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Originally Posted by Kodename47
That's all really handy info. I had forgotten about that post and it didn't appear on any Google searches either.
Typically I'm a little confused. You stated that the intake cam is adjustable from -10 to 40 which would give it a 50 degree range, but the pdf shows that the control operation range is 68 degrees!?
The exhaust system isn't too bad as I figure you have control from 0 to 50 deg retard and the diagram shows 54 degrees control range.
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Reference for above statement, from the pdf, assuming it is accurate on some level:
regarding duration, compare to reported duration for the stock cams from Crower:
Quote:
Originally Posted by DAMotorsports
The info we have for the stock cams is only the lift and duration as tested by BC.
Duration@.05: Intake 206 Exhaust 200
Lift@.05: Intake 268 Exhaust 265
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0.05 is inches, I presume the .268 is inches but that would be about 6.8 mm lift on the intake side, which seems way too low. I don't know how there could be less than 10mm lift. So maybe those measurements are suspect. Now to answer your question:
Quote:
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Do I assume for calculating overlap etc that 0 exhaust retard starts at 27 deg BBDC and the intake is 0 (on the map) intake advance starts at 14 deg ATDC?
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I would say "yes" with the caveat that we don't know what lift this diagram is at, assuming it reflects this engine at all. Doing quick duration calculations shows over 250 degrees duration at intake. So that might include the whole width of the intake cam at very very low lifts.
See the tricky thing is, we don't know what the actual ramp of the cam grind is. I've posted this diagram before, showing the full cam grind for a BMW 2.0 direct injection turbo engine at full valve lift:
this is the kind of thing you ideally need. You can calculate an overlap duration, but it's hard to get the full story from that because you don't know the grind of the cam. You really need to calculate the overlap volume at a given set of cam positions. The overlap volume is the shaded area when the two cam grinds overlap due to phasing. Also, for reference, here are the stock cam phasing maps:
