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Old 01-10-2012, 01:19 AM   #5 (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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valve open duration and

those #s do not really mean much

you are going to need EVO and EVC values and IVO and IVC values , you can calculate them if you know exhaust valve open duration in degrees -
you do not want the exhaust valve closing too soon as if it does it will not allow all of the spent combustion gases to escape ... prior to the next combustion event .

you will be adding EGR , intentionally , EGR is good , HOT EGR is not as good as cooled EGR , with regard to FE .

something that plagues those who just dial in cam advance on single cam engines .
most users who tamper with cam timing have no clue why results are so terrible
the engineers really did already provide very close to the optimum map.

you will really need to plot real time pressure / vacuum in the combustion chamber , or use the data from someone else who has this stuff .

case in point
inside the red oval see pressure spike in the combustion chamber due to advanced cam timing , and above with stock OEM cam timing , combustion chamber pressure is represented by the green traces , follow the labels in the balloons for descriptions .

in that application , 10 degrees of cam advance caused the engine to run poorly with no power and no improvement in fuel economy .

here is a Honda civic
with a advanced cam due to jumped timing belt , same issue is present

i have overlayed pressure waveforms , good and bad using AESannowave software , to show the effect i described above

that pressure spike at about 350 degrees is caused by trapped exhaust gases that cannot be vented to the exhaust , they will displace incoming air fuel mixture and effectively reduce the size of the combustion chamber , which describes what EGR does .

if that is what your goal is ... carry on .
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