The 90-95 Q45 uses an intake cam of 248 with 0 or 20 BTDC [vvt] so it closes at 112 or 92.The exhaust is also 248 and closes at 8 ATDC so opens at 120 ATDC.
Don't have a 4.1 FSM on hand but remember~~ 236 degrees duration.
Modern OBD2 engines [Q41 etc] use less duration and much less overlap.
Not necessary with big multiple valves, as the SUM of the opening flow is what counts.......the curtain area = ratio of imaginary cylinder [valve diameter less seat , less valve stem, times lift. The problem with big valves is like big cams at idle.
Extra Lift is the usual variable added to performance cams [for 32v engines]vs. duration........but tiny margins in valve to pistion clearances when extremely hot, thus flycuts in pistons.
The exhaust cam durations on both engines could be increased to gain 5-10% at the expense of idle........as the vvt engine idles with a only 8 degrees overlap vs 1500-4500 at 28 degrees and back to 8 above 4500....another 10-15 degrees might open it up to above 6200 rpm performance.
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