HORRIBLE fuel mileage

[Rawze]

(01-26-2023 )Redland1 Wrote:  Want to mention that the turbo goes up to 40psi now and saw it go a hair over that yesterday.

40 psi will eventually kill than engine. Your turbo is choking the engine at that boost level. CM870 ISX cannot take that boost level.. in fact.. NO ISX can take boost that high. It should not be more than about 37~ish max psi on it in a hard pull.

just for reference.. With no egr ... it only takes about 38~ish psi to make 900+ Horsepower with an 870 or 871. ref: http://rawze.com/forums/showthread.php?t...03#pid6803

I have seen people blow holes thru pistons at 41+ psi on the isx, so a person is dancing with razor-blades of they are letting their engine get to 40+.

If that turbo was set too aggressive then it will kill the fuel mileage across the board + eventually harm the engine.

If it was someone who made the program recommended by the forum here, then you should get with them to have that boost lowered back to normal levels, and to remove any aggressive numbers in the lower fueling ranges. -= It is not "snappy" that you want from a CM870 and its turbo settings, the air operated turbo is just too clunky for that. It needs to be a bit "lazy" .. and this will make the fuel mileage better.

Also... if it was not by someone recommended from here.. the you should know that bad delete programming is a plague.. so depending on who did it.. that might be a big part of the problem. Am curious who did the programming (pm me if you don't want to state it publicly) and/or send me a copy of the program for review.