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Old 04-10-2011, 05:45 AM   #16
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Drives: '11 Mustang GT Premium
Join Date: Oct 2010
Location: Kaiserslauthern, Germany
Posts: 1,268
VVT or Cam in Cam phasing:
Regular VVT in a single cam OHV application is limited to either the intake valve timing or exhaust valve timing. I just can't imagine the intake/exhaust valves being controlled by a single cam unless it is a VVT/VTEC combination. GM stated that this new Gen V V8 will use Cam in Cam phasing like the Dodge Viper which is another word for VVT. GM also stated that both the intake and exhaust valves would be controlled independently. This means one of three things:

1.) GM found a way to adjust the intake lobes independently from the exhaust lobes on a single cam. VVT on the exhaust for a longer burn and more horsepower and a VTEC secondary lobe for the intake for torque and horsepower under hard acceleration and regular fuel saving operation below 4500rpm. This sounds kind of complicated, that's a lot of responsibility for a single engine component. There will also be two separate VVT cam gears w/VVT oil pressure unit casting or, some very complicated camshaft nomenclature.

2.) Just break down and go full DOHC, the cost are down and the gains are huge, possibilities are limitless, and fuel economy/emissions are fantastic. This engine design will typically weigh 15-20lbs more.

3.) Create a Duel Under Head Cam design (I believe the prototype 3 valve LS7 used this). This engine design will weigh about 10-15lbs more, the heads would be slightly more compact than a DOHC. See picture below.

So, a Super complex, multi-lobe single cam VVT/VTEC, a DOHC or a Duel Under Head Cam (DUHC). This is exciting...

Last edited by thePill; 04-10-2011 at 01:26 PM.
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