Timing Belt Replacement VW TDI 4-Valve

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Yes, yes, the timing belts.
Although it is being further developed, the belt on my car should also last 180,000 km. Then, suddenly, it was only supposed to last 120,000 km. Ultimately, the tensioner pulley failed at 104,000 km...

But the belt held! However, nothing beats spur gears .

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Sure, gears also experience wear, but with today's materials and helical gearing, they last significantly longer. This is especially true when considering the stress on a cylinder head in a piston engine. And let's not forget the slightly higher friction of a 4-valve engine compared to a 2-valve engine. The tolerances in these engines are almost on a watchmaker's level, so there shouldn't be any parallelism errors. And in the upper area, a small chain could be used for a variable valve timing system if it's present. The relatively small additional cost shouldn't be a major issue for an Audi or VW. This technology definitely saves space. As an Audi driver, I wouldn't be happy if the engine flew apart because of a "cent." And mine was just a gasoline engine! Besides that, it's also a cost issue; replacing the timing belt is quite expensive. This affects all our vehicles (Audi A3, 2x A4, Allroad, T4).

Hi,

I'd like to chime in...
In the "good old days" of automotive engine manufacturing, a camshaft drive system using pushrods and rocker arms was once popular. This design almost completely disappeared in the 1980s. Some of the last examples were likely the water-cooled boxer engines in the T3, which were produced until 1992.
Now it's clear to me that a valve drive like this isn't the best solution for a high-revving gasoline engine. However, with a direct-injection diesel, the nominal speed is generally around 4000 rpm, and sometimes even lower. It's also clear to me that pump-injection and OHV (overhead valve, meaning a camshaft located in the engine block) are mutually exclusive. However, something like this might be feasible with a common-rail system or a distributor-type ESP (electronic stability program). The camshaft, located in the engine block, can be driven very well with gears, and it also doesn't have problems with the expansion of the engine block between the crankshaft and the camshaft. The drive for the auxiliary components and the high-pressure pump from the common-rail system (or distributor-type ESP, it doesn't matter) could just as easily be run with gears. I'd be interested to know what arguments there are against OHV in common-rail or distributor-type ESP TDIs?

Regards,
Jens.

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Hi Gustav,
I'm just adding a comment to your text... (I hope this isn't considered rude).

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OHV engines, with their overhead valves, camshafts located at the bottom, pushrods, rocker arms, and rocker shafts, were, on the one hand, not suitable for high speeds (a swirl chamber diesel engine rotates at 5,300 rpm, and in this case, the pushrods may "flutter" significantly

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So, a Waterboxer (you can tell I'm quite familiar with the T3 ), with its 2.1-liter fuel injection engine (MKB "DJ"), has a rated speed of 4800 rpm. I don't know the exact rev limit right now, but it's probably well over 5000 rpm. It works quite well with the pushrods, though. The rated speed of a TDI is rarely ever above 4000 rpm (the AFN comes to mind), and rev limits above 5500 rpm are probably very rare.

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On the other hand, hydraulic valve clearance compensation elements were difficult to implement.

However, the hydraulic lifters in the water-cooled boxer engine don't appear any more complicated than those in overhead camshaft engines.

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The component requirements, the weight, the manufacturing costs, the functional safety

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For me, as an advocate of OHV (Overhead Valve) engines, this seems very thin . The costs are likely to be significantly higher than those of an OHC (Overhead Camshaft) engine.

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The ease of maintenance (or does anyone still accept that valve clearances need to be adjusted?) also speaks clearly in favor of OHC.

Kann ich nicht nachvollziehen, das Argument. VW hat bei den Boxern (Luft- und Wassergekühlt) ab Ende der 70iger Jahre nur noch hydraulischen Ventilspielausgleich verwendet. It works.

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And 4-valve technology is also not feasible with OHV.

Hmm, and what about simple fork levers? I've seen those on motorcycle engines before. But as a layman, I can't really say much about it. Four-valve technology might indeed be more difficult with OHV.

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Regarding your comments: In a diesel engine with a distributor pump, such as the Ford 1.6D (granted, it's an older model, but it's still used in the Escort, Fiesta, etc.), the distributor pump is driven by the crankshaft using gears.

Who actually designed/built this engine? Ford wasn't really involved with diesel engines in passenger cars back then.

I have a question about CR diesel engines. I'm a proponent of diesel engines that perform reliably even under challenging conditions (off-road, long-distance travel on rough roads). Can CR diesels be better suited for these types of applications than PD diesels? It seems that common rail systems are becoming less common, as new engine designs rarely use them. A typical example of a diesel engine often used for such purposes is the Iveco 2.8 CR-TDI. This engine is considered relatively robust. However, I've also seen the MWN-2.8 TD in a VW LT, and recently, a CR engine as well. How does this engine compare to the Iveco engine in terms of reliability?

Best regards.
Jens.

Hi,
Ford had KHD develop the 1.6 D engines. That's why they were better than Ford's own gasoline engines.
As far as I remember, the only annoying part was changing the oil filter in the cramped engine compartment of the Fiesta.

Hello Gustav,

Thank you for the detailed explanation.