == 0
-		&& php_sapi_name() !== 'cli') // Do not override the Time Limit value if running from Command Line
-	{
-		@set_time_limit(300);
-	}
-
-/*
- * ------------------------------------------------------
  *  Start the timer... tick tock tick tock...
  * ------------------------------------------------------
  */