Some technical solutions for the internal combustion engines
1. The thinking behind a Variable Valve Actuation system (VVA) is to optimize the breathing and the combustion of the engine.
Having various valve lift profiles to choose from, the ideal valve lift profile can be approached (ideal for the instant operational conditions like revs, load, fuel quality, air temperature, water temperature, altitude etc).
The closer the approach, the more efficient the aspiration and the combustion of the engine. And the higher the rev limiter, the higher the "peak power".
The state-of-the-art VVAs have limitations on both, the "high-revving capability" and the "variability" of the valve lift
profile.
2. A fine-tuning can make the idling of a throttle-less VVA engine perfect, but the operation of the engine at high revs soon degrades the idling quality, making necessary a new fine-tuning, and so on. The idle valves can make the difference.
3. No doubt, the Variable Compression Ratio (VCR) increases the partial-load efficiency of the spark ignition engine. But the state-of-the-art VCRs, making the simple complicate, add more problems (side effects) than they solve (see Key Advantages).
To modify a conventional V-8 to a fully functional VCR V-8, all it takes is five cheap and lightweight moving parts and a control.
4. Downsizing is now in fashion.
A four-in-line, atmospheric, 1000 cc / 180 bhp motorcycle engine capable of delivering 10 Kp*m torque from below 1000 rpm, idling at 300 rpm, with
efficient and smoother running at partial loads and low-medium revs, sounds as the perfect downsizing. All it needs is a DVVA.
If the 180 bhp/lit specific power is not adequate, turbocharging can double it. The correct VVA (applicable on intake and especially on
exhaust valves and capable for true-high-revving) optimizes engine's breathing and turbocharger's performance and efficiency. The key component here is the exhaust valve lift profile that controls the exhaust gas flow and keeps the turbine at optimum.
Instead of struggling to increase the specific power of an under-powered conventional engine, one can start with a top-specific-power engine and
improve its "downtown" operation by optimizing the aspiration and combustion, keeping or even increasing the peak power.
5. Downsizing the compression-ignition engines is also in fashion.
The OPRE direct injection Diesel is a two-stroke engine, rid of the two-stroke problems (lubrication, scavenging, peaky torque curve etc). It combines the two-stroke lightweight and simplicity with full balance and extended piston dwell at combustion that allows higher revs and thereby higher power density.