Questions about GM's prototype twin-cam pushrod V8.
01-30-2004, 05:55 PM
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Questions about GM's prototype twin-cam pushrod V8.
Now, I saw this block in person on the floor of GM's R&D facility in Auburn Hills, MI, way back in 2000, and I've heard rumors about it here.
Now, the only reason I can see to use two cams, is to have 4 valves per cylinder on a pushrod motor.
If you guys have any more info on this motor, post it here... :lurk:
Now, the only reason I can see to use two cams, is to have 4 valves per cylinder on a pushrod motor.
If you guys have any more info on this motor, post it here... :lurk:
01-31-2004, 12:13 AM
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Re: Questions about GM's prototype twin-cam pushrod V8. (CentralCoaster)
No, two cams has nothing to do with the number of valves per cylinder, but one is used to drive the inlet valves and the other the exhaust valves.
The motivation for two cams is to have INDEPENDENTLY variable phasing for both the inlet and exhaust valve events.
The ability to independently phase the inlet and exhaust can be used to both control emissions and flatten the torque curve.
At the most basic level, retarding the exhaust cam increases exhaust gas dilution, so it can be used to control NOx at cruise. Minimizing overlap at idle allows a smoother idle, then then retarding the inlet cam at high revs and WOT helps keep the torque curve from falling off at high revs by closing the inlet valve later.
Duke
[Modified by SWCDuke, 9:19 PM 1/30/2004]
The motivation for two cams is to have INDEPENDENTLY variable phasing for both the inlet and exhaust valve events.
The ability to independently phase the inlet and exhaust can be used to both control emissions and flatten the torque curve.
At the most basic level, retarding the exhaust cam increases exhaust gas dilution, so it can be used to control NOx at cruise. Minimizing overlap at idle allows a smoother idle, then then retarding the inlet cam at high revs and WOT helps keep the torque curve from falling off at high revs by closing the inlet valve later.
Duke
[Modified by SWCDuke, 9:19 PM 1/30/2004]
