03 NV5600 RPMs hanging while shifting, FIX??

[SDesmarais]

My truck is an 03 NV5600 4. 10 diffs 4x4 with the following upgrades, TST R-49 with rail pressure, stock air box with homemade ram air, 4" turbo back MBRP w/silent might muffler.

My issue is that when let off the fuel pedal to shift the next gear the RPMs hang at the point where they were when i let off the pedal to make the shift instead of immediatly starting to drop down to the engagement point for the next gear. The truck has done this even when it was stock and it is almost livable when I dont run any rail pressure increase. When i do increase the rail pressure the problem gets much worst (especially when the engine is cold) to the point that i am waiting for what seems like forever to let the clutch out in order to avoid all the bucking the comes with i mis-timed shift. I assume this is due to the TST adding rail press even when I'm off the pedal and the engine is slowing down thus fueling slightly more and keeping the RPMs up for those moments between shifts.

My questions are these: Is the problem in the factory ECM programing? Will it always do this when running rail pressure increase no matter what the suorce. i. e MP-8 instead of TST adding rail press. ? Is there a fix? And finally will a programmer like the SMARTY improve the drivability of this situation? I thank everyone in advance as i know this is a lenghty post. Steve D

 

[rbattelle]

As I recall, the delay between shifts is an ECM programming issue. I think it's there for smoke reduction (helps hold boost up). At least, I think that's what we decided here a few years ago.



Can't comment on the other questions...



Ryan

 

[sag2]

You might have an injector or two that are dribbling. When you let off, the rail pressure stays high for a few seconds waiting to see if you are going to get back on the gas. If an injector is leaking mechanically the engine will rev like you never got off the pedal, especially with no load when you step on the clutch.

 

[JHardwick]

As I recall, the delay between shifts is an ECM programming issue. I think it's there for smoke reduction (helps hold boost up). At least, I think that's what we decided here a few years ago.



Can't comment on the other questions...



Ryan

You are correct, it's an EPA deal. Gassers are programmed to "clear their throat" as well. Running increased rail pressure makes it worse.



I have a dually, so I don't run it like a dragster. I let the gear I'm in "run out" brfore I roll out of the fuel and hit the clutch. It seems worse if shifting while the engine is still loaded.