scr warmup

[JimT]

(08-25-2023 )Rawze Wrote:  Actually, it is quite normal for the engine to jump back and fourth between its egr+ modes and one of its aftertreatment warm-up modes. It has to maintain 500-F degrees at the DPF/SCR, etc.. and it can only do this by jumping into a warm-up mode as those cans drop below about 450-F or so, and they cool off.

The idle alone in the EGR+ operating modes is not enough heat to keep the SCR/DPF temps under there up .. so it jumps as needed into a warm-up cycle to get them back where they need to be. It also, often, does this going down the roads every few mins, depending on weather.

If you want it to cycle less often, then an exhaust wrap to keep everything under there much warmer would help a lot.

As far as it cycling more than normal,.. it could be caused by many things including an egr valve sticking open, leaky exhaust piping, one of the temp sensors under the truck not reading correctly, etc.

I should clarify, when I speak of SCR warmup cycling too often, I mean no matter how long you've been driving or how much stop and go you are doing every time you stop at a red light or stop sign for more than 20-30 seconds the system would kick into SCR Warmup bringing the engine up to about 1000 RPM and spooling up the turbo. I always mistook it for an ongoing DPF regen until I monitored it with Insite. Also, these occurrences I reference are outside of what has been observed as normal operation over months or years of driving that same vehicle. I've personally seen the issue crop up in 2 different trucks (prior to also experiencing it in my own truck) I drove as a company driver, both I had been in since they were new and were daycabs used for distance and city driving. As to the company trucks I can only assume that driver (myself and others) and maintenance neglect (mostly Ryder) of the aftertreatment systems along with the large amount of NYC stop and go contributed to the problem. But the point is there's normal system operation and then there's excessive occurrences which is to what I'm referring.

Slightly unrelated, but the SCR warmup and DPF regens durring stop and go driving are the only reason I liked, back then, having an automated manual. It was always annoying getting ready to take off from a stop when the system would kick in and spike your RPMs without your input. I can't imagine the extra clutch wear from repeatedly having to get 80K moving from a stop while the engine is spinning at 1000 RPM.

onebadapple: Sorry, I don't have any answers for you other then test and troubleshoot. First thing hook up Insite and pull up data monitor to verify exactly which mode the engine is in when you experience this. While I can't say for sure, what you describe could be part of a Regen your interrupting and it takes a day or two before the levels once again cause the system to Regen.