Quote:
Originally Posted by Ken Fry
A Prius engine would probably bolt up to an Echo transmission. However, the Prius (the car) gets its fuel efficiency from about 100 small optimizations, and several big obvious ones (engine efficiency, higher engine loading, energy storage to promote more time at high load, regen) But to make the comparison, you would have to look at the BSFC maps of the two engines in question. (The Prius map is probably on this site.) At peak, you can figure that the Prius engine is about 37% efficient, and that the engine in a modern fuel-efficient car is about 32%. Having looked at the Prius map for quite a while, I'd conjecture that the Prius maintains that roughly 16% advantage over much of its usable load/rpm profile.
I doubt that a Megasquirt would provide the required sophistication to maintain the full 16% advantage. Getting the Prius controller to work would be, potentially a chore. Just getting the plug-in conversions to work right was not simple.
It would be a fun project.
Another variable occurs to me: if you are getting 60 mpg, chances are that you are already doing a certain amount of hypermiling, which is, in a way, the poor man's approach to hybridizing. So if you were obsessive, you would have to look at the BSFC maps from the perspective of your actual drive cycles. Different engine respond differently to things like pulse and glide.
Yet another, possibly big one: This all assumes that the stock engine and the replacement are similar hp. If the stock engine is double the hp of the Prius engine, then the gains would be expected to be greater from going to the Prius engine. (In other words, going from a 37% peak-efficiency big engine to a 37% peak-efficiency small engine alone provides potentially large gains.)
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no purchases have been made yet but i'm thinking along the lines of maybe converting an old tercel and aeromodding that.
the megasquirt 3 seems like a pretty significant step up so thats the one i would go for. as for a buch of extra controls on the prius engine honestly dont know anything about them i figure for the most part an engine is an engine, long as you can control the fuel map and timing i'm not sure what other concerns there are so any insights would be appreciated.
the example i used of a car getting 60mpg was just an example. i dont think inclueding hypermileing into an engine efficiency equation would provide an accurate answer. not that i'm not into hypermileing, i'm just sayin.