Quote:
Originally Posted by winkosmosis
I don't really understand cylinder shutdown. Why not just reduce engine RPM with a taller overdrive? Or would the cylinder speed be too low?
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On a V8 of this size, that can mean going very low in terms of rpm; way below intended operation speeds. My Mustang V8 idles at ~750 rpm. I can accelerate in fifth (top) gear from ~400 rpm, which is about 15 mph. I don't usually do this, as the result is a misfire. I also get the impression that at this speed some 'do not stall' code is written in to add more gas to keep the engine from stalling if it is operator error. The oil pump might not keep pressure at such low speeds.
When I added my underdrive pulley it looked to add ~0.5 mpg, although I haven't accurately done before/after measurements.