Jump to content


Photo
- - - - -

Mercedes D.IIIaü for Albatros D.Va and Fokker D.VII (instead of D.IIIa)


  • Please log in to reply
48 replies to this topic

#1 myfabi94

myfabi94
  • Posts: 12

Posted 06 March 2015 - 01:33

So, now this is taken from the Wiki:

 

"Many sources erroneously state that the D.VII was equipped with the 120 kW (160 hp) Mercedes D.III engine. The Germans themselves used the generic D.III designation to describe later versions of that engine. In fact, the earliest production D.VIIs were equipped with 170-180 hp Mercedes D.IIIa. Production quickly switched to the intended standard engine, the higher-compression 134 kW (180-200 hp) Mercedes D.IIIaü. It appears that some early production D.VIIs delivered with the Mercedes D.IIIa were later re-engined with the D.IIIaü."

 

"Albatros responded with the D.Va, which featured stronger wing spars, heavier wing ribs, and a reinforced fuselage.[6] These modifications made the D.Va 23 kg (50 lb) heavier than the D.III, while failing to cure entirely the structural problems of the type. Use of the high-compression 130 kW (180 hp) Mercedes D.IIIaü engine offset the increased weight of the D.Va.[7] The D.Va also reverted to the D.III's aileron cable linkage, running outwards through the lower wing, then upwards to the ailerons, to provide a more positive control response.[3] The wings of the D.III and D.Va were in fact interchangeable.[3] The D.Va was also fitted with a small diagonal brace connecting the lower section of the forward interplane strut to the leading edge of the lower wing. This brace was retrofitted to some D.V aircraft.[7]"

 

This engine has an altitude throttle similar to the current Halberstadt CL.II, so basically low altitude flying should happen at 90% throttle settings and above 1200m full throttle should be possible.

This would make for great engine options like SPAD VII 150 and 180hp.

Currently neither the D.VII or D.Va have the option for the "überkompimiert" engines.

The Albatros D.Va FM could be corrected to original values but a better high altitude engine option.


  • 1

#2 J2_Adam

J2_Adam
  • Posts: 2453
  • LocationVancouver, BC

Posted 06 March 2015 - 03:21

Yes. In regards to the real DIIIau,  Mikael Carlson said that the throttle on his DVII with the Merc DIIIau never goes to full throttle. In fact he has installed a stop to prevent it from doing so. He said that if he were to remove the stop and he were to use full throttle at take off or low altitude the engine would just simply quit due to being to lean of a mixture. 777 got this stuff slightly wrong.


  • 0

#3 1PL-Husar

1PL-Husar
  • Posts: 559

Posted 06 March 2015 - 06:33

In case of Benz engines they just didn't stop, they blow up pistons, have pictures of this happend when they use full power on overcompressed Benz BZ IVa on low altitude.
  • 0

#4 J2_Adam

J2_Adam
  • Posts: 2453
  • LocationVancouver, BC

Posted 06 March 2015 - 09:10

In case of Benz engines they just didn't stop, they blow up pistons, have pictures of this happend when they use full power on overcompressed Benz BZ IVa on low altitude.

Great. Post the pictures would you?


  • 0

#5 myfabi94

myfabi94
  • Posts: 12

Posted 06 March 2015 - 11:25

Power output: 129.75 kW (174 hp) at 1,400 rpm (rated power at sea level), 152.12 kW (204 hp) at 1,600 rpm (maximum power at altitude)


  • 0

#6 1PL-Husar

1PL-Husar
  • Posts: 559

Posted 07 March 2015 - 14:28

Great. Post the pictures would you?

 

With the throttle at full at low altitude plane lost the piston rod, blow up the second cylinder and cause damage to the propeller

 

sccm5d.jpg


  • 0

#7 myfabi94

myfabi94
  • Posts: 12

Posted 07 March 2015 - 19:46

Holy @%&+?!@, this gotta be nasty to have mid-air.

How long did he use it? Seconds, minutes?


  • 0

#8 LukeFF

LukeFF
  • Tester
  • Posts: 7853
  • LocationRedlands, California

Posted 08 March 2015 - 00:24

Holy @%&+?!@, this gotta be nasty to have mid-air.

How long did he use it? Seconds, minutes?

 

Please watch the language.


  • 0

#9 1PL-Husar

1PL-Husar
  • Posts: 559

Posted 08 March 2015 - 07:56

Holy @%&+?!@, this gotta be nasty to have mid-air.
How long did he use it? Seconds, minutes?


After few minutes climb to 1000 meters.


  • 0

#10 myfabi94

myfabi94
  • Posts: 12

Posted 12 November 2015 - 00:46

Bump?


  • 0

#11 J99=Hardy

J99=Hardy
  • Posts: 899
  • LocationGermany

Posted 19 November 2015 - 06:39

What do you think would happen if 777 makes the Fokker D.VII the plane it really was and would improve the already "uber" Albatros D.Va? I already hear the dozen of Allie Pilots whining and I'm pretty sure that it won't help you on MP-Servers because these aircraft will magically disappear from most maps to preserve the "balance". 

 

You may be right, because the Mercedes D.IIIaü was the standard engine from late 1917 on. So one would expect to see that 200hp engine in every Fokker D.VII (First flight in January 1918, delivered to the Front in April 1918).

But hey.... I bet you'll never see this in RoF, so play the game for what it is.


  • 0

img_3834.png


#12 J2_Trupobaw

J2_Trupobaw
  • Moderator
  • Posts: 4151
  • LocationKraków / Poland

Posted 19 November 2015 - 09:31

D.Vas problem is not the horsepower... it's ability to sustain a turn the D.Va airframe gets when horsepower is added.

 

I would rather see the  D.IIIaü installed in Pfalz D.IIIa than Albatros. As of D.VII, definetely, the niche between underpowered D.VII and powerfull D.VIIF needs filling.

As of Entente D.Va voes, we need the original S.E.5a, with 200 hp Hispano-Suiza 8B engines and four-blade propellers. The ones that were able to turn fight with Albatroses, unlike the high-altitude interceptor Viper variant we have now.


 


  • 1

Forum moderator.

Deputy Staffelführer, Jasta 2 ''Boelcke'' http://jasta2.org

“Now now,” Akua chided. “Personal attacks are the mark of failed argument. If you’ve no counterpoint to offer, such flailing only serves to shed further light on your incompetence.”


#13 J2_Adam

J2_Adam
  • Posts: 2453
  • LocationVancouver, BC

Posted 19 November 2015 - 16:04

I don't think I've heard of a DIIIau in a Pfalz D3a.


  • 0

#14 myfabi94

myfabi94
  • Posts: 12

Posted 19 November 2015 - 17:22

What do you think would happen if 777 makes the Fokker D.VII the plane it really was and would improve the already "uber" Albatros D.Va? I already hear the dozen of Allie Pilots whining and I'm pretty sure that it won't help you on MP-Servers because these aircraft will magically disappear from most maps to preserve the "balance". 

 

You may be right, because the Mercedes D.IIIaü was the standard engine from late 1917 on. So one would expect to see that 200hp engine in every Fokker D.VII (First flight in January 1918, delivered to the Front in April 1918).

But hey.... I bet you'll never see this in RoF, so play the game for what it is.

The Albie would be far less powerful at lower alts however. That'S my main point, less power low down, more high up. And of course the FM needs to go somewhere between the current and old one.


  • 0

#15 J2_Trupobaw

J2_Trupobaw
  • Moderator
  • Posts: 4151
  • LocationKraków / Poland

Posted 19 November 2015 - 19:22

I don't think I've heard of a DIIIau in a Pfalz D3a.

I hope it's readable through my daughters handwriting...

 

IMG_20151119_200757067.jpg

 

 

 

IMG_20151119_200904563.jpg

 

I've heard of a plane retaining D.IIIa past spring 1918. Even salvaged and overhauled D.IIIa engines were routinelyupgraded to D.IIIaü before puting them back in airframes


  • 2

Forum moderator.

Deputy Staffelführer, Jasta 2 ''Boelcke'' http://jasta2.org

“Now now,” Akua chided. “Personal attacks are the mark of failed argument. If you’ve no counterpoint to offer, such flailing only serves to shed further light on your incompetence.”


#16 myfabi94

myfabi94
  • Posts: 12

Posted 20 November 2015 - 12:52

I hope it's readable through my daughters handwriting...

 

 

 

 

 

 

 

I've heard of a plane retaining D.IIIa past spring 1918. Even salvaged and overhauled D.IIIa engines were routinelyupgraded to D.IIIaü before puting them back in airframes

+1+1+1++1+1+1+1+1+1+1+1+1+1+1+1+1+1


  • 0

#17 J99=Hardy

J99=Hardy
  • Posts: 899
  • LocationGermany

Posted 20 November 2015 - 14:06

...

 

I've heard of a plane retaining D.IIIa past spring 1918. Even salvaged and overhauled D.IIIa engines were routinelyupgraded to D.IIIaü before puting them back in airframes

 

I also have some printed information about a D.IIIa equipped with an DIIIaü engine. And it seems to be quite reasonable to me since the D.IIIa was still in service in greater numbers in 1918 and the aü variant was an improvement that could be added to existing engines IIRC.


  • 0

img_3834.png


#18 I_Got_Shot

I_Got_Shot
  • Posts: 130

Posted 25 November 2015 - 14:33

I have docs here somewhere which mention the au engine in the DV.a but what is missing from this discussion is the reason the engine was used which was to cover the increased structural strengthening of the fuselage and wings and added weight penalty due to this. The au powered engine DV.a offered no real improvement over the D.III and only a slight performance improvement. I have read that some pilots were scathing of the DV which is why the changes were made and those improvements resulted in the DV.a. By the beginning of 1918 the DV.a was only In service because of numbers available not because it was the best plane, it was obsolete and soldiered on to the end of the war due to necessity. The replacement planes like the Pflaz D.III and Roland D VIa and b were no great improvement so the Albatros remained in service even while it was clearly outclassed by superior aircraft like the Camel F.1, the SE.5a, the Spad XIII and the late war Snipe.

 

I also thought the separate altitude throttle on over compressed engines only belonged to the BMW engine of the DVIIF not the Merc au engines which just used a single throttle (but I am  not sure of this and will have to do some more reading on the subject).

 

I would like to see the Hisso engined SE as well and would certainly like the stock DVII to have a bit more grunt.

 

Regards Shot


  • 0

#19 J99=Hardy

J99=Hardy
  • Posts: 899
  • LocationGermany

Posted 25 November 2015 - 17:58

...

I also thought the separate altitude throttle on over compressed engines only belonged to the BMW engine of the DVIIF not the Merc au engines which just used a single throttle (but I am  not sure of this and will have to do some more reading on the subject).

...

 

You're correct. IIRC the Mercedes DIIIau engine had no altitude throttle. Below 1200m it was operated at max. 90% (or so) throttle.


  • 0

img_3834.png


#20 J2_Adam

J2_Adam
  • Posts: 2453
  • LocationVancouver, BC

Posted 25 November 2015 - 19:53

I also thought the separate altitude throttle on over compressed engines only belonged to the BMW engine of the DVIIF not the Merc au engines which just used a single throttle (but I am  not sure of this and will have to do some more reading on the subject).

 

Hardy is right. Mikael Carlson talked about his DIIIau and said that if did not have the stop built into his throttle and he opened it up wide, the engine would just quit due to and over lean condition. He never flies high enough to use it. Anyway I guess the more you open the throttle past a certain point the more lean the mixture gets. There is a cylinder with a few different sized holes bored into it which is inside of another cylinder with one hole bored into it as part of the carb. The inside cylinder rotates and allows different amounts of air (or fuel...I can't remember) to pass through. So basically it's an automatic mixture control.


  • 0

#21 J2_Trupobaw

J2_Trupobaw
  • Moderator
  • Posts: 4151
  • LocationKraków / Poland

Posted 25 November 2015 - 21:39

IIRC the last 10% of D.IIIau throttle lever works as altitude throttle on top of full throttle.
 

I have docs here somewhere which mention the au engine in the DV.a but what is missing from this discussion is the reason the engine was used which was to cover the increased structural strengthening of the fuselage and wings and added weight penalty due to this. The au powered engine DV.a offered no real improvement over the D.III and only a slight performance improvement. I have read that some pilots were scathing of the DV which is why the changes were made and those improvements resulted in the DV.a. By the beginning of 1918 the DV.a was only In service because of numbers available not because it was the best plane, it was obsolete and soldiered on to the end of the war due to necessity. The replacement planes like the Pflaz D.III and Roland D VIa and b were no great improvement so the Albatros remained in service even while it was clearly outclassed by superior aircraft like the Camel F.1, the SE.5a, the Spad XIII and the late war Snipe.

 

I also thought the separate altitude throttle on over compressed engines only belonged to the BMW engine of the DVIIF not the Merc au engines which just used a single throttle (but I am  not sure of this and will have to do some more reading on the subject).

 

I would like to see the Hisso engined SE as well and would certainly like the stock DVII to have a bit more grunt.

 

Regards Shot

 

D.Vas were routinely re-equipped with D.IIIaus in 1918, and the reason the engine was used was putting best engine available into best plane available in numbers... just like 180hp in Spad7 or Viper engine in SE5.a . If D.Va had no structural problems to "cover" it would still get these engines, just like D.IIIa did, because they gave planes better performance than Mercedes D.IIIa. D.Va with D.IIIau did offer advantage over original D.III... it had doubly reinforced wings.

Quick story of painful V-strutter development:
Original D.III - great performance, sheds wings.

Reinforced wings D.III - shed wings less at cost of performance.
D.V - regains performance via lightweight, streamlined fuselage while keeping reinforced wings that shed less
D.Va - even stronger wings reinforcements, loses performance again but wings shedding problem more or less solved
D.Va with D.IIIau engine - regains performance of D.V (and original D.III)  while keeping wings from shedding. Finally works as original D.III was supposed to before wing problem was discovered.

By the beginning of 1918 D.Va was in service because it was best planes available... except Dr.I, which was never intended to be main frontline fighter give to pilots of average skill. Fokker D.VII and other 1918 planes were still awaiting production orders, while Pfalz D.IIIa and Albatros D.III were inferior to D.Va. 

The moment when Albatros was only in service because of numbers available was Auguts 1918, not beginning of 1918. They never managed to replace them all with D.VIIs.

Roland D.VIa was superior to D.Va, but inferior to D.VII. D.VI was ordered in limited numbers to have production line of D.Va replacements ready if D.VII proved to be flawed. 

 

Whether Albatros being  outclassed by Se5as, Camels (?) and Spads XII is mentioned, it's never explained if they were supposed to be outclassed one on one or when numbers were equal, or were Albatros-equipped Jastas outclassed IRL where Entente had numerical advantage. German pilots believed it to outperform former two (1917 versions) one on one. The fact is, Albatros was not good enough to overcome Entente numerical advantage and bring German k/d ratios to golden standard of Bloody April. Whether it was genuinely bad on top of not good enough is speculation. 


  • 0

Forum moderator.

Deputy Staffelführer, Jasta 2 ''Boelcke'' http://jasta2.org

“Now now,” Akua chided. “Personal attacks are the mark of failed argument. If you’ve no counterpoint to offer, such flailing only serves to shed further light on your incompetence.”


#22 gavagai

gavagai
  • Posts: 15542

Posted 27 November 2015 - 13:09

I like this author's description of the Albatros D.V(a):

 

Comments about the Albatros D.V /Va should be seen in context. The Albatros D.III was the best German fighter when it appeared and was in its heyday in April 1917 and continued in production until May 1918 alongside the D.V/Va. Richthofen also flew the OAW build D.III at times. Indeed in Jasta lineups photos of Jasta 28w and Jasta 27 and other units you can see that the Jastaführers of these units, Karl-Emil Schäfer, Otto Hartmann, Hermann Göring, and countless others continued to fly the D.III. The retrofit, while not entirely solving the problem eased the fears of the pilots enough to let them focus on their task, which they did very well. The D.V appeared during this time, but the performance was not as great an improvement as the D.III had been over the D.II. (except diving) Although von Richthofen disliked the type he flew it and recognized it was the best that they had. And, he did well in it. 60 victories on the Albatros D.I,II,III, and V are not shabby at all. Consider the remark made by Paul Strähle of Jasta 18 and later of Jasta 57. He said that in his opinion it was the equal of the Fokker D.VII. A surprising remark, but he was there, and we weren't. (see the Smithsonian Albatros D.Va book by Robert Mikesh) Richthofen's comments about the "lousy Albatroses" was made to serve a purpose. He said that to get those back at Idflieg to stop resting on their laurels and foster support for more competition between manufacturers. (Perhaps he overstated it to make a point, his opinion, although highly regarded, still had to be carefully floated to the right people who could do something about the situation. He was, after all, a junior officer.

http://militaria.for....php?f=76&t=783


  • 1

#23 borntoolate

borntoolate
  • Posts: 332

Posted 28 November 2015 - 02:03

D.Vas problem is not the horsepower... it's ability to sustain a turn the D.Va airframe gets when horsepower is added.

 

I would rather see the  D.IIIaü installed in Pfalz D.IIIa than Albatros. As of D.VII, definetely, the niche between underpowered D.VII and powerfull D.VIIF needs filling.

As of Entente D.Va voes, we need the original S.E.5a, with 200 hp Hispano-Suiza 8B engines and four-blade propellers. The ones that were able to turn fight with Albatroses, unlike the high-altitude interceptor Viper variant we have now.


 

I fully support adding the S.E.5a with 200 hp Hispano-Suiza 8B engines and four-blade propellers.  


777?  Please?​


  • 0

"We had a strict code of honor: you didn't shoot down a cripple and you kept it a fair fight." Wilfrid May


#24 FitzD7

FitzD7
  • Posts: 59

Posted 07 February 2016 - 03:03

Yes. In regards to the real DIIIau,  Mikael Carlson said that the throttle on his DVII with the Merc DIIIau never goes to full throttle. In fact he has installed a stop to prevent it from doing so. He said that if he were to remove the stop and he were to use full throttle at take off or low altitude the engine would just simply quit due to being to lean of a mixture. 777 got this stuff slightly wrong.

 

I've always wondered about running vintage engines with today's available pump gas and avgas. Even today's unleaded premium pump gas has an R &M/2 octane rating of 93 octane - better than the benzole blended gas the germans were using.

 

And 100/130  AVGas? Much better. And without the abrasive qualities of the benzole blended gas.

 

Given that today's AVGas is light years ahead of 1918 in terms of octane and lubricating qualities, and given today's far superior oils and lubricants, I wonder often what yesteryear's engines would produce in terms of peak horsepower and torque.

 

Those BMW IIIas had a comp ratio of 6.4 to 1 and I suspect the Mercedes DIIIau or DIIIavu were not far behind. That is NOT high compression nowadays. On today's AVGas I suspect they would produce more HP & Torque (with more spark advance) and make more RPM without knocking a hole in a piston.


  • 0

#25 FitzD7

FitzD7
  • Posts: 59

Posted 07 February 2016 - 03:18

I've always wondered about running vintage engines with today's available pump gas and avgas. Even today's unleaded premium pump gas has an R &M/2 octane rating of 93 octane - better than the benzole blended gas the germans were using.

 

And 100/130  AVGas? Much better. And without the abrasive qualities of the benzole blended gas.

 

Given that today's AVGas is light years ahead of 1918 in terms of octane and lubricating qualities, and given today's far superior oils and lubricants, I wonder often what yesteryear's engines would produce in terms of peak horsepower and torque. I also know that AVGas has TEL and that can lead to lead build up on pistons, combustion chambers, etc.

 

Those BMW IIIas had a comp ratio of 6.4 to 1 and I suspect the Mercedes DIIIau or DIIIavu were not far behind. That is NOT high compression nowadays. On today's AVGas I suspect they would produce more HP & Torque (with more spark advance) and make more RPM without knocking a hole in a piston.

 

But, maybe the lead buildup makes the extra HP availability not worth it.


  • 0

#26 =HillBilly=

=HillBilly=
  • Posts: 5605
  • LocationSouthern Ozark Mountains

Posted 07 February 2016 - 04:33

I've always wondered about running vintage engines with today's available pump gas and avgas. Even today's unleaded premium pump gas has an R &M/2 octane rating of 93 octane - better than the benzole blended gas the germans were using.

 

And 100/130  AVGas? Much better. And without the abrasive qualities of the benzole blended gas.

 

Given that today's AVGas is light years ahead of 1918 in terms of octane and lubricating qualities, and given today's far superior oils and lubricants, I wonder often what yesteryear's engines would produce in terms of peak horsepower and torque.

 

Those BMW IIIas had a comp ratio of 6.4 to 1 and I suspect the Mercedes DIIIau or DIIIavu were not far behind. That is NOT high compression nowadays. On today's AVGas I suspect they would produce more HP & Torque (with more spark advance) and make more RPM without knocking a hole in a piston.

Think you are misunderstanding octane, higher octane gas produces less energy that low octane,but burns slower and smoother.

Modern high octane in a unmodified antique engine will not produce the same HP as the lower octane gas of the day.  


  • 0

     So Long, and Thanks for All the Fish

 
 


#27 ZachariasX

ZachariasX
  • Posts: 794

Posted 07 February 2016 - 08:16

Think you are misunderstanding octane, higher octane gas produces less energy that low octane,but burns slower and smoother.
Modern high octane in a unmodified antique engine will not produce the same HP as the lower octane gas of the day.


Now that is something new. If was that way, higher octane fuel had to be less dense (less carbon) than lower octane. Diesel produces more energy per volume burned, alcohol less.

All the octane rating does is reflecting increasing iginition temperature. Thus, you can increase compression for increased power output of the engine. Thus, on the contrary, you can have *more* power. New fuel however also burn slower for increased controllability of the combustion. This can potentially be problematic for old engines such as the monosoupape that rely on quick combustion.

Other than that, new fuels are a great thing. Also in cars, engines newer ran better than with today's fuel. Trust me. If you have a 50 year old car, that one will love V-Power. (There it is not the excessive octane rating, that makes the difference.)

Z
  • 0

#28 gavagai

gavagai
  • Posts: 15542

Posted 07 February 2016 - 13:07

Zacharias,

 

Isn't octane rating about detonation pressure, not temperature?  I looked this up on wikipedia just a year ago (for a different reason), if you'll accept that as a source.

 

 

 

The octane rating of gasoline is measured in a test engine and is defined by comparison with the mixture of 2,2,4-trimethylpentane (iso-octane) and heptane that would have the same anti-knocking capacity as the fuel under test: the percentage, by volume, of 2,2,4-trimethylpentane in that mixture is the octane number of the fuel. For example, gasoline with the same knocking characteristics as a mixture of 90% iso-octane and 10% heptane would have an octane rating of 90.[2] A rating of 90 does not mean that the gasoline contains just iso-octane and heptane in these proportions but that it has the same detonation resistance properties (generally, gasoline sold for common use never consists solely of iso-octane and heptane; it is a mixture of many hydrocarbons and often other additives). Because some fuels are more knock-resistant than pure iso-octane, the definition has been extended to allow for octane numbers greater than 100.

  • 0

#29 FitzD7

FitzD7
  • Posts: 59

Posted 07 February 2016 - 14:12

Think you are misunderstanding octane, higher octane gas produces less energy that low octane,but burns slower and smoother.

Modern high octane in a unmodified antique engine will not produce the same HP as the lower octane gas of the day.  

 

Mmmmmm....I dunno about that. Modern 100LL AvGas is blended for large-bore, long-stroke, low RPM engines which run at high altitude. That sure sounds like a BMWIIIa to me.

 

Remember, the reason for the throttle stop is to keep the BMW from higher RPMs at lower altitude because it was LIMITED by the fuel in use in 1918. Today's 100LL is way higher in octane than the old Benzole blends. 

 

As far as BTU content, it is true that higher octane fuels have a slightly lower level of thermal energy, but this is more than compensated IF it is run in an engine with a higher squeeze ratio. I capitalize "IF" because if it doesn't have a high enough C/R to take advantage of high octane fuel, running higher octane fuel through it won't produce more power.

 

The higher C/Rs more than compensate for the slightly less BTU content of high octane fuel.


  • 0

#30 FitzD7

FitzD7
  • Posts: 59

Posted 07 February 2016 - 14:21

An example of a WW1 vintage engine making more power post-war on better fuels can be described.

 

The 717.8 cubic inch Hispano Suiza 8 engines. in geared form and direct drive, made about 220-235HP in 1918. The Wright E-3 (same displacement), a post war version of the Hisso 8 with a head design with better heat transfer, made about 285 HP on the new TEL based post-war fuels. This example was from the early 20's.


  • 0

#31 FitzD7

FitzD7
  • Posts: 59

Posted 07 February 2016 - 14:32

I wonder if you could build a higher output BMWIIIa with even higher C/R, say, 6.8 or even 7.0 to 1, with a higher lift, longer duration OH Camshaft, run on 100LL AVGas, to produce, say, 300 BHP?

 

From 1164 cubic inches, that's hardly a stretch.


  • 0

#32 gavagai

gavagai
  • Posts: 15542

Posted 07 February 2016 - 14:50

In other words, what matters is what % of the thermal energy can be converted into mechanical work.  You'll capture more of that thermal energy with the higher octane fuel than with the lower octane fuel, so the slightly higher energy density in the lower octane fuel is moot.


  • 0

#33 =HillBilly=

=HillBilly=
  • Posts: 5605
  • LocationSouthern Ozark Mountains

Posted 07 February 2016 - 15:01

Thank you all for making my point, simply running 100 octane ava. gas in a 100 year old engine will not make it produce more power. :icon_e_salute:


  • 0

     So Long, and Thanks for All the Fish

 
 


#34 ZachariasX

ZachariasX
  • Posts: 794

Posted 07 February 2016 - 17:14

Zacharias,

 

Isn't octane rating about detonation pressure, not temperature?  I looked this up on wikipedia just a year ago (for a different reason), if you'll accept that as a source.

 

Sure, as one comes with the other while compressing the mixture in the piston.

 

The burn energy is the same however in theory. In practise, todays fuels will give you more energy as they burn more efficiently than the fast burning fuels of back then, meaning a better control of optimal fuel/air mixture.

 

Second is that when the combustion process is longer, you have the same amount of power distributed over a longer time, proportionally reducing torque/load on the piston and crankshaft.

 

The more efficient burn of the fuel will make your engine run cleaner. You don't have to clean your sparks all the time as you had to do it. The added lubrication stuff further keeps the engine clean.

 

A clean spark produces more power, but that is not your line of argument, HillBilly, so no matter. Thus, yes, in principle, 100 octane V-Power don't give an old car more power. It's not octane thatmakes the difference there, as said. In practise, there is a difference, especially noticeable at low rpm, where the mixture is usually overly rich. I've seen that on all kinds of cars be it old Astons, Corvette, Jag. Bad fuels will tend make your engine stall when you open throttle suddenly. Things like that make it very reasonable to put high grade fuels even in lawn mowers. No use for 3 months after winter, it still starts after the first try. Cost difference for one tank of the most expensive fuel and the cheapest you gan get from ARCOs is less than a dollar (same as in motorbikes). Even for 2 stroke bikes it makes no sense going for cheap stuff. For a car, higher octane than 98 is a "waste" anyway, as most onboard electronics are set to have given performance with that kind of fuel. If you get 81 octane, the engine will give you less power, especially on turbocharged engines. The control unit decides there.

 

The problem for a 100 year old engine is only, as stated, when the short burn is part of the design, like in the monosoupape. But the inline engines work in principle like todays engines, so better is better because of the cleaner burn. Not more power, but more reliability.

 

Z


  • 0

#35 FitzD7

FitzD7
  • Posts: 59

Posted 07 February 2016 - 22:10

Thank you all for making my point, simply running 100 octane ava. gas in a 100 year old engine will not make it produce more power. :icon_e_salute:

Not so fast there, HB. If the BMW IIIa was gate stopped to prevent full throttle at lower altitudes to avoid detonation on Benzole, then it stands to reason that running higher octane fuel, i.e. 100LL, would ALLOW throttling up THROUGH the gate stop to produce MORE power and rpm. That's with the existing engine's comp ratio of 6.4, i.e., "factory."

 

I'm saying it probably will work in this particular case. Running 100LL in an old F Head RAF 1A, in contrast, probably won't produce any additional HP. That's because it was a very under stressed engine to begin with. Not "high strung" like a high comp OHC BMW IIIa.

 

We really agree that the vast majority of WW1 vintage engines, with their low compression ratios and under stressed designs, won't produce more power on new fuels. They might run cleaner, less carbon buildup, etc.

 

However, with 100LL in an older engine with increased timing advance, they may be persuaded to produce a bit more ummph. Just maybe.


  • 0

#36 FitzD7

FitzD7
  • Posts: 59

Posted 07 February 2016 - 22:18

I know a bit about engines meself. I suspect HillBilly is of the same persuasion. 

 

You running moon down there, HB?

 

Fury%20and%20Honda_zps8gzkjzkq.png


  • 0

#37 FitzD7

FitzD7
  • Posts: 59

Posted 07 February 2016 - 22:34

there's a lot more going on here besides octane, i know that.

 

Today's fuels are markedly different than the stuff back in 1918. Different aromatic properties, burn rates, etc. And I certainly am not the last word here in terms of old vs new.


  • 0

#38 Dressedwings

Dressedwings
  • Posts: 2094
  • LocationOntario, Canada

Posted 07 February 2016 - 23:06

Think you are misunderstanding octane, higher octane gas produces less energy that low octane,but burns slower and smoother.

 

Forgetting the second part: 

 

http://www.wwiiaircr...grade-fuel.html

 

Switching to 150 octane fuel in WW2 produced more energy from the engines.

 

  130 Grade 150 Grade

Spitfire IX 335 mph - 358 mph   +25 lb

Spitfire XIV 359 mph - 366 mph  +21 lb

Tempest V 372 mph - 386 mph  +11 lb

Mustang III (V-1650-3) 360 mph - 390 mph   +25 lb 

Mosquito NF. Mk. XIX   - 363 mph   +25 lb

 

Just saying that higher octane isn't "producing less energy, burns slower and smoother" as a general rule of thumb


  • 0

TOeIhAe.png

^CHECK THE LINK^


#39 ZachariasX

ZachariasX
  • Posts: 794

Posted 07 February 2016 - 23:39

Forgetting the second part: 
 
http://www.wwiiaircr...grade-fuel.html
 
Switching to 150 octane fuel in WW2 produced more energy from the engines.
 
  130 Grade 150 Grade
Spitfire IX 335 mph - 358 mph   +25 lb
Spitfire XIV 359 mph - 366 mph  +21 lb
Tempest V 372 mph - 386 mph  +11 lb
Mustang III (V-1650-3) 360 mph - 390 mph   +25 lb 
Mosquito NF. Mk. XIX   - 363 mph   +25 lb
 
Just saying that higher octane isn't "producing less energy, burns slower and smoother" as a general rule of thumb


These are not really suitable comparisons. Increasing 'lb' gives you a different engine. New fuels allow you to +lb'
  • 0

#40 Arty_Effem

Arty_Effem
  • Member
  • Posts: 853
  • LocationR E S I G N E D 13/6/2018 veryuseful.info/rof

Posted 07 February 2016 - 23:40

Yes. In regards to the real DIIIau,  Mikael Carlson said that the throttle on his DVII with the Merc DIIIau never goes to full throttle. In fact he has installed a stop to prevent it from doing so. He said that if he were to remove the stop and he were to use full throttle at take off or low altitude the engine would just simply quit due to being to lean of a mixture. 777 got this stuff slightly wrong.

 

Modelling a carburation weakness would only cause unnecessary confusion. When some learners don't understand why their plane veers to the right or left on takeoff, the last thing they need is an engine that dies at full throttle.


  • 0


0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users