Nautilus Cycle (HCI/HCCI)

(Homogeneous Compression Ignition)
(Homogeneous Charge Compression Ignition)

This unique patented design solves the inherent challenges of pre-ignition, poor cold starting, unbalanced combustion, uneven temperatures, limited RPMs and loads.


Nautilus Cycle HCCI Efficiency

Fuel Efficiency

Our HCI/HCCI engine is projected to achieve 30% more fuel efficiency than a standard ignition engine. During an HCI/HCCI ignition, the chamber has a cleaner combustion, without leaving pockets of unburnt gases.

Engine & Propulsion System Cost

The Nautilus HCCI Cycle is a true pressure cascading compression ignition technology which means that we are not restricted by managing flame-front propagation properties.Thus Nautilus Engineering has reduced the part count and complexity of the engine propulsion system creating approximate cost-savings potential of 15% for small engines that range up to 30%+ for larger engines.  

The fundamental physics of the Nautilus HCCI Cycle is a true multi-fuel technology that enables increasing the cylinder diameter size for the additional benefits of even higher efficiencies and further packaging optimization. 

Less Toxic

HCI/HCCI engines are less toxic, producing minimal NOx emissions. You can learn more about this technology at Sandia National Laboratories


The Nautilus Cycle

The Nautilus Cycle combusts when the pressure inside the (smallest) primary chamber is at critical pressure.
When the small primary piston enters its chamber in the cylinder head the pressure ratio increases dramatically, roughly 2:1 - 3:1 versus secondary combustion chamber depending upon RPMs. The temperature and pressure is high enough to cause auto combustion of the Homogeneous mixture of gases ie. air, fuel, EGR. This eliminates the need for spark plugs at operational temperatures.

Pure Power

After reaching top dead center the ignited gases flow down into the secondary piston to create the power cycle onto the larger surface area of the secondary piston (the larger part of the piston). The valves have been reconfigured so the heat generated from the exhaust cycle is now dissipated evenly which reduces intermittent transient auto-ignition.

Simple Mechanical Solution

The Homogeneous Mixture is pre-mixed outside of the combustion chambers, this enables dramatically reduced lean/rich pockets of homogeneous gases.

This mixture is combusted in a semi-continuous cycle, which is projected to have negligible emissions. So the need for larger complex exhaust systems are reduced.



This changes everything...


The Nautilus Opposed Piston Engine

Learn More

What are the five elements of Nautilus HCCI and HCI?

They are as follows.

One fuel for energy.
Two intake air to enable combustion.
Three heat to enable cold start combustion.
Four EGR gas to preheat cylinder and to suffocate flame.
One through Four are pre-mixed.
Five compress to point of auto ignition.

Note: We withhold number five as a mechanism to control auto ignition.

Keep in mind, rapid compression = heat = pressure = auto ignition.


Piston descends INTAKE stroke takes place, valves are closed, ambient pressure is now established at bottom dead center (BDC) within the cylinder.

Piston ascends, pressure increases exponentially in the cylinder (on the COMPRESSION stroke). Primary piston enters into the primary combustion chamber, pressure is now accelerated at roughly 2:1-3:1 versus secondary combustion chamber depending upon RPMs.

The primary combustion chamber (15-35%) is allowed to achieve critical stage combustion at top dead center (TDC). While secondary combustion chamber (65-85%) maintains a lower threshold (not achieving critical stage).

Crank crests over TDC piston is now descending within the cylinder. Primary piston's combustion is exposed to the secondary chamber, allowing accelerated critical stage (pressure propagation). After TDC, POWER stroke occurs. Piston ascends, EXHAUST stroke begins as in a conventional engine.
(Cycle Repeats)

View it in 3D

For a detailed model of the Nautilus Cycle, download the eDrawings Viewer.

Then open this 3d file in the app. Download it here.

Additional links to help understand Nautilus Technology