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12 speed vs 6 speed transmission for scania and other trucks.


McLaren2876

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Hello,

 

There are many factors affecting acceleration such as horsepower, torque, rpm output of the engine, stroke times in the combustion chamber, gear ratios, differential ratio, etc. However, assuming that all other variables are constant except the transmission, a vehicle with 6-speed transmission usually accelerates better than 12-speed transmission.

 

The first thing to consider is the first gear ratio. This ratio states the number of revolutions that the engine needs to make for the transmission (while in the 1st gear) to complete one revolution. Then, there is the differential ratio. This ratio states the number of revolutions that the transmission needs to make for the wheels to complete one revolution. If you multiply these two numbers, you get the number of revolutions that the engine needs to make for the wheels to complete one revolution. 

 

That may sound a little complicated but let's see an example:

Here is a 6-speed transmission for Renault T from ETS2: https://ibb.co/H7p0mKr

Here is a 12-speed transmission for Renault T from ETS2: https://ibb.co/Rg4syVh

 

For the 6-speed transmission: (first gear ratio) x (differential ratio) = 4,70 x 3,91 = 18,38. This means that, to turn the wheels once, engine has to make 18,38 revolutions while the transmission is in the 1st gear.

 

For the 12-speed transmission: (first gear ratio) x (differential ratio) = 11,73 x 3,08 = 36,13. This means that to turn the wheels once, engine has to make 36,13 revolutions while the transmission is in the 1st gear.

 

In conclusion, assuming all the engine specifications are the same, 6-speed transmission is superior to 12-speed transmission in terms of acceleration. However, the opposite is usually true when it comes to the discussion of top speed.

 

Hope this helps :)

 

Best regards

Onat

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I've done some testing before and a 12 speed will reach 90 km/h in about 12 seconds, while the 6 speed will reach the same speed in about 8 seconds. That's all with the same truck and engine. I've also done some testing with 10 tons cargo (1 axle trailer) and 26 tons too. The 10 tons do 19 seconds for 6 speed vs 25 seconds for 12 speed. For 26 tons, it's 34 seconds for 6 speed and 38-39 seconds for the 12 speed. But do note that those tests were done on a relatively flat road with no incline. The 6 speed will struggle with heavier loads on a steeper incline. I think the difference comes from the starting gear ratio, and how many times the truck will shift.

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