Dead space in gasoline engines

Hi.

What is the purpose of the additional, but empty, space in the lower image?
Air can only flow into and out of the additional space through the branching folds. But what's the point of that?

Hmm, well, one possibility could be the twinport system, which has an intake swirl channel and a filling channel. But even that system wouldn't necessarily need so much filtered air, would it?
haithamina

dieselmartin wrote:

Hi What is the purpose of the additional, but seemingly empty, space in the lower image? Air can only flow into and out of the additional space through the branching folds. But what's the point of that?

:dig deep and look for my apple pie:

Essentially, this allows for adjusting the airflow to suit different load and speed conditions, thereby expanding the usable torque range.

Regarding the intake manifolds (very generally speaking):
Long strokes are good for low RPMs, while short strokes are good for high RPMs. Unfortunately, the opposite is also true:
Long travel distances are bad for high RPMs, while short travel distances are bad for low RPMs.

The air intake system shown is a rudimentary type of "switchable intake manifold" or adjustable "air box."


Unfortunately, I need a bit more space here to provide more detailed explanations... I think it would overwhelm the forum.

Well, I'm surprised. That it's a dead space... The air that goes in only comes out again through the entrance.

The air can only enter the cylinders through the part shown in both pictures.

The only explanation I can offer is that the intention is to have a reserve volume of air as close to the engine as possible to accommodate load changes, so that it doesn't have to pass through the air filter (which creates resistance).

Here's a schematic diagram of the smaller 1.2i engine (the image at the top).

Perhaps something like a resonator to meet noise regulations?
My Nissan Micra had something similar; there was a second, closed pipe branching off the intake manifold. No one could explain it definitively, but basically, there were two theories:
So, either to reduce noise or to influence the resonance behavior of the vibrating air column (likely more for reducing noise than for increasing power).

'PS: 50cc two-stroke mopeds often have a resonance tube on the exhaust manifold to restrict power and reduce engine revving.'


Best regards, Alex.

dieselmartin wrote:

Well, I'm surprised. That it's a dead space... The air that goes in only comes out again through the entrance

.

majesty78 wrote:

This is not a dead space. The air column in front of the ESD noticeably changes its position when this room is connected. Try searching on Google for "resonance charging" or "oscillation charging." You should be able to find something there. Otherwise, I can only recommend the book "Ways to a Four-Stroke High-Performance Engine" by Ludwig Apfelbeck (which is unfortunately very difficult to obtain these days).

...in order to influence the resonant behavior of the oscillating column of gas}.

That's exactly what it's for.

Hi,

Quote:

The air column in front of the ESD changes its position significantly when this room is activated.

Does the engine that Martin studied have a bypass mechanism at that location? If so, it would indeed be a variable intake manifold. However, I'm just assuming that Martin didn't omit any valves or other components from his sketch.

Then the static version is probably better, which in turn would have to meet the compromise mentioned above.

Quote:

Regarding the intake manifolds (very generally speaking): Long strokes are good for low RPMs, while short strokes are good for high RPMs. Unfortunately, the opposite is also true: Long travel distances are bad for high RPMs, while short travel distances are bad for low RPMs.

Best regards,

Jan.

majesty78 wrote:

Maybe something like a resonator to meet the noise regulations?

Exactly, that's what this dead space (resonance chamber) is for.

In the first picture, as mentioned before, it's a 1.2i engine from Opel, which only produces about 45 horsepower (in the Corsa B). In the second picture, I would say it's either a 1.4i with 60 horsepower or a 1.6i with 75 horsepower. The engines are very similar in construction, but due to the different displacement, the intake and exhaust sounds are quite different, and this "dead space" (resonance chamber) was used to adjust the noise levels to meet regulations."Similarly, at VW, something similar was used, but not with a container above the engine, but rather with a tube next to the air filter box (e.g., Golf 4 with a 1.6L 8-valve engine producing 102 hp and a 1.8L 20V naturally aspirated engine producing 125 hp. The corresponding Skoda, Seat, and Audi models also used it, with their transversely mounted engines)."

germa wrote:

majesty78 wrote: Maybe something like a resonator to meet the noise regulations? Exactly, that's what this dead space (resonance chamber) is for. ...

When resonance occurs, the noises become louder!

I had this box yesterday.
It's my currently modified Corsa B 1.4i (with the X14SZ engine producing 60 horsepower).

There's no valve or other access point except as described in the sketch – which is why I was so surprised.

I had already planned to try running the X14SZ with the bellows of the X12SZ (EDIT: it must be a C12... because there's no DIS module), in order to reduce noise.



You can find apple pie online...

My book budget is currently covered for the time being with "Diesel Engine Management, 4th Edition" and "Automotive Electronics, 5th Edition."

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

dieselmartin wrote:

... There's no valve or other access point except as described in the sketch – which is why I was so surprised.

With this resonance chamber, the intake manifold can be tuned to optimize performance across different load and RPM ranges.
Just like an organ pipe or a flute.

http://www.neunertreff.de/wiki/index.php/Resonanzaufladung

http://www.motorenlexikon.de/?I=454
Depending on the length, diameter, and volume of the resonance chamber, a shift in the maximum torque above the engine speed is possible. An increase in specific work is possible within a limited speed range, up to 10%, which means that an overall torque increase across the entire speed range is not easily achievable.

http://motorlexikon.de/?I=8009&R=S

Maybe something like a resonator to meet the noise regulations?

Exactly, that's what this dead space (resonance chamber) is for.
...

When resonance occurs, the noises become louder!

A Helmholtz resonator, however, acts destructively and is frequency-dependent.
So, in relation to the speed (or RPM).
'That way, I'm quiet at low speeds, but get really loud at high speeds.'

Alfa uses this thing with the Twin-Spark engines. If I remove it, the engine sounds like a Ferrari.
'As far as I know, Porsche uses the same principle, but additionally incorporates an active exhaust system.'

Best regards, Jochen.

Quote:

A Helmholtz resonator, however, acts destructively and is frequency-dependent. So, in relation to the speed.

Well, the trick with a Helmholtz resonator is that it exhibits constructive interference at some frequencies and destructive interference at others. You can tune its volume to match the rotational speed, which in turn affects the oscillation of the gas column.
In some speed ranges, it dampens the effect, while in others, it amplifies it. Ultimately, it depends heavily on the desired characteristic.

It's important to note that this not only has acoustic effects but also impacts the engine's performance and torque curve.

I happened to come across this .

I have the aforementioned X14SZ motor and I'm also wondering what that large box is for.

The older 1.4 without EGR, with the C14NZ engine, has the small air collector.
The C12NZ and X12SZ as well.

And there's no switch or anything like that inside; it's purely static.

I even think I saw an X14SZ with a small..., but I'm not entirely sure anymore.

There was probably also an X14NZ...