i had a log in
Normal H22A vs. "Type-S" H22A7/8
Intake opening (BTDC)
15°..................15°
Intake closing (ABDC)
40°..................45°
Duration: 235°.... 240°
Exhaust opening (BBDC)
40°..................45°
Exhaust closing (ATDC)
15°..................15°
Duration: 235°.... 240°
Gross valve lift measured w/1.55 rocker ratio
Normal H22A vs. "Type-S" H22A
Intake:
(mm) SAE (mm) SAE
(11.5) 0.453"..........(12.2) 0.480"
Exhaust:
(mm) SAE (mm) SAE
(10.5) 0.413"..........(11.2) 0.441"
I've just measured the VTEC profiles on the H22A and H22A7 inlet cams I have, lift measured every 2 degrees (crank) at the valve with 0.15mm clearance:
H22A Max lift 11.27mm, duration @ 0.1mm 272 degrees, duration @ 1.0mm 236 degrees
H22A7 Max lift 12.03mm, duration @ 0.1mm 295 degrees, duration @ 1.0mm 248 degrees
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Skunk
-Pro 1-
Intake: 264 deg. duration, 12.6 lift
Exhaust 264 deg. duration, 11.9 lift
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I'd be taking on a bit much to explain here how cams work, I posted this really for the benefit of those that want to be able to make proper comparisons between the standard cam profiles and after market items.
Cam profiles are typically summarised by the headline figures of peak lift, duration and sometimes advised lift at TDC. Unfortunately, these values really don't tell you much at all. You could have 10 cam profiles all rated at 300 degrees and they could all be hugely different and well or ill suited to the rest of your spec!
The H22 engines have six cam profiles on each cylinder, three for the inlet side and three for the exhaust side (primary, secondary and VTEC). The valves follow the primary/secondary cam lobes together until the VTEC switch, then the valves follow the VTEC profiles. What I've done here is measure just the VTEC profiles, for the inlet valves on the H22A and H22A7.
The x-axis of the graph is crankshaft degrees relative to the peak of the cam lobes. The y-axis is valve lift (opening) in millimetres.
The VTEC H22A7 profile is pretty clever, it combines good flow potential with fairly harsh opening and closing to ensure minimal cylinder pressure loss. So essentially, any cam more severe than this is going to be a trade off of some kind in terms of:
Valve acceleration (needs stronger springs, so valve train wear and risk of breakage increases, power is lost too due to the extra effort in opening the valves).
Greater lift (as above and modification of the head and valvetrain required, expensive!)
Greater duration (basically moves the sweet spot further up the rev range, due to the loss of cylinder pressure during the slower induction cycle in the mid range, which can be countered to some extent with higher compression and careful induction and exhaust geometry tuning. Also, if the engine needs to rev higher to reach the sweet spot, other provisions have to be made to ensure it can withstand the higher stresses.)
