The factory ecu on the cat turbo automatically targets 170kpa absolute manifold pressure. At my elevation of about 1100ft, this is about 12 psig. At 9500 ft, it is about 16.5 psig for the same absolute manifold pressure. Actual (uncorrected) hp is only slightly reduced due to the elevated intake temps and the same clutching from low elevation works fine. With free flowing exhaust (D&D Barker, Silent choice, or straight pipe) the stock turbo appears capable of maintaining up to about 190 kpa at 9500ft elevation. Even at stock boost levels, opening up the exhaust is a huge power gain. With stock muffler, the stock pressure of 170kpa is probably about it at 10,000ft. When operating on the edge of the compressor map, ambient temp also has a huge influence, with the turbo capable of much more in colder air. One thing for the non-turbo guys to remember is that the corrected hp (how you would compare to an n/a or any other motor) goes way up as you maintain constant absolute pressure at higher elevations. So when your stock boost 1100t is at 170 kpa at 10,000ft, the hp is correcting to well over 200hp. We (D&D/Boondocker) have been testing these motors since 2008, and I feel confident that most pump gas riders will be fine with the stock turbo to 10,000ft. Those running race fuel (or meth injection) boost levels will benefit more from a larger turbo.
