16 valves
Often these units set hydraulic liftersthat automatically adjust thermal gap (eight valve motor, this set is extremely rare). THAT is, you and I need to adjust the valve.
In the end, due to the increased number of inlet and outlet openings, the air-fuel mixture goes faster and faster plays, and no excessive mechanical loss. It should be noted that these options are often set shifters, which further improves efficiency. In the end, and added power in a 15 – 20 HP
12 valve variant
They also had a large number of different manufacturers. But one of the most popular, was the power unit from Hyundai Accent. However, the company did not develop it. The name of the motor from Hyundai – G4EB (there were other modifications, but the system timing, the same). The intake is here two valves, one to release. And here is applied one shaft is hydraulic lifters. Capacity – 1.5 liters (90 HP).
12 valves
It is one of variants of such power units, and so there were many more.
The reasons for withdrawing from the production in that high mechanical losses, as applicable, one shaft, three Cams per cylinder. In the production of one valve — it can't effectively remove the gases, this was a big problem. 16 – valve version was more efficient as fuel consumption and power.
As a result, in 2002 the motor was removed.
20 valve variant
This arrangement, often used in AUDI models of engines were produced, a huge amount, from 1.8 liters to 4.2 liters V8. They got the acronym ALT (AUDI/VOLKSWAGEN). Took them out of production in 2001 – 2002
20 valves
The layout here used five valves per cylinder. Intake them – "THREE" (three Cams on the camshaft), but on release "TWO". THAT is, as you guessed here uses two camshafts, one is belt drive, and the second chain with the phase shifter. There were options with the lifters.
Again, such due to the structural complexity and mechanical losses, which did not give great economy and power compared to the 16-valve version, they were removed from production.
24 valve, and it happens
And this also happens, namely, 6 valves per cylinder. One of the clearest examples of developed their HONDA for your bike, which worked, surprisingly for 4–stroke diagram, the code NR500. Was it already in 1979. The motor was a total volume of 500 "cubes" and had oval pistons.
24 valve
The engine had 4 piston (by the way, on the piston was already two connecting rod), its layout was V4.
Two rod
In the end, spun right up to 16 000 rpm and deliver up to 100 HP and this is with 0.5 liters volume.
BUT! The power unit was very heavy, complicated and expensive, weighed about 20 pounds more than other motorcycle engines of the time. And the series did not go.
Also was the development of the company MASERATI, but many who have experimented.
If you wonder — how many valves in the internal combustion engine, you can find a lot of interesting developments, of 10 or even 20-30 years ago, but not one survived to our times, although it happened that a lot of them produced (recall motors HYUNDAI and AUDI).
Scheme "8 – 16", was the most tenacious and the most correct of all. Although more old engines, which are based on the 8 valves go into the past, just because it is old, not powerful and not eco-friendly. I think that, in "the end" will only "16". WELL and further already the motors.