Hi Andrey,
I think you should try with the timeouts defined inside the ICM, this PI part is the responsible to the http connections. Check these links:
Timeout Options for ICM and Web Dispatcher - SAP Web Dispatcher - SAP Library
Increase SAP ICM HTTP_TIMEOUT Runtime - Basis Corner - SCN Wiki
Just to add these parameters:
rdisp/max_wpun_time (http://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/a4dcf62d-0a01-0010-afa5-e8edcecbc4f1?QuickLink=index&…)
SXMB_ADM -> Integration engine -> Category: RUNTIME->HTTP_TIMEOUT
Regards.