Question about V-1610-3

[tomo pauk]

Perhaps someone could shed some light about this:
Packard Merlin V-1610-3* was providing, according to the 'American Hundred Thousand' book, 1600 HP WER at 15,600ft, yet the MIL rating was 1490 HP at only 13,750 ft. All for low blower. It was providing 1330 HP at 29kft WER, while MIL rating was 1210 at 25,800ft (all for high blower).
Now, from what I've learned here at other places, maximum WER was possible at altitudes lower than maximum MIL (for same RPM blower position). Is the book wrong, or Sir Hooker was a true magician?

*edited: title was 1610, not 1650

 

[fastmongrel]

tomo pauk a typo there it should be V 1650

 

[Shortround6]

Data could be from different sources. The Combat power levels seem to line up pretty well with the "level speed" critical power altitudes. That is they include the ram effect of the 400mph or forward speed of the airplane. Critical altitude while climbing is several thousand feet lower. See: P-51B Performance Test

The level speed and climb charts.

The engine manufactures power charts rarely include ram because it changes from plane to plane with the design of the intake scoop and duct leading to the engine intake.

 

[tomo pauk]

In other words, the power graph for 1650-3, found at the book, actually includes ram effect, despite 'NO RAM' caption? Ditto for figures for COMBAT rating - all other figures are for no ram?

Fastmongrel, you're right

 

[Shortround6]

It could be.
Rolls-Royce heritage book says the 1650-3 was good for 1600hp/3000rpm/11800ft using 18 1/4lbs of boost (67in?) in low gear and 1330hp/3000rpm/23300ft in high gear with the same boost. These altitudes are about 2000ft lower than the critical altitudes for climb given in the Mustang test let alone the level speed altitudes.

I haven't found anything on the military rating yet.

 

[tomo pauk]

Quite the difference, 3800 ft lower there than at "US 100 thousands" for low blower, and 5700 for high blower.

 

[GregP]

I'm not sure what is being discussed here.

MIL rating is at mil RPM and MIL manifold pressure and is the maximum safe power level. WER is at the manifold pressure they determine to be the "Oh my God, I need to escape" level, and there is a wire across the throttle gate. You break it to go to WER and, in some setups, that also includes ADI. Takeoff is the maximum torque the rudder and ailerons can handle at low speeds.

Lo blower and hi blower are determined solely by altitude. Usually, the blower switches from lo to hi at 11,000 to 15,000 feet and switches back to low several thousand feet lower to prevent continuous switching around one altitude if you happen to be crusing there.

Most single-stage engines from WWII have a critical altitude around 10,000 to 16,000 feet and, when they switch to hi blower, the boost is good for a significant power increase up to 25,000 - 25,000 feet, and then the manifold pressure drops off normally, making service ceiling for 2-stage enines anywhere from 25,000 to 42,000 feet or so, depending on how much horseepower they need to fly level at altitude.

So, WER is usually about 3 - 8 more inches of boost, and that's all it is ... more boost for more power. The blower speed depends solely on altitude, and is usually set on automatic.

I don't see anything wrong with the power levels quoted.

 

[vanir]

Also WER can have specific guideline restrictions between manufacturers for their own reasons. The V-1710 WER is restricted to under 5000 feet and the rating is given at sea level (actual output at the rated altitude is higher, stock F-series is 1670hp measured like that). For the Merlins Rolls Royce has the WER rated at 5000 feet (close enough for the point), so the Merlin is getting about 100hp beneficiary on the way WER is being rated. Best way to compare Allisons and Packards then is sticking strictly to military ratings by altitude and to keep in mind they've both got some added character, grunt and very individual personality this doesn't account for.

Allison Division themselves said in some documentation regarding engine overspeeding, that they assessed WER guidelines based on blower ratio and bearing capabilities. Using ram-air actually raised usable throttle height with WER but this was never advised.
Some of the postwar US test pilots said when assessing a captured Fw-190F-8 that manufacturers often restricted use of WER to the low blower for no particular engineering reasons, more just a colloquial way of doing things but following detailed examination by engineers no reason was found to prohibit use of the BMW WER system in the higher blower stage and that was no difference whatsoever between this system and the one commonly found in the Fw-190A-8, which is given in the flight manual be used in the high blower gear (but low blow only for the F manual, the conclusion was it being merely nomenclature and using WER in any transitional altitude between gears was a definite no-no).

So there's all sorts of wierdy stuff in comparative WER that doesn't necessarily cross-translate well between engines and operators. Sticking to military ratings is better comparative basis and thinking of WER as unique wild cards available to each personality/engine-fitment.

 

[GregP]

Vanir,

The stock F-Series makes anywhere from 1,150 HP takeoff, 1,150 HP Mil, and no WER at all (F2R) up to 1,500 HP takeoff, 1,425 HP Mil, and 1,600 HP WER (F15R through F17L and the F30's). No Allison is rated at 1,670 HP for takeoff, Mil, or WER. WER is rated anywhere from Sea Level (F3R and F4 R/L) to 28,700 feet (F30R/L), and using WER is unrestricted ... use it when you need it regardless of altitude. The engine is designed to run without damage at 4,000 rpm in the event of a prop overspeed.

Don't know where you got your data, but it is mostly incorrect.

My numbers come from the GM / Allison engine manuals at Joe Yancey's shop (where I now work) and Vees for Victory by Dan Whitney. We build Allison V-1710's today, right now, for anyone who wants one. We can build any Allison except for early ones because we don't have the early long-nose engie reduction gearcases. If you want to see one run or check the numbers, come by the shop at Rialto, CA at the Rialto airport. We have both left and right turning engines runnable most of the time. Most of our Allisons go into P-38's, P-39's, and P-63's ... but we did overhaul one for Art Arfon's original Green Monster dragster that was recently found in a garage, was bought and overhauled, and is now running reliably for owner John Rolley from Tucson, Arizona. We also do tractor and boat engines if desired. We OWN the Aircraft-powered tractor curcit in Europe! Allisons outpull Merlins at almost every event where they meet head to head, and hold most of the records.

If someone wants to race one at Reno, we would have no problem getting 2,950 HP to the prop, normally aspirated, with an Allison at 5,000 feet (Reno) at 90 inches of MP for an aircraft engine. We get a lot MORE HP for a tractor engine. The pumped up Merlins may well make 3,850 HP ... but they don't get that to the propeller. Bring a P-63 and we'll go racing with it anytime with a HOT Allison.

The XP-51J made its initial flight on 23 Apr 1945. It had fuel metering issues (not sufficiently developed yet). Manifold pressure was limited to only 54 inches of Mercury absolute. Yet is still made 491 mph at 27,400 feet on 1,720 HP at 3,200 rpm. That's Reno speed ... at high altitude ... in 1945 ... with machine guns installed.

The P-82E went 465 mph at 21,000 feet where the engines (-119's) made 1,700 HP maximum after the fuel metering was fixed and 24,000+ pound weight. That' moving for a big, heavy airplane. There was nothing wrong with the Allison that some altitude boost from an auxilliary supercharger or a turbocharger would not cure, especilly after the fuel metering issues were fixed. Late models matched the best the Merlin ever did. Too bad they didn't do that in the war, but the US Government didn't give permission for high-altitude improvement experiments until late in the war. By then, getting it into production was too late since the equipment then in use was deemed adequate for the rest of the war. After about mid-1944, we didn't make any big production changes to fighters that weren't very minor and so would not interrupt production.

 

[tomo pauk]

I'm not sure what is being discussed here.

Long story short:
power vs. altitude graph of the V-1650-3, in the 'America's hundred thousands' book, is described as 'no ram', ie. static power, ie. power the engine can develop at the dynamo-meter (or where ever the engine power is measured). It's not - the graph is drawn for power WITH ram effect, ie. engine for the plane traveling at considerable speed. Same things for WER figures of a said engine in that book, but not for MIL, or TO or other regimes.
Contrary to that, the power graph for V-1650-7 is indeed for static power - no ram.

MIL rating is at mil RPM and MIL manifold pressure and is the maximum safe power level. WER is at the manifold pressure they determine to be the "Oh my God, I need to escape" level, and there is a wire across the throttle gate. You break it to go to WER and, in some setups, that also includes ADI. Takeoff is the maximum torque the rudder and ailerons can handle at low speeds.

Lo blower and hi blower are determined solely by altitude. Usually, the blower switches from lo to hi at 11,000 to 15,000 feet and switches back to low several thousand feet lower to prevent continuous switching around one altitude if you happen to be crusing there.

Most single-stage engines from WWII have a critical altitude around 10,000 to 16,000 feet and, when they switch to hi blower, the boost is good for a significant power increase up to 25,000 - 25,000 feet, and then the manifold pressure drops off normally, making service ceiling for 2-stage enines anywhere from 25,000 to 42,000 feet or so, depending on how much horseepower they need to fly level at altitude.

So, WER is usually about 3 - 8 more inches of boost, and that's all it is ... more boost for more power. The blower speed depends solely on altitude, and is usually set on automatic.

Thanks.

I don't see anything wrong with the power levels quoted.

Addressed above.

 

[vanir]

extrapolation of what I said

Allison Div letterhead dated Dec12 1942 letter to the Material Centre of the Army Air Force commander, from the chief engineer.

"...of the F3R and F4R type with the 8.8:1 blower ratio on which this company has agreed to the 60"Hg (+15lbs boost) War Emergency power and approximately 1570hp at 3000rpm..."

[snip]

I now direct you to document spec AN H8 Dec18 1942 specific engine flight chart and associated charts for the V-1710-39, power control chart calcated performance, 60"Hg and 1570hp at sea level is marked as approximately 1630hp at 2500 feet without ram.


so indeed my correction is 1630hp rather than 1670hp, you can see where I jumbled the figure by memory.

 

[vanir]

Hey tomo if it's just ram air you're wondering about, that just raises throttle heights and reduces rpm for the amount of air you're getting in the manifold. Engines appreciate it, much like lowering torque loading in an automobile, driving on a slight descent rather than on an incline, it's not as hard work as the engine does without ram but it does have a touch of drag. Boost setting is by calibration of the regulator and all that stuff Greg said.

blown motors already use ram anyway, it's mechanical ram air but the direct induction ram air of some planes I guess it raises blower efficiency or something, maybe keeps blower temp down (which is oil cooled so that also helps the motor itself and can mean hp)

actual effect on charts is using ram air gets you absolute performance you may have to otherwise exceed specifications to achieve. Overspeeding isn't good for an engine but sometimes can be for horsepower, well you get the same result with ram air so just open "full cold" on the carby and do a shallow power on dive, no need to blow the bearings. More like that than a nitro switch.
And rpm is about work volume in energy terms, it substitutes volumetric capacity or altitude.

Altitude.

rpm substitutes altitude. ram air substitutes rpm. see.
ie. WER map at 60"Hg on an F3R loses pressure above 2500 feet according to the charts. Calibrate 60" for maximum throttle/regulator travel on the ground and you're 58" and going down at that throttle firewalled from 2600 feet. Unless you overspeed the engine. Trim for 3200rpm and the 8.8:1 blower will give you the 60" until 5000 feet.
Big no-no because bearing and drilling is case specific and often varies even within a series, manufacturer guidelines should never be ignored and Allison is very strict about 3000rpm on that motor in that year of production (later reproductions have higher limits but use non-wartime allocations of materials).

Well use ram air and the normal WER keeps map, this is much smarter. But not absolute requirement, not all manufacturers bothered with ram air even on high performance fighters, it's not that big deal in flight mechanic terms, and a pilot is a flight mechanic.

Actually on record is some Fw-190A fitted with ram scoops findings were that increased drag almost precisely cancelled ram air benefits. But that could be different, I'm not an engineer but I know the close cowling fit system on the Fw is all involved with airflow and tons of physics.

 

[GregP]

Vanir,

We have to build Allisons today to factory specs. The F3 is a -39 engine (basically only in the P-51 and P-51A). It is rated at 1,150 HP, 11,700 feet, 44.6 inches of Manifold Pressure, military. WER is 1,470 HP, sea level, and 56 inches of boost.

The F4R and wa rated at 1,150 HP 12,000 feet and 42.0 inches MP at military and 1,550 HP, sea level, 60.0 inches at WER, and was a P-40K engine.

Those are Allison factory numbers as well as by the military overhaul crews who rebuilt the ones we have in stock, and we have about 110 Allisons in stock, and the data plates have the ratings on them.

Of course, both had takeoff, normal, military, and WER ratings, but you get the idea. Memos don't change factory ratings, all they do is clear operations to runs different rpm or boost from factory ratings; the factory ratings don't change, and if the mnilitary clears a different level ... and if the engine fails, then Allison would not honor a warranty, nor would they have to do so. When we overhaul them today, we must adhere to factorty ratings, not memos.

Today, if you buy an Allison, you are free to blow it up if you want to because none are in use by the military of the USA (or any other military, as fara s we know) ... they are all privately-owned. If a private owner wants to run 3,400 rpm and 75 inches of boost, he or she can.

At Reno last year and this year, we had a good friend beat an R-2800 Corsair with a P-40N running at higher rpm and boost than rated so, yes, it can be done and it will probably be OK to do so. He didn't damage anything at Reno. But when we overhaul them, they get factory ratings or they don't get signed off by the FAA IA inspector on the FAA forms unless the data plate matches the factory ratings for the dash number being built. You can't build a -39 and rate it differently from the factory. If you do, it isn't an approved -39.

It is true we can extract more power from ANY Allison than the military did but, in order to do so, we will be exceeding rated and data plate power and rpm. So I'm not saying you can't make the power or rpm or manifold pressures you quoted, I am saying they were not rated at those levels by the factory or on the data plate, even though they might have been cleared for those levels by military commanders. I know ... semantics. But if you want to fly a warbird, you'd better have the semantics correct on the forms or you might have a hard time getting an airworthiness certificate.

Peace, you can probably make the levels you state, and more, if you really want to. Just 2 - 3 bumps on the rpm override switch and a push on the throttle might do it and more. We already know P-40N and P-40E are faster than quoted by the factory or the often-quoted specs, and climb better, too.

 

[vanir]

Thanks for taking the time Greg, I mean obviously I'm not qualified or anything and just interested, and it's very much a work in progress with me, always.

 

[GregP]

You're welcome, and me too, actually, on the "work in progress" part. I wouldn't know if I had not made a friend of the world's best Allison builder, and happened into an opportunity to help build them.

I was always under the impression you could build a P-51 Mustang if you wanted to do so ... and you can. But you can'y fly it unless the FAA (in the USA) gives you an airworthiness certificate. You you won't get that without an original North American data plate attached to it somewhere (or CAC, too), umless you design the kit and certify it or market the kit, with FAA approval of the 51% build rule.

So, I found out through sheer dumb (in my case, at least) luck.

 

[vanir]

Well I was getting especially confused with a number of non specification boost calibrations that Allison was complaining about in the field, up to +25lbs on 130 grade (ammendment 5 aviation gasoline), in Australia (ie. New Guinea presumably), and +18lbs in the middle east on British 100 grade aviation fuel. I was busy conjuring up all sorts of theories like overseas operators RAF/SAAF/RAAF were basically writing their own manual in the field of P-40 combat settings. Making sense of it without jumping to conclusions is a bit disconcerting.

 

[Shortround6]

The whole fuel issue is confusing. From 1939 to 1943 British fuel change a number of times and at times was not the same as US fuel. We all know about the change from 87 octane to 100 octane in the BoB (or just before it). But even British 87 octane was different than US 87 octane. The British knew about rich mixture response and they wanted it, but they didn't know how to measure it. They specified a minimum amount of aromatics in the fuel to try to get what they wanted. They did the same thing with 100 octane fuel. The US didn't like aromatics in their fuel and specified that aviation fuel could contain not more than 2% aromatics compared to the British requirement of not LESS than 20%. While the two fuels behaved the same under lean conditions they were widely different under rich conditions. One batch of US fuel actually performed worse than 100 octane under rich conditions while others hovered just over the 100 mark, once the performance number scale was introduced. You can't specify what you can't measure. Early British 100 octane varied from about 115 to 125 from batch to batch under rich conditions. There was a short lived British specification for 100/125 fuel. This was quickly superseded by the 100/130 specification. I don't know at what stage the US and British decided on a joint specification. We do know that by early 1943 shortages of certain compounds forced a change in the 100/130 specification to allow a higher percentage of heavier compounds to be used, it was this change that caused some of the trouble with the P-38s in Europe.
A lot of the confusion with the Allison is what gasoline they were running in them and when. In 1940-41 the Allison factory was probably using different fuel than what was being used in North Africa and even into 1942 there could be differences.

 

[post76]

Well I was getting especially confused with a number of non specification boost calibrations that Allison was complaining about in the field, up to +25lbs on 130 grade (ammendment 5 aviation gasoline), in Australia (ie. New Guinea presumably), and +18lbs in the middle east on British 100 grade aviation fuel. I was busy conjuring up all sorts of theories like overseas operators RAF/SAAF/RAAF were basically writing their own manual in the field of P-40 combat settings. Making sense of it without jumping to conclusions is a bit disconcerting.

I read a short article on Horsepower vs Torque which actually ties them together.
It is the torque equated with the RPM that comes to the horsepower, which also answered my question why doubling the displacement doesn't
assume a double in horsepower.
Anyway, an engine makes its peak torque and then is equated with RPMs to bring about more power.
Running an engine at higher RPM usually brings about more horsepower which would make sense that the Allison produces higher ratings at 3200rpm alone. Nevermind, RAM, and increased boost.
The problem with gaining more power from increased RPMs is engine wear and other issues where the rotation of the engine moves faster than the
engine can fire. You'd need a better octane to prevent burning valves when the cylinder goes through its exhaust stroke.
I doubt this was a problem at 3200RPM, but might be a concern beyond 3500 or 4000rpm?
It would be like asking where a V12 redlines at?

Making their own manual would probably also come with an understanding of the aircraft when they train in it.
This would be true for any plane.
The rating might offer max performance but things like gaining acceleration or better zoom could be accomplished by running the engine
beyond those parameters for short periods.
There is more HP above 3000rpm if the fuel allows it. If you've ever operated a manual transmission in a car you can get more acceleration out of
the engine doing that but you wouldn't cruise down the freeway at 4000rpm either.
Its probably a better analogy to make with a bike because prop pitch is one lever like a bike derailer.
The pilot would manage pitch and RPM to where the prop is moving the most air. This would be where pitch and rpm are most efficient.
So when you ride a bike and come to an incline, you need to find the gear that lets you move the quickest with out tiring you out.
If you pick a gear that is too low, you overspeed and your legs are working for no gain.
If you pick a gear that is too high, you'd exert a higher load and your legs tire fast or you can't push the pedals with enough speed to be effective. You could think of ADI or water injection as being able to stand on your pedals to counter the load of the high gear.
Imagine what that means for planes with out ADI?
I could easily see why flying or training might also be conducive to note taking to understand what settings to use to get max performance beyond what the manual or engine chart describes.
Also, brake horsepower is what comes off the engine shaft, but might be significantly different than what actually transfer to the propeller.

 

[GregP]

For a 4-stroke piston engine, HP = (torque x rpm) / 5252.

This has the effect that at 5252 rpm, HP and torque are equal. Aircraft engiines usually turn much slower than 5252 rpm. AT half that rpm, which is typical, HP is 1/2 of the torque value.

For an ALlison, a typical rating might be 1,325 HP at 3,000 rpm. At that engine speed, torque is 2,320 pound-feet and the HP is (3,000 / 5,252) of the torque.

Shortround, good stuff on fuel.

I KNEW the European fuels had a different makeup from US fuels, and I KNEW the aromatics were not the same, but did not know the numbers and really have no way of finding out short of stumbling across the information, as in this forum.

Maybe you could generate a fuel information post that could be used for reference and would be a sticky? You seem to have access to the data ...

 

[krieghund]

Here is the chart from the FM indicating with and without RAM.