TIMING CHAINS vs. BELTS - Differences, Evolution, History and more

what is up engine heads today we'll be taking a look at timing belts and timing chains we will compare one with the other and then dive deep into the details of these two critical automotive components all while presenting objective facts on both of these so no typical over generalizations like belts are quieter but chains last longer and that's it no there's much more to it and we will try to cover off it we'll also take a look at the history of belts and chains and how one dominated over the other in different periods of automotive history and how this influenced the evolution of these components and how it affects you as a car owner but first the basics so what does a timing belt ray timing chain actually do well the key word here is timing the task of the belt or chain is to maintain the timing of the engine and by timing we mean the relationship between the pistons and the valves or the crankshaft and the camshaft this relationship must be maintained constant at all times now the crankshaft is physically connected to the camshaft via a belt or chain and what the belt or chain does is it drives pulleys or sprockets a belt drives pulleys and they chain drive sprockets now both pulleys and sprockets do the same thing together with the belt or chain they maintain the timing of the engine and a camshaft pulley or sprocket is always going to have two times more teeth so twice the teeth of a crankshaft pulley or sprocket to ensure that for every two revolutions of the crankshaft the camshaft makes one revolution so what's the big deal both timing builds and timing chains do the same thing they just sort of look different and use different materials one is metal the other is rubberish and does this topic even deserve a video well yes it does because other than having different materials using a timing belt or a timing chain has implications for the design of the entire engine as well as the frequency of its maintenance and its durability so one thing is obvious right metal is stronger than rubber which means that a metal chain is stronger than a rubber-tooted belt and if you were to hang a lot of weight from a chain and from a belt the belt would likely snap first but who cares this is a stupid example because hanging weights isn't what engines do what engines do is rotate they rotate a lot and they start rotating from the moment you turn the key and during a typical day of use an engine is going to rotate more than a million times which means that during a month of use an engine is going to rotate more than 30 million times that's a lot of rotations so this means that the issue here is in tensile strength of the chain or belt the issue is where how well do chains and belts resist wear again chains seem like the winner here because metal resists wear better than rubber but there's a catch metal resists wear battle better than rubber only when it's lubricated and this brings us to our first big difference between chains and belts belts run dry but chains need oil to prevent them from wearing out rapidly and this means that a chain needs to be sealed away from the environment to prevent oil leaks and the easiest way to tell if your engine actually has a belt or a chain is to look at the engine if it has plastic covers it likely has a belt if it has metal covers in the front it likely has a chain and because of this an engine with a chain is usually going to require a bit more space in the engine bay compared to the same engine with a belt because they're more durable than belts timing chains have much longer service intervals some timing chains don't even have a service interval they last the life of the engine which is always a good thing on the other hand you won't find a belt out there that can last the life of the engine even if you don't use your engine at all you still have to replace your belt every four to ten years depending on the engine and this is because rubber naturally deteriorates with time even if it's just standing still it's going to degrade timing belts are also sensitive to oil and coolant spills so a leaky engine is going to wear out its belt much faster than an engine without any leaks also rubber belts don't like high temperatures increased temperatures increase the wear of the rubber and as we all know things can get pretty hot in an engine bay now a typical modern engine has a belt service interval of around 60 to 80 000 miles now i'm saying modern engine because sometimes in the mid to late 90s timing built materials received a significant upgrade in general timing belts feature a rubber material with reinforcement fibers these fibers are usually kevlar or fiberglass and they increase the tensile strength of the belt the rubber itself is usually welded urethane or molded urethane or neoprene or something like that but in the mid to late 90s rubber belt started featuring hsn which stands for highly saturated nitrile and this is a material that is pretty resistant to high temperatures and it significantly increased the service interval for timing belts older engines with timing builds typically had a service interval of around 15 to 35 000 miles for the belt when it comes to timing chains when they do have a service interval it's around 80 to 120 000 miles and although metal is stronger than rubber rubber is a lot softer and lighter which means that belts typically run quieter than chains and also have less friction and less inertia which means it's easier to get them spinning which reduces parasitic horsepower losses rubber is also great for absorbing the vibrations and harmonics of an engine resulting in an engine that can feel smoother and while timing belts usually have a very similar design and don't differ much from each other timing chains come in two different types the silent chain and the roller chain the silent chain as the name suggests is silent and no matter how much you interrogate it in a never going snitch the silent chain actually reduces the amount of noise generated by the chain and sprocket assembly timing silent chains are pretty common you can find them on many engines and manufacturers love them because they're simple and cheap to manufacture a silent chain consists of multiple links held together by pins the profile of the links fits the profile of the teeth on the sprockets and lies the chain turns it rotates the sprocket yeah pretty simple now on the other hand the rover chain uses rollers on these pins and as the chain rotates the sprocket the rollers rotate on the teeth of the sprocket this of course reduces friction which is a good thing which because it reduces parasitic horsepower losses but it also reduces localized wear on the chain now roller chains are more expensive compared to silent chains when it comes to rover chains there is another catch and uh they're actually a bit noisier compared to silent chains roller chains also exist in two different types single and dual rollers and as you might already be guessing the dual roller kind is stronger more durable it's extremely hard to snap but it offers a disadvantage because it generates more friction because it has more surface area which means more prosthetic horse horsepower losses another difference uh between silent chains and roller chains is that rubber chains are a bit more sensitive to contaminants in engine oil so chains are lubricated by engine oil now this is both a strength and a weakness it's a strength because lubrication reduces wear it's a weakness because the lubrication is only as good as the oil that's inside the engine and the reason for premature chain stretch and failure is almost always one of the following three the oil wasn't changed in time the oil was of the wrong viscosity or the oil was a very low quality any of these three can significantly shorten chain life span and create a chain failure risk now roller chains are particularly sensitive to oil that's been in the engine for too long this kind of oil is going to have more contaminants in it and these contaminants can get stuck between the rollers and the pins of the chain which accelerates chain wear so provided you use the right oil and you change it on time chains are the better option after all a chain is more durable it's less likely to snap than a belt and change the offer or maintenance costs and this is what the average buyer wants and needs so chains win right well actually no they don't and to see why they don't we have to start the historical segment of our video because it's going to demonstrate how chains and belts evolved over time and how things aren't always as they seem so back in the 50s and the 60s all car engines were chain driven belts didn't exist and back then chains lasted the life of the car there are two reasons for this reason number one is that cars didn't really cover the miles they do today a car with 200 000 miles on the clock was a pretty rare sight and reason number two is that engines weren't as high strung as they are today but more about that later the first engine ever to use a rubber tube that built was a special racing engine built by bill devon in the early 50s he used to norton manx motorcycle cylinders which he installed on a paneled crankcase and the engine had an overhead cam layout and horizontally opposed cylinders which meant that using a chain for this engine was simply impossible with the technology available at the time so devin used a rubber toothed belt instead and this car with this engine won the sports car club of america championship in 1956. [Music] the first ever mass-produced car to feature a rubber belt driven engine was the west german glass 1004 it hit the market in 1962 and it had an engine which put out 42 horsepower at 5000 rpm the interesting new engine was designed by leonard ischinger who was a former employee of bmw interestingly enough bmw actually bought glass in 1966 not because they wanted the cars or the brand but because they wanted access to the timing belt patents 66 was actually a big year for timing belts because in this year fiat introduced the first ever twin cam engine driven by a romper tuted belt and in the same year the united states also got their first belt driven engine in the form of pontiac's overhead cam straight 6. so what do all these timing build pioneers have in common [Music] you guessed it they are all overhead cam engines compared to a push rod engine the distance between the crankshaft and the camshaft is much greater in an overhead cam engine so you would need a much longer chain to connect the cam to the crank and with the technology available back in the day this meant that using chains and overhead cam engines had some pretty bad results many chains on these engines would whip around and rattle and hit too much slack and wore out too fast and did all sorts of other undesirable things so many manufacturers actually went with timing belts for their overhead cam engines now this isn't to say that there weren't some good chain driven overhead cam engines back in the 60s and the 70s but the number of belt-driven engines on the market started increasing with the number of overhead cam engines on the market and this number started rapidly increasing in the early 80s and by the mid 80s actually timing belt driven engines outnumbered chain driven engines in many parts of the world timing built dominance continued throughout much of the 90s and even the early 2000s in some parts of the world but belt driven engines also got some bad rep now most spell-driven engines were totally okay and never had any issues with their belts but some engines like to snap a belt even before it was time to replace it and when this happened on an interference engine the results were almost always catastrophic both for the engine and your wallet so it's no wonder that belts got some bad rep because when you compare them to the chain driven engines which never snapped a chain they seem like an inferior choice and really can't blame the average consumer for seeing the new fangled belt-driven engines as an added maintenance cost and an added risk but by the mid 2000s manufacturers started returning to chains mostly because they could technology had improved new coatings new heat treatments better chain engineering technology it all meant that manufacturers could make chains lighter than ever they could reduce friction they could reduce parasitic horsepower losses they could improve wear resistance so many manufacturers simply switched back to chains for their overhead cam engines and it was really a win-win buyers would get the promise of increased durability and lower maintenance costs and manufacturers would improve sales the chain was back with all my chains but the second time around unfortunately there was a catch chains of old and chains of new seem to be two different things to demonstrate let's look at a concrete example two different engines one old chain driven overhead cam engine and one new chain driven overhead cam engine they're pretty different they don't even use the same type of fuel but bear with me the comparison is going to make sense our old engine is the nissan l24 it's positively ancient made from 69 to 84. it can be found in nissan 240z among other cars and it's a 2.4 liter in insects our modern engine is the bmw and 47. it can be found in a bunch of different bmw and mini cars it was made from 2007 to 2014 and it has two different displacements and it's an inline four turbo diesel so they're pretty different but they're both overhead cam chain driven engines and as you can see the bmw and 47 makes more power with less displacement and less cylinders in fact the bmw m47 was the first ever mass produced diesel engine to achieve a specific horsepower output greater than 100 horsepower per liter of engine displacement an amazing achievement for a diesel and definitely an amazing engine and it's even quieter it's smoother it's everything more than the l24 and it does it all with less fuel than the l24 which is no wonder because it's a lot more advanced being a lot more modern but unfortunately the n47 is famous for something that the l24 isn't the n47 is famous for snapping chains on the other hand finding an l24 with a snap chain is almost impossible the chain might rattle and wear out but it will almost never never snap so how come how come is the n47 which has access to more modern to better technology worse at chain durability compared to the ancient l24 and the answer to this is that the n47 has to tick a lot more boxes compared to the l24 it has to please a far more demanding car buyer over time the expectations of car buyers have exponentially increased the modern car buyer wants their engine to do pretty much everything they want power they want torque they want the engine to be quiet they want the engine to be smooth but they also want good mpg and low emissions as you can see many of these things are in direct opposition to each other and making an engine that does it all is impossible but still car makers have to sell cars so they have to try and please the modern car buyer now on top of all of this the modern car buyer also wants a low maintenance cost so bmw gave the m47 a timing chain to reduce maintenance costs but the n47 also has to make power so bmw gave it a single roller timing chain to reduce friction compared to the dual roar timing chain on the l24 but even this wasn't enough because the modern car buyer doesn't want to change oil too often so bmw gave the n47 an oil change interval of 15 000 miles compared to the oil change interval on the l24 which was 5 000 miles so the n47 has to do more of everything with less fuel and old oil it's like an athlete trying to win the olympics on a diet of junk food something's gotta snap but let's not make bmw the only scapegoat here here's something from honda k series b series b series was the older mainstay engine ran a timing belt k series is the more modern honda mainstay engine has a timing chain the belts on the b series almost never snapped not even in the hands of lazy owners who refused to change them on time on the other hand the k series had timing chain tangenting issues even at very low mileages the consequences weren't as horrible as in the n47 the timing chain of the k series wouldn't quite snap but it would stretch a lot which would cause a bunch of annoying issues and if left unattended it would stretch so much that it would skip a tooth on the sprocket which would cause the engine to run absolutely horribly so yeah what am i really trying to say here well first of all i'm trying to say that you shouldn't be fooled these are just two examples and there are many many modern engines with timing chains that have zero issues but timing chains no longer guarantee the kind of durability and low maintenance costs that they used to do in the past because of the strains and demands put in modern engines belts and chains are equalized it's now a case-by-case thing and when choosing an engine you should really research that specific engine to be able to predict the maintenance cost to see whether they fit your needs preferences and your budget because today a chain might mean actually more maintenance costs than a timing belt basically things have changed so what is the future of timing builds and chains well the future is that they might be gone completely if free valve becomes a mainstream thing but that's a topic for another video and this video is hereby pretty much over i hope you enjoyed it found it useful informative maybe even a bit entertaining if you have any other questions idea comments suggestions whatever comment section is right down there below as always thanks a lot for watching and i'll be seeing you soon with more fun and useful stuff on the d4a channel

Channel: driving 4 answers

Views: 983,179

Keywords: timing belt, timing chain, timing belt vs timing chain, timing chain bmw n47, timing chain rattle, timing chain symptoms, timing chain problems, bmw n47, timing chain tensioner, honda k20 timing chain tensioner, timing belt warning signs, how to check timing belt, timing belt price, timing chain price, timing chain noise, timing chain replacement, timing belt problems, timing belt noise, timing belt breaking, what cars have timing chains instead of belts, honda timing belt

Id: fMDHUvYJLfQ

Length: 20min 19sec (1219 seconds)

Published: Sun Aug 16 2020