Holy Grail Lean Burn Engine

The Holy Grail Lean Burn Engine was introduced in the Opportunity section of our website. It is a unique, 2-Stroke, 2-cylinder engine. See the picture below. The Holy Grail Engine can be thought of as the “perfection” of the lean-burn engine which became a reality in 2009. By “perfection” is meant a design that satisfies both the practical and the theoretical points of view, i.e. gives the lowest cost, simplest construction while giving the highest efficiency and highest power. The Holy Grail Engine has two overhead valves, an intake and exhaust valve, but does not have ports in the engine block, as does a typical two-stroke engine. Use of the term “Holy Grail” seems appropriate given it was originally used to describe our work which began some thirty years ago. The Economist in 1986 wrote about our progress on the “lean-burn” engine as “the Holy Grail of car engineers. By using more air to burn less fuel, it promises more miles per gallon and less pollution”.

This newly discovered engine became the precursor for the “perfect” lean burn engine. It goes by the more accurate technical name “2-Stroke Inverted Cross-Scavenged” engine, that belies its great simplicity, low cost, high efficiency and great power, to solve the problems of climate change to keep the price of oil low and stable. Its success depends, in part, on turning the two–stroke, cross-flow engine on its head to make it simpler, more effective and efficient.

The engine makes use of the Miller Cycle to work perfectly under all conditions, i.e. it uses an expansion ratio (ER) of 18 to 1 for best efficiency and an effective compression ratio (CR) of 10.5 for best power. See the section on Engines. Note that the air-fuel mixture near top-center (TC) has considerable turbulence due to colliding flows from three sources of squish which help the air and fuel to thoroughly mix in the shorter available time. Note that while the valves may close very late, e.g. around 75º after-bottom-center (ABC), the CR will not be too low (late closing) or too high (high ER). See the calculations below. With good scavenging, the intake air will be at 1 atmosphere when the valves close (by use of an electrical supercharger, during scavenging, on the intake), and the temperature will be at room temperature. That is, by displacing the exhaust gases with fresh intake air, the process takes place at constant temperature and pressure, at NTP, to give a full charge to the cylinder, despite the late valve closing. It is noteworthy that it wasn’t appreciated that use of scavenging in the two-stroke allows the Miller Cycle to work perfectly.

Marrying this engine with a suitable chassis can make “The Car of the Future”, i.e. a small (1 Liter), very powerful engine (200 HP), with the highest efficiency (100 mpg) and having a very low-cost (under $10,000). There are several chassis that would work well with this engine. The funds needed to build and test a single cylinder engine within one year is about $550,000. This will be followed by a 2-cylinder engine, shown below on the right, completed also within one year and costing about $600,000. The cost is miniscule when compared with developments of hybrids and EVs. The two cylinder Holy Grail Lean Burn Engine can revolutionize the industry, and save a tremendous amount of oil.

Holy Grail Lean Burn Engine

Lean Burn Lives

Below are the specifications of a two cylinder, 2-Stroke ICS engine, i.e. a one Liter, 2-Stroke ICS, 2-cylinder, Miller Cycle engine, shown below, and some of the calculations which led to its design.

Displacement: 1 liter, 2-cylinder engine, Intake = 1″ + 0.5"; Exhaust = 1″ + 0.5".

ER0 = CR0 = 18:1

Displacement ≈ 1.0 liter

Horse Power = 200 HP (estimate)

Efficiency = 100 mpg when matched to a proper car chassis.

Bore (B) = 3.5 inches (to 3.6 in)

Stroke (S) = 3.0 inches

Area (A) = 9.62 square inches

ho = S/(CR – 1) assume ER = CR

ER0 = 18:1

ho = 3/(18 – 1) = 3/17

CR = (Vd + Vtc)/Vtc

where Vd is the displacement volume at BC (Vcylinder), and Vtc is volume at TC.

Vcylinder = 9.62 * 3.0 = 28.9 cubic inches

CR0 = 18 = Vd/Vtc + 1

Vd/Vtc = 17

Vtc = Vd/17 = 28.9/17 = 1.70 ci

CR0[at 90º] is the CR0 at ½ the displacement, i.e. ½ * STROKE * Area

CR0[90º] = [9.62*(3.0/2) + 1.7]/1.7 = 8.5 + 1 = 9.5

Volume[at 75º ABC] = Volume[105º BTC] ≈ A*[90º + 15º/90º] ≈ 9.62*[1.5 + 0.16]

CR0[75º ABC] = [9.62*1.66+ 1.7]/1.7 = 9.4 + 1 = 10.4

Assume the May Fireball Engine, except that it applies to a two-stroke.

The entire combustion volume is under the exhaust valve [1.5” area].

The intake valve is at the level of the squish zone at TC.

Asq0/A = (1.5)2/9.62 = 2.25/9.62 = 0.234

A1cup = 0.234*9.62 = 2.25 sq. inches, is the area under the exhaust valve.

Vtc = 1.7 = V1 = A1cup*h1

h1 = 1.7/A1cup = 1.7/2.25 = 0.755 inches, is the height of the exhaust valve at TC.

Assuming the squish lands are flush with the base of the cylinder head, and the cylinder head has a clearance “dsc” of 0.06" with the piston (and the squish-lands), then for the same CR have to add the clearance volume V3, and reduce the main volume V21 by the same amount.

V3 = 0.06*A = 0.06 * 9.62 = 0.577

V21 = Vtc – V3 = 1.7 – 0.577 = 1.123

h11 = h1*V21/Vtc = 0.755*1.123/1.7 = 0.50 inches

Specifications of the Holy Grail Engine [2-2-2-2-2-2 or 26].

The Holy Grail Engine has the following features.

It is a 2-cylinder engine, with 2-valves and 2-plugs, based on the 2-Stroke ICS engine, having symmetrically placed, 2-squich lands, and 2-intakes, with an 18 to 1 expansion ratio (ER) for a high efficiency and approximately 10.5 to 1 compression ratio (CR) for high power, with a scavenging duration of approximately 100º ending at about 75º ABC.

It has an electrical supercharger connected to the intake to maintain the intake air-flow at just above 1 atmosphere.

The engine has two unique, highly proprietary Halo-Disc Spark Plugs, and two highly proprietary CEI high-energy coils per cylinder which are described in the button Ignition of the website.

The Halo-Disc Plug is a highly proprietary slim-line, long life plug, with the following additional features: it has about 40 pf of capacitance; large circular spark gaps of 0.60 to 0.80 inches; unique, firing ends with concave ceramic ends which serves several functions, including keeping the plug cool; and other features.

It has two squish-lands per cylinder and an intake valve which produces squish near TC.

It has an electronic fuel injector per cylinder.

The fuel turns on at the end of the scavenging period, at approximately 75º ABC.

The fuel injector introduces fuel to the cylinder by electronically controlling the spray, at a moderate pressure.

The engine has two intakes to be added later:

1. A carefully designed warm intake for cold-start of the engine.

2. A cold intake for high power.

The engine has a single-overhead cam and simple, direct drive buckets to actuate the valves.

A single cam profile operates both valves [the intake and exhaust valve].

The cam timing can vary relative to the crank (producing a phase shift when needed), but the simplicity of the system is retained, i.e. buckets are used which actuate the valves directly.

The Holy Grail Engine will be inexpensive to build despite having a fuel injector per cylinder and a small electrical supercharger at the intakes, because it has only two valves per cylinder and they have vertical orientations, and it has a single overhead cam with simple, inexpensive buckets to actuate the valves.

The ignition voltage is 42 volts, which is created from a proprietary CEI high efficiency, low cost, DC-DC converter (14 to 42 volt boost converter), which can also be used to drive the small, supercharger(s) and the fuel injectors.

The ignition requires its peak power at different times for the supercharger, the fuel injectors, and the ignition.

Assuming a standard 4-stroke engine is compared to the Lean Burn Holy Grail Engine running on CH4.

Standard Engine: CH4 + 2O2 = CO2 + 2H2O + U, where U is a unit of energy,

Holy Grail Engine: CH4 + 3O2 = CO2 + 2H2O + O2 + 2.5U

by running an ultra-lean mixture, and remembering that the engine is a perfect two stroke. The leanness factor and the high expansion ratio (ER) give the engine a 50% better efficiency, and the two stroke factor gives the engine twice the power.

Normalizing to the same energy (power) output and total input, the relation for the Holy Grail Engine becomes:

0.4*CH4 + 1.6*O2 + 1.0*O2 = 0.4*CO2 + 0.8*H2O + 0.8*O2 + 1.0*O2 + U,

and the mixture is ultra-lean (0.8*O2) and stratified charge, with an air-cushion on the outside (1.0*O2) which reduces heat transfer to the cylinder walls, further increasing efficiency.

Note that gasoline, or ethanol or other difficult-to-ignite fuels (such as low BTU fuels) may be used as fuels which will be able to be ignited by the highly proprietary, CEI type, super high-energy ignition system, with Halo-Disc plugs.

For short periods, e.g. cold-start, sparking energy as high as 1,000 mj may be available for ignition (500 mj from each plug) at a RPM, for example, of 1,500 RPM, far a period of time of, for example, one minute.