The A33 is being upgraded to support operation on spark ignited heavy fuel. The upgrades touch every part of the engine system; and many of the upgrades will be rolled into the Block-2 A33 for gasoline operation
- A new combustion chamber design, optimized for heavy fuel and for use with an angled full-size spark plug.
- New port designs for improved engine efficiency.
- Crank case injection for improved fuel vaporization and transient response with heavy fuels.
- Electric head heater for cold start with heavy fuel.
- An additively manufactured muffler that is more aerodynamic, lighter, and durable. The muffler includes a swappable stinger design to allow for trades between sound and power output.
- Front and rear cooling doors for improved heat retention during descent.
Key components of the A33HF are in durability testing now. First flight is expected in the first half of 2021.