08 ISX Boost issue

[Marajin]

(03-21-2016 )boots769 Wrote:  Gday guys .. i have a similar problem , sort of ..I have just done a {**Content removed by protection bot**} also reactivated the oil and temp shutdowns. Am now getting turbo overspeed derate at higher rpms while under load usually pulling up hill .... have already pulled the turbo min closeing tables down to 50% .. do i just need to continue dropping this table to bring turbo speed down ...or is it possible the by removeing the derates that the turbo is able to reach overspeed threshhold? have also noticed {**Content removed by protection bot**} is not enabled ( am in the possess of checking this parameter against others i have done ) could that be where my issue is coming from?? I have not seen this happen before now , has anyone else had this issue ?

I would start by verifying that you do not have the following...

* A bad turbo speed sensor.

* A leak in your CAC, EGR, exhaust manifold gaskets or mounts, turbo gasket, intake gaskets, etc.

* Good IMAP and exhaust back pressure sensors.

* The engine is in good shape and running well, and the overhead and other things have been done and are up to date.

---

Your turbo speed sensor could be reading incorrectly. I have seen some that even read 10k or 12k rpm even when the engine is not running. I have seen soot and carbon clogging in the shaft where the sensor goes make the speed sensor read high before. Some brake cleaner in the hole where the sensor goes can usually clean it. A turbo out of proper calibration can make it over-spin too.

Got new IMAP and exhaust back-pressure sensors?

What is your boost getting to?. It should not exceed 36-38 psi. That is most likely your problem if all else is good.

Make sure all else above is good, then keep lowering your adjustments until it gets back into the 36-38 psi range maximum. That is what custom tuning is all about.

It is not unusual for some trucks to need only 45% or so to get 36-38 psi.

Also, Some factory calibrations derate the engine as low as 90k rpm. The holset can go to 150k max. I have seen custom tuners set them to 115k safely to avoid derates at the upper end as they reach 40 psi on some programs.


Advice: When you do custom tuning yourself, you will need to study and understand what you are doing to a great degree. Those info's you are using are only a starting point towards whatever goal you might be seeking. Also, Rawze does not allow open detailed discussions about such things to be taking place on this forum. I hear that their mumble server is the place to discuss such detail of things.