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Old 03-25-2013, 04:46 PM   #11
Bullet Ride
Cars in Perpetual Repair
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Join Date: Nov 2007
Location: Guelph
Posts: 6,019
On an E30 I've seen a datalog where MAP started to drop from 101kpa (atmospheric) around 6400rpm and ended up levelling off around 90kpa at 7000rpm. With no airbox whatsoever on the same car, the same drop off didn't start until around 7200rpm. So above 6400 rpm the stock airbox/filter is a limitation, and above 7200rpm (where very few E30's ever drive) the throttle body/intake starts to become restrictive.

The diyautotune guys gained 3whp/wtq on an E30 by deleting the AFM and stock airbox.

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