Octane rating

[PaxMondo]

ORIGINAL: witpqs

ORIGINAL: PaxMondo

Bill's answer is about as good as you can get without going into some pretty deep science. 

This is all off the top of my head, so apologize for any inconsistencies.  Octane numbers are a bit arcane.  First off it is a scale, it doesn't relate to reality.  100 Octane meant 100% N-Octane back in 1910 or so, so going over a 100 is kinda hard to understand.  It is all about anti-knock.   Then there are two ways to calculate this, research and motor (RON and MON).  The europeans and americans use a differently weighted average of the two to establish their scale.  Then, and even more importantly, is that how octane was boosted in the 40's isn't how it is done today.  Then it was about alkylation and so the octane boost was coming from n-nonane and n-decane type fuels.  Now, it comes from FCC and that gives you alkylenes like benzene and toluene to boost the fuel.  The amounts required to boost are different and how the impact cylinder temps are different.  They also behave quite differently under temperature and pressure as their partial pressure are different.

But a lot of this isn't as important as it seems.  Once you bring methanol/water injection into play octane become less of a factor.  Still a factor, yes, but less than you think.  Let's look at the chemistry and the mechanics here.  Engines are all about gas expansion forcing a piston to move down a cylinder and turn a crankshaft.  Igniting gas is good for about a 38x factor of expansion, not counting temperature effects.  That's awful good.  Water though is good for 18x.  The nice thing about water is that it take heat to move to steam, and this is how water injection works.  You start with an engine that is running too hot, you inject water to cool it and you actually get MORE power from it as the water expands into steam.  This works really well with radial air cooled cylinders as they are all more or less the same.  With in line water engines, you always struggle to get in inside cylinders as opposed the outside (on a V8 this would be 2,3,6,7 against 1,4,5,8) to be the same temperature.  The downside to water is that it is incredibly corrosive and impurities are very dangerous to metals (like chlorine and sodium as in salt).  Now add on superchargers and/or turbochargers (twinchargers) and again you get more complex.  On top of all of this is that in the 40's all they had was analog controllers. 

By wars' end the germans (extensively) and the IJ (Dinah and some other models) were using water/methanol.  This, when coupled with charging systems, mitigates the octane issue.

When you say water/methanol, do you mean that the entire fuel was water/methanol, or that water/methanol was added to the avgas?

Injected separately from the avgas. 10 - 25% are typical proportions depending upon a host of things, including altitude.

[Historiker]

100 Octane gas was introduced to German gas stations a few years ago. So far, we only had 92, 95 and 98 (IIRC, the use of "Normal", "Super", "Super+" is common, not the octane rating).
They tested the "V-Power" 100 Octane fuel in sport cars to find out whether the significantly higher price is justified. Their finding was, that in modern car engines - of course - the increase in performance is neglible.

[JohnDillworth]

They tested the "V-Power" 100 Octane fuel in sport cars to find out whether the significantly higher price is justified. Their finding was, that in modern car engines - of course - the increase in performance is neglible.

I understand that formulations are different in the US depending on which part of the country you are in. Don't know the science but in the Mountain and Western states octane ratings are generally lower. Near racetracks you can but higher octanes. You can also buy 100 Octane in the Northest and Shell or Sunoco. They call it V-tech or something but it's a significant bump in price over the normal 93 octane premium so I never tried it. My car takes premium (93) since petrol is so expensive every other tank I but a medium grade (89). I don't hear any knocking, and the performance is about the same. I think I get slightly better mileage with the higher octane but I never really quantified it. The large majority of cars in the US have automatic transmissions. I have a 6 speed manual that allows you to either conserve gas (manual transmissions get about 3 MPG better mileage) or drive like a complete ass, so my mileage is more affected by mode than octane. Might be true of pilots too. I understand the range of the same aircraft could vary significantly by pilot. I believe Lindburg spent some time training pilots in how to conserve gas but I can't find the reference.

[crsutton]

ORIGINAL: PaxMondo

Bill's answer is about as good as you can get without going into some pretty deep science. 

This is all off the top of my head, so apologize for any inconsistencies.  Octane numbers are a bit arcane.  First off it is a scale, it doesn't relate to reality.  100 Octane meant 100% N-Octane back in 1910 or so, so going over a 100 is kinda hard to understand.  It is all about anti-knock.   Then there are two ways to calculate this, research and motor (RON and MON).  The europeans and americans use a differently weighted average of the two to establish their scale.  Then, and even more importantly, is that how octane was boosted in the 40's isn't how it is done today.  Then it was about alkylation and so the octane boost was coming from n-nonane and n-decane type fuels.  Now, it comes from FCC and that gives you alkylenes like benzene and toluene to boost the fuel.  The amounts required to boost are different and how the impact cylinder temps are different.  They also behave quite differently under temperature and pressure as their partial pressure are different.

But a lot of this isn't as important as it seems.  Once you bring methanol/water injection into play octane become less of a factor.  Still a factor, yes, but less than you think.  Let's look at the chemistry and the mechanics here.  Engines are all about gas expansion forcing a piston to move down a cylinder and turn a crankshaft.  Igniting gas is good for about a 38x factor of expansion, not counting temperature effects.  That's awful good.  Water though is good for 18x.  The nice thing about water is that it take heat to move to steam, and this is how water injection works.  You start with an engine that is running too hot, you inject water to cool it and you actually get MORE power from it as the water expands into steam.  This works really well with radial air cooled cylinders as they are all more or less the same.  With in line water engines, you always struggle to get in inside cylinders as opposed the outside (on a V8 this would be 2,3,6,7 against 1,4,5,8) to be the same temperature.  The downside to water is that it is incredibly corrosive and impurities are very dangerous to metals (like chlorine and sodium as in salt).  Now add on superchargers and/or turbochargers (twinchargers) and again you get more complex.  On top of all of this is that in the 40's all they had was analog controllers. 

By wars' end the germans (extensively) and the IJ (Dinah and some other models) were using water/methanol.  This, when coupled with charging systems, mitigates the octane issue.

Now head hurt very bad.....[;)]

But it was not just octane was it? If I recall, Japanese refining methods left a lot of impurities in their fuel as well. This would serve to degrade performance over time. And time in service. A new engine out of the box would work a lot better than one that had some hours operating on less than ideal fuel. So any plane with a new engine would be different from an engine that had 50 hours of time using a poor quality fuel. Too many factors really. All things considered, an Allied engine with a little time on it was probably in much better shape than a Japanese engine with the same amount of time. Then there is lube oil. Allies probably had better qualty in this as well but I am just spectulating.

[JohnDillworth]

Allies probably had better qualty in this as well but I am just speculating.

It goes to maintenance in general. The US was just better at providing the support and structure for maintaining complex machines. I've read that the US had a ton of kids that were used to tinkering with farm machinery when they were called up. Internal combustion engines were not unusual for them so the transition into a more complex engine maintenance was not that far of a leap. It was probably true for all engineering disciplines from aircraft mechanic to SeaBee. Education was highly regarded at the time and not at the expense of blue collar skills. This may have also been true in Germany, Australia and England but perhaps not so much in Japan. No doubt Japan had some excellent mechanics with the very best being on the CV's that were the equal of the Allies, after that it may have dropped off. Combine that with a disrupted supply chain, inter-service stupidity, sometimes poor fuel, some malnutrition and a fundamental disregard for human lives and you have an increasingly separate situation

[Sardaukar]

IIRC, higher octane fuel really helped with high-altitude fighter missions in Europe (planes like P-47 and P-51). Combat flying is lot more about raw power in higher altitudes where German planes were not that stellar (Ok, maybe Ta-152).

[Gridley380]

ORIGINAL: JohnDillworth

It goes to maintenance in general. The US was just better at providing the support and structure for maintaining complex machines. I've read that the US had a ton of kids that were used to tinkering with farm machinery when they were called up. Internal combustion engines were not unusual for them so the transition into a more complex engine maintenance was not that far of a leap. It was probably true for all engineering disciplines from aircraft mechanic to SeaBee. Education was highly regarded at the time and not at the expense of blue collar skills. This may have also been true in Germany, Australia and England but perhaps not so much in Japan. No doubt Japan had some excellent mechanics with the very best being on the CV's that were the equal of the Allies, after that it may have dropped off. Combine that with a disrupted supply chain, inter-service stupidity, sometimes poor fuel, some malnutrition and a fundamental disregard for human lives and you have an increasingly separate situation

All true. The Japanese were able to mitigate this early on by providing lavish training for a very small force. When they tried to rapidly expand their quality dropped sharply.

[JWE]

Well, here's a good one for our technical experts to comment on in this regard.

Forget who it was, but somebody taught the boys at Taiwan to fly reeeally leeean so they could get to PI and still have a couple minutes of combat power. As I recall, they were at cylinder temp red-line tho whole way. Maybe one of our experts could comment on how this was done. Maybe one of our experts could comment on what would have happened with a plane designed for a higher octane fuel and a higher head temperature. Could our planes have gone lean and gotten that much better range characteristics?

[crsutton]

ORIGINAL: Gridley380

ORIGINAL: JohnDillworth

It goes to maintenance in general. The US was just better at providing the support and structure for maintaining complex machines. I've read that the US had a ton of kids that were used to tinkering with farm machinery when they were called up. Internal combustion engines were not unusual for them so the transition into a more complex engine maintenance was not that far of a leap. It was probably true for all engineering disciplines from aircraft mechanic to SeaBee. Education was highly regarded at the time and not at the expense of blue collar skills. This may have also been true in Germany, Australia and England but perhaps not so much in Japan. No doubt Japan had some excellent mechanics with the very best being on the CV's that were the equal of the Allies, after that it may have dropped off. Combine that with a disrupted supply chain, inter-service stupidity, sometimes poor fuel, some malnutrition and a fundamental disregard for human lives and you have an increasingly separate situation

All true. The Japanese were able to mitigate this early on by providing lavish training for a very small force. When they tried to rapidly expand their quality dropped sharply.

Well, this plus the fact that only a small proportion of the Japanese population had been educated up to the high school level. Many rural Japanese's (the majority) education did not go beyond grammar school level. You can make a good soldier out of this material but not necessarily a good mechanic.

[inqistor]

ORIGINAL: JohnDillworth

Does anyone know the average octane ratings that were available to the Allies and Japan?

"Allies" is WIDE expression. Russian military policy, since WWII is to allow vehicles to operate on captured fuel, so their planes can operate on pretty crappy AVGAS. Now, what was actually used by China, while they operated planes from both US, and Russia?

Also - some interesting facts:
Germany used Synthetic Fuel. The further into war, the more % of total usage was made from coal. And it produced BETTER quality AVGAS, than oil.
As for Japan:
Take a look at my old topic about D3A2 range. Here is exact cite from this page:

This is from Aircraft in Profile #240 "Aichi D3A ('Val') & Yokosuka D4Y ('Judy') Carrier Bombers of the IJNAF (M. C. Richards and Donald S. Smith):
Fuel Capacity of D3A
"Internal 1,079 liters (235 Imperial gallons) in five unprotected tanks; two in each wing, one under pilot's seat, all containing 92 octane petrol. In starboard wing root, a small fuel tank (100 octane) for take of; 58 liter (25.8 Imperial gal.). One 60 liter (13.2 Imp.gal.) oil tank behind the engine."

Was 92 Octane standard for Japan, or only used on Carriers?

[inqistor]

ORIGINAL: JohnDillworth

Allies probably had better qualty in this as well but I am just speculating.

It goes to maintenance in general. The US was just better at providing the support and structure for maintaining complex machines. I've read that the US had a ton of kids that were used to tinkering with farm machinery when they were called up. Internal combustion engines were not unusual for them so the transition into a more complex engine maintenance was not that far of a leap. It was probably true for all engineering disciplines from aircraft mechanic to SeaBee. Education was highly regarded at the time and not at the expense of blue collar skills. This may have also been true in Germany, Australia and England but perhaps not so much in Japan. No doubt Japan had some excellent mechanics with the very best being on the CV's that were the equal of the Allies, after that it may have dropped off. Combine that with a disrupted supply chain, inter-service stupidity, sometimes poor fuel, some malnutrition and a fundamental disregard for human lives and you have an increasingly separate situation

Another fun fact:
Since 1944, there was no maintenance of planes on Japanese Carriers (no specialized crew onboard). They were supposed to be serviced only, when ships reached port.

[Historiker]

ORIGINAL: inqistor

ORIGINAL: JohnDillworth

Allies probably had better qualty in this as well but I am just speculating.

It goes to maintenance in general. The US was just better at providing the support and structure for maintaining complex machines. I've read that the US had a ton of kids that were used to tinkering with farm machinery when they were called up. Internal combustion engines were not unusual for them so the transition into a more complex engine maintenance was not that far of a leap. It was probably true for all engineering disciplines from aircraft mechanic to SeaBee. Education was highly regarded at the time and not at the expense of blue collar skills. This may have also been true in Germany, Australia and England but perhaps not so much in Japan. No doubt Japan had some excellent mechanics with the very best being on the CV's that were the equal of the Allies, after that it may have dropped off. Combine that with a disrupted supply chain, inter-service stupidity, sometimes poor fuel, some malnutrition and a fundamental disregard for human lives and you have an increasingly separate situation

Another fun fact:
Since 1944, there was no maintenance of planes on Japanese Carriers (no specialized crew onboard). They were supposed to be serviced only, when ships reached port.

Can you give me a source for that?

[inqistor]

ORIGINAL: Historiker

ORIGINAL: inqistor

Another fun fact:
Since 1944, there was no maintenance of planes on Japanese Carriers (no specialized crew onboard). They were supposed to be serviced only, when ships reached port.

Can you give me a source for that?

I am pretty sure it was in one of documents about Japanese Carriers, but I have lots of it, and hard to guess which one.

Take a look at this part from page 23 of TMJ AT A-11 "Aeronautics Targets: Aircraft arrangements and handling, facilities in Japanese Naval Vessels" 4th February 1946. Although I am sure, this is not the exact document I was reading it

[pompack]

That is a super good reference at many levels. Note that the later Japanese carriers had seperate tanks and pumping systems for "low octane fuel" and "high octane fuel"

[mdiehl]

Warspite1 has it correct.

Putting 100 octane fuel in an engine designed for 88 octane does not give you more power. The power's in the compression; high octane allows you to use higher compression. Putting 100 octane fuel in an engine designed for 88 octane gets you more heat though, and wears out the engine faster, even though it does not give you any extra horsepower. It also increases your fuel consumption significantly.

If you were japanese in 1944-45, you might put captured allied 100 O in your engine merely to avoid the general problem with impurities that plagued Japanese fuel when they tried to ramp up refinery production. You'd pay a price in reduced service life, but what the heck, in 1944 "service life" was already low for Japanese a.c. due to the use of a 17th century attitude towards logistics, so if you were stuck flying a Japanese plane you might as well use the good stuff while you have it.

[wdolson]

ORIGINAL: crsutton
Well, this plus the fact that only a small proportion of the Japanese population had been educated up to the high school level. Many rural Japanese's (the majority) education did not go beyond grammar school level. You can make a good soldier out of this material but not necessarily a good mechanic.

The US had an advantage over all other combatants because a large percentage of the population could drive and could maintain a car's engine when they enlisted or were drafted. At that time, the US was the only country that had a significant portion of their 20 something men who had cars.

Starting in the 1930s Germany and the UK both started driving schools to train up young men to be truck and tank drivers. That was not needed in the US. Not all young American men knew about cars, but enough did that there was no shortage.

Additionally since so many American men had been tinkering with cars before going into uniform, it raised the baseline quality of the mechanics quite a bit.

Bill

[JohnDillworth]

Additionally since so many American men had been tinkering with cars before going into uniform, it raised the baseline quality of the mechanics quite a bit.

and just to take this a bit off topic It seems a shame that "car mechanic" is not really a respected profession anymore. My village only has one. Fortunately he is good but the lack of completion has made him expensive. I think the emphasis on everybody getting a higher degree has really devalued skilled craftsman and tradesman. Maybe thats just my part of the world. Everybody out there have a good auto mechanic or dare I say can perform there own basic car repairs?

[wdolson]

In the town where we live, there are several mechanics. The best is a place called Hiway Fuel which has been there since the 20s, though the owners built a whole new building in the last 20 years and all traces of the old buildings are gone except a few artifacts in the waiting room lobby.

Their repair crew is about the size of a car dealership and they do good work. Very honest too. One time when my SO brought in her car with a squeaking wheel (she thought the brakes were going), the guy looked in there and said it was just a rock stuck. No charge.

The prices for car repair everywhere are high. These guys are in line with what most people pay.

The head mechanic loves my car too, a 1992 Buick Roadmaster. He's offered to buy it when I want to sell it. It's been a great car, it's 20 years old and still runs fine.

Bill

[Dili]

By wars' end the germans (extensively) and the IJ (Dinah and some other models) were using water/methanol. This, when coupled with charging systems, mitigates the octane issue.

The Italians also made methanol+water since 1942 for their torpedo bombers. An S.79 torpedo bomber was said to get around 40km/h more with injection with more 165cv per engine. As you say it also degraded the engines.

[PaxMondo]

ORIGINAL: crsutton

ORIGINAL: PaxMondo

Bill's answer is about as good as you can get without going into some pretty deep science. 

This is all off the top of my head, so apologize for any inconsistencies.  Octane numbers are a bit arcane.  First off it is a scale, it doesn't relate to reality.  100 Octane meant 100% N-Octane back in 1910 or so, so going over a 100 is kinda hard to understand.  It is all about anti-knock.   Then there are two ways to calculate this, research and motor (RON and MON).  The europeans and americans use a differently weighted average of the two to establish their scale.  Then, and even more importantly, is that how octane was boosted in the 40's isn't how it is done today.  Then it was about alkylation and so the octane boost was coming from n-nonane and n-decane type fuels.  Now, it comes from FCC and that gives you alkylenes like benzene and toluene to boost the fuel.  The amounts required to boost are different and how the impact cylinder temps are different.  They also behave quite differently under temperature and pressure as their partial pressure are different.

But a lot of this isn't as important as it seems.  Once you bring methanol/water injection into play octane become less of a factor.  Still a factor, yes, but less than you think.  Let's look at the chemistry and the mechanics here.  Engines are all about gas expansion forcing a piston to move down a cylinder and turn a crankshaft.  Igniting gas is good for about a 38x factor of expansion, not counting temperature effects.  That's awful good.  Water though is good for 18x.  The nice thing about water is that it take heat to move to steam, and this is how water injection works.  You start with an engine that is running too hot, you inject water to cool it and you actually get MORE power from it as the water expands into steam.  This works really well with radial air cooled cylinders as they are all more or less the same.  With in line water engines, you always struggle to get in inside cylinders as opposed the outside (on a V8 this would be 2,3,6,7 against 1,4,5,8) to be the same temperature.  The downside to water is that it is incredibly corrosive and impurities are very dangerous to metals (like chlorine and sodium as in salt).  Now add on superchargers and/or turbochargers (twinchargers) and again you get more complex.  On top of all of this is that in the 40's all they had was analog controllers. 

By wars' end the germans (extensively) and the IJ (Dinah and some other models) were using water/methanol.  This, when coupled with charging systems, mitigates the octane issue.

Now head hurt very bad.....[;)]

But it was not just octane was it? If I recall, Japanese refining methods left a lot of impurities in their fuel as well. This would serve to degrade performance over time. And time in service. A new engine out of the box would work a lot better than one that had some hours operating on less than ideal fuel. So any plane with a new engine would be different from an engine that had 50 hours of time using a poor quality fuel. Too many factors really. All things considered, an Allied engine with a little time on it was probably in much better shape than a Japanese engine with the same amount of time. Then there is lube oil. Allies probably had better qualty in this as well but I am just spectulating.

Refining methods in the 40's were pretty standard across the board. The real difference lay in the crude. The US was refining at that time principally TX and PA crudes, which are considered quite "sweet". This means both light and very few impurities. The Venezuela and Mexico crudes imported at the time (and continue today) are the opposite, quite heavy and a lot of heavy metals => more difficult to refine. US used those mostly for bunker oil refined along the Texas coast. Separate refineries were built just to handle those crudes. Japan was of course working with DEI crudes in the main. [;)] Those are middle, not sweet, but not terribly bad either. So, in the refining process of then, yes, IJ AV Gas would have had more impurities. 50 hours though is neglible as far as the gas contaminants from the oil are concerned. 500 - 1000 hours maybe you will see some effects (metal fatigue from trace elements), but I'm not even sure of that. You have to remember that air engines get a lot more maintenance than your car and parts like cylinders are designed to be replaced. Also, war is hard on equipment. More likely to replace a cylinder due to war damage or over boost than due to gas contaminant.

Lube oil again, yes and no. In the 40's it was straight distillation. Now, did the US refine more grades of lube oil? Yes, very likely. Your SAE 30, 50, 90 etc. IJ was likely working with a shorter list, but this again isn't that big a deal. It comes back to bearing gap tolerances in the design. You know that you have for lubricant properties and you set the gap for that. Wider gaps would mean shorter bearing insert replacement cycles, but not much more.

All in all you might be looking at a couple % difference here. Do you want that? Sure. But in the end analysis, number of aircraft in the fight would still matter more. In the early war IJ had that advantage. In the late war, the allies did. The results track that quite close. I wouldn't go looking for anything here. A few poor rivets would close the gap we are talking about with respect to gas and oil here.