TRX 2.5 and TRX 2.5R Racing Engines

Where Power Meets Technology®

The Power of the TRX 2.5 - Elevating Ready-To-Run to Ready-To Race®! The TRX® 2.5 Racing Engine is loaded with advanced engine design features such as the free-flowing rear exhaust, the unique composite slide carburetor, and innovative porting that previously would only be found on the most exotic, modified racing engines. Traxxas brings it all to you and makes it start with the push of a button.

The TRX 2.5 Racing Engine is completely designed and manufactured by Traxxas. Our engineering team spent over 2 years designing not only the engine, but also brand new, state-of-the-art manufacturing facilities to allow us to produce the engine to the absolute highest quality standards. Multiple manufacturing lines allow us to produce a large volume of engines and bring you much higher levels of quality and technology at down-to-earth prices. Since the TRX 2.5 is actually made by Traxxas rather than being purchased off-the-shelf from an outside supplier and re-branded, the TRX 2.5 is backed by Traxxas know how, and Traxxas' unmatched customer support.

With 60% more power than the TRX® Pro.15 engine, the TRX 2.5 Racing Engine installed in a stock, out-of-the-box Nitro 4-Tec took it from 50mph top speed to speeds in excess of 60mph, with nothing more than an engine change. Nitro Rustler also gained 10mph to reach 47mph out of the box. By adding a 22-tooth clutch bell 50+mph speeds were attained. The T-Maxx hit 40+mph and gained wheelies on demand! These examples are a strong testament to the power of the TRX 2.5 Racing Engine.


The great thing about TRX 2.5 power is that it feels like it is "on-pipe" across almost the entire RPM scale. There's lots of power down low for tire-spinning, wheelie popping torque, and there's big power up high for screaming, top-speed performance. The TRX 2.5 Racing Engine was built to provide big horsepower all the time, with little focus on an exaggerated peak horsepower number that occurs at an impractically high RPM. It's made for real world drivers like you (and us!) that just want to rip-it-up on the track, in a field, or anyplace you can find.

The many things that were put into the engine to maximize power output and efficiency also have the benefit of making the TRX 2.5 Racing Engine easier to tune. It's tolerant to to a very wide range of needle settings and variations in temperature, altitude, etc. The engine is tightly sealed with o-rings throughout to eliminate air leaks that can cause inconsistent running performance. The engine responds precisely to changes in the needle settings for easy, predictable tuning.

If all of that were not enough, the EZ-Start® 2 electric starting system is all new. No starting method is more convenient than the push-button system Traxxas pioneered years ago on the TRX Pro.15 engine. Since then, we've listened to customer feedback and made the EZ-Start 2 the most reliable and easy-to-use ever. It's lighter, stronger, and innovative new ideas have made it virtually bulletproof. You'll never go back to clumsy starter boxes, bulky drill drivers, or sweat-inducing pull starters!

Easy, Reliable, Push-Button Engine Starting
The new from the ground up, Traxxas EZ-Start® 2 System brings the power and convenience of push-button electric starting to the TRX 2.5 engine. Simply plug in the hand-held control unit, push the button, and the EZ-Start System automatically heats the glow plug and the lightweight, compact on-board drive spins the engine. There's no need to break a sweat yanking on a starter cord or keep up with a separate glow plug igniter.

New EZ-Start® 2 Controller
The new EZ-Start® 2 controller is ergonomically designed for easy one-handed operation with its integrated vehicle connector. The battery is fully enclosed in the compartment. The back of the controller has a handy belt clip to make it easy to transport and keep up with.

Traxxas' exclusive Smart Start™ technology monitors critical starting functions, automatically sensing and diagnosing potential problems for trouble-free engine starting every time. Current starting status is shown by two indicator lights (LEDs) on the front of the EZ-Start® controller, one for the glow plug and one for the motor. The status of the lights can tell you if the glow plug is bad or disconnected, or if the motor is stopped due to an overload or disconnected wire. Special thermal sensing MOSFETs in the EZ-Start controller cut prevent overloads and damage to the system.

Another important new feature of the EZ-Start® 2 is regulated power output that supplies constant voltage to heat the glow plug, regardless of battery condition or starter motor load. Even if your EZ-Start battery is starting to weaken, you can still be confident that the glow plug is getting sufficient voltage to start the engine. Efficient, MOSFET circuitry provides greater starting power and longer battery life.

The EZ-Start® 2 has all new, gear drive system, with efficient, compact planetary gear reduction. The new drive system is smaller, lighter, and produces more starting torque. An all-new roller clutch design ensures positive engagement of the starter every time. An innovative new elastomer cush drive output cushions the gear drive system and protects critical starter gears from damage

The EZ-Start® 2 on-board electric starter is simply the easiest and most convenient way to start the engine and these many new innovations now make it the most dependable starting system ever.

TRX IPS Crankshaft
The heart of the TRX 2.5 is its all-new 12mm IPS (Integrated Pilot Shaft) crankshaft. Vibration and inconsistent gear mesh caused by common two-piece crank designs can steal up to 10% of the engine's power. The one-piece IPS crank provides extremely precise gear mesh and virtually eliminates vibration. In addition, the crank is precisely positioned by the front bearing for nearly zero crankshaft endplay.

The IPS crankshaft undergoes multiple hardening processes. Surface preparation includes surface hardening, precision grinding, and micro-polishing for extremely long-wearing performance.

The bottom end of the connecting rod rotates on an extra large-diameter crankshaft pin, much larger than what is typically used in this size engine. This provides the reliability needed for these critical components in such a high-powered engine.

TRX Composite Slide Carburetor
The TRX 2.5 is equipped with the all-new TRX Composite Slide Carburetor. The slide carburetor is most desired by performance enthusiasts because it provides less restrictive, straight through airflow for more power and better throttle response than the more common barrel carburetor. It's an expensive option on some engines, and not even available on others!

This is no ordinary slide carburetor either. Its Molded LCP (Liquid Crystal Polymer) body is lighter than metal and greatly reduces power-robbing heat transfer to the carburetor body. In addition, the precise molding techniques used to produce the carburetor allowed Traxxas engineers to develop an integral molded spray bar for the best possible fuel atomization. The complex spray bar shape is unique to the TRX 2.5 Racing Engine and provides increased torque and efficiency throughout the engine's entire operating range. It's another first from Traxxas! The precision molding also provides a smoother, better-flowing inlet tract than cast or machined carburetors.

The carburetor, air-filter, and crankcase are tightly integrated to provide the smoothest, most continuous airflow with the least possible turbulence. Bottom line, the TRX 2.5 Racing Engine's composite slide carburetor flows more air faster and more efficiently than conventional carburetors

Convenience features include a low-speed needle with a positive stop to prevent damage to the spray bar from over-tightening. Also, a rubber dust boot seals out harmful dirt and covers the built-in throttle return spring. The high speed needle uses a fine pitch thread on the needle for super-precise tuning adjustments.

Ball Bearings
The quality and smoothness of an engine's ball bearings contribute to the life and performance of the engine. The TRX 2.5 uses only top-grade, ultra-high performance, large diameter ball bearings. Top quality bearings improve power by reducing parasitic friction. The rear engine bearing uses a high-tech composite cage for reliable operation at engine speeds that approach 50,000 RPM!

Straight-through Exhaust Flow
The Rear facing round exhaust port provides unrestricted "straight-through" exhaust flow. There are other rear exhaust engines, but the innovative shape of the TRX 2.5's exhaust port was carefully engineered to provide unrestricted exhaust flow while at the same time, maintaining a low exhaust port height. The low exhaust port height provides a longer duration power stroke for increased efficiency and total power output.

Long Rod Design
The TRX 2.5 Racing Engine's connecting rod is longer than in any other small-block .15 engine. The longer rod decreases the rod angle throughout the entire stroke of the piston, reducing side load on the piston. It adds up to less friction and more power.


Knife Edged Connecting Rod
The edges of the connecting rod are knife-edged, a feature usually found only on expensive, hard-to-get Italian engines. The TRX 2.5 Racing Engine's knife-edged connecting rod slips through the dense fuel air mixture in the crankcase, reducing turbulence and drag. Why? More power of course!

Offset Wrist Pin
The TRX 2.5 Racing Engine incorporates an offset wrist pin to further reduce piston side loading for more even cylinder wear, and longer engine life. The entire reciprocating assembly (piston, wrist pin and connecting rod) is super light to deliver a smoother, faster-revving, more efficient engine.


Smooth Tubular Header
The tubular header features smooth, rounded bends to eliminate exhaust flow restriction and turbulence. Its precise shape and length have been matched to the engine and the exhaust pipe for maximum power output over the broadest operating range.

Molded Head Protector
The molded head protector prevents damage to the head and secures the glow plug wire.

Cast Cylinder Head
The innovative cast head is engineered for the most heat reduction possible. The cooling fins on the head blend smoothly with the cooling fins cast into the crankcase for a tight, integrated look. Cooler running equals more power. The TRX 2.5 Racing Engine looks fast and is fast! The head is secured with 5 bolts (instead of the usual 4) for superior engine sealing. Handy cut outs are cast into the head for easy access to the engine mounting screws without having to use an angled ball driver. The bottom ring of the cylinder head is designed specifically to hold the temperature probe for the optional Traxxas digital temp gauge (part #4091).

TRX 2.5R PowerTune™ Head

The Powertune machined aluminum cooling head promotes even heat distribution for stable engine temps and rock-solid tuning consistency. Other mods include a new sleeve for improved engine efficiency and better power.


High-Volume Air Filter
The air filter is often overlooked as being a key to engine performance and life. Not so with the TRX 2.5 Racing Engine! It's ultra low-restriction air filter provides superior air-flow and filtration for more power and long engine life. The inside of the filter mates perfectly to the carburetor to eliminate turbulence as air passes through the carburetor. The two-stage design features a reusable oiled foam element that's easy to maintain, and a built-in fine- mesh pre-filter.

O-Ring Exhaust Gasket
The exhaust header features an extra-tough, finned mounting base that dissipates heat and is sealed with a reliable o-ring gasket. This virtually eliminates troublesome, messy exhaust leaks that steal engine power and efficiency.

Square Reciprocating Geometry
Some premium, high-performance engines develop a reputation for being "peaky" and having all or nothing power. The TRX 2.5 Racing Engine's square reciprocating geometry gives it a 1:1 bore-stroke ratio. What this means for you is no-compromise, smooth, linear power throughout the engine's entire RPM range. Lots of punch, anywhere on the RPM scale, is what makes a great engine fun to drive