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Old 01-13-2015, 08:53 PM
 
48,505 posts, read 96,551,406 times
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Beside more moving mass. of the chain.
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Old 01-13-2015, 09:42 PM
 
Location: Western USA
236 posts, read 367,620 times
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Excellent point rbohm, of course one could design a synthetic chain.

I actually have a plastic serpentine emergency replacement linked belt that sort of fits that profile. You can remove sections to make it fit the limp-home needs you have (water pump, fan, etc.).

The one thing I'm not sold on with a timing belt vs. chain is the removal (in many cases) of the water pump to get to said belt. Pricey job.

And finally, I've never had a timing chain fail and trash an interference engine.

A belt, if not replaced on schedule, can do a lot of damage to the top end.
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Old 01-13-2015, 10:42 PM
 
Location: Saint Louis, MO
3,483 posts, read 8,964,925 times
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Quote:
Originally Posted by usafracer View Post
I am going to assume that you are talking about timing belts vs timing chains.

Many engines run timing chains. They are not a accurate as belts they stretch and wear over time and need replacement as well. The belt is cheaper more accurate and in many cases stronger.
The belts also need replacement, and at intervals considerably less than a timing chain. 1985 Pontiac Firebird went over 200,000 miles on original gear/chain set. 2012 Jetta I recently purchased has a belt that requires replacement at 100,000 miles to the tune of $1,100 at the dealership. Car that is replacing it (2012 Beetle) uses a Timing Chain with no replacement interval.

While the chains do stretch and wear, with a proper tensioner it's not a major concern. And the chain will likely outlast your car.
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Old 01-13-2015, 10:54 PM
 
Location: Riverside Ca
22,146 posts, read 33,267,390 times
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How are you going to lube a exterior chain? You would have to have some sort of oil bath the chain travels through with a enclosed recovery system or grease applicator or some way to lube the sprockets. It would make a mess and add to the complexity of the system.
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Old 01-13-2015, 11:22 PM
 
Location: Out there somewhere...a traveling man.
44,555 posts, read 61,283,437 times
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Pretty obvious, massive wear & tear, rust, bang bang noise, broken accessory parts attached, metal to metal to plastic damage, cost, injury possibility, cost to adapt accessory items for wear and tear and strength, the list goes on and on.
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Old 01-14-2015, 03:40 AM
 
Location: South Texas
4,248 posts, read 4,134,442 times
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Quote:
Originally Posted by Arcenal352 View Post
Considering timing chains are generally much stronger and last much longer than timing belts, is there a reason, other than cost, why manufacturers aren't using serpentine chains as opposed to belts?
It's all about the money.

Because belts wear out faster than chains do. The manufacturer hopes you'll pay the dealership's shop (as opposed to an independent shop) when it comes time to replace the belt.
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Old 01-14-2015, 04:50 AM
 
3,046 posts, read 4,093,539 times
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Quote:
Originally Posted by Slowpoke_TX View Post
It's all about the money.

Because belts wear out faster than chains do. The manufacturer hopes you'll pay the dealership's shop (as opposed to an independent shop) when it comes time to replace the belt.
Automakers are making engines useing less parts to help reduce weight and increase mpg and bosting performance. Look at the Chrysler Pentastar v-6.

Compact and lightweight, Pentastar V-6 will be used in front-, rear- and all-wheel-drive models. Already standard on the new Jeep Grand Cherokee, the V-6 will gradually phase out seven V6 legacy engines ranging from 2.7 – liters, up to 4.0 – liters in the current product portfolio. Overall, the new Pentastar will enable Chrysler Powertrain to reduce major engine components from 189 parts to just 32, greatly simplifying the build process and improving quality. Significant cost savings also are realized with purchasing efficiencies and a reduction in limited, high piece cost parts.
Some parts, including the exhaust manifolds, will completely disappear by virtue of being cast directly into the cylinder head. Today, the engine line-up features 32 different left and right exhaust manifolds. That will drop to zero with the new Pentastar V-6.
Upper and lower intake assembles, which accounted for 21 and 11 different parts numbers (respectively) have been reduced to two upper and lower assemblies. Camshaft variations will drop from 14 to four and just two fuel rails will be required rather than the current 14.
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Old 01-14-2015, 06:16 AM
 
Location: Riverside Ca
22,146 posts, read 33,267,390 times
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You could do a enclosed gear system that bolts to the front of the engine under covers or a big cover on the front and it has keyed or splined shafts sticking out where the accessories bolt on and have a keyed or splined hole and get driven through the back rather than the typical pulley on the front.
Kind of the way that you can put a gear drive on a chevy 350 and remove the timing chain.
But that would add to the complexity and make the cars just that much more expensive. A belt driven system not only works very well, it's relatively inexpensive and easy to maintain
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Old 01-14-2015, 06:30 AM
 
27,957 posts, read 39,618,429 times
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For driving a cam, take a cue from the inline family, use gears. For 300 6 cylinder and several diesels use gears. No belts or chains.

For accessory drives electric would make sense. There are already electric fans and power steering pumps. The biggest user would be air conditioning.

Chains would be a step back.
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Old 01-14-2015, 07:43 AM
 
Location: Central Texas
13,715 posts, read 31,031,321 times
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Quote:
Originally Posted by Slowpoke_TX View Post
It's all about the money.

Because belts wear out faster than chains do. The manufacturer hopes you'll pay the dealership's shop (as opposed to an independent shop) when it comes time to replace the belt.
This is a really dumb post. The manufacturer ALWAYS hopes you service your car at the dealer instead of an independent. That gets you in the showroom so you'll be tempted to look at a new car.

But if your view was credible, then they would simply require more frequent maintenance. They would go back to carburetors. Spark plugs that lasted just one year. Or distributors with points. You'd visit the dealer twice a year.

Today's belts last 100K miles. It costs $50-75 to replace them - and independent garages are fully capable of this.
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