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Old 12-25-2012, 12:01 AM   #11 (permalink)
mwebb
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Join Date: Jul 2009
Location: New York
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no nickname , it's just a car - '04 volkswagen golf tdi
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DI injector current shows injector timing relative to TDC

injection timing does not take place after top dead center in VW in DI engines , but under light load spark does
see in RED injector currents (like multi strike 2 per cylinder at this load),
see in Green spark signal IGT for cyl 1 from the ECM and
see in BLUE cylinder pressure , the two blue peaks show TDC 720 degrees apart
2 complete crankshaft revolutions ,
later in the same capture ,spark occurs well after TDC as the engine warms up


it takes time for the flame front to build / propagate and the increase in pressure is a part of that variable

in this capture injection never happens AFTER TDC even at WOT , this shows 1200 rpm from cool start ---
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EGR does NOT increase combustion temperature OR combustion pressure
EGR when active reduces BOTH combustion temperature and pressure
EGR does kinda sorta reduce compression ratio when active ( although many will say it does not ) by reducing the amount of air fuel mixture that can be drawn into the combustion chamber
by dilution with an INert gas - exhaust -

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