TDI/SDI Engine Noise: Common Questions & Answers

Hi.

Generally, I've noticed that TDIs are quieter than their related SDIs.

Is this a matter of policy (e.g., less damping material) or a matter of principle (perhaps the turbocharger's boost pressure also provides some ??).

What I've also noticed is that G4 TDIs (including the older 90 hp VP models) sound much smoother than my "post-war" 1Z.
Even my ex's 2000 1.7 SDI Polo (AKU) sounded quite smooth yesterday, despite the freezing temperatures.

A significant change is the engine mounting system. In the Polo and G4, the engine is "suspended," while in the G3, it sits on bearings. However, you wouldn't hear that from the outside.

VW must have made one or more changes that eliminated the "tank-like" sound of the 1Z engine. Even an AFN engine sounds softer.


I can imagine changes to the injection system (pilot injection with VP???), or modified combustion chambers.

Who knows more about this?

Thank you.
m;

Hello,

'I've also noticed the difference. My SDI (ASY) engine runs very roughly, especially when it's cold. When I compared it directly to a current PD-TDI vehicle, it was extremely noticeable. The SDI has a slightly higher compression ratio, which unfortunately...'
No direct injection. Is that the only reason?

Regards,

Sepp.

Hm

The comparison is a bit of a stretch.

That's why I wrote "related" TDI-SDI.
Since there are no PD_SDI values available, the PD_TDIs are not relevant for my comparative analysis.

You can clearly hear the thrust cutoff in PD recordings, as it's characterized by the absence of that typical "tickering" sound.


Sure, here's the translation:

"Something else:"
By the way, I prefer riding the SDI in the city because it doesn't have electronic damping and it accelerates faster at low speeds (1Z compared to the AKU) when stopping at traffic lights.

m

PD and smoother running than VP? I've never noticed that. In my opinion, PD engines run harder and more precisely than VP engines. My 1Z doesn't sound as harsh as a PD engine (at least from the outside). PD engines, on the other hand, tend to be noisy. Inside the car, it's not exactly quiet (I'm probably also affected by the flex pipe - is there a way to replace it without the catalytic converter?).

Best regards, WarLord.

I don't want to say anything incorrect, but I think I read that a naturally aspirated (SDI) version will be developed from the 2.0 TDI engine, and that it will supposedly have common rail direct injection (PD). However, I might be wrong.

Since the SDI engines don't have direct injection (and I'm 100% sure of that), that's already a major reason for the engine noise.

Insulation, yes, especially with VW, you have to factor in that they tend to use less of it in "cheaper" vehicles. But in my opinion, it doesn't make sense.

Turbocharged engines are often mechanically quieter because the turbocharger dampens the combustion noises. And the turbocharger is the key difference between SDI and TDI engines.

This also applies to gasoline engines. Compare, for example, a Golf IV 1.8/20V and a 1.8T...

It gets funny when someone installs a loud exhaust system on a TDI, starts the car with high expectations, and then disappointment sets in. The same thing happens with the 1.8 T.

Best regards, WarLord.