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Manu-6S
05-28-2009, 06:28 AM
Hi guys,

I need informations about these two engines, above all fuel consumption.

Do you have any chart? Any link?

Thanks!

JG53Frankyboy
05-28-2009, 06:38 AM
http://www.franky.fliegerhospital.de/Leistung%20Bf109E-3.jpg

Xiolablu3
05-28-2009, 06:42 AM
I would expect that the DB had a higher fuel consumption, especially earlier in the war when the Merlins boost wasnt so high...

27 litres for the Merlin vs
34 litres for the DB vs
36.7 for the Griffon

The Griffon is closer to the DB in terms of displacement.

Very possibly the late Merlins with their high boost used more than the early Merlins, but I guess the same could be said for the DB engines which raised in ATA over the war years, but these were not as highly boosted as the Merlin IIRC.

Anyone know what 1.42 ATA equals in the Lbs of boost used in the RAF? I remember it being something very low.

The later DB engines needed to use MW50 and Nitrous Oxide to keep up with the Merlins, Sabres and Griffons.

Manu-6S
05-28-2009, 07:21 AM
Thanks guys!! http://forums.ubi.com/images/smilies/25.gif

uppurrz
05-28-2009, 07:46 AM
Originally posted by Xiolablu3:
Anyone know what 1.42 ATA equals in the Lbs of boost used in the RAF? I remember it being something very low.


here you go. ~5.75lb

http://img.villagephotos.com/p/2005-12/1114844/Boost.jpg

Manu-6S
05-28-2009, 12:10 PM
Hi mates,

Have anyone the SpitfireI's range chart? Something like the one Frankyboy provided for the 109?

I'm searching on the web but I only find single numbers and not a real grid based on alt and RPM.

No41Sqn_Banks
05-28-2009, 01:00 PM
According to Wikipedia:
the Merlin II (http://en.wikipedia.org/wiki/Rolls-Royce_Merlin#Specifications_.28Merlin_II.29) has a specific fuel consumption of 0.63 lb/(hp*h) (http://www60.wolframalpha.com/input/?i=0.63+lb%2F(hp*h)),
the DB 601Aa (http://en.wikipedia.org/wiki/Daimler-Benz_DB_601#Specifications_.28DB_601Aa.29) has a specific fuel consumption of 0.44 lb/(hp*h) (http://www60.wolframalpha.com/input/?i=0.44+lb%2F(hp*h)).

If we compare (http://www60.wolframalpha.com/input/?i=0.63+lb%2F(hp*h)%2C+0.44+lb%2F(hp*h)) both values, we get 1.43 (http://www60.wolframalpha.com/input/?i=0.63+lb%2F(hp*h)%2F0.44+lb%2F(hp*h)) higher specific fuel consumption for the Merlin II.

Edit: I used the wrong input values for the comparison. They are now corrected. Sorry for that http://forums.ubi.com/groupee_common/emoticons/icon_frown.gif

Manu-6S
05-28-2009, 01:03 PM
Originally posted by No41Sqn_Banks:
According to Wikipedia the Merlin II (http://en.wikipedia.org/wiki/Rolls-Royce_Merlin#Specifications_.28Merlin_II.29) has a specific fuel consumption of 0.63lb / (hp * h) * (382g / (kW * h)) (http://www82.wolframalpha.com/input/?i=0.63lb+%2F+(hp+*+h)+*+(382g+%2F+(kW+*+h))),
the DB 601Aa (http://en.wikipedia.org/wiki/Daimler-Benz_DB_601#Specifications_.28DB_601Aa.29) has a specific fuel consumption of 270g / (kW * h) * (0.44lb / (hp * h)) (http://www82.wolframalpha.com/input/?i=270g+%2F+(kW+*+h)+*+(0.44lb+%2F+(hp+*+h))).

Converted to the same unit (http://www60.wolframalpha.com/input/?i=(0.63lb+%2F+(hp+*+h)+*+(382g+%2F+(kW+*+h)))%2C+ (270g+%2F+(kW+*+h)+*+(0.44lb+%2F+(hp+*+h)))), we can see that the specific fuel consumption of the Merlin II is 2.03 (http://www60.wolframalpha.com/input/?i=(0.63lb+%2F+(hp+*+h)+*+(382g+%2F+(kW+*+h)))+%2F +(270g+%2F+(kW+*+h)+*+(0.44lb+%2F+(hp+*+h)))) higher than that of the DB 601Aa.

Wow, thanks mate http://forums.ubi.com/images/smilies/11.gif

No41Sqn_Banks
05-28-2009, 01:05 PM
Don't thank me, thank WolframAlpha http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

The first time I found a practical use for it, beside of comparisons of different aircraft (http://www33.wolframalpha.com/input/?i=Spitfire%2C+Ta+152) http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

No41Sqn_Banks
05-28-2009, 01:10 PM
Hmm wait I did use the wrong input. I will correct my post in a few minutes http://forums.ubi.com/groupee_common/emoticons/icon_frown.gif


It might be interesting to compare the specific power (http://www60.wolframalpha.com/input/?i=0.70+hp%2Fin%C2%B3%2C+0.56+hp%2Fin%C2%B3) of both engines, the Merlin II has a 1.25 times higher specific power.

Kurfurst__
05-28-2009, 02:29 PM
Originally posted by Manu-6S:
Hi guys,

I need informations about these two engines, above all fuel consumption.

Do you have any chart? Any link?

Thanks!

It depends one what power rating you are looking for - best economy or fuel consumption at maximum output?

For what its worth, here's the data for the basic DB 601A-1
(keep in mind that other engines - 601Aa, 601N, 601E also existed, and had different ratings and consumption. Frankyboy already posted for the DB 601Aa, which had slightly higher output).

DB 601A-1 in Bf 109E

Max output - 5 min
At 1.30ata manifold pressure, 2400 rpm developing 990 PS at SL, the fuel consumption was 300 liter/hour (66 imp.gallon/hour).
Same thing at rated altitude, 4.5 km, developing 1020 PS, 315 lit/h (69 imp.gallon/h)

Most economical (highest range) - at 0.75 ata, 1300 RPM: 120 lit/h (26 imp.gallon/h), at 1000 m (3,280 feet) altitude.
Most economical (highest range) - at 0.76 ata, 1400 RPM: 150 lit/h (33 imp.gallon/h), at 5000 m (16,404 feet)altitude.

Most economical (highest endurance) - at 0.70 ata, 1200 RPM: 105 lit/h (23 imp.gallon/h), at 1000 m (3,280 feet) altitude.
Most economical (highest endurance) - at 0.72 ata, 1300 RPM: 130 lit/h (28.3 imp.gallon/h), at 5000 m (16,404 feet)altitude.


Merlin II in Spitfire Mk I

Output - 5 min
At +6.25 lbs boost, 3000 rpm, it was 404 liters/89 imp gallons / hour, at 5181 m / 17 000 feet.
From the power curves charts, this translates to ~1025 HP at 17 000 feet, and at ~875 HP at SL.
Most economical cruising 113 lit/h 25 gal/hr at 14,000 feet

Merlin XII in the Spitfire Mk. II
At +9 lbs boost, 3000 rpm, it was 444 liters/98 imp gallons / hour, at 4420 m / 14 500 feet.
From the power curves charts, this translates to 1150 HP at 14 500 feet, at 990 HP at SL.

It would appear to me that fuel economy at cruising speeds were very similiar (economic speeds are also effected by the airframe though), but when high output was required, the Merlin was considerably thirstier, probably on account of its smaller displacement, neccessiating high level of supercharging, and lower compression ratio (RR - 6:1 through the war vs DB 601A - 6.9:1, later increased up to 8.5:1)

Manu-6S
05-28-2009, 02:57 PM
Originally posted by Kurfurst__:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Manu-6S:
Hi guys,

I need informations about these two engines, above all fuel consumption.

Do you have any chart? Any link?

Thanks!

It depends one what power rating you are looking for - best economy or fuel consumption at maximum output?

For what its worth, here's the data for the basic DB 601A-1
(keep in mind that other engines - 601Aa, 601N, 601E also existed, and had different ratings and consumption. Frankyboy already posted for the DB 601Aa, which had slightly higher output).

DB 601A-1 in Bf 109E

Max output - 5 min
At 1.30ata manifold pressure, 2400 rpm developing 990 PS at SL, the fuel consumption was 300 liter/hour (66 imp.gallon/hour).
Same thing at rated altitude, 4.5 km, developing 1020 PS, 315 lit/h (69 imp.gallon/h)

Most economical (highest range) - at 0.75 ata, 1300 RPM: 120 lit/h (26 imp.gallon/h), at 1000 m (3,280 feet) altitude.
Most economical (highest range) - at 0.76 ata, 1400 RPM: 150 lit/h (33 imp.gallon/h), at 5000 m (16,404 feet)altitude.

Most economical (highest endurance) - at 0.70 ata, 1200 RPM: 105 lit/h (23 imp.gallon/h), at 1000 m (3,280 feet) altitude.
Most economical (highest endurance) - at 0.72 ata, 1300 RPM: 130 lit/h (28.3 imp.gallon/h), at 5000 m (16,404 feet)altitude.


Merlin II in Spitfire Mk I

Output - 5 min
At +6.25 lbs boost, 3000 rpm, it was 404 liters/89 imp gallons / hour, at 5181 m / 17 000 feet.
From the power curves charts, this translates to ~1025 HP at 17 000 feet, and at ~875 HP at SL.
Most economical cruising 113 lit/h 25 gal/hr at 14,000 feet

Merlin XII in the Spitfire Mk. II
At +9 lbs boost, 3000 rpm, it was 444 liters/98 imp gallons / hour, at 4420 m / 14 500 feet.
From the power curves charts, this translates to 1150 HP at 14 500 feet, at 990 HP at SL.

It would appear to me that fuel economy at cruising speeds were very similiar (economic speeds are also effected by the airframe though), but when high output was required, the Merlin was considerably thirstier, probably on account of its smaller displacement, neccessiating high level of supercharging, and lower compression ratio (RR - 6:1 through the war vs DB 601A - 6.9:1, later increased up to 8.5:1) </div></BLOCKQUOTE>

Thanks Kurfy! Useful as always! http://forums.ubi.com/images/smilies/25.gif

uppurrz
05-28-2009, 03:14 PM
Can someone explain why the Merlin 45/50 had better consumption numbers for the boosts stated by Kurfurst?

http://img.villagephotos.com/p/2005-12/1114844/Spitfire_RAF_Instructions_3.jpg

K_Freddie
05-28-2009, 04:16 PM
I'm sure fuel octane and quality had a lot to do with it.
http://forums.ubi.com/groupee_common/emoticons/icon_cool.gif

Kurfurst__
05-28-2009, 04:37 PM
Originally posted by uppurrz:
Can someone explain why the Merlin 45/50 had better consumption numbers for the boosts stated by Kurfurst?

I am puzzled by the phenomenon because the later DB engines show the same trend, ie. the DB 601A is somewhat thirsty compared to them.

Two things I can think of - some improvements were made on the Merlin 45, as was on the DB 601E, improving scavanging etc.
The second, and this seems more likely, is that since the M45 used higher octane fuel, it required to waste less fuel at charge cooling (at high outputs, essentially all non-direct fuel injected engines pour a lot more fuel into the engine than it needs for a given boost, to cool the charge and thus control knocking)

No41Sqn_Banks
06-03-2009, 04:14 AM
AIR PUBLICATION 1590B
VOLUME I, 2nd EDITION
October, 1938

MERLIN II AND III AERO-ENGINES

At page 14:

<pre class="ip-ubbcode-code-pre">
(4) Fuel
Type .. .. .. Specification D.T.D. 230
Fuel consumptions-
(i) At maximum climbing 71.5 gallons per hour.
conditions at sea
level (875 b.h.p. at
2,600 r.p.m.).
(ii) At maximum cruising 0.595 pint per b.h.p. per hour.
conditions at sea
level (790 b.h.p. at
2,600 r.p.m.).
(iii)At maximum take-off 78.5 gallons per hour.
conditions at sea
level (890 b.h.p. at
2,850 r.p.m.).
(ii) At economical cruising 0.53 pint per b.h.p. per hour.
mixture strength
(automatic weak,
685 H.P. at
2,600 r.p.m. at +2 1/4 lb.
per sq. in. boost).
</pre>
http://public.41squadron.org/m...fuel_consumption.png (http://public.41squadron.org/merlin_ii_fuel_consumption.png)

There is an amendment that corrects the engine limit values for Merlin III and V engines, the engine limit values remained the same for Merlin II engines.

Amendment List No. 4
to
AIR PUBLICATION 1590B
Volume I
(2nd Edition, October, 1938)
November, 1940

At page 3:

<pre class="ip-ubbcode-code-pre">
4. Fuel
Type ... ... ... Specification D.T.D.230 (Merlin
III and V) or 100 octane
(Merlin V)

Consumtions (with 87 octane fuel):-
(i) At maximum 78.5 gallons per hour (890 b.h.p.
take-off at 3,000 r.p.m. and +6 1/4 lb. per
conditions sq. in. boost at sea level)
(ii) At maximum 71.5 gallons per hour (875 b.h.p
climbing at sea level at 2,600 r.p.m. and
conditions +6 1/4 lb. per sq. in. boost)
(iii) At maximum 0.595 pint per b.h.p./hour (790
cruising b.h.p at sea level at 2,600 r.p.m.
(automatic rich) and +4 1/2 lb. per sq. in. boost)
conditions
(iv) At economical 0.53 pint per b.h.p./hour (685
cruising (auto- b.h.p at sea level at 2,600 r.p.m.
matic weak) and +2 1/4 lb. per sq. in.
conditions boost)
</pre>
http://public.41squadron.org/m...fuel_consumption.png (http://public.41squadron.org/merlin_iii_fuel_consumption.png)

jamesblonde1979
06-03-2009, 05:56 AM
Originally posted by Manu-6S:


Do you have any chart?
Thanks!

http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif, you just walked into the lion's den and asked if they have any teeth mate.

Kettenhunde
06-03-2009, 09:41 AM
At page 3:


4. Fuel
Type ... ... ... Specification D.T.D.230 (Merlin
III and V) or 100 octane
(Merlin V)

Consumtions (with 87 octane fuel):-
(i) At maximum 78.5 gallons per hour (890 b.h.p.
take-off at 3,000 r.p.m. and +6 1/4 lb. per
conditions sq. in. boost at sea level)
(ii) At maximum 71.5 gallons per hour (875 b.h.p
climbing at sea level at 2,600 r.p.m. and
conditions +6 1/4 lb. per sq. in. boost)
(iii) At maximum 0.595 pint per b.h.p./hour (790
cruising b.h.p at sea level at 2,600 r.p.m.
(automatic rich) and +4 1/2 lb. per sq. in. boost)
conditions
(iv) At economical 0.53 pint per b.h.p./hour (385
cruising (auto- b.h.p at sea level at 2,600 r.p.m.
matic weak) and +2 1/4 lb. per sq. in.
conditions boost)




Can you post the copy of this please?

All the best,

Crumpp

No41Sqn_Banks
06-03-2009, 10:00 AM
I can do this, but first I need to convince my scanner to run under 64 bit.

Stay tuned!

No41Sqn_Banks
06-03-2009, 10:25 AM
Got it working.

http://public.41squadron.org/m...fuel_consumption.png (http://public.41squadron.org/merlin_ii_fuel_consumption.png)
http://public.41squadron.org/m...fuel_consumption.png (http://public.41squadron.org/merlin_iii_fuel_consumption.png)

Edit: Scanned the wrong one, now both are available.

Kurfurst__
06-03-2009, 10:59 AM
Excellent! http://forums.ubi.com/images/smilies/25.gif

Viper2005_
06-03-2009, 11:24 AM
Originally posted by Kurfurst__:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by uppurrz:
Can someone explain why the Merlin 45/50 had better consumption numbers for the boosts stated by Kurfurst?

I am puzzled by the phenomenon because the later DB engines show the same trend, ie. the DB 601A is somewhat thirsty compared to them.

Two things I can think of - some improvements were made on the Merlin 45, as was on the DB 601E, improving scavanging etc.
The second, and this seems more likely, is that since the M45 used higher octane fuel, it required to waste less fuel at charge cooling (at high outputs, essentially all non-direct fuel injected engines pour a lot more fuel into the engine than it needs for a given boost, to cool the charge and thus control knocking) </div></BLOCKQUOTE>

The most likely explanation is the considerable improvements made to the Merlin's supercharger efficiency throughout the war by ****** et al..

Supercharger design almost certainly improved in Germany as well, in both cases not so much because of the SFC benefit, but because the supercharger is the main thing which governs the mass flow which the engine can swallow, and the mass flow in turn directly governs the power available.

No41Sqn_Banks
06-03-2009, 11:27 AM
Originally posted by Kurfurst__:
Excellent! http://forums.ubi.com/images/smilies/25.gif

http://public.41squadron.org/AP1590B_preview.pdf http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Manu-6S
06-03-2009, 01:19 PM
http://forums.ubi.com/images/smilies/11.gif

Thanks Banks, I really appreciate your work!

Meanwhile I did a test with the E4 using the data provided by Kurfurst (and now I'm going to test the Spit).

I can's work with the LesniHU autopilot since I haven't found a way to work with throttle and PP (in reality I looked only to the guide inside the zip).

All I did was keeping the plane straight at 1000m, using a combination of throttle and manual PP to keep 1300RPM and 0,75Ata. (and I did it very well).

I did the test on the Channel map (next time I'll try it on the Crimea map)

After 20 minutes I've consumed 1/8 of the fuel tank (started full) and I fled for 115km.

This numbers for 8 give 160mins of autonomy and a range of almost 920km (maybe more since I was still consuming fuel and so decreasing weight). http://forums.ubi.com/images/smilies/16x16_smiley-surprised.gif

Very strange results...

And more strange numbers are the ones ingame:

The Il2 data are:

SpitMkI:
Fuel 320.0
Range 875.0
CruiseSpeed 370.0

109E4:
Fuel 300.0
Range 480.0
CruiseSpeed 370.0

This translates in:
SpitMkI:
Autonomy 2.36 h
Fuel consumption 136 kg/h = 189 l/h

109E4:
Autonomy 1.30 h
Fuel consumption 230 Kg/h = 319 l/h

Kurfurst__
06-03-2009, 01:54 PM
Originally posted by No41Sqn_Banks:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kurfurst__:
Excellent! http://forums.ubi.com/images/smilies/25.gif

http://public.41squadron.org/AP1590B_preview.pdf http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif </div></BLOCKQUOTE>

Juicy stuff you have there, thanks for the preview, and the scans again. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Xiolablu3
06-03-2009, 02:10 PM
Manu, when you are testing 'range'. How exactly are you doing it?

Is your 'range' how far the aircraft can fly altogther in total in one straight line?

Or is it half of the total miles flew, as in 'range' but having to get back to base after the mission?

This needs to be explained. There are many different types of 'range' as you know.

The SPit IX had a combat range of about 400miles. Which meant 800 total miles flown. I'm guessing if flying at total economical speed and power it would be able to fly around 1000-1100 miles total. But of course this is not including a combat mission in the middle.

No41Sqn_Banks
06-03-2009, 02:16 PM
Originally posted by Manu-6S:
This translates in:
SpitMkI:
Autonomy 2.36 h
Fuel consumption 136 kg/h = 189 l/h

If I apply the "0.53 pints per bhp / hour" formula for economical cruising to the 685 bhp stated for this setting at sea level, I get 47.72mL/s (http://www65.wolframalpha.com/input/?i=0.53*685pints%2Fh), which is 171.79 L/hr (http://www25.wolframalpha.com/input/?i=47.72%20milliliters%20per%20second).

When this method is applied to the maximum cruising formula I get 61.78mL/s (http://www65.wolframalpha.com/input/?i=0.595*790pints%2Fh) which is 222.41 L/hr (http://www99.wolframalpha.com/input/?i=61.78%20milliliters%20per%20second).

Manu-6S
06-03-2009, 02:21 PM
Originally posted by Xiolablu3:
Manu, when you are testing 'range'. How exactly are you doing it?

Is your 'range' how far the aircraft can fly altogther in total in one straight line?

Or is it half of the total miles flew, as in 'range' but having to get back to base after the mission?

This needs to be explained. There are many different types of 'range' as you know.

The SPit IX had a combat range of about 400miles. Which meant 800 total miles flown. I'm guessing if flying at total economical speed and power it would be able to fly around 1000-1100 miles total. But of course this is not including a combat mission in the middle.
Total distance reachable in one straight line: I think the one expressed in the data are this type, isn't it?

Because if Oleg intends in the way you do then the ingame numbers seem almost correct. But using the economical setting I should have at least 650km (so 1300km of mine "range").

I'll try again with a longer session.

Manu-6S
06-03-2009, 02:23 PM
Originally posted by No41Sqn_Banks:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Manu-6S:
This translates in:
SpitMkI:
Autonomy 2.36 h
Fuel consumption 136 kg/h = 189 l/h

If I apply the "0.53 pints per bhp / hour" formula for economical cruising to the 685 bhp stated for this setting at sea level, I get 47.72mL/s (http://www65.wolframalpha.com/input/?i=0.53*685pints%2Fh), which is 171.79 L/hr (http://www25.wolframalpha.com/input/?i=47.72%20milliliters%20per%20second).

When this method is applied to the maximum cruising formula I get 61.78mL/s (http://www65.wolframalpha.com/input/?i=0.595*790pints%2Fh) which is 222.41 L/hr (http://www99.wolframalpha.com/input/?i=61.78%20milliliters%20per%20second). </div></BLOCKQUOTE>

Wolframalpha is great http://forums.ubi.com/images/smilies/16x16_smiley-tongue.gif

Kettenhunde
06-03-2009, 10:07 PM
to the 685 bhp

That is what I was focusing on. Is the 385 bhp a typo or is the 685 bhp?

That was the only change I saw in the revision and why I asked you to post the page.

Thanks!

All the best,

Crumpp

No41Sqn_Banks
06-04-2009, 12:04 AM
Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">to the 685 bhp

That is what I was focusing on. Is the 385 bhp a typo or is the 685 bhp?

That was the only change I saw in the revision and why I asked you to post the page.

Thanks!

All the best,

Crumpp </div></BLOCKQUOTE>

Yes this was a typo, thanks for mentioning. I fixed it in the post. One number that changed is the higher RPM for Merlin III and they added the boost level, I think both is caused by the Constant Speed Propeller.

Kettenhunde
06-04-2009, 05:52 AM
Thank you for clarifying the power typo.

All the best,

Crumpp

squareusr
06-05-2009, 03:18 PM
Originally posted by Kurfurst__:
I am puzzled by the phenomenon because the later DB engines show the same trend, ie. the DB 601A is somewhat thirsty compared to them.


Edit: misread some things, reconfiguring brain logic module http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Without diving into the insanely complex details of internal combustion engines (i probably know less about those than most here) i actually would have expected pretty much the opposite, later engines having a tendency for higher fuel consumption/(time*power) numbers. My reasoning went like this:

Initially any engine gets designed to generally be a "good engine", with reasonably characteristics in all aspects.

As the war progressed one of the battles turned out to be a long distance competition between engineers trying to beat each others in raw engine power. Sure they would happily make make more and more compromises in fuel economy to get that little edge in speed if they had the opportunity - and they obviously had.

Depending on the characteristics of the aircraft, power gained through sacrifices in (specific) fuel economy can be enough to compensate the weight of additional fuel or not. But even in those cases when the win is too small to completely outweigh the loss it can be a very attractive option for many roles.

If later versions of the same basic engine have better specific fuel economy, then that could well be the same effect that's all the rage amongst car makers these days:

if you find ways to improve power output without increasing the size of the engine or rpm (e.g. by forcing in more fuel per cycle together with even more air compressed into the same volume) then the loss through mechanical friction will stay roughly the same. Same parts moved the same distance in the same amount of time. Since the total power input of the equation will increase the fraction lost to friction will sink.

JtD
06-06-2009, 03:35 AM
You can increase compression, using the same amount of air and fuel and end up with more power.

JuHa-
06-06-2009, 09:48 AM
Originally posted by Kurfurst__:
I am puzzled by the phenomenon because the later DB engines show the same trend, ie. the DB 601A is somewhat thirsty compared to them.

Logically speaking the engines became more efficient during their development. 'How' is the real question here, and as mentioned by JtD, upping the compression is one way.

Also, reducing the internal friction will help to reduce consumption on partial loads. Maybe they also adjusted the fuel/air mixture to leaner on these economy settings?

Maybe as well the shape of the cylinder head was improved thus enabling more complete buring of the mixture. I don't know if they did these things, but these are some of the ways of refining the engine for better fuel economy.

squareusr
06-06-2009, 07:43 PM
Another aspect is wear: i can't support my theories with written facts, but as engineers forced more power out of engines of roughly the same dimensions they sure made sacrifices in wear resistance: in times of (relative) peace, an engine has to be run at parameters that will allow it to survive many hours of flight. Cheaper (and thus longer) pilot training will give you more than a slightly faster plane.


But in the heat of the war a faster engine, that has to be replaced after only few hours of operation can be very economical if it raises the rate of survival for the remaining airframe and, above all, the pilot. If you can force more power from a given engine through more aggressive, wear-increasing settings you are also likely to get better specific fuel economy because some parts of the internal power losses that go into the total level of inefficiency stay constant.

WTE_Galway
06-06-2009, 08:31 PM
Originally posted by squareusr:
Another aspect is wear: i can't support my theories with written facts, but as engineers forced more power out of engines of roughly the same dimensions they sure made sacrifices in wear resistance: in times of (relative) peace, an engine has to be run at parameters that will allow it to survive many hours of flight. Cheaper (and thus longer) pilot training will give you more than a slightly faster plane.


But in the heat of the war a faster engine, that has to be replaced after only few hours of operation can be very economical if it raises the rate of survival for the remaining airframe and, above all, the pilot. If you can force more power from a given engine through more aggressive, wear-increasing settings you are also likely to get better specific fuel economy because some parts of the internal power losses that go into the total level of inefficiency stay constant.

That way of thinking has a definite Soviet spin to it.

No41Sqn_Banks
06-09-2009, 12:52 PM
Originally posted by Kurfurst__:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by No41Sqn_Banks:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kurfurst__:
Excellent! http://forums.ubi.com/images/smilies/25.gif

http://public.41squadron.org/AP1590B_preview.pdf http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif </div></BLOCKQUOTE>

Juicy stuff you have there, thanks for the preview, and the scans again. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif </div></BLOCKQUOTE>

I've seen that parts of it already are hosted on http://www.wwiiaircraftperformance.org/, how can I get in contact with Mike Williams, I could provide him scans of the whole manual.

Mike_Williams
06-09-2009, 01:48 PM
Hello No41Sqd-Banks:

Please see private message. Thanks!

Mike