The TR2 is a modern engine design and being twin cylinder the bores are smaller so burn more efficiently , this means that it will run at part load without any issues.

smaller bores more efficient?

Load of tosh.

The relationship between swept and head volume and swept and head surface area is not linear.

Volume of a cylinder is piR2H

Area of the sides of a cylinder is 2piRH

Area of the flat piston top is piR2

Area of hemi head is 2piR2

Let's take a 10 cm bore and 12 cm stroke

Swept volume is 3.14 x 5 x 5 x 12 = 942

Swept area is 2 x 3.14 x 5 x 12 = 376.8

942 / 376.8 = 2.5:1 volume to area ratio

Lets take a 5 cm bore and 6 cm stroke

Swept volume is 3.14 x 2.5 x 2.5 x 6 = 117.75

Swept area is 2 x 3.14 x 2.5 x 6 = 94.2

117.75 / 94.2 = 1.25:1 volume to area ratio

Plus, the smaller bore with a smaller swept volume will require 942 / 117.75 = 8 cylinders to develop the same swept volume.

So you can have your smaller bore with far lower swept volume to swept area ratio, far higher piston ring / liner friction length, far more journal friction, and you think this is somehow going to be more efficient than the larger bore.

Never, not as long as you have a hole in your ass.

The ONE advantage of the smaller bore as in this example is your 8 cylinder engine COULD be made, not WILL, but COULD be made with lower total piston and con rod weight than the big single of the same swept capacity.

The ONE advantage this gives you is you can rev the tits off it, pump more air in any given unit of time, thus burn more fuel, this achieve higher specific BHP, this WILL NOT equate to greater efficiency.

Even at partial load, a worst case scenario, the big single will hammer the 8 cylinder engine working at peak efficiency, when it comes to efficiency alone.

Small bore engines NEVER beat big bore engines of the same capacity and similar design for efficiency, to claim otherwise is to simply ignore Physics and invoke greater than unity efficiency or zero point energy of some other bollocks.

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forgot to do this sum.

big single 10cm bore x 12 cm stroke = 8 cyl 5cm bore x 6cm stroke in swept volume.

quite apart from area losses.

PiD = length of a circle, eg piston ring.

Single has one 3.14 x 10 = 31.4 cm length of top scraper ring

8 cyl has 8 x 3.14 x 5 = 125.6 cm length of all 8 top scraper rings

repeat and rinse for all rings, then add 10% frction due to extra losses in a small bore vs big bore engine, small bores start to burn oil at low hours...