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Old 01-01-2016, 04:56 PM
Idle Idle is offline
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Join Date: Oct 2012
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There is a lot going on in this area of the engine at this time and they all work together.

The lack of a combustion chamber in the head was a result of wanting to make a cylinder head as cheaply and as quickly as possible. Mercedes had to get back in the game quickly after WW2 and they had to go with what they had.

The cylinder head uses a smaller diameter intake valve in order to increase the velocity of the fuel mixture into the combustion chamber which is really just the top part of the cylinder. This is why the spark plug is located on the side of the engine. There was no room for it in the head.

The exhaust valve is larger in order to push out the burnt gases quickly since there is no vacuum to draw the exhaust out like there is to draw the fuel in.

In other words: It is important to get the fuel mixture in quickly and burnt before it has a chance to break apart. If it is not mixed properly it will not combust properly.

But the exhaust gas just has to get out, so the valve is larger. This valve also sees more heat so it can deal with the increased temps since there is more of it do heat up.

This design, which was 'borrowed' from GM tech of the late 30's, also allows the engine to be adjusted to the different octane levels available in the country where the car is sold. Low octane fuel needs low compression and this was accomplished by removing the head, installing a thicker head gasket, and then putting the engine back together. Mercedes also built the engines at the factory with the cars' original destination in mind, but if you moved the car from one country to another, one with higher or lower octane gasoline as the norm, you could easily adjust the engines' octane needs with this head/head gasket design.

The long runners were to even out the intake pulses set into motion by the action of the intake valves. This is too complicated to go into here but it is a reason you see these long runners on a lot of cars these days. To make runners like this out of metal, like Mercedes did, is very expensive. To make them out of plastic is cheap so now a lot of companies are using this design feature to grind out a few more HP.

Racing engines, however, used a different design that the production engines but in racing the factory could control the octane levels. Mercedes, like everyone, uses racing to test concepts so from the successful designs used in racing come the cylinder head designs we have today in production cars.

And the very best design of all? Pistons that are oblong shaped with six valves per cylinder. And as soon as someone finds a way to make an engine like this for less than $250,000 each we will be seeing this in our production cars.

Until then we will have to make do with what we have.
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