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

[Venturi]

How long one actually has will to a large extent depend on how long the variable factor is. It might be a LOT more. The point is the above has the potential to take into account the nominal plus the historical factors.

 

The alternative option to something like the above is just to do away with any modeling of detonation. So I guess it just depends on the philosophy of the devs/

[JtD]

But how were the throttle stops rigged? in a default factory aircraft

 

Cheers Dakpilot

Lever forward: Fully open. Lever back: Idle.

 

WRT random failures - we're having this for years in Il-2:1946. Both in "overheat", but also in normal operation. Like you, folks were sceptical initially, but came around soon. Also, engine failure consists of randomized parts/subsystem failures, only very few of which lead to instant engine stop. Coolant or oil leaks for instance are dead giveaways that you might be past the engines limit, but have no immediate consequence.

[Dave]

When I go through the Wire I kill and eat whatever is stupid enough to engage me or my friends below 2000.

Don't forget that it is a 3.7 ton aircraft and I don't know what fuel settings you used, but on medium fuel it turns like a kitten on Crack.

It flies like a RoF Aircraft in many ways, you can pull back on the stick a lot harder than on many other aircraft and you have to coordinate you turns, keep the Ball Centered and you no longer have that Airbrake Effect.

This hasn't been my observation. While operating at WOT will result in the highest possible MP at sea level on a given day it doesn't automatically result in a turn-fighting monster. The P40 didn't turn that well in reality and I think this is mirrored in the game (my only grievance is with the engine limits). Steege, Gibbes, Caldwell and others have all concurred in interviews that the P40E enjoyed its greatest advantage/smallest disadvantage at between 10,000' and 15,000'. Gibbes specifically noted in one interview that it was never a good idea to enter a fight below 5000'.

 

And you certainly can't "pull back on the stick a lot harder" - in fact you must be more conservative with pitch changes. Being as aggressive with the stick as with say a Yak, 109 or Mig results in haemorrhaging energy (if fast), a violent and difficult-to-recover spin (if slow), or an accelerated stall (if anywhere in between). But this is at least not contradicted by expectations or history. The P40 is heavy and thus has a lot of momentum; it isn't going to react quickly to stick inputs to alter its velocity vector (roll is a different matter). Given its mass instead the AOA will change and both profile drag and parasitic drag will increase long before the aircraft alters its flight path, reducing AOA.

Are we talking about the same aircraft?

I don't know about "proof", but I'd be very interested in squadron records.

I have mountains from the AWM but none of them are indexed making searching a very long and tedious process. Edited April 6, 2016 by Dave

[Dave]

Thought RAAf 3 SQN flew Merlin P40F's from mid 42 onwards, transitioned from Tomahawk Dec41 to P40E

 

Certainly does give a six month period of operating P-40E

 

Many other Squadrons had to make do with P-40M, not as liked as Packard version, it is to their credit and testament to their  record that they were given preference for the rest of the war until transitioning to Mustang III

 

Cheers Dakpilot

3, 77, 450 and 112 all flew the P40E (to which they had upgraded from the Tomahawk, Hurricane and Gladiator) in the Western Desert. The continued to fly the E in Italy where they were gradually upgraded to N models and the P51-D. Some Es were used in PNG - most there were N. The P40E was the most utilised P40 by the RAAF, RAF (with many of the crews drawn from the Empire Air Training Scheme) in North Africa, Syria and Palestine.

I don't quite see how Tunisia or the Far East boost limitations are relevant to the Russian front though. After all you are flying a P-40 with Red Stars on it...

Air is air. It has the same properties at a given pressure and temperature no matter where in the world it is moved to.

re doctrine, I don't think it's really about saving extra wear and tear, but as a squadron commander I would be very reluctant to report to Moscow that I now have no serviceable aircraft available to support the front, due to unauthorised use departing from limits in the manual on a fairly unfamiliar 'foreign' aircraft type, especially with the political officer looking over my shoulder..

 

Soviet Russia in 42 was not "tally ho'' in the Western Desert or "good on yer cobba" in PNG, however brutal and hard those campaigns also were

 

 

Cheers Dakpilot

If you were dead because you didn't push hard enough you weren't going to care what the Political Officer or your crew chief had to say about your handling of the aircraft. The only doctrine motivating pilots at the core of it was staying alive.

[Dave]

Exactly the point why any pilot would resort to using higher boost in combat - to survive, and bring the aircraft home. I'm pretty sure our armchair comfort somewhat clouds the judgement about how slow you want to go into combat, be it enemy fighters or AAA. The real engine didn't stop because some programmer put a time limit into the code for lack of a sophisticated engine model, and the real pilot would not hit refly after a 37mm took off his slow-and-easy-target-wing.

 

And for Dakpilot again - there's no wire on the P-40. You control throttle directly, and even if you just forgot to gradually close it in a descent, you'd fly at excessive boosts.

Well, actually there was a light gauge wire which was intended to be broken by the throttle when it was pushed past the "limit" set in SOs to designate WEP. It didn't stop the throttle or do anything else other than indicate to the crew chief that the engine had been stressed to WEP and thus required additional maintenance to be conducted to check for signs of damage and accelerated wear on the engine. Edited April 6, 2016 by Dave

[Venturi]

Well, actually there was a light gauge wire which was intended to be broken by the throttle when it was pushed past the "limit".

If this is the case, then was the wire broken at altitude to achieve full throttle height, or was it just accepted that full throttle height was lower than it otherwise could have been? Edited April 6, 2016 by Venturi

[Dave]

If this is the case, then was the wire broken at altitude to achieve full throttle height, or was it just accepted that full throttle height was lower than it otherwise could have been?

This is what I wondered. I haven't seen the wire in the P40 - just read about it being fitted. It may be the case that the wire was only fitted in conjunction with a MAP regulator - the documents I have read never made the distinction wrt the wire, possibly because their intended audience knew what they already had in front of them. It's not as though the pilot and ground crew didn't talk to one another. Edited April 6, 2016 by Dave

[Venturi]

I seem to recall reading in the technical order that a wire was to be fitted with the MAP regulator.

 

**I just re-read the technical order and still don't see any place where a wire was ordered fitted to the throttle quadrant. It makes sense that one would be fitted with the regulator, as it would not have any effect on full throttle height with the regulator installed.

However, the wire would have a definite effect on full throttle height without an automatic regulator installed, because you need maximum opening of the carburetors to get maximum throttle and boost as altitude increased past supercharger critical altitude. It's just a totally different system with the automatic regulator involved because it, rather than the pilot, is actually manipulating the throttle - without the regulator the pilot does directly control the throttle.

Edited April 6, 2016 by Venturi

[Venturi]

I just got the Vees for Victory book in the mail today and finally had a chance to check a couple of passages. It truly is a wealth of information. Anyone who is interested in not only Allisons but WWII aircraft engines should buy it.

 

That said here's a section depicting the engine situation with the "Flying Tigers" using lesser rated V-1710-33 engines and a few other things, besides. There's about 5 pages of references for each chapter.

 

Most of the pics are from Pg 123/124 and 167.

Edited April 6, 2016 by Venturi

[Dave]

I just got the Vees for Victory book in the mail today and finally had a chance to check a couple of passages. It truly is a wealth of information. Anyone who is interested in not only Allisons but WWII aircraft engines should buy it.

 

That said here's a section depicting the engine situation with the "Flying Tigers" using lesser rated V-1710-33 engines and a few other things, besides. There's about 5 pages of references for each chapter.

 

Most of the pics are from Pg 123/124 and 167.

Looks like a really interesting read. I didn't know the Tigers' engines were assembled from factory seconds parts. It makes their record even more impressive. I recognise the last page of mixture exhaust plume guidance from the Allison training manual I have a copy of.

[Dakpilot]

I just got the Vees for Victory book in the mail today and finally had a chance to check a couple of passages. It truly is a wealth of information. Anyone who is interested in not only Allisons but WWII aircraft engines should buy it.

 

That said here's a section depicting the engine situation with the "Flying Tigers" using lesser rated V-1710-33 engines and a few other things, besides. There's about 5 pages of references for each chapter.

 

Most of the pics are from Pg 123/124 and 167.

 

Lever forward: Fully open. Lever back: Idle.

 

From the above posted pages it becomes obvious that throttle /carburettor settup is not just, as you say.. "Lever forward.Fully open. Lever back .Idle"

 

But I am sure (hope) you knew that 

 

Cheers Dakpilot

[Venturi]

Carburetors on cars also have linkages. They can also be adjusted to give different inputs depending on throttle position. Invariably there is a cam which amplifies or changes the linkage rod motion on the carburetor from the throttle movement.

 

However the goal of adjustment is always the same: full throttle should move the butterflies or whatever the carburetor modulating system is, to full open - and vice versa. It is quite possible to get full open butterflies with half open throttle, for instance. It is also possible to never get full butterflies open with full throttle. The linkage has to be adjusted correctly.

 

Now as long as there is no automatic throttle control such as a map limiter, then this is the way it has to be in principle. The documents posted earlier clearly show there was no map regulators installed on these engines.

 

Rather than snipe with vague comments, Dakpilot, perhaps you have evidence that there was some other system involved we don't know about? I'm pretty sure this is the case here though.

 

Also note where the very first Allison V1710s were run for 80min at 1470hp without total failure...

 

From the above posted pages it becomes obvious that throttle /carburettor settup is not just, as you say.. "Lever forward.Fully open. Lever back .Idle"

 

But I am sure (hope) you knew that

 

Cheers Dakpilot

Edited April 6, 2016 by Venturi

[Dakpilot]

Snipe with vague comments??

 

the page you posted says very clearly the throttle was set up (by ground crew) to give 58"Hg 

 

this is not an indication of full open, as there was further adjustment to give 62"Hg

 

I asked what the default factory setting was and was told it was "full open'' talk about vague

 

I am quite aware of throttle linkages and how they work having flown/owned/operated and helped rebuild many 1000hp+ WWII aircraft engines

 

I do not know all the answers, but I do not state facts when I am not sure, seriously this is getting a bit boring and I am out 

 

Cheers Dakpilot

[JtD]

I asked what the default factory setting was and was told it was "full open'' talk about vague

That's not vague, in fact it's impossible to make it any more clear. If you can't wrap your head around the fact that on the P-40E the throttle control lever was directly linked to the throttle plate with no regulator in between, it doesn't make my statement "vague".

I have mountains from the AWM but none of them are indexed making searching a very long and tedious process.

All paper or also electronic?

[Venturi]

It seems very wasteful to have a supercharger whose crit altitude is x number of ft, but the throttle is set to avoid opening all the way so that altitude is reduced... And yet the supercharger is still drawing parasitic drag based on its max boost possible and max crit altitude possible. Do you have a technical document showing throttle linkage adjustment without MAP regulator?

Btw that early engine is still not rated for 58"...

Edited April 6, 2016 by Venturi

[Venturi]

Here is a document (PM Dave for more info) detailing stress testing of a turbo-supercharged Allison V1710 for rating at 2000hp. It is a later variant of the engine, but as the engines are basically similar structurally, this is a good indication of the basic strength of the design.

 

It details how the engine had minor scoring on the bearings, only, after 7 hours of running 2000hp. The problem was that the carburetor did not have enough fuel flow capacity to deliver a rich enough mix at that power level.

 

So, I looked into the carburetor models for the V-1710-39, without getting into too much detail - the size of the carburetor is much smaller than that used in the above test. This likely means that the fuel delivery would be very touchy at 70" of boost and probably why Greg was mentioning that mid 60's inches was the max anyone ever ran - most likely because of fear of detonation. This also would tally with the above account from the crew chief, above.

 

Personally, I would be happy with running 56" of boost for an extended period of time. Obviously the engines could take it without detonation and structurally they were plenty strong (the -39 was stronger than the -33, see the before mentioned reports of it's longevity at power).

 

And I still would like to incorporate the engine modelling in the sim that I mentioned, above.

Edited April 7, 2016 by Venturi

[novicebutdeadly]

Here is a document detailing stress testing of a turbo-supercharged Allison V1710 for rating at 2000hp. It is a later variant of the engine, but as the engines are basically similar structurally, this is a good indication of the basic strength of the design.

 

It details how the engine had minor scoring on the bearings, only, after 7 hours of running 2000hp. The problem was that the carburetor did not have enough fuel flow capacity to deliver a rich enough mix at that power level. 

 

So, I looked into the carburetor models for the V-1710-39, without getting into too much detail - the size of the carburetor is much smaller than that used in the above test. This likely means that the fuel delivery would be very touchy at 70" of boost and probably why Greg was mentioning that mid 60's inches was the max anyone ever ran - most likely because of fear of detonation. This also would tally with the above account from the crew chief, above.

 

Personally, I would be happy with running 56" of boost for an extended period of time. Obviously the engines could take it without detonation and structurally they were plenty strong (the -39 was stronger than the -33, see the before mentioned reports of it's longevity at power).

 

And I still would like to incorporate the engine modelling in the sim that I mentioned, above.

 

Hey Venturi,

 

I disagree with the comparison that you gave for a later variant of an engine to show the strength of the design as numerous minor and possible major changes would have occurred (also that it used high grade aviation fuel, as opposed to what Russia had in 1941).

 

To me it would be like saying that since later version of the DB 605 series could do 1.98 ata and produce 1973 HP that the BOS 109 G2 should not have the limit of 1.3 ata and instead be 1.42 (and so be ignoring the very real historical consequences of running that engine of that time frame at those power settings.

 

As an aside should 109 G2 "pilots" be given that option (allowed to use 1.42 ata with a time limit before damage/fire occurs), using the same argument of "what a pilot would do to try to survive"???

 

 

The P40 engines (of that time frame) may have been able to easily take 56" (for a period of time, however long people deem that to be) structurally with high grade aviation fuel, but have there been any studies on how the engines performed with Russian fuel of the BOM era?

 

Moscow is 786 metres (2578.74 feet) above sea level how would this affect engine performance?

 

Would the P40 be able to attain 60" (that some are saying should be achievable) at that altitude with Russian period fuel (also taking into account the carbi limitations that have been mentioned).

 

  

My position is wanting realism, irrespective of the country of origin of the aircraft.

 

 

I only fly LW aircraft and 99% online... when I can find a server with a low enough ping...... (so pretty much just QMB atm   )

 

 

I have suggested in a previous BOS forum that it would be good to see the deterioration of an aircraft as it gets "older" or if engine limits are exceeded (in MP), and an aircraft improving over time (in campaign) for example: 

 

In MP I believe that if you are able make it back to base, when you hit refly you should get an aircraft with performance that reflects the condition of your previous aircraft, with a count down time to reflect any repairs that need to be made (with the player given the option of flying "as is" or after certain repairs have been made so that it is at least flyable). Hopefully this should make flying in MP a bit more serious especially if they are given a 2-5 minute time out if their last ride was written off, with consequence for not repairing items, for example the possibility of your engine failing due to "engine maintenance" not being selected.

 

In Campaign mode, I believe that you should start with a sub-standard (rickety) plane, from memory the newbies always got the hand me downs while the experienced pilots got the "good stuff" (because they knew how to look after the aircraft), and the more you progress (and in theory improve) your aircraft improves as well (maybe as a result of X amount of good landings/ and returning to base with minimal damage) to the performance eventually being that of a factory fresh plane.

 

 

 

Regards

 

Novice

Edited April 7, 2016 by novicebutdeadly

[Venturi]

Read the thread in its entirety.

 

Also read this regarding lend-lease high-octane avgas. (Thanks to MM for the earlier hint)

 

http://www.oilru.com/or/47/1006/

Edited April 7, 2016 by Venturi

[Venturi]

See attached.

 

 

[Dave]

All paper or also electronic?

Electronic but not indexable. Many are typed but some are badly faded and impossible to OCR. Many are squadron operational logs which are hand written making automated conversion to something searchable very difficult if not impossible with current technology.

[Dave]

Hey Venturi,

 

I disagree with the comparison that you gave for a later variant of an engine to show the strength of the design as numerous minor and possible major changes would have occurred (also that it used high grade aviation fuel, as opposed to what Russia had in 1941).

 

To me it would be like saying that since later version of the DB 605 series could do 1.98 ata and produce 1973 HP that the BOS 109 G2 should not have the limit of 1.3 ata and instead be 1.42 (and so be ignoring the very real historical consequences of running that engine of that time frame at those power settings.

 

As an aside should 109 G2 "pilots" be given that option (allowed to use 1.42 ata with a time limit before damage/fire occurs), using the same argument of "what a pilot would do to try to survive"???

 

 

The P40 engines (of that time frame) may have been able to easily take 56" (for a period of time, however long people deem that to be) structurally with high grade aviation fuel, but have there been any studies on how the engines performed with Russian fuel of the BOM era?

 

Moscow is 786 metres (2578.74 feet) above sea level how would this affect engine performance?

 

Would the P40 be able to attain 60" (that some are saying should be achievable) at that altitude with Russian period fuel (also taking into account the carbi limitations that have been mentioned).

I didn't post that doc here because I expected people would think I was claiming the -39 could equal the performance of the -91 they tested.

That wasn't my intention so I sent it PM instead.

The reason I found it interesting is that Allison claimed in period documents that all the Allison V1710 series 33-93 were "essentially the same engine" with differences being in packaging, some header changes, supercharger ratios and the MAP regulator fitted to F4 onwards.

That said IIRC the -91 had silver plated cam followers and sodium-filled inlet valves to reduce inlet air temperatures and slightly improved oil pump flow rate and remote cooler efficiency to reduce heat-soak. Working against the -91 was the added engine load to drive the second stage supercharger. I think a 7 hour run at 75"HgA suggests that engine destruction for the -39 after 1 minute at 50"HgA is a bit unreasonable.

 

Regarding fuel - as has been stated earlier, the P40s were delivered with supplies of 104/150 octane fuel via rail from Iran. This supply was not unlimited, but the VVS apparently reserved their 104 for the more sensitive engines (Allison and Merlin) that could not perform reliably on the crap fuel that the Klimov's were designed to consume (at the cost of substantially lower output). It would be reasonable to model the Allison performance at this stage of the conflict on US/UK supplied 104/150 fuel. IIRC the DB605 is modelled on the assumption MW50 is used - which was not ubiquitously available. Incidentally the Luftwaffe had limited supplies of the high-grade lubricants and ersatz-fuels made up the majority (i think) of fuel available to them on the Eastern front. It is after all the reason Hitler initiated Operation Barbarossa in the first place.

 

Regarding comparable restrictions for the DB605 - the reasons for the DB605 engine performance changes were substantial physical engine improvements over its service life and the varying fuel quality and introduction of water-methanol injection (as described above). The Allison story is a bit different. While Allison continued to evolve the V1710 - particularly for the P38 and P63 (which produced 3000HP from the V1710 with compound supercharging) - the V1710-39 we are talking about had its published operating limits revised upward several times (a documentation change only) due to field and factory testing that demonstrated earlier estimates of physical limits for the engine were extremely conservative. That is to say the engine was capable of much more punishment that previously thought without any internal upgrades. Naturally the later V1710 models were still given these upgrades as they were developed - but the bog standard -39 could still perform at much higher MAP without them. Many people malign the Allison in favour of the Merlin. When supercharger packaging was eventually improved toward the end of the war the final P51 variants from the J on actually replaced the Merlin with the Allison which proved to be a superior and much simpler and rugged engine.

 

The effect of the altitude of Moscow and Stalingrad on performance at ground level would be to reduce maximum attainable MAP. But the effect of the colder ambient temperatures would negate that. The engine docs I have (which have been posted here already) state that Allison used a "standard" temperature of 100 degrees Fahrenheit (38 Celsius) for their measurements. Also, our altimeters are zeroed to sea-level "standard" barometric pressure. So the performance at a given indicated altitude should be in line with that experienced elsewhere once the effect of temperature on air density is taken into account. Allison also mention higher MAP limits being allowable in non-dusty operating conditions than for desert. In short the engine should perform better in Russia than North Africa.

 

Like Venturi I would be satisfied with longer time limits at WEP and MIL than we have currently. 20 minutes has been mentioned here and in a supplied document. Allison said 5 minutes in their docs but as I have said - they were being very conservative. 5 minutes is still more than we have in game. I think it has also been well established that 58"-60"HgA WEP was ubiquitously exploited by RAAF/RAF units in North Africa and I would be happy with that in Russia given all the circumstances reducing the negative effects in Russia relative to the desert.

 

I think the introduction of some randomness to the exact failure time beyond that 20 minutes at MIL/TO and 5 minutes at WEP would be welcome, as it would for all other engines. That is a failure at (time + rnd(0, time/2) would be nice as a _very_ simple improvement. There are better ways to model the variable time limit but this one is trivial to add.

[=362nd_FS=Hiromachi]

 

 

I think a 7 hour run at 75"HgA suggests that engine destruction for the -39 after 1 minute at 50"HgA is a bit unreasonable.

Not only that, the lack of correlation between temperatures and engine damage limits is also a bit weird. Its most common for me to fly with radiator open at 10-12% during winter and still the needle does not reach even the green area yet I loose the engine after 1 minute of emergency power. Allisons were of course rather well cooled engines and high temperatures would be easier to experience in tropical or subtropical climate, so if I cant overheat my engine (either oil or coolant are even below recommended green area) than I'd expect my engine to be safe.  Thermal damage should be combined with MP limits, not completely separate.  

As long as an engine is running at specified temperatures and RPM, there should be no mechanical damage to the engine.

 

Ps. Nice post Dave. 

[JtD]

At some point temperature will become a secondary issue, if bearings or pistons or connections rods or the reduction gear or something else purely mechanical can't take the load. Also, some temperature issues are not covered in coolant and oil temperature, such as exhaust valve temperatures. Too low temps are/can be also stressful for the engine.

 

Basically I agree with a correlation of engine failure and high temperatures, but it doesn't cover 100%, in particular not if an engine rated 40some inches is run at 70some.

 

This whole topic I think is very nicely illustrated if you look at the last paragraph in image 7 of Venturis excerpts from V for victory, it's a good anecdote. Throttle fully open on an aborted landing, resulting in full, not permissible boost, landed safely, but next flight resulted in complete engine failure.

[Venturi]

At some point temperature will become a secondary issue, if bearings or pistons or connections rods or the reduction gear or something else purely mechanical can't take the load. Also, some temperature issues are not covered in coolant and oil temperature, such as exhaust valve temperatures. Too low temps are/can be also stressful for the engine.

 

Basically I agree with a correlation of engine failure and high temperatures, but it doesn't cover 100%, in particular not if an engine rated 40some inches is run at 70some.

 

This whole topic I think is very nicely illustrated if you look at the last paragraph in image 7 of Venturis excerpts from V for victory, it's a good anecdote. Throttle fully open on an aborted landing, resulting in full, not permissible boost, landed safely, but next flight resulted in complete engine failure.

Yep, and the quickness of the throttle onset, as well as the slow speed (RPM was probably not full even with full pitch and low throttle setting when he punched it) and he stressed the engine even more than it would have been otherwise. Boost goes up instantly while RPMs take a few seconds. I bet he carried a metric crap ton of boost there until he got underway, regardless he obviously came around and landed the plane just fine. The other thing is that I keep seeing in tech notes and anecdotal stories that purposeful overspeed of the engine was possible via the pitch control (like Ju-87 right now on takeoff, ok). So maxing it would not have necessarily put it at 3000 with power on - it might have put it as 3500, or who knows where. The point is he might also have been at too fine a pitch for full power setting and as power went up he went over on the revs, which would give him even more than 70". Starting out, loading the engine down with low revs and high boost is much, MUCH more likely to result in detonation. Then over revving ALSO is a no-no. There's a lot of things not modeled that are germane to the issue - such as variable failure, etc. Also see proposed simplistic revs/boost mismatch model, above.

 

You see where the German simplified engine command systems were so good when you take this all into account.

 

Now, I do think the "glass breaking" on the gauge is a bit over the top. But who knows?

Edited April 8, 2016 by Venturi

[Crump]

Good Morning. Well, I wouldn't have opened this thread is wasn't interested in raising the Engine Limits and at this point I see no point in raising them above permissible Engine Limits, since all other ingame Aircraft have to do the same. 

70" shouldn't be more than either a Kill-Assurance to use when you are jsut inches away from killing someone, or an Escape Setting. 

56" are still a perfectly good setting, 1500hp make it the most powerful inline fighter Engine ingame at that setting and good match for the P-40s weight.

and at 42" you have a solid combat mode, neither bad nor amazing. 

 

I don't have solid Evidence to support petitioning for more than what I offered above, and what I'm really after is not a Super-Über Top Notch Wondersetting, but a Solid, usable combat Set-Up. 

 

 

To add to it, Klauss.

 

People do not read or understand what the Allison engineer says in that document.  

 

The 70"Hg manifold pressure did not occur when any pilot put it past the wire in standard conditions or in level flight at Vmax.

 

It occurred in non-standard atmospheric conditions  and/or with the propeller at the stops.

 

People do not read or understand what the Allison engineer says in that document.  He describes the atmospheric and maneuvering conditions that pilots are experiencing 70"Hg.

 

It is simply the result of a fixed volume manifold.  The pilot had to manually reduce the throttle back to the 52"Hg it was cleared for under non-standard atmospheric conditions or risk blowing the engine. 

 

That is why the boost regulator was added....to allow the higher boost rating and relieve some of the complexity of the aircraft so the pilot could concentrate on the fight.

[Venturi]

The Hazen letter states that the whole reason he's writing is that while the F3R engines (as in P40E1) were taking "66" or even 70" satisfactorily", the reason they are concerned is that their NEW (NOT P40E1) engines with the 9.6 blower ratio (vs 8.8 for the F3R) - because of the increased manifold air temp from the higher ratio - that attempts to run these pressures WOULD result in detonation in these new engines. So, he says "we've agreed to 60" in these new engines as being far enough from the detonation point. He's basically saying that the way people did things on the F3R won't work with the new engines.

What that letter is, is the Chief engineer for Allison addressing the actual use of power settings in the field, from a technical standpoint. He's bypassing the red tape official Army ratings, as dictated by the army, and which are being ignored in the field, and giving some REAL TALK regarding what the engines can actually do. He's trying to be straight with the guys who are setting policy.

Read the letter in its entirety and then think about what it means for modeling what an engine is capable of in the game...

 

The full letter can be found here:

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

Edited April 8, 2016 by Venturi

[Crump]

[Venturi]

[Crump]

Now you understand that 70" and 66" can only be obtained by overspeeding the engine and extremes in the atmosphere.  Good job!

 

Maybe you will help to shed light on this myth of "70"Hg being used set as WEP.

Edited April 8, 2016 by Crump

[Crump]

 

 

I haven't seen the wire in the P40 - just read about it being fitted. It may be the case that the wire was only fitted in conjunction with a MAP regulator

 

Only Allison V-1710F3R's fitted with a MAP regulator could use War Emergency Power.  Without the regulator, there was no WEP allowed on the Allison engines. 

[6./ZG26_Klaus_Mann]

Only Allison V-1710F3R's fitted with a MAP regulator could use War Emergency Power.  Without the regulator, there was no WEP allowed on the Allison engines. 

Don't forget to mention that Standard Emergency Power was allowed instead. 52"@3000, not 56". Still around 1425 hp and 56" were still safe. 

[Crump]

Yes they could use Standard Emergency but not the War Emergency Power rating.  The difference being the lack of a MAP regulator.

[Venturi]

Now you understand that 70" and 66" can only be obtained by overspeeding the engine and extremes in the atmosphere.  Good job!

 

Maybe you will help to shed light on this myth of "70"Hg being used set as WEP.

 

Read it again

 

"extremes in the atmosphere" 

 

Ramming is not "an extreme in the atmosphere" and shows you have a basic lack of understanding, regardless of your posturing.

 

70" can be obtained in a dive from 3000'

66" can be obtained at sea level in level flight at speed

 

 

 

Edited April 9, 2016 by Venturi

[Crump]

 

 

amming is not "an extreme in the atmosphere"

 

A three thousand foot change in ram FTH as mentioned is a huge change in atmospheric density.....

 

Overspeeding...well that is just overspeeding the engine.

 

In other words, your 66 or 70"Hg setting is a pure fantasy.  It was not something that could be selected unless atmospheric conditions were favorable or the engine overspeed..

 

[Venturi]

Wrong, 8.5% is not huge. Especially with a blower, which is already taking that small difference and minimizing it. Temperature would make a much bigger difference. Russia in the winter, is that what Hazen was using as his standard atmosphere for density when he quoted those numbers?

 

In any case a dive means that you end up down at sea level pretty quick.

 

Edited April 9, 2016 by Venturi

[Venturi]

Don't forget to mention that Standard Emergency Power was allowed instead. 52"@3000, not 56". Still around 1425 hp and 56" were still safe. 

 

 

Right, the whole point of this is not that we should all be able to run 70" without consequence. It is to show that overboost on the P-40 was historically and technically:

 

1. easily possible to achieve

2. used widely by the aircrews

3. did not result in immediate detonation

 

Based on the above, we should have much more than 5 min at >44" before engine destruction. We should have 20min at 56"/3000 at sea level without ram, and the capacity to reach 66"/3000 with full speed at sea level.

Edited April 9, 2016 by Venturi

[Crump]

 

 

Right, the whole point of this is not that we should all be able to run 70" without consequence.

 

Read that a few times and see if it still seems correct to you.  I get the feeling you have not read Vees for Victory or at least your mind skipped over a few important facts.

 

 

 

 

Wrong, 8.5% is not huge.

 

 Actually it is...you are still sitting on the same airfield but the airplane now thinks it is three thousand feet lower in altitude.  A density altitude change that big does happen but usually only for a short period of time.

 

Look at the pressure change required and the temps...

 

It is low density altitude conditions, at sea level or overspeed conditions......then you might see 70"Hg on the manifold pressure gauge IF the engine holds up.

[Venturi]

I have indeed read the related areas of Vees, and there are even more references than I have posted, I highly recommend anyone interested in learning more about the matter to buy a copy of Vees for Victory by Daniel Whitney (of California)

 

additional information inside Vees:

 

-regarding higher than rated boost used for long times in the F3R(-39),

-re the moribund power rating system requiring 7 hours of extreme testing that early war Air Corps used (as compared to the British who rated the engines for combat, not civilian-esque use), this was later changed after...

-re the official reports of pilots complaining of the same,

-re the widespread use of both overboost and the fact that it could not be "quantified" by authorities which led to the introduction of the MAP limiter, overboosting affecting Allison-powered aircraft both earlier and later than P-40E1

-re the AVG in China/Burma theatre using 1710-33 and -39s built from cast-off parts, without maintenance, with suspect fuel, flying high boost levels w/o detonation

-re the speed at which RPM could increase (beyond prop governor ability) in Allisons under fast changes of power and that Allison themselves cared more about RPM overspeed than boost levels as being damaging

 

I have posted accounts from current Allison V-1710 builders and racers regarding the engine's durability and potential use/capabilities

I have posted numbers from high-octane fuel deliveries to the USSR under lend-lease for use in these aircraft, showing that fuel nor oil was an issue

I have shown multiple period anecdotal stories (not all of the ones I actually have) showing the overboost capabilities of the engine - and that was at least 60", probably 65-66", in level flight at sea level, without blowing up

 

If all the above does not convince, then you have another agenda entirely. In any case it is up to the developers and I have presented the evidence. 

 

http://www.amazon.com/Vees-For-Victory-Aircraft-1929-1948/dp/0764305611?ie=UTF8&keywords=vees%20for%20victory&qid=1460248749&ref_=sr_1_1&sr=8-1

Edited April 10, 2016 by Venturi

[Crump]

 

 

the widespread use of both overboost and the fact that it could not be "quantified" by authorities which led to the introduction of the MAP limiter,  

 

The MAP regulator made life easier for pilots and reduced the engine managment required.  It also allowed for a HIGHER manifold pressure because it did not need to maintain a buffer for maneuvering.

 

The limits in the manual were set by detonation limits......

 

 

 

And as RM Hazen, Chief Engineer at Allison in December 1942 talks about.....the structural limits of the engine.

 

 

 

The fact these limits were unofficially ignored by a few led to the reputation of the Allison Time Bomb....

 

[Venturi]

Reposting pictures about the P-38's leading edge intercoolers has no bearing on the P-40

 

 

 

I have indeed read the related areas of Vees, and there are even more references than I have posted, I highly recommend anyone interested in learning more about the matter to buy a copy of Vees for Victory by Daniel Whitney (of California)

 

additional information inside Vees:

 

-regarding higher than rated boost used for long times in the F3R(-39),

-re the moribund power rating system requiring 7 hours of extreme testing that early war Air Corps used (as compared to the British who rated the engines for combat, not civilian-esque use), this was later changed after...

-re the official reports of pilots complaining of the same,

-re the widespread use of both overboost and the fact that it could not be "quantified" by authorities which led to the introduction of the MAP limiter, overboosting affecting Allison-powered aircraft both earlier and later than P-40E1

-re the AVG in China/Burma theatre using 1710-33 and -39s built from cast-off parts, without maintenance, with suspect fuel, flying high boost levels w/o detonation

-re the speed at which RPM could increase (beyond prop governor ability) in Allisons under fast changes of power and that Allison themselves cared more about RPM overspeed than boost levels as being damaging

 

I have posted accounts from current Allison V-1710 builders and racers regarding the engine's durability and potential use/capabilities

I have posted numbers from high-octane fuel deliveries to the USSR under lend-lease for use in these aircraft, showing that fuel nor oil was an issue

I have shown multiple period anecdotal stories (not all of the ones I actually have) showing the overboost capabilities of the engine - and that was at least 60", probably 65-66", in level flight at sea level, without blowing up

 

If all the above does not convince, then you have another agenda entirely. In any case it is up to the developers and I have presented the evidence. 

 

http://www.amazon.com/Vees-For-Victory-Aircraft-1929-1948/dp/0764305611?ie=UTF8&keywords=vees%20for%20victory&qid=1460248749&ref_=sr_1_1&sr=8-1

 

Edited April 10, 2016 by Venturi