Advisor
Tips & Tricks
Pistons for naturally aspirated engines and pistons for turbocharged engines
How does the design affect performance?
3 Comments
Piston design: differences in naturally aspirated and turbocharged engines
Have you ever wondered if pistons always look the same whether they are used in turbo engines or naturally aspirated engines?
Pistons are always subjected to high loads, no matter which engine they work in. But the nature of the load varies greatly, and that must be considered when designing pistons. The thickness of the material and other factors have a major influence on stability, mixture formation and much more. Here you can find out exactly what the differences are between pistons for turbo engines and pistons for naturally aspirated engines.
CONTENT
- 1. The differences between pistons for naturally aspirated engines and pistons for turbocharged engines
- 2. Why is piston design so important? – Significant load test for pistons
- 3. How important are the material and thickness of pistons for performance?
- 4. How do high speeds and friction impact pistons?
- 5. Perfect for boosting performance: the asymmetrical piston skirt from JE Pistons
- 6. Flat or curved piston crown: which piston goes in which engine?
- 7. Why are piston pins and piston pin eyes so important for durability?
- 8. Why are gas-nitrided piston rings primarily used in racing?
- 9. You want more?
The differences between pistons for naturally aspirated engines and pistons for turbocharged engines
Pistons always look very similar – whether for naturally aspirated or for turbocharged engines. But they must meet different demands and are designed accordingly. It is widely thought that pistons for turbocharged engines are only slightly thicker than those for naturally aspirated engines. However, there are a few small but significant differences in design. These influence stability, density, fuel mixture generation, weight and more. Since the two types of engine are exposed to different strains regarding pressure, heat, and engine speed, the piston design is also adapted. This is the only way to ensure maximum durability and performance. Here you will find out what matters most for decent pistons!
Here you can see that the piston crown of the “turbo piston” is larger than that of the “naturally aspirated piston". The thickness continues and tapers towards the piston skirt. (pictures by JE Pistons).
Why is piston design so important? – Significant load test for pistons
It is clear how important the custom-fit design of the pistons is for tuning when you take a look at the different forces that act on the piston in a high-performance engine. The constant up and down motion (and the associated braking and acceleration) within the cylinder result in mass inertia forces. The piston force, which is transferred to the connecting rod and crankshaft, additionally presses the piston to the side, against the cylinder wall. This lateral force, also known as normal force, depends on several factors, including the angle between the piston and the connecting rod. During the entire four-stroke cycle, all areas of the piston (piston crown, piston rings, piston pins and skirt) are thus subjected to continuously high strain.
The finite element method helps piston manufacturers detect and eliminate vulnerabilities. (Picture by JE Pistons)
How important are the material and thickness of pistons for performance?
With increased engine power, cylinder pressure and heat rise as well. The pistons for naturally aspirated engines as well as pistons for turbocharged engines are therefore coated with a special aluminium alloy. Besides similar metallurgy, pistons for naturally aspirated engines and turbocharged engines have little in common. Since turbocharged engines quickly reach three times the horse power compared to a naturally aspirated engine, the individual areas of the piston are made thicker and the free spaces are also enlarged. This ensures that the piston design functions within the strength limits. But it is not only the performance which determines the perfect design of a piston. The use and working cycle are crucial factors.
The pistons from JE Pistons are asymmetrical. These are very robust and thick on the one side and light and thin on the other.(Picture by JE Pistons)
How do high speeds and friction impact pistons?
At high speeds, tuned naturally aspirated engines cause a similar strain on the piston as turbocharged engines. The difference is how the strain affects pistons. It is therefore particularly important to ensure that the area of the pin hole is fixed and stable. This prevents the pin from being pulled out of the piston.
At high speeds, friction is created, which limits performance extremely. That’s why when designing pistons, unique skirt shapes and profiles are used that reduce friction without affecting the stability and ring seal. Piston skirt and piston ring lands are optimised to minimise the surface and thus limit friction as much as possible. As a result, you get out at least a good 10 – 20 more PS (7,5 - 14,7 kW) compared to a conventional piston.
Perfect for boosting performance: the asymmetrical piston skirt from JE Pistons
Optimisation of the piston skirt is still a popular and effective method for reducing friction. However, JE Pistons has added a little one-up: with forged, asymmetrical pistons. On one side, they are large and robust and on the other side much smaller and lighter. This means that they are perfect for the different starting surfaces of engines and save on weight at the same time, which is of tremendous importance for boosting performance.
More information about the JE pistons can be found in the JE blog. By the way: JE Pistons also offers a special coating for piston crowns and skirts .
Flat or curved piston crown: which piston goes in which engine?
Previously, pistons could be distinguished via their flat or curved crowns. Pistons for turbocharged engines had a curved crown. That’s no longer the case. Modern cylinder heads have smaller combustion chambers, which is why a curved piston is also used in naturally aspirated engines. Pistons with flat piston crowns are also used in turbocharged engines in order to reduce static compression.
In this image, you see that the piston skirt is wider for turbocharged engines. This is necessary to counteract the enormous thrust forces pistons are subjected to. (Picture by JE Pistons)
Why are piston pins and piston pin eyes so important for durability?
For most race drivers, the piston pins are just a necessary evil that contributes to the overall weight of the piston. In reality, the reduction in mass is not nearly as important as the resistance against bending. The piston pins are responsible for transferring the cylinder pressure exerted on the pistons to the connecting rods. When the pistons move from the TDC (top dead centre) towards the BDC (bottom dead centre), the pins prevent them from impacting the cylinder heads. Piston pins that are bent due to insufficient wall thickness can also strain the piston.
The diameter of the piston pin is normally determined via the low diameter of the connecting rod. With increased performance, however, piston manufacturers often also increase the wall thickness. Higher-quality alloys can also be used. The design of the piston pin eye also plays an important role in durability.
The smooth piston crown prevents load points since there are no hard edges.
Why are gas-nitrided piston rings primarily used in racing?
Although naturally aspirated and turbocharged engines are exposed to different heat and pressure levels, both have benefited from the significant improvements in piston ring technology over the past decade. Most piston rings for racing are made from a gas-nitrided steel ring and a expandable, hook-shaped second ring. This combination allows better oil control, lower ring tension, reduced friction and improved shape adaptation and ring sealing.
You want more?
If you have any questions about pistons or other tuning parts, please get in touch! We are here to help: give us a call or contact us via chat!
Create comment
Please leave us a comment.
Comments
Jackfred
22.04.2024, 04:04 Uhr
Any forged piston kits for Toyota mark 2 jzx 90?
Dean
23.04.2024, 07:16 Uhr
Hi,
Thanks for the comment. Sadly, we don't have fitting Pistons for your vehicle in our shop.
Unk
10.07.2024, 12:00 Uhr
Can I put turbocharged piston on NA engine? 2nr-ve
His first car was a Polo Mk1 with a 40 Weber twin carburetor and 129 PS (95 kW). His second was an Audi 50. Today Bartek tunes Lamborghinis to 1000 PS (735 kW). Even as a young boy, Bartek disassembled vehicles and put everything back together better. He wrote his high school diploma with oil on his fingers. The trained automotive mechanic with a focus on engines and gearboxes was determined to go into motorsports. In his 10 years in Formal 1, he supervised 73 races, including as engine mechanic for Ralf Schumacher at Toyota. Since 2010, he has dedicated himself fully to his company BAR-TEK® and helps his customers to bring VW and Audi engines to peak performance.
Expert in
Engine
Gearbox
