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Cars: 2015

Its an interference motor, timing of valves to pistons, if the belt breaks, pistons hit valves and head is junk. They change water pump because its driven by timing belt and the labor to do so is way more than the water pump, so might as well change while they are in there. The belt change is a must
 
Kepler said:
I thought only trucks had timing chains?

For real.
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Most Mazda, BMW, and Mercedes cars have chains. I think Cadillac too, but am not certain. The Mazda thing might just be the Skyactiv-G engine, now that I'm thinking about it.

I think initially they were used for engines with big cylinders because they are heavier and take more fuel.
 
Kepler said:
I thought only trucks had timing chains?

For real.
Click to expand...

I don’t recall what my Subaru has, but my 2000 Nissan Altima had a chain. I don’t know why companies choose chains or belts in design (beyond costs), but they’re not strictly limited to class of car.
 
St. Clown said:
I don’t recall what my Subaru has, but my 2000 Nissan Altima had a chain. I don’t know why companies choose chains or belts in design (beyond costs), but they’re not strictly limited to class of car.
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NVH is one big thing- chains make a lot of noise.

Not having to have another massive area to seal for oil is appealing.

And belts are slightly more efficient- there's less friction loss in a timing belt.

Chains are not perfect, BTW, they stretch over time, throwing off cam timing. And the chain guides wear out- just like the belt tensioners do.

Many cars are non-interference engines, so the valves never hit the heads even when they are open.

For the most part, most belts were on 4 cyl engines, some V6s, and a handful of V8s.
 
The Sicatoka said:
https://knowhow.napaonline.com/timing-chain-vs-timing-belt-why-do-cars-use-one-or-the-other/
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I figured belts were used because chains were heavier and therefore required more torque to get going. Makes sense for diesels, less so for stop-go people haulers. I'm guessing that's probably not the case in practice though since I can't believe that changes the overall energy equation that much.

It has always bothered me that the engineers chose belts over chains. Especially when the consequences are so great.
 
dxmnkd316 said:
I figured belts were used because chains were heavier and therefore required more torque to get going. Makes sense for diesels, less so for stop-go people haulers. I'm guessing that's probably not the case in practice though since I can't believe that changes the overall energy equation that much.

It has always bothered me that the engineers chose belts over chains. Especially when the consequences are so great.
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Relative to all of the rest of the rotating assembly, chains are pretty minor. More than a belt but not enough to really notice it relative to the force needed to open the valves.

And most old chain driven systems were two rows- so more noise. Now, better metallurgy has given us single row chains (like your bike).
 
dxmnkd316 said:
I mean, how much noise are we talking?
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Enough to be irritating. It will sound like a whine, which is kind of unpleasant. OHV V8's have such a small system, it's very buried in the engine. But OHC engines put that noise right at the top.

Ironically, with a brand new and tight timing belt, they are pretty noisy, too.

I know it sounds really bad to use a belt instead of a chain, but it took some good advancement in chain technology for everyone to change. For most, belts are incredibly reliable. And really easy to build. There's a reason that the 1.8l Honda engine that MT has in her car isn't known for failures, even 13 years from being new.
 
state of hockey said:
I don't notice it in my Mazda, but most cars for years now pump white noise through the speakers to deaden engine noise, no?
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Not really. Some cars do, but most don't. There are little baffles and volumes that help mitigate the noise, but active noise suppression is not common. Heck, the new real noise source on new cars is the high pressure fuel pump that is used to make 3000psi for direct fuel injection. Those things are really loud if you take the covers off.
 
MichVandal said:
I had that sound when I got a new timing belt on my Miata... If that's new, then the mechanic was right.
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Assuming luck, I should be able to get it to work tomorrow, and then over to a repair shop. And then hope repair shop has a loaner I can use for the weekend, because Meijer is making me work all of it.
 
MissThundercat said:
Assuming luck, I should be able to get it to work tomorrow, and then over to a repair shop. And then hope repair shop has a loaner I can use for the weekend, because Meijer is making me work all of it.
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That's the right decision. After all, the repair shop has both the necessary equipment and specialists. Not all repairs can be carried out independently.
 
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