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2019 Titan XD Pro4x Cummins
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Right…If the RTC is commanded to 1 of the 3 modes of operation and vacuum pressure is achieved by the CBV this would redirect energy to the EGR system or bypass valve. That could be where loss would occur. All this would be before the down pipe. In most sequential set ups, boost is primarily at the low pressure turbo. The small high pressure turbo is used to assist low end speed and bigger turbo’s lag due to energy applied (drive pressure). That’s why I’m bringing up the CBV, it’s not a variable operation. It’s open or closed. This would be considered watergate operation. I think the differential pressure calculated at the ECM isn’t exhaust back pressure. It’s the DPFs differential pressure sensor you are seeing. It’s used to determine soot load. I’ve attached the Cummins operations manual for reference in what you were describing.
There isn't enough like buttons presses available for that attachement.

I don't have my after treatment anymore and the indicated exhaust pressure directly correlates to manifold pressure and appears to respond in kind to the situation.

I setup some pretty aggressive exhaust braking from 2500-3800rpm. I had to soften it a bit as I saw some back pressures north of 70psig. It still slows down faster than my Leaf on full regen.
 

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2019 Titan XD Pro4x Cummins
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Thank you for that!

Learned something. I had the open/close of the compressor bypass confused. Not directly relevant to our turbine conversation but now makes clear why there is a big hole in the boost map at full throttle.
 

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Discussion Starter · #23 ·
Thank you for that!

Learned something. I had the open/close of the compressor bypass confused. Not directly relevant to our turbine conversation but now makes clear why there is a big hole in the boost map at full throttle.
I learned a lot simply by talking this out. I’m glad we were able to discuss this and on the fly I found that guide. It’s 10x more helpful than anything else I scoured. Let me know how your tuning goes. I’m in search of something other than what I have. I’m half tempted to teach myself and write my own tune like you’re doing.
 

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2019 Titan XD Pro4x Cummins
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I learned a lot simply by talking this out. I’m glad we were able to discuss this and on the fly I found that guide. It’s 10x more helpful than anything else I scoured. Let me know how your tuning goes. I’m in search of something other than what I have. I’m half tempted to teach myself and write my own tune like you’re doing.
It's one hell of a road. Most of my code is on github, predominantly done in c#. Though to be fair, a good portion of it deals with my specific issues of converting a bin into xcal and a winols map pack back to a cummins style ecfg. once that's done the editing part is straight forward. I'm eventually going to completely release my work into the wild, at least in terms of the editor, etc. I don't think I can legally sell/transfer the ecfg and xcal though.
 

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Discussion Starter · #25 ·
It's one hell of a road. Most of my code is on github, predominantly done in c#. Though to be fair, a good portion of it deals with my specific issues of converting a bin into xcal and a winols map pack back to a cummins style ecfg. once that's done the editing part is straight forward. I'm eventually going to completely release my work into the wild, at least in terms of the editor, etc. I don't think I can legally sell/transfer the ecfg and xcal though.
I can imagine. You’re doing the work of a saint right now. It’s been hell trying to narrow down good tune profiles vs bad ones…The support from venders is non existent now. It is really starting to boil down to personal tuning just to understand behaviors happening within a powerplant that is no longer in production for these trucks. Like I mentioned before, troubleshooting is all on our own. Tuners like GDP provide no support and only recommend shotgunning parts until the problem goes away. It’s just not something I’d ever do in my career. I’m a firm believer of root cause then repair/replacement since parts are not cheap and usually not returnable after install.
 

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Anyone out there have problems with GDP’s tuning on a 17 Titan XD Pro4x? Just hit 108k miles. I’ve installed the EZ lynk programmer no SOFT and have some weird issues. Set up: EGR intact, DPF removed. first issue: loaded 120hp v1.8 profile and truck ran fine day 1 no WOT. Day 2 drove truck 15 minutes still no WOT, shut down, started truck remotely then heard the engine lope like it was losing fuel pressure. Immediately cut the truck off, restarted with ignition, truck loped then shut off on its own. Primed fuel system, started and was able to get home. DTC showed U1300, U1266. Cleared fault installed 0hp v2.2, boost appears to be scavenging low pressure and high pressure turbos around 75mph, no fuel pressure issues. I have zero help from GDP as they state they have 1000s of trucks with these profiles and no issues. Reinstalled DPF system, returned to stock profile and boost seems normal, no fuel pressure issues. Flashed 0hp tune DPF/EGR installed/disconnected same boost failure but no fuel pressure issues (decided to rule out fueling). All tunes minus returning to stock appears to be scavenging for boost between low/high pressure turbos around 75mph. If I WOT the truck with any tune other than stock it pops a coolant flow restricted DTC P00B7 and puts the truck in limp mode (engine power reduced).
What company is “GDP”?? My truck is almost out of warranty and was plan on deleting with EZ LYNK… want to make sure I don’t end up with these issues.
 

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After my week long back and forth phone call with GDP I would second guess anything you stated. I wouldn’t recommend anyone purchasing tunes from them. This is my daily driver and it’s stuck in limp mode now. I’m at a loss other than returning it completely stock and eating the cost of the programmer and tuning profiles. I don’t know of any other tuning for this specific truck.
I used pd tunes installed 10 momtys ago no issues and support Is good too. Have 17 sl model
 
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