Quote:
Originally Posted by roflwaffle
From the perspective of BSFC it's consistent, but emissions tend to be the opposite. At least for older diesels, particulates go up w/ load, NOx/CO goes up w/ load and speed, and HCs are roughly the same.
That's pretty much what manufacturers have been moving towards for the past decade or so via drive-by-wire, variable cam phasing, eleventy billion speed automatic transmissions, cooled EGR, and so on. |
Thanks for the link to the paper. Saved that one.
Unfortunately, the maps shown in that paper reference an increase in emissions when road speed and load are increased steadily, which should be obvious.
What I'm referring to is steady state RPM with varying loads. In other words, when you're cruising, and you start going up a hill, then going down the other side. If you're not using all the available power, you're pretty much wasting fuel. You can tell if you're properly loading your diesel engine by checking EGT's though. You should be in the ~600* range for best efficiency in most cases, IIRC.
The thing about diesels is that it's hard to control load without metering airflow, so it would be very difficult to test for emissions properly. When you floor it in a diesel, it starts injecting fuel based on a pre-set pump that was supposedly tuned.
The general rule of thumb is to turn it up until there's smoke, then turn it back down until just after the smoke disappears. Of course, if you're interested in better fuel economy than power, you could back it off a bit more, as well.
Often, the fuel rack limiter can be adjusted to not allow full throttle fuel input, as well, further reducing max power output by a negligible amount, and reducing the chances of smoke under harsh conditions.