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Question about V-1610-3
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MikeGazdik
Senior Airman
GrepP, is there any work done on cylinder head flow with these engines? Have you ever seen any comparisons of the flow of the Allison or Merlin? This is some cool stuff!!
Fuel confusing definitely. I was talking to crumpp (who's mechanic on a rebuilt Fw190 and known around the web) and he has tons of hard to get Focke Wulf documentation on BMW specs, original FW workshop manuals, minutes of meetings, wartime fuels, the full shebang, for obvious reasons. He was telling me the late war German 100 octane C3 was equivalant to 150 grade american. He said in the early war C2 (natural) and C3 (synthetic) were both equivalent to british 130 grade. Differences between the Merlin and the Daimler I've inferred would be more related to swept capacities and blower fitment than fuel variation, in documents going back to the mid-30s the "low octane, standard grade, and high performance grade" of aviation gasoline were introduced successively within months of each other between nations like Germany and the UK. B4 wasn't the prewar fuel, it's the 87 octane synthetic (but is actually a higher grade than british 87), in 1933 Germany had a lot of 80 octane natural fuel which was the standard grade, the UK used a very low grade like that then too. About 1938 87 octane "standard aviation fuel" was introduced throughout much of europe as it behaved better with blown motors (up until the early 30s most not all aero engines even used superchargers, the American Liberty engine and blower was actually forefront technology in 1930).
GregP
Major
C2 is very well documenrted as 100 Octane. The Germans typically quoted lean condition, and the rating, such as the Allies would use, is 100/130 or 95/125, depending on your source of information.The B4 that was run for a lot of first half (and later) in the war was 87 OCtane, again well documented, but the 87 is in lean condition.
None of the European fuels were cmparable to any American fuels. They had quite different chemical makeups. When our planes got to Europe, we had fuel issues. When we got European aircraft for comparative testsing here in the USA, we had fuel issues with them running American fuels. I don't think the American (or European) fuel was better or worse, just different from one another.
An engine carbureted for European fuel ran great on European fuel. Likewise, an enguine carbureted for American fuel ran great on American fuels. Neither one was happy when the alternate fuel was substituted.
About the Allison and Merlin head flows, I'll ask. I am not currently aware of any comparative head flow work that was done. Most of the work I am aware of was done to improve flow on the Merlin or the Allison, not to ompare with one another. The only interchanging I know of is Merlin racers using Allison G-6 series rods because the stock Merlin rods are not as strong.
There is nothing wrong with Merlin rods at stock Merlin power levels but, for racing purposes, they will not stand up to 3,400+ HP. The Allison G-6 rods will, and more. Both Strega and Voodoo (and the former Gallopping Ghost) run Allison G-6 series rods in their Merlins.
None of the European fuels were cmparable to any American fuels. They had quite different chemical makeups. When our planes got to Europe, we had fuel issues. When we got European aircraft for comparative testsing here in the USA, we had fuel issues with them running American fuels. I don't think the American (or European) fuel was better or worse, just different from one another.
An engine carbureted for European fuel ran great on European fuel. Likewise, an enguine carbureted for American fuel ran great on American fuels. Neither one was happy when the alternate fuel was substituted.
About the Allison and Merlin head flows, I'll ask. I am not currently aware of any comparative head flow work that was done. Most of the work I am aware of was done to improve flow on the Merlin or the Allison, not to ompare with one another. The only interchanging I know of is Merlin racers using Allison G-6 series rods because the stock Merlin rods are not as strong.
There is nothing wrong with Merlin rods at stock Merlin power levels but, for racing purposes, they will not stand up to 3,400+ HP. The Allison G-6 rods will, and more. Both Strega and Voodoo (and the former Gallopping Ghost) run Allison G-6 series rods in their Merlins.
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Nah I have charts somewhere, the German octane ratings are from a different rating to the RON we're all used to. They've about five columns and a very wide number of variations in composition for B4 and C3 types of fuels, some are labelled by their aromatics, hang on I'll search through my drives and find it.
I'll come back.
note, I don't actually know what I'm really talking about, but just sharing stuff I read...I'll be back, you guys can probably explain the data better anyway I don't know what it all means
I'll come back.
note, I don't actually know what I'm really talking about, but just sharing stuff I read...I'll be back, you guys can probably explain the data better anyway I don't know what it all means
From wartime documents (IG Farben Industries 1941):
Test engine BMW 132F
DHD high performance fuel: benzine ex hard coal, 50vol% aromatics, ON (motor method) 86.5(T)
C2 high performance aviation fuel: 80vol% DHD, 20vol% ET110 (I believe this is ethyl propyl bensol), ON 90
CV2B high performance fuel: aromitised benzine ex hard coal, 50vol% aromatics, ON (motor method) 91
C3 high performance aviation fuel: 80vol% CV2B, 20vol% ET110, ON 95
C1 high performance aviation fuel: 50vol% aromatics, 50vol% benzine, ON 100
B4 standard grade aviation fuel: aviation benzine type ON 87
Meanwhile the rating for B4 is 94 octane by motor method, 104 by research method, and under operating conditions lambda-m0.9 (don't ask I've no idea) octane 81 and at lambda-m1.1 it's octane 60.
Dude, you make sense of it, gave it my best shot
Test engine BMW 132F
DHD high performance fuel: benzine ex hard coal, 50vol% aromatics, ON (motor method) 86.5(T)
C2 high performance aviation fuel: 80vol% DHD, 20vol% ET110 (I believe this is ethyl propyl bensol), ON 90
CV2B high performance fuel: aromitised benzine ex hard coal, 50vol% aromatics, ON (motor method) 91
C3 high performance aviation fuel: 80vol% CV2B, 20vol% ET110, ON 95
C1 high performance aviation fuel: 50vol% aromatics, 50vol% benzine, ON 100
B4 standard grade aviation fuel: aviation benzine type ON 87
Meanwhile the rating for B4 is 94 octane by motor method, 104 by research method, and under operating conditions lambda-m0.9 (don't ask I've no idea) octane 81 and at lambda-m1.1 it's octane 60.
Dude, you make sense of it, gave it my best shot
Shortround6
Major General
I am no expert either, I just know what I have read, the funny thing about fuel "octane" ratings is that the depend, to some extent, on the engine they are tested in. You will not get identical results if you use a different model or type of engine. Octane ratings are not chemical composition, they are a performance test. On a given day the test engine is run on one or more reference fuels and it's "knock" limits are noted and then the fuel under test is run and it's "knock" limits are noted and compared to the reference fuels. Engines with different bore stroke ratios, different combustion chamber shapes and different cooling will give slightly different results. The Waukesha engine company supplied most of the test engines ( a special single cylinder engine, later supplied in supercharged form) in the US prior to the war and built several hundred in short order as the US ramped up production and standardized fuel with Britain. Research labs, refineries, and government purchasing agencies all needed to be testing the same things the same ways.
GregP
Major
Shortround,
Octane test engines are like dynamometers ... no two give the same result. But if you use one consistently, you can easily mark improvements.
In the automotive hot rod world, there are two poopular dynamometers, a Dyno-Jet and Mustang Dyno. The Mustang Dyno give lower numbers than the Dyno-Jet, but both will let you chart improvemnts to your setup as you modify it because both are consistent in their measurments ... they just get different numbers. In the end, most people wan to improve their engine, not get the same numbers from two different dynos.
Octane test engines are similar in that most manufacturers want to know if they are getting better, worse, or the same fuel from batch to batch, so consistency is more important than the number ... as long as the testing ageny usues a consistent test.
It's ilke WWII fighter conference tests. If they want to let, say, a Mustang be outstanding, they wash it inside and out, polish it, wax it, and tune it up, balance the prop, and keep it covered and inside between tests. if they aren't concerened about an aircraft, they just leave it outside and fly it as delivered, without any extraordinary maintenance or preparation. This cn easily make a difference of 10 - 15 mph in tests, and nobody ever tells you which one got the attention to detail.
Mostly, in British tests, the British aircraft got careful maintenance. In American tests, the American aircraft got careful maintenance, unless the Navy sent in people to take care of their own planes.
I say the only real way to tell is toa verage all the etsts. But then you'll never find out the real performance of the types nobody ever paid "special" attention to ... so it's tough to say which tests were "objective."
Octane test engines are like dynamometers ... no two give the same result. But if you use one consistently, you can easily mark improvements.
In the automotive hot rod world, there are two poopular dynamometers, a Dyno-Jet and Mustang Dyno. The Mustang Dyno give lower numbers than the Dyno-Jet, but both will let you chart improvemnts to your setup as you modify it because both are consistent in their measurments ... they just get different numbers. In the end, most people wan to improve their engine, not get the same numbers from two different dynos.
Octane test engines are similar in that most manufacturers want to know if they are getting better, worse, or the same fuel from batch to batch, so consistency is more important than the number ... as long as the testing ageny usues a consistent test.
It's ilke WWII fighter conference tests. If they want to let, say, a Mustang be outstanding, they wash it inside and out, polish it, wax it, and tune it up, balance the prop, and keep it covered and inside between tests. if they aren't concerened about an aircraft, they just leave it outside and fly it as delivered, without any extraordinary maintenance or preparation. This cn easily make a difference of 10 - 15 mph in tests, and nobody ever tells you which one got the attention to detail.
Mostly, in British tests, the British aircraft got careful maintenance. In American tests, the American aircraft got careful maintenance, unless the Navy sent in people to take care of their own planes.
I say the only real way to tell is toa verage all the etsts. But then you'll never find out the real performance of the types nobody ever paid "special" attention to ... so it's tough to say which tests were "objective."
Then I would say this remark is brought into question
With all which has just been discussed it is perfectly legitimate to suggest that C3 fuel was equivalent to british or american 130 or 150 grade standard at any given time in a particular engine, obviously it is not the same fuel but even more obviously what is being stated is that the measure of octane is completely unrelated to its aviation fuel qualities, Crumpp was basically saying you could run a daimler on british standard or german B4, you could run a bmw on british 130 or german C3 in 1942 but in 1944 if you're not going to run your Fw-190A-9 on C3 then you better use american 150 grade because 130 might ping.
I don't give a crap about pissing matches and I see no logical reason why this statement wouldn't be realistic considering the source operates a working Fw-190A and has proven the extent of his FW documentation countless times, he's got half the company's bookkeeping ffs. He's already cleared up tons of nifty facts about the type and never been wrong once, but what he says isn't always popular because it challenges generally erroneous conventions that develop about historical things.
People have often remarked about Merlin versus Daimler supercharger pressures quoting fuel quality, but I do not believe this to be the case, and have repeatedly tried to assert a culture of weights and measures and research methods which disguise close similarities as distant aliens and unique qualities as generic features. German 87 octane is up around british 100/1941 qualitively as far as knock rating goes in a fafnir engine. Some of those German compounds by modern conventions would be rated 150ron not 90 like they do, I'd say you can take octane ratings as any kind of comparative measure between german, british, american and japanese fuels as completely irrelevant and just toss it out the window completely.
that would also include downgrading C3 to the equivalence of modern automotive premium unleaded, whilst elevating "us wartime av fuel" to figures like 150 grade, it's like a pissing contest and inherently misleading. What it means isn't really what it means.
With all which has just been discussed it is perfectly legitimate to suggest that C3 fuel was equivalent to british or american 130 or 150 grade standard at any given time in a particular engine, obviously it is not the same fuel but even more obviously what is being stated is that the measure of octane is completely unrelated to its aviation fuel qualities, Crumpp was basically saying you could run a daimler on british standard or german B4, you could run a bmw on british 130 or german C3 in 1942 but in 1944 if you're not going to run your Fw-190A-9 on C3 then you better use american 150 grade because 130 might ping.
I don't give a crap about pissing matches and I see no logical reason why this statement wouldn't be realistic considering the source operates a working Fw-190A and has proven the extent of his FW documentation countless times, he's got half the company's bookkeeping ffs. He's already cleared up tons of nifty facts about the type and never been wrong once, but what he says isn't always popular because it challenges generally erroneous conventions that develop about historical things.
People have often remarked about Merlin versus Daimler supercharger pressures quoting fuel quality, but I do not believe this to be the case, and have repeatedly tried to assert a culture of weights and measures and research methods which disguise close similarities as distant aliens and unique qualities as generic features. German 87 octane is up around british 100/1941 qualitively as far as knock rating goes in a fafnir engine. Some of those German compounds by modern conventions would be rated 150ron not 90 like they do, I'd say you can take octane ratings as any kind of comparative measure between german, british, american and japanese fuels as completely irrelevant and just toss it out the window completely.
that would also include downgrading C3 to the equivalence of modern automotive premium unleaded, whilst elevating "us wartime av fuel" to figures like 150 grade, it's like a pissing contest and inherently misleading. What it means isn't really what it means.
GregP
Major
I don't think German B4 is anywhere near British 100 / 130/ it is more like 92 / 110. You can't run the same boost on B4 as you can on British 100/130.
We don't know the real ratings of most German fuel, comparable to Allied fuel, so you can't say definitely. Sorry I have to disagreee with you here.
We CAN say that German engines running German fuels ran well and consistently in that fuel. It got better with time, as did Allied fuel.
Allied fuels were in two camps, British and American. Each engine designed to run each fuel ran well on that fuel, but no so well on other fuels ... mostly.
That's about all we can say definitely. There is no German B4/C2/C3 left, so we may never really know.
There is no way 87 Octane fuel equals 130 Octane fuel in any real world. The potential power difference as a reasult of 87 / 130 is tremendous.
The German fuels did NOT reach the poptential of Allied fuels or their engines would not have had to be so big in displacement to get equivalent power. In the real world, they DID have to have more dispalcement, so the fuels could NOT have been equivalent or the German engines would have been more powereful than they were in real life.
We don't know the real ratings of most German fuel, comparable to Allied fuel, so you can't say definitely. Sorry I have to disagreee with you here.
We CAN say that German engines running German fuels ran well and consistently in that fuel. It got better with time, as did Allied fuel.
Allied fuels were in two camps, British and American. Each engine designed to run each fuel ran well on that fuel, but no so well on other fuels ... mostly.
That's about all we can say definitely. There is no German B4/C2/C3 left, so we may never really know.
There is no way 87 Octane fuel equals 130 Octane fuel in any real world. The potential power difference as a reasult of 87 / 130 is tremendous.
The German fuels did NOT reach the poptential of Allied fuels or their engines would not have had to be so big in displacement to get equivalent power. In the real world, they DID have to have more dispalcement, so the fuels could NOT have been equivalent or the German engines would have been more powereful than they were in real life.
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At the end of 1942 a different kind of C3 began to come into service with a still higher performance, and was equivalent to the Allied 150 grade. This fuel contained some 5% more iso-octane then the previous version, but the aromatic content was maintained at the previous level by dehydrogenation of the higher boiling naphthenes in the fuel. The new fuel was an outstanding development and was a result of the introduction of the DHD process which delt with under hydrogenation.
GregP
Major
While what you say may well be true, I have not seen anything to tell me that the C3 in 1942 and laeter was different from that before that time. I've never even seen a hint of it.
Can you post some detail?
Can you post some detail?
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I can post alot of detail straight from the US Navy. Technical Report 145-45 - Table of Contents
GregP
Major
Your report (in "conclusions) says the B4 fuel was 91 octane and the C2 was 95 Octane, both motor method.
We used (research + motor method) / 2 and the research Octane is not indicated, but nowhere is the German fuel anywhere close to 130 Octane. much less 150.
It is as I have always known, the B4 wa low-grade fuel (for aviation use) and teh C3 was decent, but not as good as 100 / 130 much less 150, and contained 40% aromatics. Ours, at 100/130 rating, had less than 2% aromatics.
No wonder the Germans needed 2,500 cubic inch engines! I wonder that they didn't develop MUCH bigger engines, given the fuel.
We used (research + motor method) / 2 and the research Octane is not indicated, but nowhere is the German fuel anywhere close to 130 Octane. much less 150.
It is as I have always known, the B4 wa low-grade fuel (for aviation use) and teh C3 was decent, but not as good as 100 / 130 much less 150, and contained 40% aromatics. Ours, at 100/130 rating, had less than 2% aromatics.
No wonder the Germans needed 2,500 cubic inch engines! I wonder that they didn't develop MUCH bigger engines, given the fuel.
Shortround6
Major General
Too many things interrelate to say that German engines would have been smaller (closer in size) to allied engines if their fuel was better.
Both sides were pretty much stuck with what ever engines they had either in production or on drawing boards in 1939-1940. I don't beleive any clean sheet of paper engine after that time made it into production by the end of the war.
This means that even 1944-45 engines carried a lot baggage from the late 30s, for good or ill.
In the Mid 30s. (1934-39) everybody's fuel was pretty much the same, 87 octane in lean condition but with some different compounds that affected rich mixture. How much effect it had nobody knew yet, although they did know that differences existed. The Germans did pick large engines because of fuel, they picked them because for the same weight they could build a large displacement, slow turning engine instead of a smaller displacement faster turning engine. 34-35liter engines at 2400rpm move the same amount of air as a 27 liter engine at 3000rpm given the same intake manifold pressure. At the lower rpm a lighter crankshaft and crankcase can be used which offsets the larger dimensions. Once the factories are tooled up it is a little late to make sweeping changes so both sides have to make do and improve what they have. R-R takes advantage of improved fuels and keeps the rpm the same while increasing the boost with better superchargers. DB and Junkers go easy on the boost but raise the rpm ( and compression in the cylinder, high cylinder compression limits the amount of boost that can be used). Other things come into play, fuel injection is often credited with allowing slightly lower octane fuel to be used but fuel injection (German style) does not allow the 25 degrees C or so of lowered intake temperature the fuel evaporation in the supercharger gives the the Merlin and Allison. And so on......
I am not a Chemist or a fuel specialist. I believe the German fuel got a better as the war went on. I think the Germans didn't take as much advantage of the rich rating as they could have. I will note that by 1946 the Americans had 73, 80, 87, 91/96, 100/130 and 115/145 fuel standards. The British skipped 80 octane and had 100/150 instead of 115/145. The last is not just different terminology or different names for the same thing, the two fuels not only had different operating characteristics (115/145 allowed for higher cruise ratings) but may have needed different base stocks or refining techniques. The Americans at least (not sure about the British) also tried 100/135 and 100/140 fuels and at some point (post war?) had 108/135. The 100/135 and 100/140 were very short lived as they only showed improvement in some engines (liquid cooled?) but not all engines.
The Germans also seem to be much more concerned with fuel efficiency of their engines than the allies which lead to different choices being made. It seems that many of their choices actually didn't have much to do with the fuel quality which seemed to change faster (for both sides) than new engines could be designed. Old engine designs can be reworked or modified to take advantage of new fuels as was done.
Both sides were pretty much stuck with what ever engines they had either in production or on drawing boards in 1939-1940. I don't beleive any clean sheet of paper engine after that time made it into production by the end of the war.
This means that even 1944-45 engines carried a lot baggage from the late 30s, for good or ill.
In the Mid 30s. (1934-39) everybody's fuel was pretty much the same, 87 octane in lean condition but with some different compounds that affected rich mixture. How much effect it had nobody knew yet, although they did know that differences existed. The Germans did pick large engines because of fuel, they picked them because for the same weight they could build a large displacement, slow turning engine instead of a smaller displacement faster turning engine. 34-35liter engines at 2400rpm move the same amount of air as a 27 liter engine at 3000rpm given the same intake manifold pressure. At the lower rpm a lighter crankshaft and crankcase can be used which offsets the larger dimensions. Once the factories are tooled up it is a little late to make sweeping changes so both sides have to make do and improve what they have. R-R takes advantage of improved fuels and keeps the rpm the same while increasing the boost with better superchargers. DB and Junkers go easy on the boost but raise the rpm ( and compression in the cylinder, high cylinder compression limits the amount of boost that can be used). Other things come into play, fuel injection is often credited with allowing slightly lower octane fuel to be used but fuel injection (German style) does not allow the 25 degrees C or so of lowered intake temperature the fuel evaporation in the supercharger gives the the Merlin and Allison. And so on......
I am not a Chemist or a fuel specialist. I believe the German fuel got a better as the war went on. I think the Germans didn't take as much advantage of the rich rating as they could have. I will note that by 1946 the Americans had 73, 80, 87, 91/96, 100/130 and 115/145 fuel standards. The British skipped 80 octane and had 100/150 instead of 115/145. The last is not just different terminology or different names for the same thing, the two fuels not only had different operating characteristics (115/145 allowed for higher cruise ratings) but may have needed different base stocks or refining techniques. The Americans at least (not sure about the British) also tried 100/135 and 100/140 fuels and at some point (post war?) had 108/135. The 100/135 and 100/140 were very short lived as they only showed improvement in some engines (liquid cooled?) but not all engines.
The Germans also seem to be much more concerned with fuel efficiency of their engines than the allies which lead to different choices being made. It seems that many of their choices actually didn't have much to do with the fuel quality which seemed to change faster (for both sides) than new engines could be designed. Old engine designs can be reworked or modified to take advantage of new fuels as was done.
GregP
Major
I'm sure there is some meaning to "Oh Lordy" but it escapes me. Perhaps you can clarify?
My post is correct about the "conclusions" section of your referenced report.
The pics of another report are notwithstanding, and mean nothing wthout data. They look like newspaper type reports, which are not reliable. Opinons vary.
Mine stands the test of data and engineering corroboration.
On the other hand, if you have real data, post it with references that can be corroborated. I also stand by my conclusions. If German engines were running the equivalent fuels and superchargers, they would have made the power that their displacement indicated. In the real world, they didn't. Ergo, something was lacking in either engineering or fuel. It could not be the air since we all used the same air. German engineering is not in question. That leaves fuel ... to me, at least.
My post is correct about the "conclusions" section of your referenced report.
The pics of another report are notwithstanding, and mean nothing wthout data. They look like newspaper type reports, which are not reliable. Opinons vary.
Mine stands the test of data and engineering corroboration.
On the other hand, if you have real data, post it with references that can be corroborated. I also stand by my conclusions. If German engines were running the equivalent fuels and superchargers, they would have made the power that their displacement indicated. In the real world, they didn't. Ergo, something was lacking in either engineering or fuel. It could not be the air since we all used the same air. German engineering is not in question. That leaves fuel ... to me, at least.
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Shortround6
Major General
Our fuel had less than 2% aromatics when? US 100 octane in 1939-40 did have less than 2% aromatics but it wasn't 100/130 fuel. British 100 octane in 1940 (BoB) had NOT LESS THAN 20% aromatics and it was NOT 100/130 fuel. 100/130 fuel was later, 1941 or 1942.
As noted in a previous post. Germans used low revving 34-35 liter engines that WEIGHED the SAME as the 27-28 liter high revving Merlin and Allison in 1937-1939. The displacement had more to do with the RPM limit (or piston speed limit) than it did for any difference in fuel when when the engines were designed and first developed.
edit>"they would have made the power that their displacement indicated."
DB 601s (early ones) ran at 2400-2500rpm at peak power. even the late 605s ran at 2800rpm. How much power does an Allison or Merlin make at 2500rpm?
Jumo 213s did pretty well for their displacement, they did use a higher rpm limit, but for the same displacement they gained about 500lbs of weight. You can't have all three, large displacement-high rpm-light weight...... Pick two!
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GregP
Major
Opinions vary, as I said, and we have people at the Planes of Fame who were in WWII. They didn't think much of German fuels, Octane-wise ... and importantly to me, they were there. I was not.
I happen to be one of three people in the world, as far as I know, who have helped restore a WWII pulsejet engine from a German V-1. We have it at the museum and we spent a year making it run after a 4-year restoration. It runs quite well.
The original ran on B4 fuel. We have run it on 87-Octane unleaded, 91-Octane unleaded premium, and 100 LL avgas. As the Octane got better, the engine ran worse; it barely rat all at idle power on avgas. it didn't run at full power on avgas at all.
It runs best on 87-Octane unleaded fuel, making us all feel as if that is the fuel grade best suited to the engine, and closest to the original. You, of course, can draw your own conclusions. We have our own, and the opinion about B4 is 87 Octane, and we are very comfortable with that evaluation as it matches that of the US military as we know them personally over 60+ years of museum association, including fuel engineers.
We run the pulsejet about once a year or so, and on 87 Octane, it starts and runs quite relaibly. We never let it get over about 1,000°F to 1,100°F, and never run it longer than about 1 minute 30 seconds or so, so we think the valves will last awhile longer.
If you wish to revise history of the B4 formulation, show the reports with dates and sources. Otherwise, our opinion matces the data we have, and that includes presentations from both Allied and German pilots form WWII.
I happen to be one of three people in the world, as far as I know, who have helped restore a WWII pulsejet engine from a German V-1. We have it at the museum and we spent a year making it run after a 4-year restoration. It runs quite well.
The original ran on B4 fuel. We have run it on 87-Octane unleaded, 91-Octane unleaded premium, and 100 LL avgas. As the Octane got better, the engine ran worse; it barely rat all at idle power on avgas. it didn't run at full power on avgas at all.
It runs best on 87-Octane unleaded fuel, making us all feel as if that is the fuel grade best suited to the engine, and closest to the original. You, of course, can draw your own conclusions. We have our own, and the opinion about B4 is 87 Octane, and we are very comfortable with that evaluation as it matches that of the US military as we know them personally over 60+ years of museum association, including fuel engineers.
We run the pulsejet about once a year or so, and on 87 Octane, it starts and runs quite relaibly. We never let it get over about 1,000°F to 1,100°F, and never run it longer than about 1 minute 30 seconds or so, so we think the valves will last awhile longer.
If you wish to revise history of the B4 formulation, show the reports with dates and sources. Otherwise, our opinion matces the data we have, and that includes presentations from both Allied and German pilots form WWII.
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