Quote:
Originally Posted by Piwoslaw
Actually, most BSFC maps suggest that IC engines are most efficient around 80% load, with rpms around max torque.
The BSFC chart thread |
Just two things to keep in mind about peak efficiency point on a BSFC.
#1> It is just about engine efficiency on a stand , does not take into account a moving vehicle with factors like wind resistance that increase exponentially with higher speeds ... ie , if you have to increase your speed by 20% to get the ICE RPMs up to see a 1% increase in ICE efficiency ... it might be a net loss of MPG even with the 1% increase in ICE efficiency due to the higher losses from the faster vehicle speed.
#2> The BSFC assumes you need and / or want exactly 100% of all the power generated at any point on the BSFC ... no more , no less ... If at that peak efficiency point the ICE would be producing more power than you wanted or needed ... it might just be wasted ... more power than you wanted / needed would give you acceleration you didn't want ( and wastes fuel energy to give it to you ) ... even if the ICE was more efficient in the conversion of fuel chemical energy to shaft mechanical energy.
ie ... peak ICE efficiency does not necessarily = peak vehicle efficiency.