The TRX 2.5 is an ABC .15 cubic inch displacement nitro engine made by Traxxas. Its name refers to the displacement in cubic centimeters.
The engine was the standard one for most nitro-powered Traxxas vehicles until the introduction of the TRX 2.5R. This engine is similar to the TRX 2.5, but the sleeve has been ported for more power. Output of the TRX 2.5 was 1.33 horsepower while the 2.5R has an output of 1.99 horsepower.