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Water Methanol Injection Explained In Detail


II./JG27_Rich
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II./JG27_Rich

As for those who know later 109 engines were equiped with the water methanol injection system for the boost effect or as we in gaming call it WEP/ War Emegency Power.

 

http://www.youtube.com/watch?v=HkPFZWd8wj4

 

 

http://freespace.virgin.net/john.dell/bf109/Bf109engines.htm

Edited by II./JG27Richie
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water/methanol injection and War Emergency Power are two different things, but interesting links nonetheless :)

Edited by Sternjaeger
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4./JG53_Wotan

Water methanol is injected into the eye of the super charger where it evaporates cooling the charge - this prevents detonation and as such allows for higher ata.

 

Wotan

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The German ADI (Anti Detonation Injection) Alkohol-Einspritzung and the United States ADI using water injection were the same thing. 

 

post-1354-0-95746800-1383660890_thumb.jpg

 

MW50 manual.pdf

 

These over boost conditions are not as useful as gamers tend to believe.  Not only does it represent a huge strain on the engine to the absolute limits of the engineering technology but at high density altitude you end up with more propeller slip than power transfer and the aircraft will slow down when over boost is applied.

 

High density altitude conditions can occur on the ground on a hot, humid, summer day.

 

The strain on the engines means these are very short period burst's of power.  Of course there is some variation in what was allowed by the POH but 5 minutes is about average for these over boosted conditions.

 

Gamers tend to put up a performance curve that in reality represents the aircraft for 3-5 minutes at a time.  Because of the nature of the speed stable portion of the power required curve, it takes most airplanes 2-3 minutes to reach Vmax in level flight.   That means any point on that entire performance curve is only attainable for 2-3 minutes at most.

 

 

So when these huge performance debates erupt, you can laugh at the fact they are discussing 2-3 minutes of the airplanes performance envelope like it is meaningful.

 

Gamers hit the over boost condition every flight and every combat.  It is not quite the outstanding event it was in reality.

 

It would be nice if IL2 BOS treated these systems more realistically IMHO.

 

 

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"Gamers hit the over boost condition every flight and every combat.  It is not quite the outstanding event it was in reality.


 


It would be nice if IL2 BOS treated these systems more realistically IMHO."


 


So true, I may be wrong but didn't most engines have to have at least a stripdown inspection if not a full rebuild if the performance boosts were used.


 


You would soon fall out of favour with your mechanics and storesman let alone your C/O in a real war/logistics situation


 


But...this is only a game  :) especially online  ;)


 


Cheers Dakpilot


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Dakpilot said:

 

So true, I may be wrong but didn't most engines have to have at least a stripdown inspection if not a full rebuild if the performance boosts were used.

 

You would soon fall out of favour with your mechanics and storesman let alone your C/O in a real war/logistics situation

 

Absolutely, the standard was an inspection after a specified amount of use.

 

In the P-51 after each period of WEP use, it was a oil change, pull the plugs and inspect, filters replaced/inspected, valve cover removed/valves adjusted, rocker arm studs, valve spring inspection, each valve checked for blow-by by hand, engine and mount for cracking, supercharger impeller for chafing, at any evidence of malfunctioning, the engine was replaced.

 

After 5 hours of use the engine was torn down and overhauled.

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The Merlin engine in the P-51 is typical of the kind and level of work done after each use.  It represents about 8 hours of labor to get all of that done.

 

...and that's an optimistic time estimate. If repairs were needed, and according to the magnitude of the damage, the engine would be substituted altogether.

 

WEP was forbidden unless needed as an evasive means, it would make quite a difference if this could be taken into account in career mode.

If nothing broke  ;) which was rather the norm than the exception

 

Cheers Dakpilot

 

exactly, often the failure of a single component would trigger others, with obviously dramatic consequences.

 

It's interesting to compare the ruggedness and resistance of a radial engine to a liquid cooled one: the former could come back with whole shot out cylinders and still run!

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The German ADI (Anti Detonation Injection) Alkohol-Einspritzung and the United States ADI using water injection were the same thing. 

 

attachicon.gifWaterInject.JPG

 

attachicon.gifMW50 manual.pdf

 

These over boost conditions are not as useful as gamers tend to believe.  Not only does it represent a huge strain on the engine to the absolute limits of the engineering technology but at high density altitude you end up with more propeller slip than power transfer and the aircraft will slow down when over boost is applied.

 

High density altitude conditions can occur on the ground on a hot, humid, summer day.

 

The strain on the engines means these are very short period burst's of power.  Of course there is some variation in what was allowed by the POH but 5 minutes is about average for these over boosted conditions.

 

Gamers tend to put up a performance curve that in reality represents the aircraft for 3-5 minutes at a time.  Because of the nature of the speed stable portion of the power required curve, it takes most airplanes 2-3 minutes to reach Vmax in level flight.   That means any point on that entire performance curve is only attainable for 2-3 minutes at most.

 

 

So when these huge performance debates erupt, you can laugh at the fact they are discussing 2-3 minutes of the airplanes performance envelope like it is meaningful.

 

Gamers hit the over boost condition every flight and every combat.  It is not quite the outstanding event it was in reality.

 

It would be nice if IL2 BOS treated these systems more realistically IMHO.

 

In 109, there was mw/50 for ~20 min use. You could use it 10 minutes at time, 5 minutes pause was needed between them.

I agree that it is too easy to use wep most games, so far only DCS Mustang have it modelled correctly in my opinion.

Edited by DB605
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II./JG27_Rich

No the opposite What's the opposite of FANTASY


SARCASM....: the use of words that mean the opposite of what you really want to say especially in order to insult someone, to show irritation, or to be funny

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More engine kabooms would cure the overuse methinks. Though, that level of realism would probably hurt the player base. Turns out most of the fliers probably aren't hardcore simmers. I suppose as a full switch option though it would be fun. 

 

"Oh look, your engine threw a rod. That's going to suck for you."

Edited by Cobol
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II./JG27_Rich

More engine kabooms would cure the overuse methinks. Though, that level of realism would probably hurt the player base. Turns out most of the fliers probably aren't hardcore simmers. I suppose as a full switch option though it would be fun. 

 

"Oh look, your engine threw a rod. That's going to suck for you."

Engine kabooms are easy in Cliffs of Dover in a 109 E 1 or E 3 if you screw up with your manual propeller pitch. It takes practice to learn how to dogfight and work the prop pitch at the same time without bogging or over reving the engine

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I agree that it is too easy to use wep most games, so far only DCS Mustang have it modelled correctly in my opinion.

If you check engine test runs, you'll find that they did stuff like running them 100 hours straight at WEP. Service conditions are certainly a little more demanding than test lab conditions, but overall a couple of minutes give or take at WEP don't make a lot of difference - provided you stay with other limits, such as temperature limits. That's why you can find stories of pilots running from the enemy at WEP for half an hour, which I guess you can't hear from DCS pilots.
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"If you check engine test runs, you'll find that they did stuff like running them 100 hours straight at WEP"

 

True, but most engine stress comes from fluctuations in power/loads and temps, a constant load does not put much strain on a well designed engine, the most common time for engine failure is on first power reduction after T/off

 

​For all the stories of escaping while abusing engine limits (rather understandable in an actual life or death situation) I am sure there are plenty of unsuccessful ones that have not been told...for obvious reasons  :) 

 

anyway getting rather off topic

 

Cheers Dakpilot

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Dave Hastie talks about his Spitfire and the boost

 

 

Looks like he was lucky enough to live to tell the tale of what in all probability was the normal result of exceeding the over boost condition limits. 

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4./JG53_Wotan

More engine kabooms would cure the overuse methinks. Though, that level of realism would probably hurt the player base. Turns out most of the fliers probably aren't hardcore simmers. I suppose as a full switch option though it would be fun. 

 

"Oh look, your engine threw a rod. That's going to suck for you."

 

Most engine restrictions have nothing to do with "engine kabooms" - the limits set are based off maintaining serviceable aircraft. The more pilots pushed their aircraft to and beyond those limits meant more time the "black men" had to spend doing inspections and repair. Aircraft engine life was based on hours. Its not realistic to have all engines going "kaboom" just because a sim pilot ran his aircraft 1 minute over some power restriction. 

 

If you want realism then limit the overall number of aircraft on a server and then pull aircraft from "service" for the various maintenance routines. Very few would want that so we will continue to get a brand new aircraft every time we spawn in.

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Yes, on the Merlin engine Mustangs, 5 hours at WEP = overhaul limit

That 5 hr engine knockdown inspection, from the P-51 Flight Manual, also includes a 5 minute (unless otherwise ABSOLUTELY necessary) time limit.

 

 ... however ...

 

USAAF Material Command conducted tests of 100/150 fuel in the Mustang during which WEP was changed from 67" to 75".   During these tests full WEP climbs to 30000 feet (roughly 10 minutes) were conducted at full gross weights comparing the two boost levels, with the 75" setting taking about one minute less than the 67" setting and it was noted that all engine temperatures remained normal.  These tests were conducted alongside max speed tests at varying altitudes.  No unusual engine problems were encountered, although spark plug life was cut by about half, to 12 hours.  They didn't seem to be expecting catastrophe by exceeding the limits and, frankly, I don't think they expected any problems even though it was noted that about 25 pilots of all grades of experience participated.  The Merlin was finally awarded a 7 1/2 hour 75" @ 3000rpm War Emergency Rating.  As it turned out, the 8th AF opted for a "conservative" 72" limit.  Interestingly, 1st Lt James Hinchey actually put in an after action report that he used 74" for fifteen continuous minutes while chasing two 262s (and states that if he could have run 80" he would have caught them), and in numerous other after action reports where WEP is mentioned it's almost always used chasing bad guys.  That, gentlemen, is the American way.   woohoo    

 

The bottom line is that as the war progressed, engines, fuel and oil were being continuously developed and experience was gained in the use and maintenance of them so that operating limits at one point in the war quickly became standard operating procedure not much later ... it's a moving target.  Heck, today Mustangs have a 55" limit  ... ahhh ... kind of a step backward, I guess ...  but that's on pump gas.  No, wait, Dago Red runs at up to 140" at 3400rpm.  :D    Not really a -7, though (at all, try 622), and it's got Allison rods ...

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that operating limits at one point in the war quickly became standard operating procedure not much later ... it's a moving target.

 

 

Yes, as technological changes are made that allow an increase in the overboost at the same limited safety margin.

 

 

Or 60 uses.

 

 

Or one use. 

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Heck, today Mustangs have a 55" limit  ... ahhh ... kind of a step backward, I guess

 

 

No, they are expensive and owners are not willing to run them at ~138% of capacity 67" represents.

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Although I agree that flying under WEP conditions is something happens too often in games I disagree with the huge generalization here. One example posted DB605. Another one could be P-40E's V1710-39 engine. Early in the war there were 3000 rpm / 45.5'' Hg WEP limited for 5 minutes with comments in pilot's manual instructions as never exceeding limit. But in fact the reason was saving money from tax payers. Engine itself could run under such limitations for 150 hours at least. But soon after US had joined the war it became clear that some operational units in Australia and Middle east used 3000 rpm / 70'' Hg.

 

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

 

Btw, it talks about prolonged time of using such high boost. It's interesting because the 5 minutes maximum was usually considered as "short time use".

 

Another good example of how "official" limitations worked in real world is described here:

 

http://www.wwiiaircraftperformance.org/p-38/p-38-wayne.html

 

Short quote:

"The first P-38s to arrive in England were rated at 42" up to about 20,000 feet, 40" at 25,000 feet, with further reductions above that. Colonel Hough decided the best way to find out how much power was actually available without blowing up the engines was to remove the throttle stops and find out for himself. This made full throttle available at any altitude. Operating like this, Hough spent two weeks "abusing the engines", searching for their maximum limit. "We found that below 25,000 feet we could pull up to 60" of manifold pressure without material harm, and we could run as high as 40" at 40,000 feet (60" would yield around 1600 + bhp/ engine). He did warn that this kind of abuse should be of short duration. Col. Kelsey was busy doing the same thing at the Lockheed plant in California."

 

Problem is that there is no official and general purpose definition of WEP. So until there are no other specifications of the which plane, engine, boost and rpm condition and altitude of WEP are we talking about then statements like "it shall be 2 - 3 minutes limit" are totally useless.

Edited by II./JG1_Pragr
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Agree, the conservative use of WEP in real life as compared with computer games is not so much about immediate engine failure or troubles, but more about economics (service life) of the engine and time constraints. If you're a WW2 pilot outbound on a two hour mission, you don't really care if the climb to altitude takes five minutes or eight - in particular if the chances of encountering an enemy are less than 5% and near zero for the duration of the climb. In game, when you happen to have half an hour of spare time, and 100% certainty of encountering the enemy, at any time, knowing that whoever starts with altitude advantage already has half the victory, you adjust the engine management accordingly. In real life you'd do the same - I don't think US pilots at Pearl Harbour worried a lot about engine life.

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II./JG27_Rich

I did have a service schedule for a daimler benz 605 on a disk some place but do you think I can find it. I'm getting into that habit of "Put it away in a safe place" Never find it again for 10 years. Just like dear old Dad. :o:

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Does anyone know what the small tank is for located in the motor mount with the last three letters FL-D printed on it?

It contains pressurized oil for the hydraulic systems - landing gear and radiator flaps.

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Heck, today Mustangs have a 55" limit  ... ahhh ... kind of a step backward, I guess ...  but that's on pump gas.  No, wait, Dago Red runs at up to 140" at 3400rpm.  :D    Not really a -7, though (at all, try 622), and it's got Allison rods ...

 

Today's warbirds are often not an accurate comparison with WW2 standards: the aircraft are often much lighter, as unnecessary weight is removed (old radios/batteries, extra tanks, armour, weapons). We normally take-off with the P-51 with 75% throttle, even with a passenger, since there's plenty of power in a Merlin, but you still have operators and owners that firewall the throttle, which can turn out to be a costly habit. 

Superior lubricants and gas also mean a better longevity, but your TBO will always be 500 hours. And you can always have instances where components slowly start degrading (we're talking about 70+ years old parts sometimes!), but it's all about catching the early signs, i.e. metal particles in the oil, irregular timing, misfires etc... 

It contains pressurized oil for the hydraulic systems - landing gear and radiator flaps.

 

JtD is it a reservoir outside the pressurized circuit or is the tank pressurized as well?

Edited by Sternjaeger
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Although I agree that flying under WEP conditions is something happens too often in games I disagree with the huge generalization here. One example posted DB605. Another one could be P-40E's V1710-39 engine. Early in the war there were 3000 rpm / 45.5'' Hg WEP limited for 5 minutes with comments in pilot's manual instructions as never exceeding limit. But in fact the reason was saving money from tax payers. Engine itself could run under such limitations for 150 hours at least. But soon after US had joined the war it became clear that some operational units in Australia and Middle east used 3000 rpm / 70'' Hg.

 

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

 

Btw, it talks about prolonged time of using such high boost. It's interesting because the 5 minutes maximum was usually considered as "short time use".

 

Another good example of how "official" limitations worked in real world is described here:

 

http://www.wwiiaircraftperformance.org/p-38/p-38-wayne.html

 

Short quote:

"The first P-38s to arrive in England were rated at 42" up to about 20,000 feet, 40" at 25,000 feet, with further reductions above that. Colonel Hough decided the best way to find out how much power was actually available without blowing up the engines was to remove the throttle stops and find out for himself. This made full throttle available at any altitude. Operating like this, Hough spent two weeks "abusing the engines", searching for their maximum limit. "We found that below 25,000 feet we could pull up to 60" of manifold pressure without material harm, and we could run as high as 40" at 40,000 feet (60" would yield around 1600 + bhp/ engine). He did warn that this kind of abuse should be of short duration. Col. Kelsey was busy doing the same thing at the Lockheed plant in California."

 

Problem is that there is no official and general purpose definition of WEP. So until there are no other specifications of the which plane, engine, boost and rpm condition and altitude of WEP are we talking about then statements like "it shall be 2 - 3 minutes limit" are totally useless.

 

 

I think that article confuses operational testing with something that is fully operational.

 

To quote another part of the article:

 

 

Ben Kelsey (now a Colonel) and Colonel Cass Hough, of the Eighth Air Force Technical Section

 

They are engineers responsible for the Operational testing I would imagine. 

 

If so, then this is typical of operational testing.

 

The technical issue in this case was the intercoolers and they were replaced allowing for increase cooling and the increase in power.  Additionally, the Operational limits adopted were much lower than Colonel Hough and Kelsey recommended.

 

 

In March Kelsey reports: "I finally succeeded in reaching limiting carburetor air temperature at altitude. I got excessive roughness, cutting out, and backfires at 190 and 200 degrees F [88 and 93 degrees C]. at about 25,000 feet"… one intercooler was actually blown up". "We very evidently have much larger tolerances in temperature, back pressure and carburetor air pressure than we anticipate".

Kelsey and Hough were looking for a compromise…they wanted the most power available without engine damage. Kelsey recommended a combat rating of 47" at 3000 rpm (1325 bhp) to 20,000 feet. He also recommended a 5-minute limit at 50 degrees CAT. Eighth Fighter Command was more conservative; they eventually established a War Emergency Power rating of 45" up to 25,000 feet. Wright Field, with more responsibility, was even more conservative and recommended a Military Power of only 41” (1150 bhp). War Emergency Power was not recommended. This was essentially the same power available to the XP-38 in 1939!

In the end, the various U.S. Air Forces set their limits somewhere between Kelsey and Wright Field.

 

Most over boost ratings hover around the 130% of rated capacity as a general statement.

 

So, we have engineers who are looking to break the engine to find its limits using "best available data", which in this case Lockheed has listed the CAT as the limiting factor.  The perception that this something that is typically done in a normal operating fighter squadron outside of operational testing without factory/engineering "best available data" is false.

 

The "huge generalization" part of your statement is somewhat confusing. 

 

Are you saying these engines are not over boosted and are reliable when operated as such? 

 

No, there is a very good engineering reason the inspections after each use of over boost are required.  

 

The best resource is the operating instructions for the aircraft and the engine.

Edited by Crump
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which one of the many, Crump? I know that you're a "done by the manual" guy, and that's the most sensible approach, but there were so many variations, amendments and updates on these manuals, that it's often hard to pin the right manual with the right period/aircraft, not to mention that manuals and operations weren't always followed by the book in operative situations, especially in remote or advanced bases, where the availability of spares and tools was often very limited.

Edited by Sternjaeger
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