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I was reading about the more difficult and resource intensive processes needed to obtain C3 fuel, of which they never had enough except for a part of Jagdwaffe. I recall seeing somewhere that they could only make 70% C3 fuel for any B4 quantity given, not sure how accurate that is.
Now even before the war the germans recognized their severe lack of most resources, hence among others the metal substitution program that wrecked their engines by 1942. But let's say they extend this to fuel, what if they recognize they can't afford the C3 fuel (they already gave up on C2 before the war) and just focus on B4 production.
On one hand they have more fuel, maybe 1/3 more than whatever C3 quantity they produced during the war, so more fuel for operation and crucial things like training. It also eases the logistical burden, and iirc easier to store as well?
On the other hand some engines will be affected, such as the DB-601N and BMW-801D plus several late war DB and BMW models which will have to de tailored for B4 fuel, so less power. On the DB-601N though they might avoid the oil dilution problem perhaps, and also rubber fuel tank corrosion. Presumably they have to reduce the CR on the 601N but they can still have the higher rated supercharger(s) and increased rpm? And about the redesigned cylinder head, was that specifically to cope with C2/C3 fuel or was it adapted from the 601E? What kind of power can they get from a B4 powered 601N? Rough guess about 1100 PS at rated altitude (datasheet says iirc 1175 PS at 4900 metres with C3)?
As to the BMW-801D, could they get it to run eventually on B4 (at reduced power, probably not much more than the 801C at around 1600 PS)? The next step would be to try to adapt it for MW-50 boost for more power, which i understand posed serious issues with cylinder head cracking. They would have to get it to work somehow if they want more power though, they could probably get 1800-1900 PS out of a hypothetical DM, while from TS (TSM?) maybe not more than 2000 PS with MW-50, am i in the ballpark?
On the other hand, if they can't get the 801D and later models to give more power with barely acceptable reliability with B4 and MW-50, then perhaps they would relegate the BMW-801 as a bomber engine and put the DB-603 and Jumo-213 in the FW-190 a soon as the absolute bare minimum of reliability is reached, so FW-190C and FW-190D but earlier.
So more fuel for operations and training, but on the other hand the E/N and F1/2 models and the FW-190A models from A-3 onward have a bit less power and hence performance compared to OTL.
Also late war DB-605AS/D engines would only run with B4 and MW-50, so probably can't get much past 1800 PS,
What gives then, better or worse for Luftwaffe to just run on B4 only?
You can find a diagram on page 159 of the Secret Horsepower Race, and a more detailed explanation, but tl;dr: C3 was, in a way, "spiced up" B4. Put B4 through a dehydrogenation reactor to increase the aromatics fraction, and then add 10-15% high octane alkylate (largely iso-octane). IIUIC the C3 production was largely colocated with the B4 (Bergius plants) production.Was C3 direct-produced in the Bergius plants or was it a spiced-up B4 with aromatics produced in Fischer-Tropsch plants?
The above post from another topic in large part answers to the question of BMW-801 evolution if only B4 was available.FWIW, some options with the BMW 801, that can avoid the need for C3 fuel and still be very worthy of service. Will probably require BMW cancelling any other engine that is not the 801, though.
- install the better, debugged parts from the 801D (like the chrome-coated valves and spark plugs, etc) on the 801C, so the reliability is where it should be
- 2700 rpm operation for 2nd gear as standard for the 801C, as it was supposed to be from late 1941 on (keeps the 190 competitive at high altitudes until mid/late 1943)
- retrofit the supercharger system from the 801E on the power section of the 801C, for the better power all-around (hopefully in ballpark of normally rated 801D)
- later, cut the CR even further so that engine (801C with E's S/C) can play well with the turbo while still on B4 fuel
- MW 50 system for the 801s all-around, also for the turbo version
- external air intake, where high altitude performance is needed; these are also conductive for the installation of dust filters
- devise the better external air intakes, that are more streamlined for lower drag and better speed
- not a part of the engine, but ditch the cowl MGs ASAP
We can take a look at the graph here (the base I can show on the topic of low CR vs. high CR, same engines). It shows that the high CR version of the Jumo 213E has some 10% more power, CR in question of 6.5: vs. 8.5:1 (a rather high jump?). So we'd probably be getting 5% less for the 7.2:1 CR version of the 601N? That is a deficit of about 50-60 HP at max rpm and boost. It would've been getting a bit worse mileage, too.So what would roughly be the power ratings of the DB-601N on B4 fuel, 2600 rpm, probably CR of 7.2 and probably 1.4 ata?
Thanks for your insightful comments as always Tomo. I just realized something though, the oft quoted figures and table seen for DB-601N of 1175 PS for TO and at altitude are they not for the DERATED 1.35 ata version? Probably derated because of the oil dilution issue (among others?), which shouldn't really happen with B4? Elsewhere you calculated about 1250-1260 PS for a fully rated 1.42 ata DB-601N.We can take a look at the graph here (the base I can show on the topic of low CR vs. high CR, same engines). It shows that the high CR version of the Jumo 213E has some 10% more power, CR in question of 6.5: vs. 8.5:1 (a rather high jump?). So we'd probably be getting 5% less for the 7.2:1 CR version of the 601N? That is a deficit of about 50-60 HP at max rpm and boost. It would've been getting a bit worse mileage, too.
Well the 601N was running at higher rpm ie 2600 rather than 2400-2500 of the 601A, and ITTL probably at a CR of 7.2 which is a bit more than the 6.9 of the DB-601A?a 601N on B4 would be just an 601A
Has flat top pistons with no bowl at all, so its not just a 601A with better fuel.a 601N on B4 would be just an 601A
The USN July 1945 report states that they guesstimated that 66.66% (2/3) of the fuel supply was C3 by the end of the war. In reality, it was closer to 50% (1/2) when one reads various fuel stock reports. The Luftwaffe also went to desperate meansures to approximate C3 fuel with B4. Engine manufactures were opting to create engines running on B4 as that was the safest bet considering the war.
Thanks for your insightful comments as always Tomo. I just realized something though, the oft quoted figures and table seen for DB-601N of 1175 PS for TO and at altitude are they not for the DERATED 1.35 ata version? Probably derated because of the oil dilution issue (among others), which shouldn't really happen with B4? Elsewhere you calculated about 1250-1260 PS for a fully rated 1.42 ata DB-601N.
So my logic is that our hypothetical DB-601N on B4 at 1.4 ata (because DB-601A models wre already able to do so?), maybe even 1.42 ata like the DB-601E, should actually run at the more or less the same power as the DERATED OTL DB-601N? Am i close or there's a flaw in my thinking that i haven't though about? I do recall that there were frequent supercharger changes both on the A and N models, not sure how this affects my theory.
Well i've just looked at a chart of a DB-601Aa showing 1.45 ata and 2500 rpm, unless there is a typo somewhere (looks like 1175 PS TO and 1250 PS at 1000m, but seems this setting can't be used above 2000 metres)?
Since the CR is only 7.2 ITTL compared to 6.9 for an A, probably about 1.4-1.42 ata should still be achievable? I'm just guessing hence why i appreciate input from people who really know their engine stuff.
Ok so going the conservative route, if we say this B4 DB-601N remains at 1.35 ata, then we shave 75 PS and we say 1100 PS TO, 1100 PS at rated altitude with around 1175 PS at 2000 metres or so, does this sound realistic enough?
And possibly, like the DB-601A the 1.40-1.42 ata boost might be allowed for TO only with again roughly 1175 PS?
601N was running at extra 200 rpm at rated altitude vs. the 601A, so we indeed should be getting better power at altitude.These ratings still bringing some extra PS at altitude compared to the A models, and if reliability is good enough (and better than the OTL N) many more N engines would be built for new or retrofitted Bf-109s and Me-110s, and even bombers (aiui a number of He-111Ps and maybe a few Do-215s had N engines?), since it's not limited by C3 stocks.
On the issue of CR ratio, the two-stage DB-601C/D was also 7.2 like the E, so it seems DB adopted this CR for the newer DB-601 versions which almost certainly would also apply for our B4 DB-601N.
Finally, materials wise was the N worse than the A and E built around that time more or less in parallel? Again my understanding is that the 2 biggest issues of the OTL 601N were oil dilution due to C3 fuel vaporization point being too high, thining the oil hence wrecking the bearings, rods and so on, and secondly same C3 fuel dizolving the self sealing fuel tank coatings thus clogging the engine. So the two above issues shoudn't happen with B4. It is true that the E was derated for at least six months, and i can't recall now reading what were the reasons? We have pretty good idea of the DB-605 faults with valves, sparkplugs, oil system etc. and how they were fixed, how about the 601E?
I used the (very good!) index of "The Secret Horsepower Race" [1] to reread all mentions of the DB 601E, and it seems the E suffered from the issues with the sparmetall valves, but also in particular, it had an issue with poor fuel atomization causing knock or detonation with rich mixtures (the opposite of what you'd expect in any "normal" engine). Eventually this was solved by increasing the fuel pump pressure, but that was too late for the 601E and was done to help the same issue on the 605 when they wanted to crank up the boost of that engine. For the 601E, the more immediate solution to the problem was to bore out the cylinders, thus creating the 605. Or IOW, the 601E was withdrawn from service without the derating restriction ever being lifted.It is true that the E was derated for at least six months, and i can't recall now reading what were the reasons? We have pretty good idea of the DB-605 faults with valves, sparkplugs, oil system etc. and how they were fixed, how about the 601E?
Yes. One would have too.you have a weird nerdy fascination with WWII aero engines, you owe it to yourself to get the book.
I'd beg to disagree.Or IOW, the 601E was withdrawn from service without the derating restriction ever being lifted.