08 ISX Boost issue

[Marajin]

(03-21-2016 )boots769 Wrote:  Thanks Marajin ,, I usually test run anything ive tuned and have found that the overlays for 550/1850 running in most chassis in Australia will run to just over 40psi when pushed hard and will cruise about 20-25 psi , usually get good mileage (2-2.4kpl) ,,just have not seen turbo overspeed derate even in 600/2050 cals that if you dont bring boost right down will blow to 45psi ,, will recal tgc min opening to 45 max and set turbo derate threshhold from 105k to 108 or 110k and test run the sucker ..all seems to go well until pulling hard at or around max power ,, I usually expect to see max boost around max torque , just seems a little strange to be overspeeding at higher rpm

Verify you have a good speed sensor, etc. like I mentioned above. (i was editing post when you replied). I have seen it several times where speed sensor reads incorrectly too. 38 psi should be about 92-96 krpm in most of them, but there is variation depending on truck design.

You could also document the program to a text file and look for turbo related settings that are as low as 90 krpm in the print out. maybe that will help too.

45 psi is too much for that engine. it only takes 40 psi to make 900 horsepower. 600 - 700 horsepower should only peak about 38 - 39 psi max.

it is also generally safe to set turbo to go 115k - 120k rpm in most of them too if need be. higher is pushing your limits.