AFAIK, Full performanced La-5FN produced in september 1943.

[Panthera]

11 minutes ago, JtD said:

Most likely detonation occurred under conditions more challenging than the conditions in the lab during type testing. It's one thing to run a new, well tuned engine 5 minutes at 1.42ata under standard atmospheric conditions, it's another thing to run 1.42ata at all when outside temperatures are 25K higher and valve timing, fuel metering and ignition timing are set to be just inside the tolerances, with critical parts like spark plugs being of poor quality. You don't need the pilot to abuse an engine, you just need adverse conditions.

 

Given that one of the first measures undertaken to remove the/a cause was to cool the spark plugs and to change the type of spark plugs, illustrates that the problem wasn't pilot abuse, but of an unexpected technical nature under front line conditions.

 

Good points.  But like I also noted above the run in procedure specifying 2x 5 min at 1.42ata appears in a document dated Nov 43, at which time 1.42ata had long been cleared for use. So it's entirely possible that immediately upon the banning of 1.42ata for operational use in June 1942, the run in procedures were also lowered in max permissable boost or perhaps limited to 1 min runs at 1.42ata here as well. Upon clearance of 1.42ata around Aug 43 the run in procedures were then re established as 2x 5 min at 1.42ata.

 

Seems logical to me.

Edited April 2, 2018 by Panthera

[JtD]

All approved German aero-engines had to complete type test of 100 hours with a cycle of 30 minutes combat, 5 minutes emergency and 25 minutes max. continuous, repeated 100 times. During that cycle checks, maintenance and fixing of small problems were OK, major problems like detonation and damaged pistons would have cause the engine to not be approved.

 

Imho, there's no point in not running 5 minutes of emergency power at engine run ins early on, because the approved engine design would be able to take it. You would need to make sure that the individual engine shows no defects, even under the approved maximum stress. So you need to go to max, but you don't need to do it 100 times.

[Dakpilot]

58 minutes ago, Panthera said:

 

58 minutes ago, Panthera said:

 

That is because you keep thinking of static C/R whilst I am talking about dynamic C/R where valve timing, piston speed, fuel/air mixture & boost pressure comes into play. 

 

But since one can't have a debate with you without you turning it personal with insults left and right I am glad you have decided any further discussion is pointless. I just really hope you communicate better in the real world.

 

I hate to further comment again but this is clearing up your previous 'misconceptions'

 

theoretical dynamic compression ratio has nothing to do with what happened to DB605A and D increase in C/R to use C3 fuel

 

engine specs are static C/R and always have been, anything else is your inferred red herring sidetrack

 

It may be so that you can increase dynamic C/R with valve timing changes

 

BUT You cannot increase even dynamic C/R unless you get rid of  valve overlap as the method

 

The DB605A and DB601E had considerably INCREASED valve overlap (as often in very high performance engines) the increased volumetric efficiency and scavenging that  INCREASING valve overlap gave, enabled the 2800 rpm increase from 2600rpm and improved power at high range

 

You have mentioned and put forward this irrelevant impossible situation multiple times as justification for your theories and previous posts

 

Just accept that the compression ratio was increased to use C3 fuel instead of going off on a redundant tangent as typical

 

My Aunt would have been called BoB if she was a boy, but she isn't and wasn't

 

I shall leave you alone to debate further but please don't quote/answer me direct in your continued convos in this thread 

 

best regards

 

Cheers, Dakpilot

Edited April 2, 2018 by Dakpilot
double post

[Panthera]

So now youre saying I am denying any changes in compression ratio?? 

 

I have been talking about dynamic C/R since the beginning,  and that because the static C/R difference is clear for everyone to see on the engine charts. As also noted the AM engine featured the same 1:8.5/8.3 compression ratio as the D series, and there was no reduction in valves pr. cylinder between all versions.

 

Bore, stroke &  no. of valves remained the same between the A and D variants, thus with my admittedly very limited knowledge on high performance engines, and based on the original engine charts,  I suspected that the following could've been modified:

- valve timing

- ignition timing 

- air/fuel mixture

- boost pressure (obvious) 

- piston heads

- cylinder heads / top of combustion chamber

 

Could I be wrong on some? For sure, I expected to be so as well, I merely listed the above as possible changes. 

 

For sure however none of the above warrants your tone and accusations of 'making stuff up' against me. 

 

Finally consider that this whole debate started with you attacking me for saying that for the DB605 to run reliably at 1.8ata demanded the use of C3 or MW50 injection.Yet nowhere did you manage to disprove this. 

 

Edited April 2, 2018 by Panthera

[JtD]

You don't change compression ratio with boost pressure as such. Compression ratio is pretty much the ratio between the volume inside the cylinder when the piston is fully down and the volume inside the cylinder when the piston is fully up. An engine has the same compression ratio running at high or at low boost, as long as nothing else changes. You would need to go into fluid mechanics if you wanted to determine if a change of boost has an impact on compression ratio at all, and if so, which effect it has. It would, in all cases, be marginal and probably be smaller than production tolerances of the hardware. Same goes for the air/fuel mixture.

 

Most likely change is a different piston or cylinder head.

[Panthera]

Alright, thanks for the explanation JtD

 

I was aware that the static C/R is simply the ratio between piston fully up and down volume in the combustion chamber. However I was under the impression that the C/R could be further increased by how high a pressure the air was pushed in there.

 

The reason I listed boost pressure increase as an obvious modification between the A and subsequent variants is because we know that did occur, being the whole point behind most modifications  

 

 

Edited April 2, 2018 by Panthera

[Bearcat]

On 3/31/2018 at 3:42 PM, Willy__ said:

 

Thats standard procedure for the forum police, its how they operate. 

 

 

You need to curb that rhetoric.. There are forum "police" here.. and it isn't them.. They are community members like you .. so if you want to keep posting here please back off from the national bias insinuations and the snide comments to folks who are tired of hearing it.. We are tired of getting reports about it and we have been very patient with you and others who have insinuated that sentiment .. but that patience is wearing thin. 

[=LD=Hethwill]

First hand sources. At best second hand sources. Anything beyond that starts to become diluted and at the fifth hand sources it becomes historical reinterpretation. That's what I learned.

[JV69badatflyski]

On 01/04/2018 at 2:31 PM, Dakpilot said:

 

I can understand the frustration

 

But let's just look at the Klimov M105PF for example Vs DB605A

 

It is of similar cubic capacity to DB605 but makes 1250hp maximum on 95 or 100 octane fuel

 

whereas the DB605A makes 1475 hp on 87 octane fuel

 

if you were to put 95 octane in the DB and run it at 1250hp (about 1.27-8 ATA?) it will also run all day

 

there is no magic Russian "Stalinium" engine tech, the klimov is just less stressed and running on better octane fuel allowing fairly high MP without detonation,

 

one can also reason that the 605 is basically a bored out 601 which had come to the end of its performance design limits at that cubic capacity 

 

There is a reason for the performance difference between German and Russian in climb and many other important regimes

 

Russian engines (most) were designed for more basically trained aircrew and for simple operation

 

 

 

We all know that the 1 minute is a 'game function' timer and how this also works on British and American engines

 

but there is plenty of evidence of 601 and 605 engines self destructing due to detonation to enforce bans of 1.42 ATA and a 1 minute limit in manual at times in their lives, it was close to engine design limits, and even clockwork limited on 601

 

Cheers, Dakpilot

Nice try but i think you forgot something
B4 in43  wasn't 87 but 89( that's just for the precision), but the other part is that B4 was 89octane at LEAN and when you push the engine at high RPM's you're in RICH mixture what was between 110 and 115 for the B4 depending of the raffinery...but for the russians the 95 was the RICH octane rating just like the 130 or the 150 for the Brittons/Usa'rs.
So yes there has to be some Stalinium in those engines (at least in this game, can't call it sim anymore) and what you wrote doesn't simply make sense.
And by the way, a Bmw801 could run at 1.42 continuesly in winter conditions (russian winter style) because the heads and oil coudn't get overheat due to low temperatures, even in climb.

[LukeFF]

1 hour ago, JV69badatflyski said:

And by the way, a Bmw801 could run at 1.42 continuesly in winter conditions (russian winter style) because the heads and oil coudn't get overheat due to low temperatures, even in climb.

 

Source?

[Dakpilot]

11 hours ago, JV69badatflyski said:

Nice try but i think you forgot something
B4 in43  wasn't 87 but 89( that's just for the precision), but the other part is that B4 was 89octane at LEAN and when you push the engine at high RPM's you're in RICH mixture what was between 110 and 115 for the B4 depending of the raffinery...but for the russians the 95 was the RICH octane rating just like the 130 or the 150 for the Brittons/Usa'rs.
So yes there has to be some Stalinium in those engines (at least in this game, can't call it sim anymore) and what you wrote doesn't simply make sense.
And by the way, a Bmw801 could run at 1.42 continuesly in winter conditions (russian winter style) because the heads and oil coudn't get overheat due to low temperatures, even in climb.

 

I am not trying anything 

 

I think you are missing the point

 

look at it from the other way then

 

Put B4 in the Klimov , increase the compression ratio , give it some radical valve timing like the 605A, tune it up and let it produce 1475hp

 

I bet the M105PF's ability to 'run all day' at that output would change,

 

much the same as if you de-tuned the 605 to only be able to produce 1250hp maximum

 

like a lot of Russian equipment, it is more of a simpler less sophisticated  'rugged design' they also did build 129,000 of them so longevity was not such an issue, nor was supply chain compared to Germany, as with many Russian weapons continuous uninterrupted quick production was important doctrine, and a different way to tackle a problem

 

Cheers, Dakpilot

[=EXPEND=13SchwarzeHand]

To me this sounds like you are saying the less powerful engine was a deliberate design choice (correct me if I am wrong). I just don´t buy that.

If longevity and production as you say was not a problem for Russians, which is correct, they really should be interested in getting the last out of their engines.

If the cause for German engine restrictions is longevity we are on the same page. This contradicts the current in game set up, where engines detonate after a brief time at full power.

Edited April 3, 2018 by =EXPEND=SchwarzeDreizehn

[FTC_DerSheriff]

2 hours ago, =EXPEND=SchwarzeDreizehn said:

To me this sounds like you are saying the less powerful engine was a deliberate design choice (correct me if I am wrong). I just don´t buy that.

If longevity and production as you say was not a problem for Russians, which is correct, they really should be interested in getting the last out of their engines.

If the cause for German engine restrictions is longevity we are on the same page. This contradicts the current in game set up, where engines detonate after a brief time at full power.

I have no facts on that, its merely a thought. But I actually think that might be true. it fits into the russian design philosophy. Basically an engine cut of, just ot make sure that poorly trained pilots do not wreck their engine at the first instance. 
But that's only what I think when I see those relatively low revving engines and relatively low manifold pressures.

Basically the settings were the last bit they could squeeze out of the engines without having sophisticated engine setting manuals.  

Edited April 3, 2018 by DerSheriff

[Barnacles]

I don't think these planes were designed to run 100% all the time, if you look on the throttle on the la5 there is an obvious detent at around 75% throttle opening, clearly to make the operators default to something below 100% throttle unless positively needed. The design authority probably placed more emphasis on control design rather than training to prevent excessive wear on the engines. 

[=EXPEND=13SchwarzeHand]

It was the last bit they could squeeze out of the engines period. The many overheating problems yaks had speak for themselves. I believe, for the Russians, there was a technology gap upward and no doctrine to adjust engines to pilots downward.

[JtD]

Directly comparing engines is never a good thing, the Klimov and the DB outside of being V-12 of 35-36l displacement pretty much have nothing in common. One's upright, the other inverted. One's got direct fuel injection, the other's got a carburettor, one's got four valves, the other three, one's got a removable cylinder head, the other doesn't - it's just an endless list of really important differences. That said, the Klimov at 100% is running near 1.43ata, but has a lower full throttle altitude than the DB. Total compression, taking first supercharger gears and different compression ratios into account, is about the same as on the DB605 at 1.15ata. So if you want to compare apples to oranges, it really doesn't look very stressful for the Klimov.

 

However, I still disagree that the Klimov was designed to be underperforming - the fact that it was uprated twice from the PA over the PF to the PF-2 and that lack of engine power was a constant source of complaint from everyone involved in the development of Soviet WW2 aircraft shows that efforts were made but that things weren't easy. Had they been able to reliably squeeze out another 100hp or so, they would have done it. They weren't. The Yak-3 was the last fighter to use the last version of the engine, and the PF-2 started into service with a load of trouble. It should also be mentioned that the M-105 was at its core a Hispano-Suiza 12Y engine, and if you look at all the derivates of the engine, developed and used well into post WW2 era, you won't find variants that gave a lot more power trouble free.

A bit of trivia, the end of the development of the 12Y is the 12Z, which gave up to 1800hp take off power, but development was halted when France surrendered. It's pretty much an equivalent to Jumo211 to Jumo213 development.

 

Bada, do you have a source to confirm that 95 octane specified in Russian docs is in fact for rich mixture? Basically all aero-engines of the time were developed around 87 octane fuel, be it B4 or any others nations specification. It was just advanced commercial and basic military standard at the time. Upgraded engines typically required higher octane fuel. The French used 85/100 for 5.8 compression ratio 12Y engines and upgraded to 92/100 octane for their 7.0 compression ratio 12Y. I doubt the Soviets could have achieved 7.1 compression ratio at higher boosts with considerably lower octane fuel.

Edited April 3, 2018 by JtD

[Dakpilot]

There were many early overheating problems, especially initially with the PF,  Vladimir Klimov was initially against the power increase over the PA model due to potential reliability issues, however with revised cooling this was solved fairly early in the production cycle, and Yakovlev who pushed for the PF version was justified in this instance, the bulk of the 129,000 produced were PF models

 

There was a little further development left with the VK-105PF2/PF3 which was used in the Yak-3/Yak-9 which had a limited WEP/takeoff power according to some manuals I have seen , but better confirmed by Russian expert/speaker (as with most of this info)

 

The VK 107 was first flown in 42 and could have been started in production then, although a new engine it was basically a 'hotrodded' 105, with 4 valve heads, (basically same displacement as 105) but it was never given enough development priority, as maintaining the high production output and uninterrupted supply of VK-105 was considered more important from high up, in mid 44 when the flow of the war had changed it was put into production but was poorly developed and seriously a bit of a stinker although it produced 1650hp at WEP this was very unreliable and was rarely used, even at normal levels of 1450hp it was unreliable and often only had 25 hour engine life, mistrusted by Pilots and disliked by mechanics due to the very complicated exhaust and  unusual intake route/valve system, it was used in Yak-9U and some later Yak-3

 

Not really sure there was such a 'technology gap' more the lack of production facilities and tooling to take risks on mass producing unproven designs, not to mention the "political atmosphere" of the time

 

 

Cheers, Dakpilot

[Blutaar]

4 hours ago, JtD said:

is about the same as on the DB605 at 1.15ata.

 

Are you sure that 1.15ata is about the same horspower output as 1250hp klimov at 1.43ata or did i completely misunderstood you? The G2 for example has about 1310hp at 1.3ata and full throttle would be 1475hp. So im really bad at math but 165hp drop for -0.12ata and another -0.15ata drop from 1.3 to 1.15ata is just 60hp less? I dont mean to provoke just to learn something. Maybe it so that power drops not linear when decreasing throttle and it would be nice to know if there is a way to find out at which poweroutput an engine is at a certain throttle position.

[JtD]

No, I wasn't referring to engine power, I was referring to total compression of intake air. Simply put, the DB had the bigger supercharger, which during compressions heats up the air more than a smaller supercharger would. And this in addition to the higher compression ratio inside the cylinder. So the DB would need to run considerably lower boosts for the same thermal stress. But like I said, it's apples and oranges.

 

At 1.15ata with 2300rpm the DB produces about 1075hp at sea level.

Edited April 4, 2018 by JtD

[Blutaar]

Ok my bad, thx for explaining.