There are some snippets from Friedman's British Submarines in Two World Wars.
As you noted in your quote in the first post above. Vickers had difficulty with engine-driven air compressors for fuel injection so used solid injection instead. The main side effect of this was very smoky exhaust products which led to Vickers abandoning solid injection until the late 1930s, yet other nations had returned to solid injection as the RN abandoned it. Vickers claimed a more compact engine as a result.
Most British diesels tended to be four-stroke, although by the 1920s it was recognised that a two-stroke engine was more suited to obtaining high surface speeds. And running diesels at high speed resulted in torsional vibrations as they reached the critical speed limit of the engine which resulted in damage - this problem blighting the X1 submarine. The USN would overcome this by moving to diesel-electric drives.
HMS A13 was the first submarine to receive a diesel in 1906. The engine was a Hornsby-Ackroyd design (not a diesel but a heavy-oil engine with hot bulb rather than injection), the company having produced a 125bhp single-cylinder which was scaled up into a 4-cyl 600bhp engine and they offered Vickers production rights. In the event the engine needed to be rebuilt following its first running, rpm was reduced in June 1905 but it never produced more than 400bhp and ended up being used in a power station in Simonstown. Vickers guaranteed 500bhp from its engine designed at Barrow in October 1905, but that guarantee proved impossible and even after rebuilding it only managed 450bhp. Serious defects in March 1907 delayed the trials in A13 for trials until August, it was generally successful apart from the compressor injection. [rated at 500bhp at 380rpm, 13 x 14in cylinders, 81lb/bhp]
HMS D1 was to use two 600bhp engines but Vickers designed a new engine, design approved in June 1907 but not ready until early 1909. Vickers could not guarantee 1,200bhp but hoped for 900bhp. Following the problems with the air compressor Vickers began experimenting with solid injection in 1910, patented in November 1911 and fitted to D2 but failing. One engine for D5 was tested for 6 hours in a shop test and one engine of both compressor and solid injection were fitted to D6 for comparative trials. The solid engine was 2 tons lighter, more reliable but did produce more smoke. But the success achieved by early 1913 saw it used on the E-class.
The desire to solve the problem saw Engineer Lieutenant Floyd Rabbidge being ordered by the EinC to join Vickers, becoming in time their head of diesel development in May 1913. Rabbidge began to redesign the fuel injector nozzle (Vickers had previously focused on the injection pressure) which solved the tendancy for the injectors to deliver different qautities of fuel into different cylinders so improving the efficiency (200nm more radius achieved on E9) and reducing vibration. The exhaust was still smoky though. Thereafter the war stopped further work on nozzles for larger engines so Vickers resorted to adding cylinders rather than enlarging them when more power was required - resulting in a 12-cyl 1,200bhp engine (used on the F and L-classes) and a smaller 8-cyl 450bhp engine (H and R-classes). D'Enycourt at one point proposed a modified 12-cyl engine with lightweight cylinders for 1,600bhp for the L-class but this went no further. But smoky exhausts proved a problem throughout the war and enabled submarines to be easily spotted.
These early problems saw the two-cycle MAN and Sulzer engines as well as the Carels being considered for the E-class, four did receive the Carels but it was unsuccessful and replaced by Vickers engines. The F2 had MAN diesels built by Whites. Denny had offered the Sulzer which was 4 tons lighter than the Vickers engine and was using Burmeister & Wain engines for submarines it was building in the Netherlands. The G-class would also have used Sulzer and MAN engines had the war not intervened, G14 received FIAT engines and the cancelled G16 would also have had White-built MANs. The Fiat diesels were a failure. To some extent all these problems with diesels (smoke, vibration and supply) influenced the decision for steam submarines. After 1918 the comparisons with the more reliable and smooth-running German diesels and their superior engine mountings to the hull showed even more starkly how far the 1914 Vickers design had falled.
In response to these shortcomings the Admiralty in 1917 formed the Admiralty Engineering Laboratory (AEL) with the aim of developing lighter and more powerful engines. It soon experimented with double-acting and two-stroke engines but without immediate success and it fell back to the four-cycle engine with an air compressor. In September 1917 a Vickers cylinder was set up by Ruston & Hornsby and AEL began increasing the pressure and engine speed - fitting aluminium pistons. AEL also seems to have published Vickers work much to the firm's chargrin. AEL's aim was to match the latest 10-cyl 3,000bhp engine.
A single test cylinder, the 100bhp 'Digit' running at 300rpm with a 20in bore and stroke ran in November 1919. The resulting 10-cyl 21.5in bore & stroke 3,000bhp was selected for X1 over propsals from other British firms as well as MAN and Sulzer, the EinC declaring it the best for size and weight. Bench tests were completed in May 1923.
In the meantime the EinC had ordered a two-stroke test cylinder of 1,000bhp. There was some arguement that the 6,000bhp Sulzer was superior but it was pointed that if it powered its own auxiliaries the power dropped to 4,800bhp.
In the end the engine as fitted to X1 was a failure due to vibration. The four-stroke 6-cyl 1,350bhp at 400rpm with 18.5in bore & stroke engine fitted to the Oberon-class were not much better, being de-rated in 1936 to 1,160bhp due to piston seizures. The Australian Ottway-class had a 1,500hp development with 19.25in bore and stroke but after severe problems they were removed.
Further developments were better; a 2,200bhp with 20in bore & stroke for later O's, an enlarged 10-cyl 4,000bhp at 350 rpm with 21in bore & stroke for the River-class (later supercharged to 5,000bhp), 6-cyl 1,650bhp at 400rpm with 20in bore & stroke for the minelayer submarines.
A closed-cycle diesel had been proposed in 1924 but rejected, resurrected in 1926 due to rumours of such engines in Germany (for Japan) and America, again dying until rumours of the German Erren engine emerged in 1936 - taking the Admiralty 2 years to realise that the Erren engine was useless. But in 1939 a closed-cycle engine using bottled oxygen and carbon dioxide or an oxygen, carbon dioxide, argon mixture with a research contract awarded to Ricardo. The outbreak of war stopped further work.
A lengthy history but it shows that development was tricky even post-war and that Vickers had problems with injection methods and injector valves right up to mid-1914 so it seems that larger engines would have been affected too, the emphasis going to the submarine engine and the results being less than stellar.
