Quote:
Originally Posted by Daox
Assuming all variables stayed the same (yes, I know thats impossible), can we say that if an engine has greater volumetric efficiency or torque that it is also more efficient? I would tend to think yes.
I'd really like to hear some theoretical conversation on that idea, but I'll also share my situation as an example. I bring this up as I will be working on getting my 1993 Tercel back on the road fairly soon. The engine is going to need work in to the not too distant future (217k and burns oil), and I'm thinking about updating to a newer engine (5E-FE or 1NZ-FE). The newer engines are the same displacement, but put out more torque and at lower rpm, and thus I would imagine they're more efficient. Obviously (if you know Toyota engines), the 1NZ-FE is quite a few years newer technology than the stock 3E-E and would be the optimal choice. That also means it will be the most work to put in too...
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I would lean towards volumetric efficiency.Toyota's most advanced engine is a gasoline direct-injection type,(no throttle),which takes the 'parachute valve' out of the intake tract completely.All rpm control is done with EFI.
These engines match the mechanical efficiency (43%), of a turbo diesel,lacking only the additional Btu content of the diesel fuel itself.
Some of the proprietary pent-roof cylinder heads designed for SAE Eco Marathon competition stressed easy-breathing for both intake and exhaust as a strategy for 7,000 + mpg racers.
What would be helpful,is a set of 'charts' for available engines,developed on dynamometers,illustrating :indicated power,friction power,net power,pumping losses with and without the head,mean effective pressure,torque,BSFC,and such across the rpm band.
It would give us really valuable insight into any particular power plant.