Doubling the Compression Ratio of a Gas Engine Leads to Unpredictable Outcomes.

      Garage 54/YouTube

      Raising an engine's compression ratio is a well-known method to boost horsepower, but there comes a point where the benefits taper off. The crew at Garage 54, the Russian mechanics who constructed a V16 from chainsaw engines, explored this concept by doubling the compression ratio of an aging Lada Samara four-cylinder to determine its limits and the consequences of excessive modifications. Spoiler alert: the outcome is not pretty.

      The initial phase of the project was quite simple. One of the mechanics took off the cylinder head, a relatively easy task on a decades-old Lada hatchback, filled the combustion chambers with clay, and reassembled the engine. He then manually turned the engine several times to open and close the valves, creating impressions in the clay, which were cleverly used as a reference point. While this method isn’t the most sophisticated or precise for measuring an engine's compression ratio, it was effective.

      By removing 1.25 millimeters from the cylinder head and carefully welding an aluminum plate atop each piston, the compression ratio increased from 9:1 to 22:1. However, the Garage 54 team deemed that ratio too high and added a second head gasket to bring it back down to 16:1. Surprisingly, the engine started! It was noisy, but it ran smoothly and idled remarkably well.

      Then came the pivotal moment: could it drive? The answer is both yes and no. It could move under its own power, but during an acceleration test, the engine failed, which was somewhat predictable. Parts of the aluminum welded to the piston detached, and one piston split in half—even with 100-octane fuel. So, Garage 54 took a practical approach: they removed the broken piston, raised the compression ratio back to 22:1, and reassembled the engine. This unfortunate Lada is now equipped with a three-cylinder engine that has more than double the original compression ratio.

      The engine doesn’t last long. It starts, runs (if that can be called running), and then fails spectacularly. Interestingly, the cause of its demise isn’t the elevated compression ratio; it’s the knocking from using the wrong fuel type. Garage 54 stops the experiment there but notes that increasing the compression ratio isn’t out of reach; it simply requires more extensive modifications, like upgraded rods. Could this be a hint at the next phase of the project?

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