The difference I'm wondering about in my older post is not so much the mechanisms used, but the power deliverey of the two systems. So what I'm getting at in my Dual VVTL-i post is that Toyota may be waiting to employ cam phasing and switching on both intake and exhaust if it is possible. I don't think any company does this right now.Originally posted by AntiCt:
The differences between VVTL and dual VVT are that:
1. VVTL is cam phasing only on intake cams
2. VVTL also has cam switch on both intake and exhaust.
3. Dual VVT is cam phasing on both cams
4. Dual VVT doesn't use switchable cams
The Celica uses a system that uses engine oil pressure to drive both VVT and the "L" portion (driven seaprately). I believe the Altezza uses a set of helical gears driven from the ECU and oil pressure to phase the cams - similar to IS, GS, and LS.