X15 with a Non-VGT turbo

[Dr watson]

One of my customers previously had his original isx engine engine deregulated and had since gone through 3 turbos. He had a catastrophic failure in cylinder #3 and had me do an engine swap. We installed an X15, but he is still using the reprogrammed ecm from the ISX. I was able to make it work after re-pinning a couple of pins to make it communicate. He also had me install a non-VGT turbo at the same time. He has probably put about 20k mi since the swap, {has a} CEL for the turbo Comm, but I'm concerned the ISX ecm may cause long term damage due to the different fueling rates. I need some help to reprogram his X15 ecm that came with his new engine to match his current vehicle configuration. Please, any guidance would be greatly appreciated.

[Rawze]

(03-05-2026 )Dr watson Wrote:  One of my customers previously had his original isx engine engine deregulated and had since gone through 3 turbos. He had a catastrophic failure in cylinder #3 and had me do an engine swap. We installed an X15, but he is still using the reprogrammed ecm from the ISX. I was able to make it work after re-pinning a couple of pins to make it communicate. He also had me install a non-VGT turbo at the same time. He has probably put about 20k mi since the swap, {has a} CEL for the turbo Comm, but I'm concerned the ISX ecm may cause long term damage due to the different fueling rates. I need some help to reprogram his X15 ecm that came with his new engine to match his current vehicle configuration. Please, any guidance would be greatly appreciated.

First and foremost ...
The reason why it went thru 3 turbo's is more than likely a BAD DELETE!!!. - Its not the fault of the trurbos themselves unless maybe they were buying chineesuim or other garbage knock-offs.

Next...
This is also most likely WHY the engine failed as well. .. BAD DELETE!.
Everything in your post you have there screams this loudly.

More than 90% of all the de-mandate programs that I review each year are absolutely HORRIBLE engine (and turbo) killing trash!. This is the NORM,and not the exception.

... and FOR ANYONE to recommend that the VGT turbo be removed... THEY ARE COMPLETELY CLUELESS on how these engines run, and what progressive damage over time that occurs by running it too lean at at speed + too rich at the bottom end with a constant bad fuel-air mix, shortening the engine lifespan by half or less as a result.

The ISX uses THE TURBO to set the proper fuel-air mix... NOT THE FUELING.. so removing it is like taking a sledge hammer to everything and it takes its toll over time. Its like chalk on a cave wall vs. the writing pen... that is the difference between precise fuel-air control (which the isx needs for proper longevity) at all rpm and speeds, using a VGT vs,. an old school dumbo turbo.

... It has been seen time and again .. over and over around here... Removing the VGT and replacing it with non-vg causes increased friction all the time, typically shortening the engine life by half or less. Anyone who would argue this is someone who has NO CLUE how these modern engines run at all, nor what changes that need to happen in the programming to keep them trouble free for a million miles after a de-mandate is done to them.

... Lowers fuel mileage by significant amounts on average, much more-so over time than simply buying a replacement turbo at the 600k ~ish miles or so when it finally does wear out.

... Causes the engine brake to become non-existent.. which is NOT GOOD for anyone driving in mountainous regions.

... Makes the engine very lazy on the bottom end, or black smoke like all h#ell if its set to overcome it.

... and causes it to over-boost on the top end without proper waste-gateing.

== NONE OF WHICH ARE GOOD!>... there are ONLY NEGATIVE RESULTS and HIGHER LONG TERM OPERATING COSTS at the end of the day!.

== Even in heavy haul applications, + PROPERLY DE-MANDATED,.. the VGT turbo lifespan is about 600k miles at a time.
- If that truck went thru 3 of them.. THEN SOMETHING IS VERY WRONG!!!... IT IS NOT THE TURBO OR ENGINES FAULT!... ITS 99% LIKELY BAD PROGRAMMING that is over-spooling the s#it out of the turbo because the engine is trying to still warm up the missing DPF CAN!..,.. it stuck in its dpf rapid warm-up engine operating mode, killing the turbo and making the liners dance in the block. This is due to BAD DELETE PROGRAMMING where ecm still thinks everything's there.. and some idiot just blocked a bunch of fault codes from showing up int he dash. - I.E.> This is the most common type of trash-can delete out there, and it kills the ISX's longevity and causes premature turbo failures to boot.

So ... my advice to you is IMMEDIATELY PUT BACK THE VGT TURBO and get the garbage engine and turbo killing programming copied out for a proper review of what some yahoo did in there. - Otherwise you can just tell them to save his moneys like mad.. because the next inframe is just around the corner.

(a warning)...
-- There are some people soo damn stubborn and ignorant on this subject that come around here every so often,.. I will tell them this same advice,...and then they want to argue it away. = So just be warned right now,.. if that is what you want to do,. then you will get kicked off here real fast!,.. because I do not tolerate fools that want to justify torturing a $40,000 commercial engine into an agonizing death spiral with garbage redneck engine killing mods. It does not belong on this wwwsite.

== PUT THAT VGT TURBO BACK ON IT!.
== FIND OUT WHAT WAS KILLING THEM PREMATURELY AND SOLVE THE ACTUAL PROBLEM!
== COPY the program from the ecm and e-mail it over to me... GET THAT GARBAGE DELETE PROGRAMMING REVIEWED AND REPAIRED OR REPLACED THAT WAS KILLING IT TO BEGIN WITH!

Then maybe it has a change of running and living a full life like its supposed to. Otherwise, your on the wrong wwsite if you looking for advice on how to make that redneck trash work correctly.

[mikkhh]

Since this thing is swapped from ISX to X15, besides the ECM what other ISX parts should be ran? VGT turbo from ISX?

After getting the proper turbo for it the ECM has to be reprogrammed to match the engine engine hardware.