riff_raff wrote:The "VVT" system that I am working with, for the ubiquitous OHV pushrod V8 engine, can vary both intake and exhaust valve lift and duration, infinitely and independently, but cannot change the"lobe center" characteristic.
I don’t know, obviously, the details of your system but to implement a VVL on a OHC engine is indeed very simple, you just need to change the length the of pushrod and there are several ways to do it. More complex it becomes if you want to change lift and duration independently (something that Valvetronic doesn’t allow). Anyway the real problem isn’t the packaging, it’s the opportunity to do it. What you call “small” block is a big V8 of 6 or even more litre with just 2 valves per cylinder and revving at less than 6k rpm. Such design shouldn’t need a VVT and even less a VVL.
riff_raff wrote:The only production VVT system that I have seen for OHV pushrod engines is GMs "D-O-D" lifter. It de-activates four of the eight cylinder engine's valves, during part throttle operation, thus reducing FMEP/throttle losses in their SI engines.
DOD certainly isn’t a VVT, isn’t even a VVL, on and off, that doesn’t mean variable. Then it’s better if I don’t start to talk about the logic behind the DOD, half of the cylinders going up and down with no function at all as a way to improve efficiency... But hey, it improves the rated mpg at constant speed so it surely works...
DaveKillens wrote:I would believe there is still a need for being able to ask the engine for maximum torque as it exits a slow corner. Even in F1
They have variable length intakes to optimise the volumetric efficiency at the different rpm levels, but the requirement for the torque curve is very different from, for example, rally. Rally cars requires a easily “tractable” engines on a very large range of rpm because of the driving technique, of the different surfaces, of the limited knowledge of corner’s condition in that precise moment etc etc... there’s a lot more improvisation there and an “easy” engine is required.
In F1 you have 6-7 gears, damn fast gearboxes and each movement of the driver, on steer, throttle, brake, paddle shifters... is very precisely timed and repeated lap after lap after lap with a limited variation of the track conditions, the setup is expressively selected for these few corners. If you find yourself in a situation where at corner exit rpm are too low for the selected gear there’s a good chance it was because you made a driving mistake.
Furthermore in a F1 the TC works up to 180-200 km/h, isn’t torque at low speed what they lack, the car with best acceleration out of a slow corner isn’t the one having more “low end torque” from the engine, it’s the one having the most grip and the best TC to exploit it.