BMW DISA

Explanation

DISA: Differentiated intake system

On the differentiated intake system there is a connecting valve between the intake pipes. This is closed when the engine is turning at low speeds to create high torque due to the long intake distance. When the engine is turning faster the valve opens – to produce a short intake distance and therefore more torque and power.

DISA uses a physical phenomenon – when the length of the intake pipe has been adjusted to the engine speed, a “reboosting effect” is created by the vibrating air column before the inlet valve closes. This optimises the torque in both the lower and the upper engine speed range.

Advantages

Conventional engines have a fixed intake distance, which cannot be altered. However, optimal torque values can only be achieved with a long intake distance at low engine speeds and a short intake distance for a fast turning engine. Optimising this for low engine speeds would therefore result in reduced power in the upper engine speed range.

This is where the DISA comes into it – when the engine is turning slowly it provides a long intake distance and when it is turning faster it switches to the shorter intake distance. This means high torque and high power at all times.

Benefits

An annoying situation. You are driving along a busy motorway behind a truck. All the cars in the overtaking lane are at least 40 kph faster but they are too close together for you to join them. You wait for ages for a gap and then your engine lets you down.

With the differentiated intake system this is no longer a problem. The engine offers high torque from the very lowest engine speeds, without any loss of speed at the top end of the range.

References:

http://www.bmw.com.au/scripts/main.asp?PageID=21778&WhichPage=1&PageSize=10&Screen=ShowResults&ModelID=1000079&TGID=50&TGCategoryID=0&SearchText=

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