Since this started, I've been doing some online checks & there is so much more than my books or what I've heard said over the years, & a lot of it contradictory. Late war fuel production was bad, & the supply of isoparaffin so short, that to get even 100 octane was a stretch. Some say it was closer to 95, German numbers. The Allied numbers were about 130 to the German's 100. Just a different way of figuring it out. Methinks low to high alt was in there someplace. Think about it, around the clock bombing on roads, rails, & industry. There were no luxuries afforded to fuel for trucks, fuel for tanks, fuel for different aircraft, etc. On some air bases, from what I've read, there were differnt fuel tanks for the different planes & one better get the right fuel for the the proper application or all Hades would break out. There was always a shortage so the lowering of the CRs for all AC was beneficial to all concerned.
Now to the concave pistons, for an example, Chev had an engine called a 327 & this egine, over its' life span, was put in family cars, corvettes, & trucks. HP ratings from 210,225,250,275,300,325,350,& 375, all from the factory, all from the same basic engine. The pistons were either concave, for some trucks, flat tops for your family cars, & dome tops for the muscle ones. The concave gave more cylinder volume for better volumetric effiency, but also lower CR which adversely affected HP output. Also, a lower grade of fuel could be used as compared to the muscle cars. Now when I read about the Concave Pistons in later DB engines, I naturally assumed that the process was the same. Unless they increased the piston stroke, I still stand behind the concave theory. Domes for more, concave for less. The one other thing they might of done, was change the cylinder head dimensions, thus the squish band. Now this could increase Compression Ratios.
I've got an tape of actual footage of 262s taking off & there is black smoke. I'm going to try & find it & play it again & see what else is on it. Stay tuned.

FWIW,
Good Hunting!

PS. I hope I don't sound like I'm turning this posting into a who's right or wrong rather than a what's right or wrong. Me trying to sound the more intellegent to boost my ego by faulting the other person is just plain BS. I've been known to do it all so really trying not to do so.

USSBS


Strategic Air Attack on the German Chemical Industry
http://www.angelfire.com/super/ussbs/ussbsappa.html#lead

The relative volumes of production of the two grades cannot be accurately given, but in the last war years the major volume, perhaps two-thirds (2/3) of this total has the C-3 grade. Every effort was being made toward the end of the war to increase isoparaffin production so that C-3 volume could be increased for fighter plane use. The isoparaffin usage in that grade had already been cut to a minimum

http://www.fischer-tropsch.org/primary_d...0Specifications

Man, I really screwed up here. From too much fire/smoke to fuel production was quite a leap & I guess I started it. Me bad!
What was being produced & what was reaching the fighting & training units are two different stories. Books Iv'e read, written by first hand pilots, have said that the fuel quantities were low & that new recruits coming in had very little flying time because of this shortage of fuel. Production is moot if it's not reaching the consumer. Sometimes only a few planes got into the air & the others stayed on the ground with empty tanks. Also, because of a real shortage of higher octane fuel, the engines were being modified to burn the more common lower octane fuels @ the front lines. Shipping one is much simpler than shipping multies & more of a chance of getting enough to the front lines.
Anyways, over the years, even before I came on here, there was always discussions of German fuel quantity & quality. The ones who opt for the quantity/quality think that's why Germany lost the war & the other camp rigorously refuted that. The graphs would come out & in a lot of case, some graphs contradicted each other. Who knows what is true in graph land but I still believe more of the ones who were there, not so much the history books.
The fuel problem, quantity & quality, sure curtailed the German war machine & I THANK THE GODS FOR THAT!!!!!!!!!!!

FWIW,
Good Hunting!

Kraut, you do know that the Fw190 with the BMW801 engine required C3 fuel.

No, I didn't know that. I do remember reading someplace where the later 190 radials had spark plug problems & it was fuel related. Now if this was an isolated incidence or not I don't know. I do know that low octane/quality fuel can cause preignition & detonation which plays havoc on plugs so I assumed this was the problem here. What was required & what was available are two different things & the articles I read from the pilots themselves also could be isolated incidences. I've run a tank of Esso summer fuel that's had been sitting for a while, in mid winter, I had a tendancy to blame Esso Oils. One time & I'm quick to blame.
I've been an engine nut for over 55 years starting with my parents lawnmower so this stuff interests me. I had a ball in the 60s with muscle cars & now just focus on Harley Davidson bikes. Just going to do a top end overhaul on my new toy, an 84 Evo engine. To think, these V Twins from are a spin off of a 7 cyl. radial AC engine.
Anyways, KraziKanuk, thanks for all your info. It sure has broadened my knowledge base & even @ my age, I can still learn more about things that I thought I knew.
I think I use to call you KK a few years ago. I asked about the AC War Museum in Ottawa & the wife & I rode down & saw it out @ the airport. Great ride, great country, & a must see Museum.

FWIW,
Good Hunting!

German fuels had more aromatic content than Allied fuels. This is why the British test of the Fw190A had engine problems.

Data sheets on some DB engines
http://www.fischer-tropsch.org/Tom%20Reels/Linked/A5464/A5464-0638-0654%20Item%206A.pdf

Next time you are up here, visit the Gateneau airport.
http://www.vintagewings.ca/page?s=63&lang=en-CA

Great stuff there. I especially like the address you gave about the Gateneau Airport. There's some great reads on that site, most info being completly new to me. I don't know how many books & mags I've read over the years about WWII AC, but lots. Reading autobiographies from pilots gave me some moments. Like the plane they flew was the best when the 'books/charts' said otherwise. Just reading from that above site about the 109 flight contradicts what other pilots have said. Even that British test pilot who flew one was more in favour. Hades, I've read where Charles Linberg & Major Al Williams gave rave reviews after flying a 109 in 1938. Lindbergs quotes, "The plane hsndled beautifully". "The 109 takes off and lands as easily as it flies". Those statements are not we read & see today but the 109 pilots loved them, the ones who survived the early days of flying them. Now back to fuels, who in hades knows due to the different charts & statements. My guess, nobody. Just look @ the charts for flying, fighting, speeds, ROCs, etc., etc. & they're all over the board. Pilot Notes are more accurate but even then, some contradictions come out. I base my stuff on my 45+ years of repairing cars & light trucks & I'm not saying it's all right. The rules that apply to car/truck engines also apply to aero engines. An internal combustion engine is an internal combustion engine no matter what vehicle its in. Compression, fuel, spark @ the right time, & an expulsion of the exhaust gases is all that's needed. Altitude is what really sets aero engines apart in the fuel dept. Rich makes black smoke & overheats the exhaust system. Poor fuel or incorrect timing makes for knocking thus holes in pistons. Too low an octane does the same thing & in either case, poor performance.
FWIW,
Good Hunting!

Just two of the books I read were
Messerschmitt BF109 at War by Armand van Ishoven &
The Messerschmitt BF109 by James F. Craig

Linberg and Williams flew early models of the 109, much lighter a/c with a lower HP motor. The 109C weighed 5,062 lb while the 109E-3 weighed 5,062 lb, the 109F weighed 6,054 lb, the 109G-6 weighed 6,940 lbs and the 109K-4 weighed 7,400lb.

On late war lower CRs, the DB605D powered the 109G-10 and K-4.

Sorry posted the wrong link in a previous thread. Should be
http://mitglied.lycos.de/luftwaffe1/aircraft/lw/DB605_varianten.pdf

As can be seen, the CR was 1:8.5/8.3. The G-10 and K-4 were the major production models, late war. This engine could run on B4, B4 + MW50, C3 and C3 + MW50. From what I have read, it only took the use of a screw-driver when switching fuels.

The DB engines did not have removable heads like on the auto engines you mentioned Kraut. (are you familiar with the old Hurricane outboards from Mercury?) To change CRs the piston crown had to be changed.

I knew they were early models with just the rifle cal. MGs on board, but they were having problems even then. With the E line it even got worse and really bad, as you mentioned, as the weights & HP increased. The torque would be large on those landing gears & on an approach, sudden throttle changes were to be avoided if at all possible. I have numbers someplace on the problems with the first 109s even before opperational status. So when I read about those two gentlemen & thier experience, it just muddied the water, again. Williams did complain about the outward retracting LG & was assured by Udet that it would be changed to to fold inward. On a side note, a 109 engine in 18 could be changed and the AC ready to go in under 12 minutes. A standard USA engine between 24 & 36 hrs.
There's a faint recollectionf the cyl. heads but so faint as for me not to believe it. To bore & hone out an engine block from one end is really foreign to me & sounds so , well so weird, totally. If they put concave pistons in without legthening the stroke or doing work on the squish area, the CR would be less & they could burn a less octane fuel.They started with B4(87Octane) & then in 44 went to C3(100) & then back to B4 & MW50.
I've never worked on a boat engine except help change a plug & even then I wasen't in command of the tools. I've saeen model AC engines with that arrangement but I find it hard to bring my head around the same process for big cube engines.

Oops, gotta go & again thanks for your info. ya got my gears agoing!

FWIW,
Good Hunting!

Actually Kraut C3 was available during BoB and used by a 109 Gruppe and the 110.

One thing to think about is if the they thought the 109 was a sweet flying a/c, what does that say about American a/c.

On the engine change times, there is a lot not mentioned. example: Was the a/c already striped of prop and cowl panels? Were the oil and coolant lines already disconnected?

To attach the lift chain, remove the engine mounting bolts, lift the engine out and then reverse the procedure, it might be possible in 6-9 minutes but the a/c is surely not ready for flight.