Attachment 268124
I'd like to tell you about the events in the engine. Without calculating (it already expects
enough), but with logic, in a way that it can understand a 12 year old. This is just in the area
my knowledge of German.
Look at the picture some HFD-1.
There you'll see a cylinder. Above the piston is a volume VZYL and therein a pressure prevails Pzyl.
Then comes an exhaust manifold. It contains a mass of gas. The moves are not enough.
After the elbow is the exhaust volume Vout and the pressure is there Paus.
Now we consider what happens when the engine is running in thousandths of seconds. But we have
not in a hurry, we take the time to step by step to follow closely and rethink.
Case 1: The piston has just released the exhaust port. The pressure in the cylinder Pzyl is higher than the pressure
Paus in the exhaust. This means that the gas mass in the left elbow is more crowded than the right.
The mass will be accelerated on the right night. It flows from the gas cylinder in the manifold and thereby
the cylinder pressure drops Pzyl.
At the same gas flows from the exhaust manifold in volume, thereby increasing the exhaust pressure Paus.
As long as the cylinder pressure of the exhaust pressure Pzyl Paus is the gas mass in the manifold
accelerated and the flow velocity on the increase.
This goes on until Pzyl Paus is the same. Then the gas mass reaches its maximum speed.
Because the flow from left to right, ie running from the cylinder to exhaust, remains in the cylinder always
less gas left, so the pressure drops Pzyl ever. And the exhaust is it just the other way.
There is always flowing into it more gas, so that the pressure continues to rise Paus. Paus is therefore higher than
Pzyl. The right of the elbow will be more crowded than on the left and the flow in the manifold is always
decelerated more, until it completely stops.
The crowd is right now much stronger than the left, so the currently stagnant gas mass in the
Now bend to the left accelerates back to the cylinder.
The acceleration remains active until Pzyl Paus again is the same. Then the mass of gas has reiterated its maximum
Speed is reached, but this time left. After growing Pzyl beyond Paus and after the
left flowing gas mass decelerated again until it stops.
Now we are back at the starting point: the cylinder pressure Pzyl is high, the exhaust pressure is Paus
lower, and the mass of gas in the manifold is stationary. She has now performed a complete oscillation of
left to right and back.
Case 2: Imagine that the cylinder volume is now twice as big VZYL. The cylinder is so much
more gas as in Case 1 Now, if gas from the cylinder flows in the manifold, the cylinder pressure decreases Pzyl
much more slowly. So down it takes longer now to Pzyl up at the Pau-value.
It takes longer to stop the flow. And then when the flow goes to the left, back to the
Cylinder increases, Pzyl at much slower and takes longer to stop this reverse flow.
Everything just takes longer.
Case 3: Let us now before the exhaust volume Vout also made twice as large. If dan
Gas from the exhaust manifold flows in, the pressure Paus also much slower. It takes longer to
the flow is slowed down to the right and the return flow comes to the left in motion. And so on.
Case 4: Now we do the Krümmerdurchmesser much smaller, as in Figure HFD-4.
The piston is released to the exhaust port. The mass of gas in the manifold is on the pressure difference
Pzyl-Paus back to the right and accelerates the flow velocity increases again. But because
the small Krümmerdurchmessers comes despite the gas flow rate less mass per
Second from the cylinder to the exhaust. The cylinder entlehrt So slowly, the pressure drops Pzyl
slower, the pressure rises more slowly Paus, everything is slower.
Case 5: the elbow regains its original diameter, as shown in Fig HFD-1. But now
we make, such as image HFD-5 shows the manifold much shorter.
All other values VZYL, Pzyl, Vout and Pau are the same as in Case 1
The pressure difference Pzyl-Paus of the acceleration provides the mass of gas, is again the same.
But the mass itself is now much smaller! Therefore, it is accelerated harder.
The flow rate increases faster, the cylinder pressure Pzyl decreases faster and the exhaust pressure
Paus is increasing rapidly. The flow velocity reaches its maximum value is more likely, rather slowed down,
rather, the direction changes from right to left, there is also decelerated more. In short, the
whole vibration plays in less time.
Leak
Now to another topic. I have stated several times: gas flows from the manifold in
Exhaust volume, thereby increasing the exhaust pressure Paus. But even in HFD-1 image you can see the hook:
the tailpipe! The exhaust has a leak. It comes in. Although gas, but also some same time escaped.
Therefore, the pressure Paus not nearly as fast as you expect without the tail pipe like it.
The pressure in the exhaust behaves as if the exhaust volume would be larger in reality. And
the larger the pipe diameter increases slower Paus Paus, and the lower is the peak-
be. The final hole acts like a shock absorber in the system.
Far left of the images are somewhat remarkable: the overflow. Once the piston
the scavenging port releases, has not only the exhaust volume, but also the cylinder volume a leak.
The cylinder pressure drops Pzyl though because gas flows away from the cylinder above the elbow, but as soon as
Pzyl comes under the irrigation pressure, fresh gas is refilled. Pzyl decreases less rapidly so as to
closed transfer ports.
Once through the opening of the overflow valve, the cylinder volume is brought into communication with the crankcase volume,
Thus it behaves as if it were greater in reality. The vibration in
this coupled volume and tube-dan system is running slower, and the system frequency drops.
Now you have something to ponder:
An increase in volume of the exhaust system reduces the frequency.
A reduction of Krümmerdurchmessers well.
A shortening of the manifold increases the frequency.
An enlargement of the Spülsteuerwinkels lowers the frequency.
An enlargement of the tail pipe diameter reduces the frequency and weakens the pressure fluctuations in the
Exhaust.
Originally Posted by Frits Overmars
- almost as bad as Hon*a....
(Whose computer is it anyway ???
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... it was hard enough to get down to 130 and EngMod2T points to 85mm Now I will have to look at Fritz's Idea.
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