8 hours ago, sethoflagos said:

Worth noting that from WWII to the early '50s the British public didn't have access to anything above 70 octane. Consequently production vehicles were built with low compression ratios. Hence the first family car I remember (1960-61ish) a hand cranked A30, would have had a compression ratio of about 7:1.

Indeed, in fact 7.5:1 according to Wiki, with the original 803cc version. : https://en.wikipedia.org/wiki/BMC_A-series_engine

By the time my Minor was built it was 948cc and a compression ratio of 8.3:1, eventually raised further to 8.8:1 by the time of the 1275cc version in the go-faster Minis, in the 1970s. It seems that, after the revamp to the A+ the same basic engine continued until 2000, by which time the compression ratio was 10.1:1. Power output was originally 28hp and in the final version was up to 76hp. Quite an evolution.

But I think one does tend to get this with IC engines. The 16SVT in the Class 40 diesel locomotive was rated at 2000hp, 2700 in the Class 50 (with intercooling) and in the much later Class 56, 3250hp. I've seen similar progressions with marine diesels. It seems because a new engine is such a big investment, the basic fixed components like the block are often generously designed to allow a lot of subsequent development.

Interestingly this a a little extra I did just learn from Wikipedia.

I had thought the industrial problems of both Austin and Morris did start untill the 1960s but apparantly it went back a lot further and even affected the war effor when morris were attempting to build spitfires.

In 1935, the Air Ministry approached Morris Motors Limited to ask how quickly their Cowley plant could be turned to aircraft production. In 1936, this informal request for major manufacturing facilities was replaced by a formal scheme, known as the shadow factory plan, to boost British aircraft production capacity under the leadership of Herbert Austin. He was given the task of building nine new factories, and to supplement the British car-manufacturing industry by either adding to overall capacity or increasing the potential for reorganisation to produce aircraft and their engines.^[34]

In 1938, construction began on the Castle Bromwich Aircraft Factory (CBAF), next to the aerodrome, and the installation of the most modern machine tools then available began two months after work started on the site.^[32] Although Morris Motors, under Lord Nuffield, who was an expert in mass motor-vehicle construction, managed and equipped the factory, it was funded by the government. By the beginning of 1939, the factory's original estimated cost of £2,000,000 had more than doubled,^[35] and even as the first Spitfires were being built in June 1940, the factory was still incomplete, and suffering from personnel problems. The Spitfire's stressed-skin construction required precision engineering skills and techniques that were beyond the capabilities of the local labour force, and some time was required to retrain them. Difficulties arose with management, who ignored Supermarine's tooling and drawings in favour of their own, and the workforce continually threatened strikes or "slow downs" until their demands for higher wages were met.^[36]

https://en.wikipedia.org/wiki/Supermarine_Spitfire

10 hours ago, TheVat said:

Heck, if the octane were much lower it would be halfway to being diesel.

Good call. It was basically straight kerosene.

Urkh! If so, the heavy end traces would foul the engine.

6 hours ago, studiot said:

Interestingly this a a little extra I did just learn from Wikipedia.

I had thought the industrial problems of both Austin and Morris did start untill the 1960s but apparantly it went back a lot further and even affected the war effor when morris were attempting to build spitfires.

https://en.wikipedia.org/wiki/Supermarine_Spitfire

I remember my grandad telling me that, to get around the scarcity of engineering skills needed for the war effort, everything was jigged where possible. This cut out a lot of the learning time needed to manufacture parts from the ground up, which was the norm then. He joined the RAF in 1936 as an airframe and engine apprentice.

Edited April 20Apr 20 by StringJunky

2 hours ago, TheVat said:

Urkh! If so, the heavy end traces would foul the engine.

Paraffinic heavy ends would resemble light luboil, so I’m not sure it would be that much of a problem. After all, diesel engines are built to a very similar design and don’t get gunged up. But there could be trouble with the carburettor, I’d have thought, with atomisation of the fuel.

1 hour ago, StringJunky said:

I remember my grandad telling me that, to get around the scarcity of engineering skills needed for the war effort, everything was jigged where possible. This cut out a lot of the learning time needed to manufacture parts from the ground up, which was the norm then. He joined the RAF in 1936 as an airframe and engine apprentice.

This is why the Mosquito was such an innovative aircraft, it did not require anywhere near so much highly developed skill or specialist machinery to make.
Indeed many furniture makers were redirected to manufacture large parts of the airframe.

6 hours ago, exchemist said:

Paraffinic heavy ends would resemble light luboil, so I’m not sure it would be that much of a problem. After all, diesel engines are built to a very similar design and don’t get gunged up. But there could be trouble with the carburettor, I’d have thought, with atomisation of the fuel.

Thanks, yes my vague reference to "foul the engine" - you have the specific problem pinpointed. I would guess it would need preheating and then much higher injection pressure to vaporize properly. Carb wouldn't do it.

Enjoying a thread where we seem to have a couple members like you who have some pro knowledge in this area. All I have, like @StringJunky , is a grandfather who really knew engines. But that was something.

8 hours ago, TheVat said:

Thanks, yes my vague reference to "foul the engine" - you have the specific problem pinpointed. I would guess it would need preheating and then much higher injection pressure to vaporize properly. Carb wouldn't do it.

Enjoying a thread where we seem to have a couple members like you who have some pro knowledge in this area. All I have, like @StringJunky , is a grandfather who really knew engines. But that was something.

I think it may be more to do with droplet size. My understanding is that carburettors atomise the fuel into a fine mist rather than necessarily converting all it to vapour. But for sure the heavy ends have quite a low vapour pressure so won't evaporate quickly and may start to coat the sides of the inlet manifold, for instance. (It is noticeable how messy the ground can get at filling station fuel pumps that dispense diesel fuel. Any spills hang about instead of evaporating.)

7 hours ago, exchemist said:

I think it may be more to do with droplet size. My understanding is that carburettors atomise the fuel into a fine mist rather than necessarily converting all it to vapour. But for sure the heavy ends have quite a low vapour pressure so won't evaporate quickly and may start to coat the sides of the inlet manifold, for instance. (It is noticeable how messy the ground can get at filling station fuel pumps that dispense diesel fuel. Any spills hang about instead of evaporating.)

Could it be down to the use of SU carburettors on most British cars of the time? There seems to be a suggestion that the piston/metering needle principle design they used may have simply been better at creating a fine aerosol out of dodgy fuel like wartime 'pool petrol' across a broad range of operation than the fixed venturi carburettors used elsewhere. It was certainly widely copied in later years.

SU carburettors feature a variable venturi controlled by a sliding piston type air valve. This piston/air valve has a tapered, conical metering rod attached to it (usually referred to as a "needle") that fits inside an orifice ("jet") which admits fuel into the airstream passing through the carburettor.[20] Since the needle is tapered, as it rises and falls it alters the open area of the fuel jet, regulating the passage of fuel, so the movement of the piston controls the amount of fuel delivered, depending on engine demand. The exact dimensions of the taper are tailored during engine development.

The flow of air through the venturi creates a reduced static pressure in the venturi. This pressure drop is communicated to the upper side of the piston via an air passage. The underside of the piston is open to atmospheric pressure. The difference in pressure between the two sides lifts the piston. Opposing this are the weight of the piston and the force of a spring that is compressed by the piston rising. Because the spring is operating over a very small part of its possible range of extension, its force is approximately constant. Under steady state conditions the upwards and downwards forces on the piston are equal and opposite, and the piston does not move.

If the airflow into the engine is increased - by opening the throttle plate (also known as the "butterfly"), or by allowing the engine revs to rise with the throttle plate at a constant setting - the pressure drop in the venturi increases, the pressure above the piston falls, and the piston is pushed upwards, increasing the size of the venturi, until the pressure drop in the venturi returns to its nominal level. Similarly if the airflow into the engine is reduced, the piston will fall. The result is that the pressure drop in the venturi remains the same regardless of the speed of the airflow - hence the name "constant depression" for carburettors operating on this principle - but the piston rises and falls according to the rate of air delivery.

Since the position of the piston controls the position of the needle in the jet and thus the open area of the jet, while the depression in the venturi sucking fuel out of the jet remains constant, the rate of fuel delivery is always a definite function of the rate of air delivery. The precise nature of the function is determined by the profile of the needle. With appropriate selection of the needle, the fuel delivery can be matched much more closely to the demands of the engine than is possible with the more common fixed-venturi carburettor, an inherently inaccurate device whose design must incorporate many complex fudges to obtain usable accuracy of fuelling. The well-controlled conditions under which the jet is operating also make it possible to obtain good and consistent atomisation of the fuel under all operating conditions.

Edited April 21Apr 21 by sethoflagos
sp

41 minutes ago, sethoflagos said:

Could it be down to the use of SU carburettors on most British cars of the time? There seems to be a suggestion that the piston/metering needle principle design they used may have simply been better at creating a fine aerosol out of dodgy fuel like wartime 'pool petrol' across a broad range of operation than the fixed venturi carburettors used elsewhere. It was certainly widely copied in later years.

I think a post of mine three days ago, in which I directed some fulsome praise at Skinners Union (briefly owned a 1971 Datsun with an SU carb) for their VV carbs, never posted. A couple other members have mentioned this disappearing posts effect, so I will exercise caution. The fuel efficiency (in addition to its fuel flexibility) and ease of tuning made them simply elegant.

My retro dream car has an SU carb(s). If it's an old VW bug, then it's added on aftermarket. And works with E10.

53 minutes ago, sethoflagos said:

Could it be down to the use of SU carburettors on most British cars of the time? There seems to be a suggestion that the piston/metering needle principle design they used may have simply been better at creating a fine aerosol out of dodgy fuel like wartime 'pool petrol' across a broad range of operation than the fixed venturi carburettors used elsewhere. It was certainly widely copied in later years.

Possibly, though I’m not sure why it would be an advantage. But yes I remember dismantling and tuning SU carburettors - and also the solenoid diaphragm fuel pump. The Minor used to stall towards the top of a steep hill going out of Oxford, which I eventually traced to fuel starvation. New contacts in the pump for £1.50 and a couple of hours fiddling solved the issue.

TIL that rainforests do not provide 20% of our atmospheric oxygen, as is popularly believed. They are important ecosystems but they are not "the lungs of the world."

There is a misconception that the rainforests contribute significantly to the oxygen we breathe. In reality, the animals and microscopic life living in the rainforest consume most of the oxygen. As a result, the net production of oxygen by the rainforest or any forest is actually close to zero. The commonly reported figure of the rainforests contributing 20% of the Earth’s oxygen supply is definitely a misrepresentation.

https://newportbay.org/ask-a-naturalist-do-phytoplankton-produce-more-oxygen-than-a-rainforest-if-so-does-the-oxygen-they-produce-go-into-the-atmosphere-or-does-it-just-remain-dissolved-in-the-ocean/

So where does most of it come from? 50-80% (depending on the season) from phytoplankton. And 20% of ocean oxygen is from one species, prochlorococcus.

Prochlorococcus produces vast amounts of oxygen, but rising ocean temperatures are predicted to cause sharp declines in its productivity.

Warming waters could impact the fundamentals of life in the ocean.

New research has looked at the impact of higher ocean temperatures of Prochlorococcus, a bacteria which carries out as much as 5% of all the world’s photosynthesis. As a result, it’s responsible for as much as 20% of oxygen in the oceans, and plays key roles in the cycle of other nutrients and minerals.

https://www.nhm.ac.uk/discover/news/2025/september/climate-change-threatens-major-oxygen-producing-bacteria.html

Belated happy Earth Day! And take care of your oceans, puny humans!

9 hours ago, TheVat said:

Belated happy Earth Day! And take care of your oceans, puny humans!

+1

But remember it is not the whole ocean that supports these organisms, only the very top layer and only over parts of the ocean surface.

9 hours ago, TheVat said:

So where does most of it come from? 50-80% (depending on the season) from phytoplankton. And 20% of ocean oxygen is from one species, prochlorococcus.

There is a story that back in the early days of WW2 when mathematicians, linguists, crossword solvers and academics of every type were being hurriedly recruited in great secrecy and sent off to Bletchley Park to become Enigma code-breakers under the leadership of Alan Turing -  that one new recruit called Geoffrey Tandy turned out to be a marine biologist who specialised in the study of cyanobacteria, a family of which Prochlorococcus  is a member.

https://en.wikipedia.org/wiki/Geoffrey_Tandy

Some Bletchley staff were were still uncertain why he had been recruited into the Enigma program until they rechecked his file card and found he was listed as an authority on ‘Cryptogams’ - (from Ancient Greek κρυπτός (kruptós) 'hidden' and γαμέω (gaméō) 'to marry') meaning "hidden reproduction”) - a more general scientific name for these photosynthetic organisms

Fortunately he turned out to be quite good at solving cryptograms as well, and spent the rest of the war as a code-breaker.

Other sources say that while Tandy did indeed work at Bletchley Park, he wasn’t actually recruited by mistake.

Today I learned about alpha-gal syndrome, a potentially life-threatening allergy to mammalian products such as meat and milk, acquired from tick bites. Specifically, it is an allergy to the epitope of the carbohydrate molecule galactose-alpha-1,3-galactose ("alpha-gal"). According to the Wikipedia article, the alpha-gal molecule is naturally found in the bodies of all mammal species except catarrhines (apes and Old World monkeys), the taxonomic branch that includes humans. Alpha-gal can also be found in the saliva of insects including certain tick species. It is through the saliva of tick bites that humans can become sensitised to alpha-gal, a substance foreign to humans, and therefore become sensitised to mammalian products. Alpha-gal is also present in many manufactured products, including medication and medical products.

Edited 6 hours ago6 hr by KJW