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Yes they are I have something similar on my 10cc car but I have not managed to make one that works for a 2.5cc car. Need track time to do it as it works on centrifugal force.
The car is weighed ready to run lubricated and fueled ready to run. No top ups allowed on the track.
This is one of my modern tether cars powered by a 2.5cc glow plug engine with a tuned pipe. Fuel is 80% methanol 20% castor oil. Engine revs to around 40,000.