[Jsjarz]

My bad, you're right. Just had mine diagnosed (P226 code) I need a new turbo actuator, too. Was told in the USA 1500 have been ordered, 418 on back order. Guess I'm last in line. Service mngr said OK to drive in this condition but "take it easy" whatever that means. I'm towing a 20' trailer (7000 max.) It came up from FL to NY ok, hope it makes it down as well (twice as hvy.)

Does anyone still own their 2017 Titan XD who has finally found and resolved all the issues or are you still getting codes and service work???? Bought ours used in 2021 and have had all theses issues should we dump it and run??

 

[Zurconium]

if you still have full waranty, hang on to it and let Nissan fix it. When the warranty runs out look for something else before it quits and costs you your retirement savings.
my nickels worth.

Zurc.

 

[NavyCuda]

My bad, you're right. Just had mine diagnosed (P226 code) I need a new turbo actuator, too. Was told in the USA 1500 have been ordered, 418 on back order. Guess I'm last in line. Service mngr said OK to drive in this condition but "take it easy" whatever that means. I'm towing a 20' trailer (7000 max.) It came up from FL to NY ok, hope it makes it down as well (twice as hvy.)

That's a really really bad piece of advice from the service manager.

If your turbo actuator is not working, do not pull weight with the truck and limp it everywhere you take it... or better yet, don't drive it.

Our trucks do not have a conventional wastegate. The rotary valve first only exposes the turbine inlet for the high pressure turbo. All of the high pressure turbo exhaust is directed to the turbine of the low pressure turbo. Then the gate opens further and exposes the exhaust to both the low pressure and high pressure turbines. Depending on throttle and a few other variables, in the area of 1800-2200 rpm the transition occurs where all the workload is passed off to the low pressure turbo.

At very high rpm, the rotary valve will open far enough to expose the "waste-gate" port.

At startup the valve is supposed to be clamped almost completely shut (I don't understand why, but that's how the stock maps are setup).

So if the rotary valve is not working, you have no idea the position of the valve, no idea the amount of drive pressure it's putting on the engine. You could be massively over spinning the high pressure turbo. The drive pressure may be pushing significantly more egr into the intake. Your drive pressure could be lifting valves. The industrial version of the ISV appears to be able to handle ~100psig drive pressure for exhaust brake purposes, but our ecus appear to only allow a peak of 60psig. Do we have softer springs? Could excessive exhaust pressure lift a valve?

tl;dr
Don't drive the truck until you have a new rotary valve.

 

[realbored]

That's a really really bad piece of advice from the service manager.

If your turbo actuator is not working, do not pull weight with the truck and limp it everywhere you take it... or better yet, don't drive it.

At startup the valve is supposed to be clamped almost completely shut (I don't understand why, but that's how the stock maps are setup).



tl;dr
Don't drive the truck until you have a new rotary valve.

The valve is closed to 1% at startup to help bring the engine up to operating temperature quicker by routing the exhaust gases back into engine through the EGR system. This is why it doesn't increase rpm's like the Rams do when starting in cold conditions.

 

[NavyCuda]

The valve is closed to 1% at startup to help bring the engine up to operating temperature quicker by routing the exhaust gases back into engine through the EGR system. This is why it doesn't increase rpm's like the Rams do when starting in cold conditions.

I agree with you partially, however...

It seems to do it when the engine is up to temperature too. I converted some of the maps to a google sheets page while developing the initial setup of my turbos. You can see stock, the commanded position for the turbine bypass valve is 0 for all the working area of the high pressure turbo. The charge air manager will override that commanded position once the requested boost level has been achieved. You can see some of my earlier attempts, but I eventually gave up and just commanded the bypass valve to 90%(lp, hp turbines fully exposed but dumpoff closed), so now the charge air manager closes the bypass valve until requested boost is achieved.

I initially thought that it was to maintain a certain exhaust pressure for correct egr function, that might even still be the case as I still see almost universally a 2:1 drive pressure ratio. 0psig manifold pressure, 4psig(-~2psig sensor offset) exhaust pressure.

 

[realbored]

I agree with you partially, however...

It seems to do it when the engine is up to temperature too. I converted some of the maps to a google sheets page while developing the initial setup of my turbos. You can see stock, the commanded position for the turbine bypass valve is 0 for all the working area of the high pressure turbo. The charge air manager will override that commanded position once the requested boost level has been achieved. You can see some of my earlier attempts, but I eventually gave up and just commanded the bypass valve to 90%(lp, hp turbines fully exposed but dumpoff closed), so now the charge air manager closes the bypass valve until requested boost is achieved.

I initially thought that it was to maintain a certain exhaust pressure for correct egr function, that might even still be the case as I still see almost universally a 2:1 drive pressure ratio. 0psig manifold pressure, 4psig(-~2psig sensor offset) exhaust pressure.

View attachment 47679

The primary condition under which it is closed (Exhaust throttle mode) is during a regen event to drive EGR and for SCR thermal management.

 

[NavyCuda]

The primary condition under which it is closed (Exhaust throttle mode) is during a regen event to drive EGR and for SCR thermal management.

Can you elaborate on that further? I’m just going by the maps for the different engine operating modes and from basically 0-2000rpm in any operating condition the commanded position is fully closed and charge air opens as needed.

 

[NavyCuda]

... apparently duplicate post... please remove.