P-40 Engine Settings as I found them (a bit weird)

[Venturi]

Oi, Snake oil salesman stop changing your point.]

 

Lets see what the report says

"The 60" war emergency rating on the 8.8 blower ratio was somewhat further from the detonation point [in relation to 9.6 blower ratio) but was limited by structural limitations of the engine to the 60" value."

 

It doesn't matter if 70" could be achieved only at sea level and at narrow range of atmospheric conditions, again you are trying to misdirect the conversation like a politician., if you had enough ram-effect, if the atmospheric conditions were right and you advanced the throttles, it would achieve 70" and it would not detonate.

You're right, RoflSeal, but at some point detonation will occur, but this likely has more to do with pre ignition of the mixture before piston reaches TDC. That's due to running high power for long duration which heats certain parts of the cylinder head to very high temps, high enough they will cook off the a/f mix before TDC. This is the reason for hollow sodium filled exhaust valves for instance. The sodium is actually a liquid inside the valve when it heats up and bounces from valve head to valve stem to transfer heat, reducing the temp of the valve head and preventing preignition/detonation. Overpressurization just lowers the threshold at which this occurs, which is why the engineer is talking about safety margins being different b/w the two supercharger gearings. A higher gearing equals more boost, or a different rate of change of boost with throttle advancement, which is why he's saying that he's concerned that pilots will take what's safe for the -39 engine with 8.8 gearing (66-70") and apply it to later Allison variants coming out with 9.6 gearing, which reduces the safety margins.

 

Bottom line, there's still safety margins for the engines with 8.8 gearing such as the -39, even at 66-70" mp and the engineer is warning that although this is ok with one variant it isn't with another variant with differences (s/c gearing) that lay people (pilots) might not understand. This is an important warning b/c it also shows the reason why Allison provided boost regulators. They didn't think pilots could operate the engines close to their true potential without blowing up the engines. The end result is that the Allison V12 gets historically maligned compared to the Db601/5 and Merlin, when in reality it was excellent.....

 

I've talked about all this at length before and I'd love for more accurate engine modeling to be implemented. But I think it's more germane to ensure that overall, the engine is putting out power levels and giving performance in accordance to how it was actually historically used.

Edited March 31, 2016 by Venturi

[Crump]

 

 

pre ignition of the mixture before piston reaches TDC

 

Pre-ignition is not the same thing as detonation....

 

 

 

"Pre-ignition" is another abnormal combustion event that is often confused with detonation, but in fact is completely different. Pre-ignition is the ignition of the air-fuel charge prior to the spark plug firing.

 

 

 

 

But if the combustion process moves too fast and the pressure peak occurs too early, the result can be excessive pressure, excessive temperatures, and unstable pressure pulses known as "detonation."

 

 

 

Detonation is something that occurs near the peak pressure point in the combustion event, after the air-fuel charge has been ignited normally by the spark plugs. It is characterized by abnormal pressure spikes near the peak pressure point, caused by spontaneous combustion of end gas due to excessive temperature and pressure.

 

https://www.savvyanalysis.com/articles/detonation-and-pre-ignition

 

Detonation is actually "after ignition" and not pre-ignition.

 

 

Detonation is the spontaneous combustion of the end-gas (remaining fuel/air mixture) in the chamber. It always occurs after normal combustion is initiated by the spark plug.

 

 

 

 

Pre-ignition is defined as the ignition of the mixture prior to the spark plug firing. 

 

From:

 

 

 

Engine Basics: Detonation and Pre-Ignition

 

http://www.contactmagazine.com/Issue54/EngineBasics.html

[Venturi]

Crump, some of us don't care about your fine distinctions. If you've ever built a boosted engine and tested it until it detonates, you get "pinging" before you get detonation. Preignition transforms into detonation. Semantics.

[Crump]

Crump, some of us don't care about your fine distinctions.

 

 

 

Professional Aircraft Engine Analysis

 

https://www.savvyanalysis.com/home

 

It is not my fine distinction.  It is just engine basics and what is correct.  You tell an A&P you have pre-ignition, he is going to be looking for something very different than if you tell him you have detonation.

Remember you were the one screaming about knowing your stuff when it come to engines.  I mean really, I am only certified and licensed to exercise the privileges of an Airframe and Powerplant mechanic...what could I possibly know about aircraft engines or how they are maintained, LOL.  

 

You built an engine in the back yard...guess that makes you the man.

 

 

 

Engine Basics: Detonation and Pre-Ignition

Written by Allen W. Cline

Reprinted from Issue 54 of CONTACT! Magazine, published in January, 2000

 

http://www.contactmagazine.com/

 

Just pointing out that perhaps you do not know as much about it as you spout......

 

 

 

If you've ever built a boosted engine and tested it until it detonates, you get "pinging" before you get detonation. Preignition transforms into detonation. Semantics.

 

Totally wrong, btw.  There is no ping with pre-ignition and the two are not related.  Two different things with different causes and effects.   It is usually just a bang and a whimper as the engine dies...

 

But again, You the engine expert and maybe under the shade tree, they are the same.  

 

 

Remember, the spark plug ignites the mixture and a sharp pressure spike occurs after that, when the detonation occurs. That's what you hear. With pre-ignition, the ignition of the charge happens far ahead of the spark plug firing, in my example, very, very far ahead of it when the compression stroke just starts. There is no very rapid pressure spike like with detonation. Instead, it is a tremendous amount of pressure which is present for a very long dwell time, i.e., the entire compression stroke. That's what puts such large loads on the parts. There is no sharp pressure spike to resonate the block and the head to cause any noise. So you never hear it, the engine just blows up! That's why pre-ignition is so insidious. It is hardly detectable before it occurs. When it occurs you only know about it after the fact. It causes a catastrophic failure very quickly because the heat and pressures are so intense.

An engine can live with detonation occurring for considerable periods of time, relatively speaking. There are no engines that will live for any period of time when pre-ignition occurs. When people see broken ring lands they mistakenly blame it on pre-ignition and overlook the hammering from detonation that caused the problem. A hole in the middle of the piston, particularly a melt ed hole in the middle of a piston, is due to the extreme heat and pressure of pre-ignition.

 

http://www.contactmagazine.com/Issue54/EngineBasics.html

Edited March 31, 2016 by Crump

[JtD]

Don't lose your cool, buddy. You're getting dragged down to a level where he's going to beat you with experience. So stay up.

[Venturi]

I wrote a long reply. But I'm done with this thread. Have fun Crump.

[Crump]

 

 

But I'm done with this thread

 

The issue has been resolved.  There was no clearance for 70"Hg or even 60"Hg for the V-1710F3R engine by April of 1943.   

[MiloMorai]

The issue has been resolved.  There was no clearance for 70"Hg or even 60"Hg for the V-1710F3R engine by April of 1943.   

 

Didn't stop the engines from being run at the higher boost pressure.

[Crump]

Didn't stop the engines from being run at the higher boost pressure.

 

I agree Allison initial instructions were probably somewhat confusing and mistakes were made.  I have a very hard time believing this was done intentionally and Allison certainly wrote a letter to squash this very dangerous practice immediately.

 

 

 

 

 

 

[6./ZG26_Klaus_Mann]

With or without a boost regulator, the April 1943 V-1710F3R could use 10 minutes of power settings above normal rated power as long as the engine gauges remained in the green.

[Disclaimer: I'm on Nobodies side here, just on the P-40's, I think you have all made your points, now we have to get Precise, this is what I offer]

 

Ignoring Dave and Venturi, and the vague reports of increased boost times, and ROFLSeals Table for Models apparently fitted with Regulators, unlike ours with Simple Throttle I think it would still be quite likely to push it beyond 60", simply due to the throttle body, even if not permissible and very damaging in certain atmospheric conditions, I think we can still reasonably assume:

 

-Standard Emergency Power (52"@3000 for 5 Minutes, recoverable after 20 Minutes?)

 

-Overboosting, beyond permissible limits (60+", depending on atmospheric conditions, up to 2 Minutes, subtracting from Standard Emergency, non-recoverable)

 

-Military Rated Power (42"@3000, Normally 10 Minutes, of which Emergency Ratings subtract, if no Emergency Power is used for more than 30 Seconds maybe for longer, up to 15?, recoverable after 20 or so Mins as well?)

 

-Take-Off Power (45.5"@3000 for 5 Minutes, available only once per flight)

 

And Normal Cruise Settings. 

 

All of these would be an improvement over the Current Situation of Engines not lasting more than 5 Minutes above 3000rpm, no matter the Manifold Pressure. 

And we could reasonably ask the Devs for exactly this at least for now. 

If we could open a PM thread with Han, Crump, Me (Middleman) and whoever CAN BEHAVE LIKE A CIVILIZED HUMAN BEING AND NOT SHOUT IN CAPS-LOCK maybe we can get the Ball rolling for the P-40 at least to some point. 

 

@Crump: Thank you for the Charts provided, personally I side with the 70" group to a certain point, but I respect your contributions a lot at least concerning the Normal Settings. 

 

@Venturi, ROFL and Dave, this is the most we can do with the Charts Given plus a bit of wiggle room for 70". If we get bogged down in this uselss dispute about 70" or not, we will simply get ingored. We need the longer times for the lower settings much more. 

Edited April 2, 2016 by 6./ZG26_Klaus_Mann

[Crump]

Ok, I will help you out.  Open up a PM and let's discuss it.  

[6./ZG26_Klaus_Mann]

Ok, I will help you out.  Open up a PM and let's discuss it.  

Apparently you were banned from PMs. 

[Venturi]

I posted some reasonable time limits a while back, I still think they are a better conservative approximation of what the real engines were capable of compared to what we have now, although a variable time factor would even better help in recreating a more realistic experience. I also posted a very simple example for a method of coding that a while back.

It's amazing to me to see some documentation maligned by some individuals because it comes from non-usual sources such as chief engineers, books in the subject, and period reports from Air Force generals, and yet on other planes such as the 190 the same characters have no problem using non-native operator, subjective test pilot reports to justify their claims. I think that in the pursuit of perfect rationality we are missing the actual point, which is to recreate a historical reality with fidelity. Now I expect that certain individuals will be along shortly to obfuscate this simple point, but there we have it.

The product is a simulation, which must integrate multi variate and sometimes vague but qualitatively reliable sources to provide a visceral experience which is convincing. The devs have admirably held to certain standards, and this is appropriate when those standards are of equally complete historical application, but in some instances these do not provide the complete picture. This is where good judgement based on historical sources must come in. It is a mistake to think that no matter the quality of the information, that all necessary factors in a complex historical simulation like this can be calculated and "plugged in". There is always some judgement used in creating a sim like this, in reality, regardless of the amount of concrete information plugged in from flight reports and wind tunnels. This is why it is important to have multiple sources providing a complete historical picture to those highly qualified individuals which must make sense of all historical sources. The other alternative outcome will be that whomever wrote the manuals which were most taxing on whichever the relative airplane is will have a better performing aircraft. The P40 could and did compete with the Bf109E and F in North Africa and its performance record there against the best of the Luftwaffe is not too shabby.

In reality the Allison V1710 engine in its single stage supercharger form powered not only the P40, but also the P39, and also like the P40, the P39 was used similarly hard by the Soviets. It too did not have a boost regulator so could run increased levels beyond the manuals parameters. The Allison could take it from all accounts and actually the P39 developed one of the best kill/loss ratios against the Luftwaffe of any Soviet operated aircraft.

Additionally the Allison was utilized in the early P51 and we have already read how the regulator was often removed to get the same over boosting effects. Later variants of the V1710 were then uprated post hoc by Allison to clear the pressures already in use in the field. So this has far reaching implications for future sim development, as the Allison V1710 was the major inline engine used in American aircraft until the licensure agreement with Rolls Royce for the Packard Merlin in the later variants of the P51 circa 1944.

[Crump]

Apparently you were banned from PMs. 

 

 

No, I got a box full of them.

In fact I am in a couple of them that are actively ongoing....

In fact I have one with Han from a while back.  

[Crump]

PM started

[Venturi]

I think this post is illustrative...

 

http://forum.il2sturmovik.com/topic/461-aircraft-performance-thread/?p=8307

[Crump]

 

 

I think this post is illustrative...

 

 

Yeah that is typical.  That was a conversation about which engines the RAF got in their P-400 and P-38's.  Some sources had said they got the sea level engines.  Then the whole conversation breaks down because folks do not know what that even means.

 

They think a supercharged engine cannot be a sea level engine....

 

[Venturi]

In that post you are arguing that the Allison was a sea level engine which dropped in power as it increased in altitude?

[Venturi]

 

@Venturi, ROFL and Dave, this is the most we can do with the Charts Given plus a bit of wiggle room for 70". If we get bogged down in this uselss dispute about 70" or not, we will simply get ingored. We need the longer times for the lower settings much more. 

 

I agree however to justify a longer time at lower power levels it must be assumed that the full capability of the engine is present - IE that depending on ram effect, the boost can be brought up to levels which "weren't rated" at sea level, and that further this does not implode the engine through detonation/preignition immediately.

 

Using this logic we can assume that the engine could survive easily 56" of boost for a period of time far in excess to what we currently have which is 4 or 5 minutes.

[Venturi]

 Please see the following reply to my inquiry regarding the Allison V-1710-39 from an authoritative source:

 

 

[Holtzauge]

No, I got a box full of them.

In fact I am in a couple of them that are actively ongoing....

In fact I have one with Han from a while back.  

 

Wow! That's impressive Crump! 

[=362nd_FS=Hiromachi]

@Venturi

 

Nice one. I know Greg for a while and would take any technical info he provides at hand. Considering he is working at Planes of Fame museum and is running all kinds of warbirds (from common and known models to a bit more rare aircraft like Zero with original Sakae engine, He-162, P-51A and amazing Flying Wing N9MB) he knows what he is talking about. 

[Crump]

Greg's specification file shows the exact same thing posted in the thread already.

[MiloMorai]

Has this been posted?

 

http://www.raafwarbirds.org.au/targetvraaf/p40_archive/pdfs/Allison%201710-39%20abuse.pdf

[LukeFF]

Greg's specification file shows the exact same thing posted in the thread already.

 

 

Why am I not surprised by such a response from you? So, you just hand-waved away everything else Greg wrote as being irrelevant?

Edited April 4, 2016 by LukeFF

[LLv24_Vilppi]

I'd say that with the Allison Engineer's letter, the interviews and (auto)biographical information, including Greg's answer there is enough materials to make a strong case to present it to the devs to allow the P-40 engine to run longer and with higher MP.

 

The problem here is that there are no formal tests on what should be the actual times for the engine modes (or have I missed something), so in the end it is up to the devs to decide if they want to stick to the official manuals as a policy to leave any guess work out, or if they would include this kind of information in the game.

 

Here's a suggested draft, feel free to fill out any facts as they have appeared in this discussion and edit. Let's see if we can make a community created letter to the developers:

 

--

 

Item: P-40 Allison Engine (V-1710-39) performance

 

Currently in the game, the engine limits for the P-40 are as follows:

 

[insert the limits here]

 

There are several anecdotal references that point to the fact that these limits were not observed strictly during combat, without any catastrophic effects to the engine:

 

[placeholders]

1) Russian pilot NN states in his memoirs... [a book reference]

 

2) In the interview ..... [magazine / URL reference]

 

3) GregP, the ? of Planes of Fame museum [some biographical information about Greg] states that.... [Link to the original discussion between GregP and Venturi].

 

4) ...

 

To corroborate the above anecdotes and interviews, there is an official letter from a Allison Engineer to the Commanding General of the Army Airforces Materiel Center, dated December 12th, 1942, where he confirms these reports of using the V-1710-39 engine above its recommended levels for prolonged periods without immediate detrimental effects.

 

[Link / attachment of the letter]

 

While we were unable to find any formal test data to show how long the engine can be run with different MP and RMP, we believe the above evidence shows that de facto the engines were run with higher settings during combat operations than their de jure limitations given in the manual without immediate detrimental effect.

 

We request that the current P-40 engine limits in the game are re-evaluated in the light of the above evidence to allow more correct historical operation of the plane in the game.

 

Signed,

Richard A Nixon

[or list of community members who are willing to sign this, or whoever sends it]

--

 

I would suggest NOT giving any suggestions on what the times and the levels should be, but to let the devs figure it out themselves. We engineers can be petty and have our nerdish pride if someone comes and tells us how to do our work I also suggest we do not elaborate or write out too much on the materials to keep the suggestion short, a reference should be enough.

 

Like I said, in the end we can only provide the evidence and present it in logical manner. The final decision lies with the devs and managers of Il-2: BoS/BoM in terms of where they want to take their product. Or they come back with a counter argument which we can then further discuss.

 

EDIT: The Allison engineer's letter wasn't internal as I initially wrote, but addressed to the Commanding General of the Army Airforces Materiel Center.

Edited April 4, 2016 by PitbullVicious

[Venturi]

Nixon would be the perfect signitary for that letter, but I have a feeling that the right people are already aware, or have been notified - and the decision is truly in their hands. I have been around long enough to know how these things work, and to me it is apparent the devs care about the product and are more attentive than they let on.

 

I think moving towards a design position which incorporates and responds to the sorts of quandries this Allison situation poses is a huge step forward in the right direction towards historical and simulation fidelity, no matter what nationality the aircraft originates from. I understand the devs concern to maintain a "high standard of proof" regarding FM modeling, and historical documentation should always be needed when considering incorporating something like this. It is difficult to make these judgments and skepticism is always needed - the burden of proof is and should be even higher when such changes are not "officially approved". But I feel that the standard has been met from multiple angles in this case. It also helps that we have expert, current aircraft operators and builders of these engines in close proximity to help us clarify any questions.

 

A desire to recreate history, as it was, is apparent in the IL2 BOS/BOM effort, and why I have supported it from the beginning, even though I fly much less often nowadays than I used to (life exigencies). And as I argued earlier, these sorts of judgment calls are by necessity already taking place regularly in all sorts of ways in the design decisions made in the sim, just from the nature of translating vague history into tangible product. That's why universities are still handing out Ph.Ds in history, and why historians are always writing books... because history is never completely clear and constantly needs interpretation. The important thing is that the devs desire to do so in accordance with historical reality, as far as proof can take it.

 

I believe that if the project were to take action on this specific issue, it would be the correct step forwards towards pursuing a more realistic engine management (it is already pretty good) and also raising the bar for historical fidelity in regards to relative aircraft performance. Flying piston engine fighters is not like flying jets. They are 80% engine management and so to get the essentials correct, while still keep things flyable and fun, is a real accomplishment. I would argue that this mix of realism while still keeping flying fun is one of the major reasons ROF was such a success and one of the biggest selling points of BOS/BOM over its competitors. I cannot tell you the amount of interest engines generated amongst those I interacted with that flew WWI fighters there. Players here too will appreciate the fidelity to history and the detail, they always do, and that is how reputations are made amongst the community. It is worth doing. People do not have to be experts to appreciate the details - details which aren't onerous and are unique to aircraft make them feel like they are there... flying over Stalingrad...

[6./ZG26_Klaus_Mann]

Well, we did Suggest new Engine Settings per PM, backed them up with official Charts, they may not be huge leaps, but we might get 10 or more Minutes at 42" Military Rating and 5 Mintes at 52" at Standard Emergency (56" actual Limit, but without MAP Regulator the Allison Engineers decided for a Lower MAP Limit)

[Venturi]

When you say "we" who do you mean Klaus?

[6./ZG26_Klaus_Mann]

When you say "we" who do you mean Klaus?

Since all the Documents you provided are perfectly Vague, I stuck to the Charts provided by Crump, because even though Imperfect, they still provide us with higher Limits than we currently have and are perfectly reasonable.

We will probably still have the 70" but not as a setting for more than 2 Minutes, but 52" as WEP for 5 are still perfectly adequate. 

[Venturi]

2 min at 70" and 5 at 52"? You know 40 is already continuous so 10 mins 42" is hardly an improvement, and we already have 3-4 min at 70". So your numbers actually sound like a downgrade, if that's what you're going for.

 

Not to mention it is ahistorical. Personally that's not enough for me to want to fly it except as a curiosity.

[6./ZG26_Klaus_Mann]

 

3000RPM Automatically limit you to 5 Minutes.

2800 does as well

Edited April 4, 2016 by 6./ZG26_Klaus_Mann

[Venturi]

And so does MAP. Currently 40" 2600 is continuous. 70" 3000 is 3-4 min. 20" at 3000 is 3-4". So how are your settings better?

 

10 min of 42 at 2800 is not much of an improvement. Especially if it comes at the cost of removing 40" at 2600 as continuous. At that point it is a downgrade. In fact Crumps document you are so fond of shows continuous at 37" and 2600. So if you've sold the devs on that you've just bought a reduction in power.

 

In any case it will not make much difference and will still be ahistorical to the way the plane was actually used.

Edited April 4, 2016 by Venturi

[6./ZG26_Klaus_Mann]

And so does MAP. 40" 2600 is continuous. 70" 3000 is 3-4 min. 20" at 3000 is 3-4". So how are your settings better?

 

10 min of 42 at 2800 is not much of an improvement. Especially if it comes at the cost of removing 40" at 2600 as continuous.

70" is a timed, TIMED 2:00 until Warning, and 2:30 to complete Engine Failure. 

44" at 2800 is some Miraculous Rating that lasts for 5, engine damage after 7:30

and 42" at 3000 is a 5 Minute Rating with Engine Damage after 5:30.

Higher Revs of course mean more power

These do not add up, these are in a single flight. 

 

We are trying to achieve: 52/56" at 3000 for 5 Minutes, that's more than the probably 3 Minutes right now.

We are trying to achieve: 42" at 3000 for an additional 5 Minutes adding up to 10, that's 5 more Minutes

We Might also get Take-Off 45.5 at 3000, however that's going to work

2800 Revs will no longer be associated with any MAP

And I frankly don't care about a 3" change in continuous, although that might still be just as possible. 

[Venturi]

The problem is that unless all of those are recoverable in a relatively short timeframe, the drop in continuous will be more significant. 5 mins extra time is nice and a few minutes extra might help in a fight, but it is not going to make much difference to climbing, running, or multiple fights whereas the continuous will. It also will not make an appreciable overall difference to the way the aircraft is used or perceived. Still far from competitive with any 109E let alone F. And still ahistorical.

 

A better solution would would be to increase the time significantly at higher power ratings, on the order of 15-20 mins 52", 3 mins 70", and accept the drop in continuous. This would be a better compromise and might change the way the a/c is actually able to be used. Vis a vis a 109e, it might be able to survive given a good pilot with these settings. Of course my money is still on the 109e, but it is more plausible.

Edited April 4, 2016 by Venturi

[6./ZG26_Klaus_Mann]

40"@2600 are based on NOTHING, no chart presented anywhere close to here. 

[Venturi]

I know. I know that is the actual limit in game, because I fly the plane....

[6./ZG26_Klaus_Mann]

I know. I know that is the actual limit in game, because I fly the plane....

Then it's most likely NOT GONNA CHANGE (watching a bit of Scrubs, imagine a Doctor Cox Voice for that last bit, Thx)

[Venturi]

Unless you are a doctor, then you should not try to impersonate one. Thx.

[6./ZG26_Klaus_Mann]

Unless you are a doctor, then you should not try to impersonate one. Thx.

Unless you have actual Points to make, make none.