When I push the gas paddle, the engine speed is immediately sped up like 3 time but the car is only accelerating slowly, what mechanism is it that make cars acceleration not like the ones like bikes where the “engine” speed is the synced with the wheel speed?
In: Engineering
Your car has different gear ratios.
As an example, first gear might have a ratio of 3.1:1, which means for every 3.1 turns of the engine, you get 1 turn of the driveshaft. Second Gear will have a gear ratio around 1.9, so for every 1.9 turns of the engine, you get 1 turn of the drive shaft. Eventually you can get to something like 0.8:1 in 5th gear, where for every 0.8 turns of the engine, you get 1 turn of the driveshaft.
If you then look at what’s going to happen, if you hit 5,000 RPM in 1st gear, you need to keep a constant number of turns of the driveshaft as you gear up. Since that means you’ve got ~1600 RPM on the driveshaft, in second gear that needs ~3000 RPM, so (assuming an automatic transmission), your car will automatically lower the engine speed to match and then second gear goes in.
One major difference compared to a bike is that, if a cars wheels spins, they are directly connected to and will spin the engine. With a bike, the tires do not have the same effect, so the pedals don’t get turned by the tires.
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