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View Full Version : DB 605, switching from B4 to C3?



Abbuzze
06-02-2004, 04:49 AM
A simple question- how long did it take to switch from the worse B4 fuel to the higher octane C3 fuel?.
What kind of changing at the DB605 were necessary?
Thanks!

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Abbuzze
06-02-2004, 04:49 AM
A simple question- how long did it take to switch from the worse B4 fuel to the higher octane C3 fuel?.
What kind of changing at the DB605 were necessary?
Thanks!

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Jumoschwanz
06-02-2004, 07:58 AM
I have spent my whole life working on internal combustion engines. There are a lot of wives tales about fuel octane. The most common is the one where someone says they put "racing gas", "av-gas", or high octane fuel in thier car or bike or whatever and it suddenly had so much more power it was all they could do to hang on!

WEll that is bull$hit. The only time an engine gains power when you put in a certain octane fuel is when it was running on too low an octane fuel to begin with.
High octane does not mean "more power", it means the fuel is less volatile, in other words it will be harder to ignite!

Why is this an advantage? Because in the combustion chamber of an internal combustion engine, at many times the pressure and temperature of your living room, it is damned hard to keep fuel from spontaneously igniting. and if it ignites at the wrong time while it is in your engine, it will sooner or later destroy it.

The catch-22 is that heat and pressure is the energy that makes the engine run. So to make more power, we have to have the engine run as hot as it and the fuel can stand before it exceeds the capability of the fuel and the materials the engine are made of.

IF you have access to higher octane fuel, you can change minor features of the engines mechanical design and tuning to wring more power/increase the heat in the engine, before it starts to fall apart.

Usually to use maximize the use of high octane fuel you have to physically change the design of the piston head or combustion chamber, or if fitted, increase supercharger boost to increase compression, and change the ignition timing and fuel air ratio. Minor improvements can be had with ignition and carburetion tuning. To get the maximum effect though would require supercharger changes and possibly total dismantling of the engine to change the pistons and/or cylinder heads.

The me109 was supercharged. IF it was a mechanical roots type blower, then the drive ratio of said blower would have to be changed, if it was a exhaust driven turbo-supercharger, then manifold plumbing or waste-gate adjusments/tuning would be in order.

This does not answer your specific question, but if you do find info specific to the engine type, then maybe you will have a little better idea of what is going on if they say they did a piston swap, or increased the boost, etc...

Jumoschwanz

KIMURA
06-02-2004, 08:29 AM
Abbuzze

If you're intersted I could ask my bike dealer how much working time and working effort is needed to change an engine from standard compression to a higher compression which is used in bike racing sports.

Indeed the whole thing is funny because many guys at these forums still thinks an simple increase of octane would change something - at least in the output of more power. http://ubbxforums.ubi.com/images/smiley/35.gif http://ubbxforums.ubi.com/images/smiley/52.gif

Kimura

Cragger
06-02-2004, 08:43 AM
Jumo, while I completely agree with you its most likely the DB605 was orginally designed to run on C3 fuel. However, the lack of available C3 fuel led for the engines to be tuned to run on B4. Which as you know involves changing the charger ratio, ******ing the timing, richer mixture,etc. The MW50 injection was a method of recooping on this by allowing more boost pressure and higher temperatures without the B4 fuel predetonating the engine apart.

The real tricky part is which way should the aircraft in the game be modeled. They way they where meant to be at peak performance... Or the way there actually where with what was available for their time in the war. This is where Oleg's team has potentially slipped up, by including some fantasy aircraft whos FM can only be determined from projected data, and some aircraft like the Bf109G14 from the Hungary plant data you have plans in the game as best as they where meant to be. And then others such as the aircraft powered by the DB605 and others are modelled as tuned for B4 fuel... Its going in two different directions at the same time and shows no presedent to make conjectual decisions on.

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Jumoschwanz
06-02-2004, 08:51 AM
Well the later luftwaffe planes certainly were not slower than the early war ones. So as long as the sim gets that right, it is still fabulous in my book and I am grateful for whatever work the creators have done. S!

Jumoschwanz

DmdSeeker
06-02-2004, 09:03 AM
"The me109 was supercharged. IF it was a mechanical roots type blower, then the drive ratio of said blower would have to be changed"

I believe the the 109 had a centrifugle rather than Rootes type blower; and that it was driven by a continuously variable; stepless viscous coupling.

One other, more simple way of changine compression ratio is to either use thinner head gaskets; or to shave (mill) either the head lands or the block lands. To a certain limit; of course! http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif

LilHorse
06-02-2004, 10:00 AM
As I recall from an earlier discussion that touched on this subject, the Germans tended to attempt to make hp gains by going for higher compression ratios with a relatively low manifold pressure. Whereas, the Americans and Brits leaned more toward higher manifold pressures and moderate compression ratios. Given the German approach I would think that in addition to timing and mixture changes that thinner gaskets or head shaving (as mentioned above) might have been employed as a means of optimising for the higher octane.

p1ngu666
06-02-2004, 12:13 PM
dont think the germans could do high manifold pressure cos of poor fuel quality
i thought octane was how potent the fuel was, oh well http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif
oh the sim models as new aircraft which is fair enough cos how do u degrade performance fairly?

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Abbuzze
06-02-2004, 12:59 PM
Well explained Jumoschwanz!
And you are correct Kimura, I real like this funny stories about 150oct fuel in the tank and 200% more power! http://ubbxforums.ubi.com/infopop/emoticons/icon_wink.gif or better than 150cot- take some Kerosin! http://ubbxforums.ubi.com/infopop/emoticons/icon_biggrin.gif

It´s pity but I dont´t know what kind of changes are necessary, but maybe some experts know more than me...

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Abbuzze
06-02-2004, 05:40 PM
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Cragger
06-02-2004, 06:55 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
i thought octane was how potent the fuel was, oh well http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif
<HR></BLOCKQUOTE>

I made a post on this long ago. Very bascially the more octane in gasoline the less total chemical energy it has. However, an engine designed towards the chemical properties of high octane fuel can be more efficient and get a larger percentage of the chemical energy in the fuel converted to mechanical energy.

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Helvik
06-03-2004, 01:36 AM
By March '45 only a few 109 gruppen were using C3, one of the few being the II/JG11 which was responsible for testing the *605DB/DC in January-March 1945.

*FYI,
There was no DB605DB and DB605DC per se, since they refer to the same engine the DB605D. It could be configured for either fuel just by turning a screw to accept either B4 or C3 fuel.

C3 was not used by 109 units until the 1.98 ata boost was cleared. 109s relied on B4 + MW50. C3 for the most part went to the 190 units. D-9 units relied mostly on B4 + MW50 as well but could use C3 but only if no B4 is available.

Even after the 109 was cleared for 1.98 ata (March '45) only few gruppen got it because of shortage of C3 and the fact that C3 was needed for the 190s.

In March '45 only two gruppen, IV/JG 4 the other being II/JG 11, were using C3 (both flying the G-10). No K-4 gruppen were using C3 at this time.

Helvik
06-03-2004, 02:29 AM
http://www.fischer-tropsch.org/primary_documents/gvt_reports/USNAVY/tech_rpt_145_45/rpt_145_45_toc.htm

An engines power is the result of sustained RPM in a given condition. To maintain power as altitude increases it is necessary to either maintain manifold pressure, to sustain RPM, or increase it as altitude is gained. An engine is designed to accomodate an aircharge with a designed flame front, or speed at which the fuel/air mixtures burns. By using a super or turbo charger which compress air to increase manifold pressure, which in direct proportion increases air temperature, it is necessary to cool this air by either a subtantial mechanical aircooler or by adding a fluid to the aircharge in an expansion phase that will cool the charge. If this is not done the high temperature of the Fuel/air charge entering the engine is so close to it's ignition temperature that the flame front in the cylinder will be too fast or instantatious, this is called detonation.

Detonation will cause damage to the engine. To prevent detonation the LW used MW50 in combination with B4 fuel to run at a higher boost.

Higher octane fuels produce gases that take longer to autoignite. So you can run at a higher boost before detonation is a factor then lower octane fuels.

Compare the DB605D using B4 and C3. It´s the same engine but if the DB605D is set up to use B4 max boost is 1.8 ata.

If the DB605D is set up to use C3 then max boost is 1.98ata. You get a .18 increase in ata, in both cases using MW50.

So yes a fuels quality and octane rating determin how much power you get out of an engine.

Combustion temperature and pressure is higher for C3 and there actually is an increase in power output when using the higher grade fuel.

[This message was edited by Helvik on Thu June 03 2004 at 03:39 AM.]

butch2k
06-03-2004, 02:50 AM
Lot of not so exact facts...

There were two kinds of DB605D with MW-50 support, the first ones being the DB605DM rated at 1.75ata max. Later on (02/1945) the DB605DB (1.8ata max)/DC(1.98 ata max) was produced and it introduced some changes, including the possibility to change the fuel type and gain extra performance gain from this change. The change was made at front line technical centers, at there were some engine parameters to adjust. The engine was considered as a DB when set for running on B4 and DC when set for C3 use. The way the engine was set was clearly indicated on the engine left side by the technical centers mechanics.
So the change was not a matter of minutes but rather of hours or couple of days.


The C3 fuel is roughly equivalent to a 95/140 fuel, because of it's very high TEL and aromatic content, note that B4 is not 87 octane as usualy believed but 92.

Abbuzze
06-03-2004, 04:25 AM
Thanks butch! So it was not possible to modify the engine at the airfield.
I asked, cause I remember a report of a 109 Pilot who forced a P51 to bellyland close to his airfield.
He saw this, and against official orders (to report such a landing cause of the highqualityfuel inside the plane), he organised a fueltruck and drove to the plane to suck the fuel out of it.
He mentioned the higher quality of the P51 fuel, and that his engine would run better with this fuel.
So I wonderd what better meand- just a bit smoother or with more power?
If it took so long to change the enginesettings, and it was only possible at a tech-center, it seems to be just the smoother running engine.
Thanks!

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butch2k
06-03-2004, 04:32 AM
The late war B4 was especialy low quality and it's not surprising pilot prefered using captured fuel. But i'm not sure the plugs liked it either as the fuel composition was somewhat different.

KIMURA
06-03-2004, 04:38 AM
Even regarding the better knocking resistance of the higher graded fuel, a smoother run of the engine is NOT a logical consequences. IF the engine parameters are set well and were chosen right to run lower graded fuel, you'll not see any effect on higher graded fuel running in the same engine. If the engine is running at 87 oct without any knocking behaviour at high performance output, the higher octane fuel has no effect - expect it's more expensive.

Kimura

Abbuzze
06-03-2004, 05:15 AM
100% correct Kimura, but it should had an advantage (not today for sure!!), cause the pilot didn´t care about orders, was driving in a truck instead of stitting in a chair with a beer... http://ubbxforums.ubi.com/infopop/emoticons/icon_wink.gif
maybe the fuel they had in this time didnt
reach the B4 standarts for 100%- so they got an andvantage by using better one.

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butch2k
06-03-2004, 05:53 AM
Yes B4 seems to have been very low quality and maybe not up to the standard in some cases.

Cragger
06-03-2004, 12:28 PM
If the story is even true its probably just a psycological effect. 90% of the people out there think that putting premimum in the car designed for 87 octane makes it run better and perform better. While I can and have shown it to the opposite on a dyno.

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ZG77_Lignite
06-03-2004, 10:54 PM
I liked this thread. Maybe Butch will explain to us (again) how the FW190A 'WEP' was operated. Just to get the ball rolling, I am under the impression it was C3 fuel injected directly into the supercharger to cool the air charge, similar to MW-50 as stated above. Wasn't it determined to be as effective as the MW-50 was?

Helvik
06-04-2004, 04:28 AM
"Erh¶hte Notleistung" - C3 injection:

The airline of the blower was bled to induce a fuel surge and use it as a charge cooler. C3 was injected into the eye of the blower. It allowed increased boost by its charge cooling effect.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>The pilot had a small push-pull control which operated two *****. The first **** opened an air bleed in the boost pressure regulator chamber, causing the regulator to open the butterfly throttle to provide +8.8 lb. boost instead of +5.5 lb. boost at sea level. The second **** opened a pipe line from the fuel pump to a spray nozzle fitted in the port air intake.<HR></BLOCKQUOTE>

Abbuzze
06-04-2004, 04:39 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Cragger:
If the story is even true its probably just a psycological effect. 90% of the people out there think that putting premimum in the car designed for 87 octane makes it run better and perform better. While I can and have shown it to the opposite on a dyno.

http://redspar.com/redrogue/cragger_sig.jpg <HR></BLOCKQUOTE>

Today you are right, but a pilot at this time nearly lived together with his mechanics, they helped them to get in and out of the cockpit, so I´m pretty sure they would tell the pilot that it is just psychological! http://ubbxforums.ubi.com/infopop/emoticons/icon_wink.gif and not worth the time to get the fuel if it has no advantage...

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