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Engine Specific Info and Questions => IDI Engine => Topic started by: lyeinyoureye on May 22, 2007, 02:54:39 pm

Title: Timing chain retrofit?
Post by: lyeinyoureye on May 22, 2007, 02:54:39 pm

Has anyone ever bounced this idea around before? Could gears that fit on the shafts and some kind of sealed oil bath be fabbed? Not really thinking much about it, just something to throw out there.  :)

Title: Timing chain retrofit?
Post by: jtanguay on May 22, 2007, 02:59:52 pm

it could be done.  but it would be a bit noisier... (probably won't hear it over the regular diesel noise though)

Title: Timing chain retrofit?
Post by: lyeinyoureye on May 22, 2007, 04:12:26 pm

I'm wondering why VW didn't bother w/ it... Did they want to motor to be timed fairly often? Could chain stretch have made this an issue? In other words, did they figure the chain could've stretched enough that re-timing at the belt interval was needed? Maybe it was part of the cost cutting platform sharing...

Title: Timing chain retrofit?
Post by: Turbinepowered on May 22, 2007, 04:19:44 pm

I imagine it was a cost and complexity issue. I know that there are Mercedes out there running with several dozen thousand miles on their original timing chains, even their original timings; chains are durable, but complex in my opinion. They have to be constantly oiled and they're more expensive to manufacture, among other initial setup issues.

I seem to recall hearing that the new V6 TDI, the 3.0, is chain-driven timing for the cams. And the Subaru flat four diesel has a timing chain, too.

Title: Timing chain retrofit?
Post by: jimfoo on May 22, 2007, 05:53:41 pm

My old Land Rover has an ingenious timing chain system. There is a tensioner that gets pushed into the chain by oil pressure. It also has a pawl with teeth that lock it in place, keeping the chain tight at all times. Some of the engines have 200-300k miles on them.

Title: Timing chain retrofit?
Post by: RabbitJockey on May 22, 2007, 06:58:25 pm

whats the advantage of a chain over the belt we have?

Title: Timing chain retrofit?
Post by: jtanguay on May 22, 2007, 07:10:25 pm

Quote from: "Trev0rbr"

whats the advantage of a chain over the belt we have?

longer lasting... thats pretty much it.

but if you think about it... 60'000km or 100'000km is a good time to replace such things as water pump, inspect motor etc...

Title: Timing chain retrofit?
Post by: tylernt on May 22, 2007, 07:54:10 pm

The timing belt was a cost issue. VW engineers had to make the diesel as similar to the gas as possible to simplify machining. That's why the injectors are mounted at exactly the same angle as the spark plugs, and why the block is pretty much identical except for a deeper and stronger girdle/skirt thingie, and why the vacuum pump is mounted in place of the distributor.

Title: Timing chain retrofit?
Post by: Vincent Waldon on May 22, 2007, 07:59:30 pm

I once read a document from the guys at VW who designed the company's first diesel... reusing as many parts and technology was a key design criterion all the way along.  The timing belt for the gasser was picked for cost but also for noise.... chances are it was one more thing that made sense not to change on the diesel.


Vince

Title: Timing chain retrofit?
Post by: Black Smokin' Diesel on May 22, 2007, 09:42:05 pm

Chain driven engines rely a lot on quality oil and regular oil changes. Cheap out on them and you're in trouble.

You'd have to fab a "backplate" that would go between the side of the engine and the pulleys to include the IP sprocket. Find a way to seal the plate against the block and find a cover that would seal everything. Then you have to figure out what to do about the V-belt, how to mount the pulleys to the thoothed sprockets and find a way to prevent oil from leaking out. After that you have to find a way to keep everything oiled and tight.

IMO it's not worth the trouble. TBs' are relatively easy to do so why make it harder?