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HI.

My BMR has a plastic intake manifold.

Can someone explain to me what this is and what kind of problems it might cause?

Okay, I can imagine that something like this is easier to injection mold and glue than a conventional metal fitting.

Does it also offer advantages for me, for example, that plastic is more flexible and doesn't cause as much stress due to different thermal expansion coefficients?

m;

Hello!

I would say it's purely for weight reasons. The 1.4i 16V aluminum engine in the Golf, Polo, Lupo, etc., also uses a plastic intake manifold.

Greetings.

I'm also leaning towards cost and weight considerations.

Regarding thermal expansion: A metal sleeve would likely exhibit similar behavior to the engine block. I suspect it's better if the materials expand in a similar way.

"Plastic is naturally more flexible than a cast spout, but presumably a rubber hose will be attached to the spout anyway, so it probably won't make a difference."

Hopefully, the plastic is oil-resistant enough for the sludge in the intake area and won't melt if you really push the bike hard.

Rubber hose???

At one end is the cylinder head (metal), and at the other end is the EGR control valve unit (metal), as you can see in the picture from another thread.
/files/bmr_damper.jpg

But even if... what effect would a rubber hose have if the cylinder head and intake manifold expanded differently?

There must be at least two coefficients for the expansion.
The amount by which a material expands per degree Celsius and the force it exerts during that expansion... And I think the force is lower in plastics (but that's just a pure guess).

m;

Perhaps the plastic intake manifold is contaminated by the EGR due to its surface structure much less than a metal intake manifold?

I don't think you even need to think about these things. The plastic part is simply cheaper, and that's the deciding factor. I'm an aspiring engineer myself, and I know for sure that 'up there,' nobody cares about thermal expansion. They just look at the cost of aluminum casting versus plastic injection molding, and that's all that matters.

dieselmartin wrote:

Can someone explain to me what this is supposed to be and what kind of problems it might cause? Okay, I can imagine that something like this is easier to injection mold and glue than a conventional metal fitting. Does it also offer advantages for me, for example, that plastic is more flexible and doesn't cause as much stress due to different thermal expansion coefficients? m;

Hi,

In my opinion, this is probably only related to the price, or possibly to the fact that cheaper seals can be used. Metal can warp, while plastic can be designed in a way that it has a greater degree of bending between the screws, which creates a better seal because it's under more tension.

The disadvantage is the material's stability at higher temperatures, and of course, we're all familiar with aluminum prices. I once had the unpleasant experience of a plastic hose bursting between the charger and the battery, and here, we also have significantly higher temperatures under pressure.

Well, there's been a lot of speculation. There are many possible reasons. However, thermal expansion is probably not a major factor in this case, as the device is likely cooled by relatively "cold" air and is certainly mounted in sockets made of some metal. Also, the shape in the photo is highly curved. It's also possible to achieve better shapes with plastic than with aluminum die casting. However, as you mentioned, the part is also apparently available in aluminum casting... go figure.

Sure.

In the Passat BMR, the part was made of aluminum up to production date 3C.7.120000, and then it was switched to plastic.

Here are the photos again.

Aluminum in the BMN.
/files/bmn.jpg

...and plastic in the BMR.
/files/bmr_damper.jpg

It's quite simple. Every manufacturer has a department dedicated to cost reduction. Once a car is in mass production, it goes through another review, and clever people analyze where they can save 1 or 2 euros. While 50-100 euros might not seem like much for a single car, consider the savings when you multiply that by 1,000,000 units. A friend of mine was an intern at Ford in one of those departments for a few weeks.

Nowadays, it's better to buy a car from the first model series.

For example, the first 150 horsepower 1.8T gasoline engines had a more robust crankshaft and connecting rods, larger intake channels in the cylinder head, a larger throttle body, and an intercooler piping system made entirely of aluminum. These engines are now very popular for tuning, but there aren't many of them available.

Okay, personally, I would prefer the intake manifold to be made of plastic. That eliminates the need to smooth the intake channels, so the gunk doesn't stick as easily, and the weight is reduced. Durability isn't really an issue anyway; those are just things people talk about at gatherings. After all, the 1.4 16V aluminum engine was one of the lightest engines ever made. So, I'm sticking with my opinion: it's just a matter of weight and cost. Although, the potential cost pressure here isn't a disadvantage. I think it's fine if someone is thinking about eliminating truly useless junk. } It just needs to be done in a sensible way. }

Greetings.