Quote:
Originally Posted by fatoni
dont forget the use of multiple cam profiles. thats a pretty big deal if you ask me.
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Quote:
Originally Posted by Jond63
At 2Krpm this D4S puts out more torque than my '02 S2000 did at 7krpm. And around town about 7mpg better. I like it.
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Yep that's the key. Older engines (Honda's K20 and F20, in particular) made 100+ hp/L using variable lift cam profiles. Lower torque in the lower rpms, but the trade-off was an engine that could maintain torque to 9000 rpm thanks to the higher lift cam profiles.
The FA20 lacks variable lift, but uses direct injection, which gives it the ability to run a higher compression ratio without constant detonation (12.5 vs. 11.0 for the F20/K20). This basically means more torque, but also an engine that won't breathe as well past 7400 rpm due to the lack of variable lift cam profiles.
You can see the difference in respective approaches in this f20 vs. fa20 dyno:
Subaru/Toyota were pretty much forced to go this route because of emissions and fuel economy standards. That's pretty much what killed off those older Honda's engines and what makes them irrelevant for purposes of comparing engines today.