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Old 04-05-2014, 05:10 PM   #1
FlamingRectumSyndrome
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Dumb First Question

So I'm an old guy with a lot of experience with ancient technology like carburetors and points ignition. Don't know nothing about ecu tuning. So a couple of questions.

I keep hearing about the flat spot in the power curve. And when you look at a dyno chart, it's staring you right in the face:


Big ol' drop off in torque and horsepower between about 3200 and 4700 rpm (red line on this chart), compensated somewhat by tuning (blue line).

My question is where does this drop off come from in the first place? Is there some sort of intake resonance that's interfering with flow in that rev range? Sure, you can fix it to some degree with tuning, and to a greater extent, apparently, with forced induction, but it would make sense to actually fix the problem, rather than band-aid it. Is this a characteristic of the Subaru flat fours, or is it unique to this particular version?
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