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Old 11-24-2012, 09:37 PM   #679
Ziggyrama
Scooby Specialist
 
Member#: 53665
Join Date: Jan 2004
Chapter/Region: NESIC
Location: Northboro, MA
Vehicle:
2011 STI Stg2 w/EBCS
2012 Tribeca Ltd.

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Quote:
Originally Posted by Jubert69 View Post
Hear me out on this, let me know if I need to clarify.

0 AVCS = Acts like Small Cams
20-30 AVCS = Acts like Bigger Cams

So around low loads, you want little to no overlap, which is low AVCS and higher loads want more AVCS because of overlap?
Not really. It does not work like that. Unfortunately, it is not that simple. The muscle car example was just an illustration of how overlap can affect an engine. In our case, it really depends on the scenario. Load is just one axis. You also have to consider RPM. Some low load situation call for fair amount of overlap to produce internal EGR effect which yields better fuel economy and lower emissions. In high load situations, you typically do not want lots of overlap because the positive pressure on the intake side will force the charge into the chamber and the engine does not rely heavily on scavenging to improve volumetric efficiency. I say typically because the exhaust side also influences this and depending on what you're running there, the overlap requirement may change. The more flow you can get on the exhaust side, the more you might be able to use overlap to improve VE.
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