MrMopar64 wrote:
The KJ has 1-2 pilot injections and 1 main injection. The pilot injections will drop back to 1 when the second...can't really talk about when/where/why (it's confidential) but it happens.
The 04.5-06 Cummins truck are the same setup. 1-2 pilots and then the main = 2-3 injections. These trucks are also solenoid injectors, just a bigger version of what's in the KJ. The pilots' main contribution is NVH, turn it off and it sounds like a 12-valve. There is no post injection on these engines for NOx control, etc - this I do know for a fact.
The Cummins engines use only Bosch injection components. They write their own software in-house for their ECUs.
On the KJ there is no "superflous" final injection for Nox control, the ISB325/610 engines have no "final" injection for NOx control. If it did, you'd watch your EGTs run 500-650 degC all the time then. For the Cummins most programmers will cut it back to one pilot all the time and advance the timing with a slight increase in rail pressure. That will help both mileage and power noticeably.
If you advance the timing you'll see a definite increase in mileage. You want to focus on the light load / low RPMs areas to realize the most benefit. Of course the noise can be horrendous but the mileage increase can be stellar.
For the DPF regeneration that gmctd mentioned farther up, these injections are actually torque forming, especially the post injection closest to the main injection. Because these are torque forming injections, the main injection is reduced so that the transition from non-regeneration to regeneration and back is seamless. Also, the Lean NOx trap that is used requires a "rich" phase to purge the accumulated oxides off the catalyst substrate. This rich phase is accomplished by a slight burst of post-injection. Because the EGTs haven't risen yet, the raw hydrocarbon from the burst cleans off the catalyst. For the regeneration, 20 min at 600-650 degC and you're complete. Of course, if you work the truck hard pulling down the road and manage to keep the EGTs above 400-450degC then you're accomplishing passive regeneration which will extend the interval at which the regen due to post-injection is required.
Lots more to share later, that's enough to digest for one post i think.
I love those technical posts! I crave for more!
Sometimes I wonder if I should have chosen the mechanical engineering route instead of the electrical one...
A little question regarding EGTs.
Can you define a few ranges for me, I consider buying an EGT gauge to monitor the EGTs so I'd like some CRD specific knowledge of the EGTs.
Range 1: Low temperatures (idle, newly started engine, idle to allow turbo to cool evenly)
Range 2: Medium low temps (cruising at 50mph flat country)
Range 3: Medium high temps (cruising at 65-75mph various country)
Range 4: Towing at speeds over 50mph
I'd like this just to give me an idea of where I should expect the temps to be...