Apparently a DC Ambulance skipped a few steps in its Diesel emissions cycle and went to "regeneration" during a call. The patient on board died at the hospital after the call was delayed for 5 to 7 minutes.
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I really don't like this system one bit. It seems illogical that a relatively new emissions system with demonstrated potential for failure has the power to derate and shutdown the engine without any possibility for override. It takes an emissions issue and turns it into a safety issue for the driver and those on-board.
A lot of the comments said that people should learn how to read, and I don't think you read the report too carefully. The system that shut the engine down is not required in ambulances.
the anti-diesel fud will continue for as long as there are bigger profits to be made selling [literally] watered-down gasoline. can't have the proles getting a taste for all that euro-diesel economy and reliability...
I'm confused... I thought that the DEF/urea and regen cycle were two different things... the regen cycle is to clean the particulate filter (which traps soot) and the DEF is injected into the exhaust upstream of the catalyst to allow the oxides of nitrogen to be catalyzed (into water and nitrogen, hopefully.)
Now if the ambulance went into a regen cycle, if it works similarly to BMW, it would still run, but at reduced power - the engine management would essentially try to create a high EGT to burn off the soot in the DPF. Whether or not that would have impacted the travel time I don't know, but the vehicle should not have simply shut down. I know that newer heavy trucks sometimes require a "parked regen" but I was not aware of any medium-duty trucks that would require that, so a regen would *not* cause a shutdown, merely a light on the dashboard and reduced power for a while. What I'm thinking happened is that the vehicle simply ran out of urea/DEF - and then did shut down, as that is typical behavior for a Diesel vehicle that is completely out of DEF. It may not be required for an ambulance, but it is likely required for passenger cars and even other vehicles that share the same chassis and drivetrain.
The one thing that the news article appears to have gotten correct is that the engine is not supposed to simply shut down with no warning - if it really was a low DEF situation there should have been warning lights/messages on the dashboard well in advance of actual shutdown. So, either there was operator error involved, the system did not work as intended and did not give sufficient warning, or something else happened that isn't clear to us given the info in the news story.
One possible explanation that doesn't involve either operator error or a vehicle software/firmware fault is that the vehicle may have ran over some debris on the way to the hospital, puncturing the DEF tank and allowing it to run dry quickly. Having driven on DC-295 before that does not seem completely implausible to me.
I did on one car for ten years or so. They were OK, no complaints.
Then again I have been in some situations where judicious application of a matchbook and a wrench were sufficient to not die by the side of the road. Engine guru says,"you can just replace the whole module", which is true I suppose if you just happen to have a spare one with you...
My concern is largely outside of ambulances. Assuming this isn't operator error (ignoring the warning lights) this could affect any diesel vehicle. A tractor-trailer full of hazmat negotiating a railroad crossing could just as easily be stopped in its tracks.
The video clarifies that the vehicle went into regen, rather than running out of DEF. Another article that I read on this event commented that emergency vehicles make short runs and the EGT may not typically get high enough to burn the soot off in normal operation.
Right, I watched the video and saw the same, but unless the new PSD is unusual, regen should *not* force a vehicle stop and continued driving during regen is not only possible but normal operating procedure. The one condition that commonly *does* force a vehicle stop is running out of DEF.
I'm hoping someone can chime in who has actual experience with the newer PSDs and can confirm/deny that there is no forced "parked regen" mode.
Wait, this is a Washington DC city vehicle? DC, the city with the exploding manholes and the bridges falling down? What makes me suspect that this could possibly have been a matter of poor maintenance? Maybe it's the time a couple years ago when an ambulance got into an accident because the brakes were shot?
Things have improved in DC a whole lot in the past decade, in part because of a reduction in crack use by mayors, but this is still not saying a lot.
I have my doubts about that. My 60 dodge still has the factory stock points system. It starts just fine and does high rpm just fine. I think the main thing CD ign does is allow you to get along without as frequent, if any, point maintenance. But that's a maintenance issue, not a design issue. Back when I had my first 69 firebird which had old fashioned single points it never had any problems hitting it's
5000 rpm redline. Had to clean or replace the spark plugs about every
5000 miles though due to all the crap that built up on them from the lead in the gas and the lack of good fuel system detergents. But again, the point system works well when it properly maintained. And for more demanding applications you can always go to dual points. I'm not knocking the more modern systems, just saying there is really not much wrong with the old style other then the extra maintenance required.
Meh, I got a much healthier spark (verified visually) out of my Stude when I changed it from points to a distributor with a MoPar pickup and "orange box" ignition. Opened the gap up wider on the plugs and it both started quicker and seemed to run smoother by the butt dyno. After I'd done this I then found that I probably could have bought a GM HEI module, even though the distributor was at that point essentially a Chrysler RB distributor in a Studebaker/Prestolite housing, and achieved even better performance, but I was happy with it and it was done.
There is, of course, always the possibility that the old distributor had sloppy shaft bushings and/or advance mechanism. The one that I swapped in had been rebuilt by the guy that converted it from points to the reluctor pickup.
I don't believe that I changed the coil when I did this, but it was a while ago so I don't 100% remember.
that's true, maintenance intervals are hugely extended with electronic ignition [very few use c.d btw, they're almost always inductive] BUT, if you scope points output vs electronic trigger output, it's night and day. electronic generates a much better spark and will start/run a motor that points will just cough at.
reduced maintenance requirements aside, you can easily got 10% or better power and economy improvements with electronic ignition vs. points. that doesn't mean that points don't work, but it's a very crude system. scope the outputs and you'll see a world of difference.
What these folks are talking about is taking an engine with points and adding an aftermarket CDI system to it. You still get the same timing variations that you got ith the stock system, but you get a hotter spark that lasts longer, and since hardly any current flows through the points they last a lot longer.
It's not a night and day improvement and it's not as much of an improvement as a magnetically or optically timed system, but the points and plugs last a lot longer, cold weather starting is far easier, and if you decide you don't like it, you can remove it and go back to the stock configuration.
snipped-for-privacy@panix.com (Scott Dorsey) wrote in news:konfua$ssm$ snipped-for-privacy@panix2.panix.com:
It is much better to just use a electronic replacement system, you can also use a CD unit with it if you want to. but the points weakness will be gone. KB
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