How did a backyard builder created a 5000+hp, 15.7L, 12-rotor engine!?

If you are a fan of big engines, the 15.7L, 12-rotor engine that Tyson Garvin created will blow your mind. This backyard builder developed an alternative to traditional marine performance by building an engine that can produce over 5000 horsepower with race fuel and methanol.

Tyson Garvin is a self-taught engineer and mechanic who has been building high-performance engines for over 25 years. He is the founder and owner of his own company, Tyson Garvin Performance (TGP), which specializes in custom engine builds and performance upgrades for a wide range of vehicles, from street cars to race boats. Garvin has gained a reputation for his innovative approach to engine design and his ability to push the limits of what's possible with custom builds. He has also been involved in marine racing for several years, which helped inspire his creation of the 12-rotor engine.

Design and Development:

The idea for the engine came about when Garvin decided he wanted to pack as much power as possible into the space normally occupied by a marine big block Chevrolet V8 engine. He determined that 12 rotors would fit perfectly into this space, and set about designing the engine accordingly.

12 Rotor, Three sets of Four rotors Stacked

The 12-rotor engine has a displacement of 960 cubic inches and weighs in at 376kg (830lbs). It consists of three banks of four rotors, with the eccentric shafts connected to the three banks of the rotors. The top two banks are connected to the centralized lower bank by gears on the back of the engine block, which is in turn connected to the output shaft. Garvin handled all of the design work and machining in-house, with only the rotor itself shared with the original Mazda 13B 2-rotor.

Side view of 12 Rotor Engine

When the engine runs, the front and rear rotors move in one direction while the middle two rotors move in the opposite direction, which helps balance the engine. Unlike most rotary engines, this engine has adjustable timing, meaning the user can choose how the rotors fire and when. This is a unique feature that is not available in most rotary engines. Essentially, the design of the 12-rotor engine involves firing twice as many times as a typical piston engine, but Garvin implemented a two up, two down counter-balancing system to address any potential issues. While the design is similar to a flat plane crank, the rotaries fire every 360 degrees as opposed to the 720 degrees required for a piston engine's four cycles. Despite this difference, the rotary engine's lack of counterweights and harmonics make it more efficient than a piston engine in this regard. Overall, the 12-rotor engine is an impressive feat of engineering.

Intake and Exhaust Porting

Intake and Exhaust Porting of 12 Rotor

The engine block has a pocket designed for water to flow around and reach all the necessary holes. The water enters from both sides and passes through this pocket, which allows for greater clearance to clear the bolts. The water then flows around to each hole, which are positioned lengthwise on the engine block.

In summary, the gears are not directly connected, and they rotate in opposite directions, like the gears in a clock tower watch. The oil pressure runs through the length of the gears and sprays onto the gear face. To ensure that the bearings get enough oil pressure, they were pressure fed with oil. While machining, the only problem was that the machine did not have enough clearance, and they had to adjust the angle. The motor is incredibly powerful, and the rear 35 spline axles are rated for almost 10,000 foot-pounds of torque.

Gears on 12 Rotor Engine

The drilling had to be precise in order to clear certain obstacles, and the side plates are made of cast iron. The port timing can be changed by swapping out the plates, and the most important part is the contact with the sleeve. The engine support is a one rotor design with a splined shaft and no play, and the bearing sits across both rotors, with oil pressure locking it in place. The degree can be adjusted to change the timing of the rotors.

Oil passages and cast iron plates

This is an oil pump with a wide, five-suction pressure section and a drive on the back for a mechanical fuel pump. It also includes an oil filter.

Oil Pump


This engine has a unique design, featuring a single rotor splined e-shaft. This allows for easy rotation and clocking of the rotor, while the oiling system ensures both sides are supported by a single bearing. The lack of play in this design is impressive and offers the ability to change timing and rotation to achieve different outcomes. This setup is different from the standard two rotor engine with 32 splines, which can only be clocked at degrees divisible by four.



The engine was tested on a Dyno with a carburetor, as fuel injection computers were not available at the time. Initially, two Jaguar V12 computers were used to run the ignition. However, carburetors were limiting the power output of the engine, and it could only produce up to 100 horsepower at 8,000 RPM. The engine was run at higher RPMs, but it wasn't making a lot of power due to the lack of fuel and air supply. It produced around 800 foot-pounds at 2,000 RPMs, which is an insane power for a naturally aspirated engine. The engine was running at an air-fuel ratio of 17:1, which caused it to shut off. The goal is to push the limits of the engine and see what it can do.


The engine is designed to be flexible and can be used in pleasure boating at around 1,400 horsepower for up to 400 hours between scheduled maintenance. It could also be turbocharged with a pair of 122mm turbos to make 2,400 horsepower for about 200 hours for poker runs and other spirited adventures. Both those power numbers are on 87 octane fuel. Increasing the boost to 25 pounds on race fuel could push the power levels beyond 3,600 horsepower. Jumping up to 50 pounds of boost could result in over 5,000 horsepower. For steady-state running, recommended rpm will be in the 8,500 to 9,000 range. But an all-out drag version could spin up to 14,000 rpm.

During testing, the 12 rotor engine produced an impressive 497 horsepower at only 3200rpm, less than 1/3 of its proposed redline. The engine is capable of producing over 5000 horsepower, although that number has not yet been reached.

Cost and Accessibility:

The estimated cost for this engine exceeded $500,000USD, and it's not a project for the faint-hearted. Nonetheless, Garvin's creation is a testament to the power of a backyard builder's creativity.


In conclusion, Tyson Garvin's 15.7L, 12-rotor engine is an incredible demonstration of the power of backyard innovation. With the ability to produce over 5000 horsepower with the use of race fuel and methanol, this engine is truly a monster. Its flexibility, capable of producing up to 3600 horsepower with the help of turbos and race fuel, makes it an impressive feat of engineering. The design and development of this engine involved custom machining and modifications to create an internal structure that could accommodate the additional rotors, and the testing and tuning process ensured optimal performance. Garvin's 12-rotor engine is an incredible example of what can be achieved with creativity, ingenuity, and a lot of hard work.



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We would like to extend a special thanks to Garvin for his informative YouTube video on the 12-rotor engine and to Rob Dahm for his contributions to the subject. Without their insight and expertise, this blog post would not have been possible. Additionally, some of the images and video footage used in this post were sourced from their channels, and we would like to give them proper credit for their work.

Please note that the opinions and views expressed in this blog post are solely those of the author and do not necessarily reflect the opinions or views of Garvin or Rob Dahm.

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