The set 8365 Tuneable Racer has tunability as its main feature, meaning the motor's parameters can be changed by adding, removing or swapping certain additional elements. However, these parts seem to be purely cosmetic, and not in any way mechanically or electronically relevant.

The instructions illustrate their intended functionality:

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And similarly with the B-Model:

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Based on these images, the functionality of the individual parts seem to vary in different combinations, as the last two setups for the A model hint on

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having better performance than

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but the B model seemingly has it inverted.

So how does this set work? My current best theory is that there are buttons inside the technic holes used to connect these parts and their states affect the motor's characteristics somehow, but I'd like to know if someone has better insights into its workings.

The first two images for the B model suggest different capabilities for the same setup, which must be an error on TLG's side, or is there something I have missed?


This Polish forum has a review of the set with an image depicting the switches inside the Technic holes:

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The text states (as translated by Google):

it can be seen that in the places where the pipes are to be finally inserted, there are buttons that control the engine's operation.

can be tuned using regular pins, using them as jumpers

This eliminates the "rotating pins providing resistance" theory, but I'm still looking for any experimental results, authoritative information or preferably a full analysis of the different combinations regarding speed and torque.

  • The varied horizontal positions of the B model suggest that the different combinations affect speed differently to the maximum climbable slope. The last 2 configurations of B model seem to have consistent speed effect as A model Commented Feb 22, 2021 at 22:46

2 Answers 2


I do not own this item, but observing the pictures leads to a logical inference.

The pins are in different locations.

If you look at parts, you will see that they are 5 pins wide. One part has pins in positions 1 and 5, the other has pins in positions 2 and 3.

You then connect the parts to the motor. With switches inside the motor, it can detect which holes have pins in. This is similar to how the LEGO Super Mario figure knows which Power Up is attached - a simple way to test would be to attach normal pins in those locations, rather than the special parts that came with it.

This may not even be electronic, the pins may be physically changing the gear ratio inside the motor. Which answers the last part of your question: why do the performances appear to be reversed?

Because a high gear means lots of speed, but no torque (power), and a low gear means low speed, but lots of torque (power). You can test this yourself on a bicycle. On a flat path, a high gear will let you go really fast, while a low gear will mean you are slow. But, going up a hill, a low gear will let you easily climb steeper hills, and a high gear will leave you stuck, exhausted, at the bottom! So, the "high gear" item gives better performance on the "speed"/"racing" model, but the "low gear" item gives better performance on the "power"/"steep ramp" model

  • Wow, I completely missed the fact that the pins are different distances apart... Commented Feb 23, 2021 at 21:10

I don't own the set (or parts), but I might have a guess.

Of the two exhaust tubes, one seems to have pins that can rotate, and the other has fixed pins.
If the engine block they attach to outputs some of the torque to those pinholes, then attaching the exhaust parts adds resistance, therefore redirecting torque to the wheels.
The exhaust can then be configured in 3 ways;

  • Without tubes, providing no resistance
  • With single exhaust tube, providing some resistance
  • With triple exhaust, providing maximum resistance

The same theory could apply to the air intake, but I'm not sure how it would make it better at hill climbs. Perhaps some fancy gear ratio magic. If I get my hands on one I'll definitely try to take it apart.

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