December 12, 2019

How can different materials affect performance in cars?

Ceramic materials have an extensively wide range of applications in many fields, and especially in the mechanical and automotive industries. Let's take a look at some of the benefits.

How can different materials affect performance in cars?

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Table of contents

Introduction to the article

One of the main end goals of innovation and research in the automotive industry is improving the performance of an engine or vehicle. The benefits of using different materials help us achieve exactly that. The factors that are influenced the most by these advancements are:

  • Increased speed
  • The ability to stop rapidly and safely
  • General stability of the vehicle

In the course of this article, you will be able to see how and why all of these can be improved just by changing the material of certain components!

How to increase the speed of a car by using ceramics

Everybody knows that the speed of a car is dependent on the engine. That is indeed true, but let’s go a bit deeper and take a look at what’s inside an engine: the component that interests us is the shaft, as it is its rotation that dictates the motion of the wheels and by extension - of course - the car. All that’s left in the engine will be considered as magic by you and me until our dear car-whisperer-extraordinaire Mayssa will be able to teach us more about that, so stay tuned.

Photo by Garett Mizunaka

Improvement inside the engine

The mechanical improvements that were hinted at in the previous article are directly related to the shaft. One can always provide more power to the engine and make it go faster, but that will bring a considerable amount of problems, ranging from inefficient fuel consumption to a lack of stability in the engine (and consequently in the vehicle). That’s why car manufacturers were able to allow the shaft to speed up by designing new valve systems to allow for a better control of the thermodynamic cycles happening in the cylinders and by developing the OverHead Camshaft (OHC).

So far that’s been fine and dandy, but what if you want more? The answer is ceramics! You can make the shafts and the valves way lighter, improving stability AND speed by using an advanced ceramic like silicon nitride (Si3N4), which has seen successful use so far only in the racing world [1] replacing metal alloys in the valve system.

Supercharging

Another common technique that’s used for improving performance is called supercharging. It comes from the common practice in airplane engines of restoring the standard air pressure when planes get pretty high and the atmosphere gets thinner. Supercharging is essentially just increasing the pressure of the air that’s being pushed into the cylinders, and in doing so the generated specific power can reach extremely high values (all this fancy engineering jargon just means that it’s more fuel efficient and therefore can be faster).

Photo by RKTKN

It’s obvious that to reach this kind of high pressure there’s a need for a compressor, called turbocompressor (it’s what you find in cars that are labeled “turbo”). What this means is that yes, you do get more speed out of your engine, but you have to wait for the compressor to get the air up to the desired pressure, and that can take some time: this delay between the pressing of the accelerator and the actual acceleration of the car is called turbo-lag. What can be done to improve it? You guessed it, ceramics!

Studies have compared the turbo-lag in a compressor with a ceramic (silicon nitride) rotor and a common metal one, and they have found that there’s a decrease of the delay amounting to ~36% [2]. That’s caused by the fact that lighter shafts are faster to accelerate (and subsequently reach operating rotational speed) than heavier metal ones.

I know, it sounds amazing right? Well, it partly is, but there are some drawbacks. The first difficulties started to come out way back in 1982, with the first experiment of an automobile equipped with a ceramic gas turbine engine [3], which, as you may have guessed, didn’t go well. The problems were identified and analyzed in the “Advanced Gas Turbine” project in 1989:

  • Failure of ceramic rotors due to foreign object damage
  • Gas leaking through the joints
  • Brittle failure due to thermal deformation
  • Insufficient lubrication of rotating parts
  • Low strength of ceramic materials at elevated temperatures
Photo by Adrian Dascal

But that was 1982. Now we have made major strides in the advanced materials technologies, and most of these problems can be - if not already - solved.

How to improve safety using ceramics

Using ceramic materials in your car doesn’t only give a boost in performance, but it has many other benefits, like improving the safety of driving a car (yes, despite the catastrophic failure mentioned in the previous article.

Photo by Milan De Clercq

Let’s be real, everybody either forgets or hates to keep the car always maintained and we just resort to going to the mechanic when something breaks, and that’s a seriously risky decision: we might want to be as safe as possible while driving metal monsters that weigh a few tons. That’s where ceramics come into play.

Ceramics have amazing wear resistance, and can have low friction in parts where it’s needed (that means one can skip on lubrication too). In this case ceramic parts don’t need to be changed even half as often as their metal counterparts, if at all, and the maintenance required is much lower!

The better performance in ceramic brakes also helps with the stopping of the car before it’s too late thanks to high friction values even at high temperatures and their very low weight, so that’s definitely a plus.

Photo by Julian Hochgesang

How to improve stability using ceramics

Stability is very important. Along with speed, safety and efficiency, stability - i.e. the smoothness of the drive & the reliability of the car - is the main quality drivers look for in a new car. It is mainly achieved by the advancement of electronics and sensors in the auto industry, and advanced ceramics are some of the key components in these sensors, as we’ve seen before.

Photo by Alex Read

As an example, the knock sensors prevent the knocking phenomenon in the car. They work by using a piezoceramic material that catches the vibrations that happen just before the knocking. This sensor is connected to the electronic control of the ignition of the candle that stops the spark before it can cause any damage in the engine.

Conclusion

We have now seen how changing the material of certain key elements can bring small or huge improvements in the efficiency or power of a car. Since many material technologies are still stuck in research hell, it’s more than likely that we will see huge innovations and refinement in the auto industry in this decade. In the next article, we’ll analyze how ceramic materials can lower a car’s harmful emissions that are afflicting this planet.

References

[1] Okada A. (2009), Ceramic technologies for automotive industry: current status and perspectives, Materials Science and Engineering B 161: 182-187.

[2] K. Katayama, T. Watanabe, K. Matoba, N. Katoh, SAE Paper, No. 861128 (1986)

[3] R. A. Harmon, Mech. Eng. 104 (4) (1982) 26.