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| One key take-away is that just because an engine is making more horsepower doesn't mean you're using all that extra horsepower all the time.
If you were to take two similar engines and operate one at 400 hp continuously and the other at 600 hp continuously, the latter is going to use more fuel. However, if you take both those engines and put them into the same truck, but the 600 hp one is geared to turn a bit slower you may be able to make use of that extra horsepower for the short durations you need it while spending the majority of the time turning a bit slower and perhaps saving a little fuel.
As others have said, it's also possible that one engine may be tuned more for emissions in which it may be giving up a bit of economy. In this case the new cam might be a bit more aggressive about giving fuel or has more advance which may do things like drive up combustion temperatures. This would increase economy, but also increase NOx emissions. | |
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Straightening Cat crank
