Fuel Injection: Why Driven by Timing Belt?

Hello everyone,

The design where the camshaft is driven by the timing belt has proven to be effective. This approach is cost-effective and largely maintenance-free.
The problems arise because VW is adding the ESP system, which, in my opinion, is completely unnecessary. The ESP system doesn't have to be located at the top; it could be placed lower down.
The fact that VW is not satisfied with the situation is evident from the latest examples involving wheel bearings.

http://www.buschtaxi.de/de/05umbau/technik/zahnriemenwechsel.html

The link shows an example of how it's done on a Toyota 1HZ. This engine is practically considered indestructible and is installed in all 'bush taxis' around the world, so it's a simple, robust, third-world technology. While the replacement interval is also 100,000 km, I think that hasn't been fully explored. The procedure for replacing the timing belt is also much simpler because you don't have to access the crankshaft pulley from below, and simple markings are sufficient for the large pulleys at the top.

Why isn't this possible with modern engines from developed countries, or are there any manufacturers that do something similar (like Toyota Germany)?

Hello.
Wolfgang.

Wolfgang, syncro16 wrote:

... Why doesn't something like that work with modern, first-world engines...?

Hi Wolfgang,

because the modern high-pressure (TDI, CDI) ESPs would crush the gears.

However, the timing belt technology, in conjunction with the VP pumps, wasn't really a (major) problem. It only became an issue when the use of PD (presumably a specific technology or setting) increased the load on the timing belt to the point where it couldn't handle it anymore, at which point more robust timing belts had to be installed.
And why the Toyota system doesn't work with the PD system, I probably don't need to explain. Or do I?

Hello Bertil,


because the modern high-pressure (TDI, CDI) ESPs would crush the gear .

Really? You mean, a timing belt lasts longer than a gear?
Alternatively, the timing belt provides better damping .

However, the timing belt technology, in conjunction with the VP pumps, was not (a major) problem either.

Well, you don't hear anything good about the 5-cylinder TDI engines either, and they even have two timing belts, which I still can't quite understand.

Und warum beim PD System das Toyota System nicht funktioniert brauche ich doch wohl nicht zu erklären. Or?

Sure .

Hello.
Wolfgang.

Hi,
Well, you don't hear anything good about the 5-cylinder TDI engines either, and they even have 2 timing belts, which I still can't quite understand.
So, I only hear GOOD things about my 5-cylinder engine.

As far as I know, the negative things people say about these engines are mainly due to the unsuitable maintenance intervals.
Initially, there was no interval at all [doesn't that seem right?], and later there was one of 120,000 km. That is clearly too much.

Regarding the 2 timing belts:
I think that can also have advantages.
Because the ESP is driven by its own belt (at the 'rear' of the engine), the main timing belt is slightly less stressed.
If the timing belt on an ESP engine breaks, it will certainly stop the engine, but fortunately, nothing else will be damaged besides the belt itself.

Wolfgang, syncro16 wrote:

Hello Bertil, Quote: because the modern high-pressure (TDI, CDI) ESPs would crush the gear . Really? You mean, a timing belt lasts longer than a gear? Alternatively, the timing belt provides better damping .

Hi Wolfgang,

The lack of damping is what causes the problem! Even a chain can be softened significantly by a CR pump. After 120,000 km, they are also worn out!
While a gear may last longer temporarily than a belt, over its lifespan, the stiffer material (gear) will likely cause more problems (e.g., chipped or damaged teeth with all the resulting consequences).

It's certainly an advantage in those "Bush taxis" because any reasonably skilled mechanic can make a gear (although not with the same precision required for a TDI engine).

Hello,

Okay, I don't understand why there's always so much complaining about timing belts. After all, VW has also built engines with timing chains (like the VR6).
Reading through various online forums, you can really appreciate having a timing belt engine. People are almost constantly replacing their chains and related components after 100,000 km (and it's often a requirement). And it's not as simple or 'cheap' as replacing a timing belt.

gaspedaluser wrote:

Hello, Okay, I don't understand why there's always so much complaining about timing belts. After all, VW has also built engines with timing chains (like the VR6). When you read about it in various forums, you can really be glad to have a timing belt engine. They almost all have to replace their chains and accessories after 100,000 km (mandatory). And that's not as simple or "cheap" as with a timing belt.

Hi,

... exactly what I'm talking about!
And it's not just VW that has these "problems" with the timing chain.

Deleted upon request.

Hi diesel.gustav,

diesel.gustav wrote:

... A minor correction: A properly sized chain drive in modern diesel engines can last for several hundred thousand kilometers.

... a properly sized timing belt drive will last forever...
But the problem is that it's hard to get the sizing right.

Quote:

It is very durable and requires minimal maintenance, and is designed to last for the normal lifespan of the engine without requiring any parts replacement.

I hear somewhat different tones from the development departments.

Quote:

It is true that the chain will lengthen after a short period of use. However, this can be easily compensated for during the initial setup. Alternatively, the chain manufacturer may already "stretch" the chain as part of the manufacturing process, which has been a standard practice for years. After a long period of use, the chain may stretch further. However, instead of replacing it, the pump setting and the control system are adjusted to compensate.

I am familiar with the procedure. I also know that this is how it is applied today. However, this method slightly reduces the initial elongation, but unfortunately also shortens the lifespan of the chain.

Two years ago, I happened to witness a material test comparing chain drives to belt drives. Before that, I was a staunch opponent of timing belts, but since then, I've seen things in a more nuanced way.

Quote:

This is the typical case. Exceptions occur - just like with a timing belt, for example - and are due to the materials used and the manufacturing process.

I share that opinion. I certainly won't demonize either the timing belt or the timing chain. Both systems have their advantages and disadvantages.
In the case of a PD (presumably referring to a specific type of suspension or mechanism), I see the chain being at a disadvantage because the non-negligible impact loads on the PD elements would quickly destroy the chain (due to the lack of longitudinal damping).
In the case of cross-country riding, I think the chain has an advantage because it experiences less impact stress and more consistent, sustained stress.
For gasoline engines, I would also prefer the timing chain, as the relatively low stress on the camshaft(s) and ignition system should allow this more affordable and quieter design to function perfectly well.

Of course, the precise execution and sizing are crucial, regardless of whether it's a timing belt, chain, or gears.
The lack of elasticity in the "metallic" versions could also be compensated for by using a torsion spring or similar device on the pump shaft. Preferably with rubber or PU elements, so that they can be replaced occasionally.
CR has an advantage because elasticity does not affect the injection timing.

I once worked in a service department, and we had a Mercedes 250D automatic, manufactured in 1986, with 90 horsepower and a heavy superstructure. The engine (2.5-liter five-cylinder, pre-chamber naturally aspirated diesel, fully mechanical inline injection pump) always ran at full throttle (which isn't necessarily a bad thing) and it had, please note: 1,180,000 km (one million and one hundred eighty thousand)! The engine had the original timing chain, the original injection pump, and the original cylinder head gasket, so it had never been opened. The oil consumption was approximately 0.6 liters per 1000 km, and it still started well even in winter. Of course, all maintenance was always done meticulously. By the way, the automatic transmission was also the original one.

gaspedaluser wrote:

So, I don't understand why people are always complaining about the timing belt.

Hi,

Well, if I look at the failure statistics for TDI engines and read what engine specialists are saying, I have a completely different impression. You should probably, as Hansemann already said, look at what "state of the art" means at Mercedes... or are Mercedes diesel engines noisy, weak, and do they stop starting after 20,000 km?

haehnlein wrote:

...or are Mercedes diesel engines noisy, underpowered, and do they stop starting after 20,000 km????

Hi,

No, the DC Diesels are quiet (because they are better insulated), heavier (because of the extra insulation), and therefore "consume" about a liter more! However, DC engines now also rattle quite a bit, and the overall quality has deteriorated significantly in recent years.
Unfortunately, the DC (Direct Current) service appears very rarely in the statistics because every DC customer is usually enticed with generous concessions if they contact the DC service directly instead of the automobile club.