Carbon Fiber Inside the Engine - How CF rods and pistons change engines and why you can't have them

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Let's say you want a car part that's strong. Something that can survive massive forces. How massive? Well, let's say around 100,000 Newtons. How much is 100,000 Newtons? Well to put it into perspective, an average person like myself can throw a punch with a force of around 1000 Newtons. That's if I'm lucky. A sledgehammer blow, something pretty powerful, can manage around 5000 Newtons. So 100,000 Newtons, that's twenty times stronger than a sledgehammer blow And this is the force generated by the combustion pressures inside the engine. A force to which engine internals are subjected to thousands of times each minute when the engine is running and under load And 100,000 Newtons, that's the stuff that economy engine generate nowadays. Modern forced induction engines and diesels, can manage up to 200,000 Newtons with their combustion pressure. Now, engine internals as we know, consist of the crankshaft, the connecting rod, and the piston. Now, the crankshaft only rotates. The piston only reciprocates. But the connecting rod has a more complicated travel path. It both rotates and reciprocates at the same time, which means that it's exposed to the most complex and problematic forces. Also means that it's under the greatest amount of stress. And to ensure that the connecting rods handle the stress that they can survive it without yielding, we usually make them out of steel. But sometimes we also make them out of aluminum. Now, steel is strong. Here's just how strong it is. A small bar of steel which has a cross-sectional area of 1cm2, and made from a high strength alloy like 4340 steel, for example This little thing can survive 75,000 Newtons before breaking apart. Now, aluminum is not as strong Even if we make our little bar from a high-grade aluminum alloy like 6061 or 7075, it will only manage around 55,000 Newtons before failing. Compared to this, carbon fibre is in a league of its own. The same little bar made from carbon fibre can manage 250,000 Newtons. So this little thing alone can survive inside the engine. But here's the funny thing. We put rods made from the weakest material here, which is aluminum, into our most powerful and most extreme engines. The engines that generate the highest combustion pressures, and have the highest probability of mangling their internals. Why do we do this? Well, we do it... ..because aluminum is light. Now, a small cube with sides of 1cm, so 1 cubic cm When made from aluminum is going to weigh around 2.7 grams. The same widow cube when made from steel, is going to weigh around 7.85 grams. So as you can see aluminum is much lighter than steel, and this is good news Because it gives us ample room, to compensate for the reduced strength of aluminum by increasing the amount of material, while sacrificing just a bit of weight. In other words, we're going to make the connecting rod all chubby, increase its cross-section And the end result is a connecting rod, which is as strong as a steel con rod, while managing to weigh half as much And when it comes to engine internals, the less they weigh, the better Because the less they weigh, the less engine work and energy is wasted on getting them up to speed And they also carry less momentum when they are at speed. The end result is an engine which has reduced parasitic losses, higher RPM capabilities, and is more responsive. But aluminum has to pay price for its low weight. And unfortunately, the price is longevity. To put it in more technical terms, aluminum actually has no fatigue limit. It may sound like something cool and powerful but it's actually not. It's bad. And to understand it we have to observe this little graph. Now, this line right that's steel and the horizontal part is a very distinctive fatigue limit of steel. This line actually stretches into infinity. Now, our horizontal axis, is the number of load cycles applied onto the part And as you can see, as long as the force magnitude of the load cycle is below the value of the fatigue limit, the steel part is going to last forever. In other words, you can keep repeating the load cycles into infinity, and as long as the force is low enough, the part is never going to fail. And as we know steel is pretty strong, so you can apply pretty high forces forever onto a steel part. But unfortunately aluminum is different. This line It keeps going down And eventually, after a certain number of load cycles, the part is inevitably going to fail, even under the smallest of loads. In practice, this means that steel connecting rods last the life of the engine. But aluminum connecting rods usually last only 10 to 20% of the engine's life Making them really only suitable for racing and motorsport applications, where short engine life and frequent rebuilds are a given. So it seems that with metals, we have to compromise. We can either have low weight, or long life. We can't have both. But what about carbon fibre? Well with carbon fibre we don't have the compromise. Just like it blows steel out of the water when it comes to strength, it also blows aluminum out of the water when it comes to weight. That same cubic cm, If we make it from carbon fibre, it's going to weigh only 1.8 grams. So, this makes carbon fibre the ultimate material for engine internals, right? It's incredibly strong, and it has incredibly low weight. There must be some catch, right? It probably has horrible fatigue life. Well, just like aluminum, carbon fibre does not have a clear fatigue limit. Meaning that after a certain number of load cycles, it's inevitably going to fail But thanks to its absolutely ridiculous tensile strength, the number of load cycles that a carbon fibre part can survive, makes it pretty much infinite for practical purposes A nice practical example is this: Helicopter blades, if they're made from aluminum, they usually have to be replaced every 6,000 or 7,000 hours, or something like that If the helicopter blades are made from carbon fibre, they are considered to be infinite And although they do have a finite fatigue life in theory, in practice fatigue life is so long that it's longer than the life of the airframe. So, carbon fibre is the absolute champ. Super strong, super light, no real fatigue issues. It's the best possible material for engine internals. So, if it's the best possible material, why are there zero mass-produced engines with carbon fibre internals And why are there zero aftermarket carbon fibre internals that you can buy today? Well, the answer to that question is, that this little table that I have given to you, is misleading And it's misleading in the same way as tabloid-style sensationalist statements. You know the kind of stuff that you can read online, how carbon fibre is 4x or 10x or whatever, a million times stronger than steel And only a fraction of the weight. That kind of stuff is an oversimplification, and as such it's misleading. So now allow me to explain why it's misleading, and why you can't buy carbon fibre connecting rods Here's issue number 1 Carbon fibre does not exhibit isotropic properties. When a material is isotropic, it exhibits the same mechanical and thermal properties in all of its parts. Steel is isotropic. Let's take this imaginary block of steel. If we apply a load in this or in this direction, or in any other direction, it's going to take the same amount of force to deform or break the steel block Regardless of the direction in which we apply the load. But carbon fibre isn't this. It's not isotropic. It's orthotropic. In other words, it's a bit like wood And this is because parts made from carbon fibre can't be one solid chunk, like steel parts Instead, they must be made by layering up individual layers of carbon fibre one at a time. These sheets of carbon fibre are composed of intertwined carbon fibre tow And the tow itself is composed of thousands of individual carbon fibres. Now, if we imagine that we stacked up our layers or fibres like this, Then just like wood, this carbon fibre block is going to be extremely strong along the grains, it's going to be stronger than steel along the grains But if we apply the load in a different direction, across the grains for example The carbon fibre block isn't going to be nearly as strong in fact if we change the direction of the load, then the strength of the carbon fibre part is going to be highly dependent on the number of layers used, and their orientation and distribution And if you recall, at the beginning of the video we said, that connecting rods face very problematic and complex forces. In other words, they face multiple forces from multiple directions. Meaning that the isotropic properties of metals are actually very desirable for engine internals. Another problem is the manufacturing process. When making stuff out of carbon fibre, you can use dry layers or sheets of carbon fibre And then manually brush or roll the resin onto them to bond them together. Or you can use pre-preg, which is carbon fibre sheets pre-impregnated with resin which then eliminates the possibility of human error from the resin application process. Once the resin is applied, advanced manufacturing processes usually involve an autoclave. Parts are put into the autoclave, which then exposes them to high pressures and high heat in order to ensure the best possible part in uniformity and finish. And as you can see, this process of manually stacking up the layers, together with the long curing times and the high cost of the raw material itself Explains why stuff made from carbon fibre can be so expensive But there's another issue, And it's that this manufacturing process of stacking up layers, can be extremely difficult or even impossible to adapt to complex parts, with intricate shapes. Now, connecting rods are relatively complex, thick, solid parts which must be made with the highest consistency, and very rapidly, in order to be viable for mass production. On the other hand, the typical carbon fibre manufacturing process is best suited to thin or hollow parts, that have relatively simple shapes, and are made in very small volumes, or even just as a one-off part. But this didn't stop manufacturers from trying to seize the amazing properties of carbon fibre for their mass-produced parts. And thus in 2010, at the Paris Motorshow, Lamborghini in cooperation with the Callaway Golf Company, and Lamborghini Lab unveiled the Sesto Elemento A very striking, very limited production run Race car. Now, Sesto Elemento means the sixth element, which is the atomic number of carbon And indeed the car did feature a lot of carbon fibre in the body, the chassis, the drive shaft And even suspension components But it wasn't the first car to feature so much carbon fibre. Instead, it was the first car that features something known as forged composites. And this is a completely new way of manufacturing stuff from carbon fibre, pioneered and of course also trademarked, by Lamborghini. But the big news is that 'forging' composites actually promises to make it possible to mass-produce stuff like carbon fibre connecting rods. Instead of manually stacking up the layers one at a time the forging process involves using chopped up carbon fibre too, which is then immersed in a resin and then exposed to heat and pressure And that's it. You're done. The process is both shorter and more consistent than traditional carbon fibre And the randomly distributed fibres also give the part more isotropic properties. The added bonus is that you can also make more intricate and complex structures. But of course because now we have randomly distributed fibres, we don't really have the incredible tensile strength of carbon fibre along the lines of the fibres. However Lamborghini claims, that the same strength of an equivalent steel part can be achieved using this process While of course also maintaining the incredibly low weight of carbon fibre. And indeed the Lamborghini did make all sorts of cool parts using this process But the big news came in 2016, when they announced that they wanted the next generation V12 engine in their Aventador to feature carbon fibre connecting rods, made using their trademarked forged composite process The engine was expected to launch in 2020 or 2021, and today it's 2022 And as you probably know, we never got a production version of this engine There were some cool prototypes displayed, but that's about it It never really happened And the question is why? I mean if anybody has the R&D capacity, it's giants like Lamborghini I'm sure they can make it happen And I mean if they made complex and structural parts using this forged composite process, right after unveiling the technology in 2010, why don't we have rods 12 years later? To get a bit more insight into why it didn't happen, we have to come back to our sensationalist statement from the beginning of the video Remember this one, carbon fibre is 5X stronger than steel, only a fraction of the weight. We already explained that it's a lot stronger in steel, only if you applied load in the same direction But there's another problem with this sentence And it's this, carbon fibre That word Because what we're doing all the time when talking about carbon fibre, is comparing carbon fibre alone to metals And none of the parts that you see have seen in this video, or that you've probably seen in person, or that are used on cars. None of this is carbon fibre alone. All of it is carbon fibre plus epoxy resin. Epoxy resin is the substance which bonds the layers, or strands of carbon fibre together. The resin is the matrix within which the carbon fibre takes shape. And here's the problem. Epoxy resins hate heat. And there's a lot of heat inside the engine. Epoxy resins also hate acids, and acids can form inside the engine and the engine oil. Also epoxy resins really hate coolant, and of course coolants exist inside the engine. It means that a failed head gasket could lead to a snapped rod, and you really don't want this All in all, the insides of an engine are an extremely hostile environment for epoxy resins and if the resin fails, the entire part fails, no amount of carbon fibre tensile strength can protect against this and as far as I know, no currently commercially available epoxy resin can guarantee reliability and longevity in the environment that exists inside the engine So if the epoxy resin is the problem then, let's get rid of it. Sure no problem. We have actually something like that. It's called carbon-carbon, and it's carbon fibre in a matrix of graphite. It's an incredible material. We use it on the nose and the leading wing edges of space shuttle. It has incredible heat resistance Low weight, good tensile strength You name it Bunch of amazing properties. In fact, in 1994, NASA made and tested carbon-carbon pistons inside engines, and they found that they outperformed aluminum pistons in every way. A better torque, lower weight, better resistance to detonation, you name it. But in 2003, we got to see in practice a big problem with carbon-carbon. When a small piece of foam fell off and hit the wing of the Columbia space shuttle, and shattered it, leading to the death of all the crew members on board. And this happened because carbon-carbon has absolutely pathetic impact resistance This means that inside the engine, a small piece of debris, or maybe a small piece of carbon build up from combustion, or maybe even slightly more aggressive engine lugging which simulates something similar to an impact All of this could potentially lead to the compromising, or even shattering of carbon-carbon engine internals On top of this, as NASA demonstrated in their paper, making stuff from carbon-carbon requires multiple different parts which are then fused together and in general carbon-carbon manufacturing is very expensive, and time-consuming. So all of this means that we're actually better off with epoxy resin. But there's another problem. As you know, to attach the cap to the body of the rod, you need bolts. And where there's bolts, there's also going to be threads. But making threads directly in carbon fibre is not possible. The material is very much unsuitable for this. The threads end up being weak. The material starts to fray, or delaminate, or whatever. It just doesn't work. So carbon fibre connecting rods have to use metal inserts, and this is not really an optimal solution. So with all this in mind, I decided to send an email to every possible Lamborghini company address I could find. I asked whether they have overcome the challenges of resins and threads, and whether they have still plans to make the carbon fibre connecting rods reality. Boss I just received this Email from this YouTube ragazzi driving quattro something. He asking about our connecting rods-a. I need to reply to him, right? Yeah, as you might expect Months passed, and I never ever got a reply from anybody over at Lamborghini. I honestly didn't even expect it But don't worry, Lamborghini isn't the only one dabbling with carbon fibre engine internals. There are three more companies, in fact. The first one I came across is called Naimo Composites And they tried a crowdfunding thing to get money for their carbon fibre rods. They got around $125, so they were out of the picture. The next company is called Extreme Tuners from Greece, and they're posting a lot of cool stuff on their social media. It looks like a generative design, together with 3D printing. They've been posting this for a while, so I sent them an email as well. Yeah, again no response ever But there's another company AWA Composites from California And on their website they claim some really cool stuff, but they also don't just make carbon fibre connecting rods, they also make pistons, composite push rods, wrist pins, lifters And even something called Kiptanium rod bolts They're also the only company that has ever displayed their rods at the SEMA show And the only company ever to put an actual price tag on their carbon fibre connecting rods That is $18,000 You counted the zeroes correctly. So I sent them an email as well, and this time I got a response. Now, as you might expect we didn't really get any concrete actual insight into the materials used, or the manufacturing process, you know, because at this stage of the technology and with multiple potential competitors in the field It's all about who's going to be first to market, and so it's all proprietary top secret stuff. However AWA composites really demonstrated impressive confidence, and they claimed that they have overcome all the issues with resins. They claim that their pistons offer less thermal expansion, and higher temperature capabilities. They also claim that their parts reduce engine damage, if the parts fail due to the lower weight and the lower momentum of the parts. They also claim that their rods can handle up to an incredible 12,000 horsepower And these are just some of the benefits listed. We did get actual concrete info on weights, and the AWA composite rod and pistons, seem to weigh around 40% less than aluminum rods and aluminum pistons Also, the prices seem to have dropped, and AWA composites now aim to push the rods, to get the rods to market at around $1,000 to $2,000 per rod Meaning that the minimum possible price for a set of eight rods is now $8,000. it's still a lot of money But it's definitely better than $18,000 However, we really don't have any information on whether and when the rods will actually be on the market. So, it's undeniable that this is all very impressive stuff And I will choose to remain optimistic about the claims of AWA Composites. However, there is a point I disagree with And it's the application. Currently, AWA Composites is developing their rods for extreme drag racing applications. Basically, top fuel racing And they claim that this is as a proof of concept, to reassure their clients that their rods can handle pretty much anything But they also claim importantly that there is space for their products in mass produced OEM daily driven applications, due to the superior fatigue life of their products over metals, like steel and aluminum. Now, first of all and we covered this, carbon fibre cannot have a superior fatigue life over steel. Aluminum sure, but steel definitely not. We explained this earlier in the video already. Second, and this is just my subjective opinion. Top fuel racing is not a good proof of concept. Basically have a few high-powered runs that last a few seconds each, and then the engine gets torn apart and rebuilt. The engine never has to sustain very high operating temperatures, nor does it has to have to survive you know wide open throttle for prolonged periods of time in varying conditions. Again just my opinion, but not a very good proof of concept. But these are all just secondary issues. The primary issue here is that I think that in this decade, the chances of us seeing carbon fibre connecting rods in massproduced OEM applications are zero. First of all, carbon fibre engine internals will never be as cheap as their metal counterparts, nor will their production process ever be as rapid. Now, a set of aftermarket forged 4340 rods cost around $1,500 That's a fraction of the minimum possible currently predicted cost of a set of eight carbon fibre rods And these are all of the rods, some of the most highly regarded and priciest rods in the American muscle market And this is again the aftermarket we're talking about. The OEMs they make their rods themselves. They want them as quickly as humanly possible, and they expect to spend maybe a 100 bucks to make a set of eight rods. The lead times and cost of carbon fibre engine internals can really only be justified for high-level motor sports and very very exotic cars. Why? Well, the answer is simple. It's because steel is a very good material for connecting rods. Those Oliver rods we just mentioned Well for $1,500 bucks they can easily take 1,000 horsepower And let's be honest, how much more do you need or can handle When talking about carbon fibre, many choose to compare to steel And then they portray steel as this obsolete primitive material, which fails in comparison to the amazing properties of carbon fibre Well, this is wrong and misleading Because it means that we're either taking for granted or forgetting that we made countless amazing engines which turn out thousand and thousands of horsepower, using humble steel rods And they do so consistently and reliably. The gains and responsiveness and performance are really only relevant in motorsports. Why? Because reducing rod and piston weight by 50% doesn't increase power and efficiency by 50%. Let's not forget the engine is already lugging around the entire vehicle, and removing a few hundred grams from the internals isn't going to change the world. There are gains and improvements, but they are marginal, and completely irrelevant for a daily driven average vehicle. Your average Joe driving a Camry would never notice a set of carbon fibre rods and pistons under his hood. The ability to sustain 12,000 horsepower doesn't matter when your engine is making 200 horsepower. The ability to rev 1000 or 2000 RPM more doesn't matter if the rest of your engine can't take it But your car suddenly costing $8,000 more. Well, that's definitely something you're going to notice. So, let's summarize it. Are carbon fibre engine internals amazing? You bet. Do you need them? No Unless you're doing something pretty extreme.
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Channel: driving 4 answers
Views: 2,712,154
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Keywords: carbon fibre, carbon fiber, carbon fiber conrod, carbon fiber connecting rods, carbon fiber 3d printed, carbon fiber pistons, carbon fiber piston rods, carbon fiber vs steel, forged carbon fiber, lamborghini, sesto elemento, forged composite, extreme tuners, naimo, awa composites, awa connecting rods, aluminum connecting rods, steel vs aluminum, top fuel, 1000 hp, carbon fiber prepreg, 4043 steel, 6061 aluminum, 7075 aluminum, forged rods and pistons, carbon-carbon, NASA
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Length: 24min 11sec (1451 seconds)
Published: Sun Jun 05 2022
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