Tuesday, September 20, 2011

Atkinson cycle: a nice marketing strategy to fool the hybrid car buyers

Back in 1882, British inventor James Atkinson was intending to overcome some patents of Otto's 4-stroke engine. Then, he developed an articulated crankshaft that allowed his engine to have all the 4 strokes in a single flywheel spin, instead of the 2 spins required in the Otto cycle. It also had a power stroke longer than the compression stroke, and then a higher efficiency was achieved.

But the articulated crankshaft is more expensive to produce, and demands a more accurate lube system to avoid failures, then it ended up becoming not so popular. It's also usually heavier and larger.

Nowadays, with the hybrid cars trend, the Atkinson label has been applied to some Otto engines, because of a different setup of the intake valve timing, that are held open for a longer time, allowing a portion of the intake air to return, leading to a reduction of the so-called pumping losses, and a smaller amount of fuel is required. However, its side-effect is a decresement on power and torque, even followed by the raised compression ratio due to the lower cylinder heads also employed.

This cheap workaround has been presented as a really advanced feature, but actually it's more about marketing to make the same engines be perceived as "greener" in a low-cost way. But, alongside the auxiliary electric drive system, the so-called Atkinson engines end up as another excuse to get a higher price tag at the dealership...


  1. I'm trying to develop an Atkinson-type engine by myself, using an autorickshaw as the test mule. Not just due to the higher fuel-efficiency, I still want it to get an enhanced throttle response and higher power to achieve a cruising speed more suitable to highway traffic.

  2. Toyota claims that the modified Atkinson cycle increases engine efficiency by 15%. That's a huge increase. Most other hybrids also use modified Atkinson engines. So your claims about it being just a marketing ploy to price the cars higher is incorrect.

    1. That's not the point. The point is the incorrect usage of the Atkinson-cycle nameplate to promote a non-Atkinson engine. Just because it simulates an Atkinson effect, it didn't turn into a real Atkinson engine, remaining as a modified Otto engine.


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