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RarlyL8 RarlyL8 is offline
Crotchety Old Bastard
 
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Join Date: Jan 2000
Location: Huntsville, AL
Posts: 14,078
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Boost threshold is the point (rpm) where boost is first observed when accellerating on a flat surface in high gear (3rd is good). The point where the boost needle first lifts off of zero.
For example, my old red rocket would move off of zero at ~1700rpm in 3rd gear and reach 1.0bar at ~2700rpm. Boost threshold 1700rpm, full boost 2700rpm. The last 500rpm of that range went by very quickly. If cruising above the full boost rpm, such as 70mph @3400rpm (915 tranny) the transition from vac to boost was instant with the movement of my big toe. I could adjust my driving habits for optimal fuel mileage by watching the vac/boost gage.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 06-15-2013, 06:54 PM
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