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Piston stroke
What does the stroke mean for engine tuning?
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What is the piston stroke and what does it mean for tuning?
So, you want to know what the piston stroke is all about and what you can do with it to achieve more power when tuning? Here you can find out everything about the stroke ratio of different engines, and how you can increase the cylinder capacity. After all, increased cylinder capacity is vital for enhanced performance.
CONTENT
- 1. What is piston stroke?
- 2. Short-stroke, long-stroke, and square engines
- 3. Increasing the cylinder capacity – what does the piston stroke mean for engine tuning?
- 4. How do we increase the cylinder capacity?
- 5. Do you need our support?
- 6. You want to know more about piston rings, piston coating etc.?
What is piston stroke?
The piston moves up and down in the cylinder. The path your piston takes between the top and bottom dead centre (TDC and BDC) is called piston stroke. The space in which the piston moves is the cylinder capacity and is usually expressed in cubic centimetres (cm³) or litres. Various factors influence the stroke: for example, the crank radius of the crankshaft and a possible offset through which the cylinder axis and the crankshaft axis don’t intersect. With the piston stroke and the cross-section, you can calculate your engine’s cylinder capacity and compression ratio, which have a significant impact on your engine’s performance.
Short-stroke, long-stroke, and square engines
With the stroke ratio, also referred to as the bore/stroke ratio (the ratio between the piston stroke and cylinder cross-section), a distinction is made between short-stroke, long-stroke, and square engines.
With short-stroke engines, the stroke ratio is greater than the one, because the cylinder bore is wider than the length of the piston stroke. It is very well-suited for higher speeds, because the average piston speed is lower. Here, you also have space for larger valves in the cylinder crown, thus enabling a higher flow. This, in turn, provides you with more torque and power, making this design perfect for motorsport.
If the stroke and bore are equal in size, this is called a square engine. If the bore diameter is smaller than the stroke, we refer to long-stroke engines. Long-stroke engines are particularly strong when it comes to torque. They generate higher torque even at low speeds.
Increasing the cylinder capacity – what does the piston stroke mean for engine tuning?
‘Nothing can replace cylinder capacity except even more cylinder capacity.’ This well-known quote expresses how crucial cylinder capacity is for your engine’s power. That’s why a frequent question in engine tuning is how to increase cylinder capacity. However, we usually refer to tuning in the sense of boosting performance through various measures while maintaining the same cylinder capacity (e.g. chip-tuning and exhaust tuning). However, we can also achieve more power by increasing the cylinder capacity. The greater the cylinder capacity (at the same speed and with the same effective medium pressure), the more fuel-water mixture can be burned per intake stroke. And increasing the throughput boosts performance. Raising the cylinder capacity thus results in increased torque across the entire speed range, which is immediately noticeable in terms of driving thrills. However, the performance increase is not linear. So you can’t assume that greater cylinder capacity will have a direct effect on your car’s performance. Here, a formula applies that may vary depending on the engine:
Power density (in hp) of the existing engine x newly achieved cylinder capacity (in litres) x 0.8 = performance boost
In order to discover the potential performance you can achieve by increasing the cylinder capacity, you can simply get in touch with our motorsport professionals. Click here to go to our Contact page.
How do we increase the cylinder capacity?
One option for increasing your engine’s cylinder capacity is to ream the cylinder bore bigger. Of course, this cannot be done with all engines. It depends on the design and materials, since the walls must always be sufficiently thick (at least 5 mm). Also the webs between the cylinders and the seal have to be sufficiently strong. If you decide to increase cylinder capacity through reaming, of course you must install larger pistons that fit the bore and can withstand the increased power.
Another option for higher cylinder capacity is to use a different crankshaft. This will enable you to have a direct impact on the piston stroke in order to extend it. A combination of the two options is also frequently used in tuning. When modifying the crankshaft, it is always advisable to get help from experienced professionals, because hobby mechanics will run into increased wear and tear, among other issues with these tuning jobs.
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Do you need our support?
We’re happy to help if you have any questions about piston stroke or increasing cylinder capacity. Just get in touch.
You want to know more about piston rings, piston coating etc.?
Here you will find everything you need to know:
- Piston stroke
- Piston pins
- Piston coating
- Piston cooling
Perfect pistons for your engine tuning:
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.
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