Interesting thread.
Theory: EGR increases the specific heat capacity of the charge, reducing peak temperatures and pressures in the combustion chamber and reducing NOx formation. It effectively slows combustion and reduces efficiency.
Application: MOST engines will have a target MAF map based on some measure of load and speed. In a typical European application, this map will extend across approx. 50% of the full load range (to 10 or 12bar BMEP) and perhaps up to 2500rev/min. This covers legislated emissions cycles and what is generally feasible in terms of EGR tolerance and durability.
Removal: Removing EGR in a
modern diesel engine will cause a plausibility error between measured MAF and target MAF. It is also really a bit of a halfway house - if you're
really not bothered about NOx then you'd also want to advance the timing and perhaps wind up the rail pressure. You'll get a noisy engine, but better combustion efficiency and hence FC.
Quote:
Originally Posted by Diesel_Dave
Not sure where you got the information that EGR doesn't operate at max power. I've seen lots of diesels where there's EGR all along the torque curve.
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This seems very odd unless you're referring to heavy duty engines or very old engines! I've seen NO Diesel passenger car engines that run EGR at full load. As EGR displaces air, this would reduce performance/increase smoke considerably. This compromise is unnecessary because legislated drive cycles don't include regions of full load operation.
Biofuel: I don't have much to add on this other than that I wouldn't use it on a CR engine until I'd seen evidence of no lubricity issues. Maybe that's out there, but I haven't seen it (possibly my bad!)
Tease: there are easier ways to trick an engine into operating without EGR that would have the added benefit of operating on a manufacturer developed cal...