Quote:
Originally Posted by Ecky
You could possibly increase the compression significantly more (e.g. 16:1) and run an Atkinson-cycle; to do this, you'd give the intake valve longer duration, and advance it to the point that it stays open partway into the compression stroke. It's easier to do this on engines with variable cam timing, because the fuel economy improvements come at the expense of power, and variable timing would allow you to switch it on or off at will. This is one of the tricks Toyota and Hyundai's hybrids use to get near 60mpg, and the loss in power is made up for by adding an electric motor to add torque down low.
On that note, I wonder if you could retrofit a servo or somesuch that would allow you to modify the cam advance on the fly, so you could get the best of both worlds - Atkinson while cruising, and OTTO while accelerating. You wouldn't be able to run astronomical compression, but you'd still see gains.
Other than that, you could play with the heads and see if you can get a stratified charge, to allow for leaner operation. My Insight is able to lean out to over 24:1 AFR on the highway, giving it diesel-like efficiency.
Other than that, taller gearing will probably make more difference than anything else.
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Unfortunately, I don't have the budget of General Motors to conduct the
Real McCoy research and development to really turn this
"obsolete" motor into a truly fuel efficient and superior version of it's former self. Besides, with all the newer technology out there from variable-timing to direct-injection and direct-ignition,
and cylinder deactivation (!), for the money I would spend to go nuts on an engine design over twenty years old, I would be better off swapping a 2014 LT1 into my Trans Am. However, with all the work required to make such an engine work with my factory gauge cluster, the computer required by this engine, and all the wiring from my existing 1990's equipment to work with the 2014 computer for this motor, it is more cost effective to salvage my existing motor and improve upon it with existing parts and coating.
The biggest problem is reducing internal friction, that is easily solved with the new anti-friction engine coatings that are now sprayed on the motors. I can have this same coating sprayed on the motor parts. I already use full-synthetic motor oil so this is one step in marginally increasing power output and increasing fuel efficiency! The other steps involve lower end torque production which, if the car can start moving from a dead stop easier thanks to lots of torque on tap, this helps in overall fuel economy. If I can drive the car mostly under 2000 to 2500 RPM, with full manifold vacuum, this all ties in to better fuel economy.