Schematische Produktgrafik zum Hubverhältnis eines Motors mit Kolben: Kurzhüber 0,50, Quadrathüber 1,00 und Langhuber 2,50 im Vergleich.

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Piston stroke

What does the stroke mean for engine tuning?

by
Bartek Bartoszewicz Tuning Professional

#Kolben

#Motor-Tuning

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.?

Technische Grafik eines Verbrennungsmotors mit Kolben, Pleuel und Kurbelwelle zur Veranschaulichung von Hub, oberem und unterem Totpunkt sowie Kurbelwinkel

What is piston stroke?

The piston moves up and down in the cylinder. The distance your piston travels between the top dead center and the bottom dead center (TDC and BDC) is called the piston stroke. The space in which the piston moves is the displacement and is usually given in cubic centimeters (cm³) or in liters. Various factors influence the stroke: for example, the crank radius of the crankshaft and any offset, where the cylinder axis and the crankshaft axis do not intersect. With the piston stroke and the cylinder cross-section, you can calculate the displacement and the compression ratio of your engine, which have a significant influence on the power of your engine.

Grafik zum Hubverhältnis bei Kolbenmotoren mit drei Darstellungen: Kurzhuber 0,50, Quadrathuber 1,00 und Langhuber 2,50

Short-stroke, long-stroke and square-stroke engines

For the stroke ratio, also called stroke-bore ratio (the ratio of piston stroke to cylinder cross-section), a distinction is made between short-stroke, long-stroke and square-stroke engines.

In short-stroke engines, the stroke ratio is less than one, since the piston stroke is smaller than the cylinder bore. It is very well suited for higher engine speeds because the mean piston speed is lower. You also have space here for larger valves in the cylinder head, which ensures a greater flow. This in turn gives you more torque and power and makes this design perfect for motorsport.

Here you can find cylinder heads

Here you can find piston rings and piston accessories

If stroke and bore are the same size, it is a square-stroke engine. If the bore diameter is smaller than the stroke, we speak of a long-stroke engine. Long-stroke engines are particularly strong in the torque range. They also produce higher torque at low engine speeds.

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Increasing engine displacement – What does piston stroke mean for engine tuning?

“There is no replacement for displacement except more displacement.” This well-known quote expresses how essential displacement is for your engine’s power. That’s why a frequently asked question in engine tuning is about increasing displacement. However, we usually talk about tuning when we increase power at a given displacement by using various measures (for example through chip tuning and exhaust tuning). Nevertheless, by increasing displacement we can also generate more power. Because the larger the displacement (at the same rpm and the same mean effective pressure), the more air-fuel mixture can be burned per intake stroke. And when throughput increases, power increases as well. Increasing displacement therefore results in higher torque across the entire rev range, which is immediately noticeable in driving pleasure. However, the power increase is not linear. So you cannot directly infer the gained power from the larger displacement. Here a formula applies that can also vary slightly depending on the engine:

Specific output (in hp per liter) of the existing engine x newly gained displacement (in liters) x 0.8 = power gain

To find out your potential power through an increase in displacement, you can simply get in touch with our motorsport professionals. Click here to go to the contact page.

Here you’ll find everything for chip tuning

Here you’ll find everything for exhaust tuning

How do we increase the engine displacement?

One way to increase the displacement of your engine is by overboring, in which the cylinder bore is enlarged. Of course, this cannot be done with all engines. This depends on the design or the material, as sufficient wall thickness (at least 5 mm) must always be ensured. The bridges between the cylinders and the gasket must also be sufficiently strong. If you decide to increase the displacement by overboring, you naturally also have to install larger pistons that fit the bore and can withstand the increased power.

Here you can find forged pistons

Another way to achieve a larger displacement is by using a different crankshaft. This has a direct effect on the piston stroke, which is thereby increased. A combination of both options is also often used in tuning. When changing the crankshaft, it is always advisable to draw on the experience of professionals, as immense problems can arise for hobby mechanics here due to higher wear and the like.

Here you can find crankshafts

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Do you need our support?

We are here for you if you have questions about piston stroke or increasing engine displacement. Just get in contact with us.

You want to learn more about piston rings, piston coating etc.?

Here you will find everything you need to know:

Perfect pistons for your engine tuning:

Mahle Forged Pistons (56)

Wiseco Sport Pistons (95)

JE Pistons (91)

JP Pistons Markenlogo in Blau und Rot mit weißem Hintergrund

Wössner Pistons (8)

Rotes Wössner Markenlogo mit dem Schriftzug „High Performance Pistons“ und „Research & Development“ – Hersteller für Hochleistungskolben

Piston Accessories (18)

Nahaufnahme eines Motorradkolbens mit aufgelegten Kolbenringen als Motorkomponenten und Ersatzteile

Bartek Bartoszewicz

Tuning Professional

His first car was a Polo Mk1 with a 40 Weber twin carburetor and 129 hp (95 kW). His second was an Audi 50. Today Bartek tunes Lamborghinis to 1000 hp (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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