Charge Air Cooler Sizing: Guide & Calculation

I'm planning to fabricate my charge air pipes as a single piece and I'm wondering what difference it would make if the pipes, which normally have an inner diameter of around 44mm, were made smaller or larger.

What impact would this have on pressure build-up, flow rate, etc.?

Does anyone have experience with this? I was thinking of using components with an inner diameter of 50mm because my boost pressure is already higher than normal (1.25 bar).

Thank you very much.

chris

Hi,

It is a common belief that intake manifold resonances have no effect in turbocharged engines. However, this may not be entirely correct, as even a turbocharged engine uses valves, which means that air is not delivered to the cylinders uniformly, but in pulses. This creates a vibrating column of gas, at least in the area between the intake valve and the turbocharger, even under higher pressure conditions. The dimensions and volume, as well as the speed of propagation of the vibrations, are the main factors determining the resonances in the intake manifold (which should more accurately be called the 'forced-air intake'). The latter is relatively constant and changes only slightly due to the turbocharging.

If you change the cross-sectional shape of the pipes, the following parameters would also need to change as a result:
1. the resonance frequency of the tube due to the increase in volume.
2. the air velocity in the pipe.

It's probably only possible to determine the exact outcome through experimentation, or with very expensive simulation programs.

I suspect that the characteristic curve of the cylinder filling volume changes depending on the engine speed, which in turn affects the exhaust emissions.
In terms of performance, the difference might not be significant, as a TDI engine typically operates with an excess air ratio of around 20%. If you increase this ratio to, for example, 23% by enlarging the intake passages, you won't gain anything because the amount of diesel injected isn't automatically increased.

It becomes interesting, however, when you tune the intake path to resonate at the engine speed range where the turbocharger is not yet active.
That might make a difference.

But as with so many ideas, the same applies here: practice makes perfect .

Best regards,
Eike

Are we talking about the charging air ducts?

'Things get interesting, however, when you tune the intake path to resonate at the engine speed where the turbocharger is not yet active.'
'That might make a difference.'

I need to tune the intake manifold to resonate with something. Is it with the valves, or how? I'm not really understanding any of this, lol.

While it's logical, I highly doubt the engineers at VW could get anything to resonate with that cobbled-together turbocharger system.

Sure, here is the translation of the text from German to English:

'cu' is a Spanish abbreviation for 'con usted,' which means 'with you.' It is often used in online communication to indicate that the sender is available to chat or talk.

Here is an example of how 'cu' might be used in a conversation:

Person A: 'Hey, I'm bored. Want to chat?'
Person B: 'Cu!'

This means that Person B is available to chat with Person A.

'Cu' can also be used to indicate that the sender is thinking about the recipient. For example, if Person A is thinking about Person B, they might send a message that says, 'Cu.'

In general, 'cu' is a friendly and informal way to communicate with someone online.

Does the diameter of the exhaust pipe also play a role? I could go on and on. How much is too much pipe diameter for the exhaust system? Is a Group A size of 63.5mm too large? Would that create too little back pressure? What happens then?

'Diesel' is usually spelled with a capital 'D'.

'Get as much air in as possible, and then, after combustion, get the hot air out as quickly as possible.' Wouldn't a large pipe diameter help with that?

Sure, I'll help you. Thank you.

chris

Hi,
Try to follow this:
das Einlaßventil vor dem Zylinder ist verschlossen, der Ladedruck steht vor dem Ventil an. Das Ventil öffnet, die aufgestaute Luft setzt sich in Bewegung und stömt mit hoher Geschwindigkeit in den Zylinder. Da Luft ein gewisses Gewicht hat ( bei Umgebungsdruck ca. 1,2 kg / qbm bzw bei 1 bar Ladedruck 2,4 kg/qbm), hat sie dann auch eine Bewegungsenergie (Massenträgheit). Das bedeutet, das die Luft weiter in Richtung Zylinder strömt, auch wenn das Ventil gerade schon wieder geschlossen hat. Die sich bewegende Luft prallt gegen das Ventil und es entsteht eine Druckwelle, die wieder zurückläuft (ähnlich wie eine Welle am Strand). Diese Welle (es ist eine akustische Welle aus verdichteter Luft, wie beim Basslautsprecher) läuft zurück und wird zum großen Teil am Turbolader reflektiert. Von dort läuft sie wieder richtung Zylinder. Idealerweise ist kurz vorher schon das Einlaßventil geöffnet und schließt genau in dem Moment, wo diese Druckwelle das Ventil passiert hat und zusätzliche Luft in den Zylinder gepresst hat. Das The game restarts, and the next wave is on its way...

This is the principle of intake manifold resonance, which also works in turbo engines, but doesn't increase power because there is already enough air entering the cylinders (during turbo operation).
Ideally, in practice, there's also an intercooler, and numerous bends and edges in the system where sound waves can reflect. Furthermore, this one path also feeds three other cylinders. Therefore, there will be a collection of resonances that can be altered by changing the dimensions, which in turn will have an impact on the entire system.

The same applies to the exhaust system. This is especially true for engines without turbochargers. Otherwise, what would be the point of using header manifolds? However, since the turbocharger is located very close to the exhaust valves, resonance is not to be expected in this area. It is also unlikely to occur behind the turbocharger, or only to a small extent, because the turbocharger's inertia creates a more even exhaust flow.

Ultimately, the turbocharger draws the energy it needs to compress the intake air from the pressure difference before and behind the compressor and from the exhaust gas volume. Increasing the cross-sectional area here might offer some improvement.

Regards,

Eike.