Why the La7 is so Uber(important)

[Spritle]

214thCavalier,

You TARD.  Did you read my post?  

Are you actually suggesting that the Russians in 1944 somehow developed an engine that was TWICE as efficient as any of its contemporaries?!?!?!? NOT!

It's a rhetorical question dolt.  

In fact the difference in efficiency between those engines would probably be in favor of the R-2800 based on numerous factors.  Like time of development, materials, production techniques, pure R&D,...etc.  

ra hit the nail right on the head.  This discussion has NOTHING to do with airframes.  I don't care if these engines are mounted on blimps or Hellcats, or La-7's the discussion is about fuel consumption under full load.  Drag is NOT part of the equation.

The fact of the matter is that both of these engines would be within a few percentage points of one another in efficiency which does NOT account for the difference in fuel consumption under full load.

Spritle

[F4UDOA]

Easy with the name calling kids. Lets keep it civil.

Anyway,

The F6F carried 250 gallons of fuel weight  1500LBS

The La-7 carried 122 Gallons of fuel weight 732LBS.

Which means that since both A/C in AH have the same endurance then all things being equal the F6F has to fight with a 768LB weight tied to it reducing climb acceleration and turning ability.

This is even worse for the P-47D-25/30, P-38, P-51, F4U-1 and Mossie since they carried even more fuel than the F6F. The more you carry the worse the penalty is compared to La-7, Spit, 109 and  190's.

This should not be.

Currently the Hurricaine has longer range than the F4U, F6F, P-38 and is equal to the P-47. Funny I don't remeber the Hurri being a long range escort fighter??

[J_A_B]

"JAB MA is 2.0 those fuel tests were done for a Scenario which used a 1.5 fuel modifier. "

It says right on top of that chart that it's for a 2.0 setting.  I doubt the guy who made it labeled it wrong.

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"Why does a short range fighter like a Spit have greater range than the F6F?? "

It doesn't, unless the guy in the F6F makes a point of wasting as much fuel as he possibly can.  If both the Spit and F6F pilots actually TRY to maximize range, the F6F will outrange the Spitfire.


I notice that in the F4U chart you posted, it shows a number of 275-290 GPH for MIL power, but only 245 GPH for WEP.   That strikes me as being sort of odd.   If by some fluke that chart has those numbers backwards, everything would make a lot more sense.  Unless, amazingly, the fuel use of the F6F/F4U dropped by 45 GPH despite the engine developing 250 more HP.

You should take note of this--if the F6F did indeed run at 290 GPH at MIL, then it should use all its internal fuel in only 54 minutes, or 27 minutes with the MA fuel modifier.  This would mean the F6F in AH actually has TOO MUCH range at MIL power, not "too little"!  

Since the F6F in AH runs out of fuel exactly when I would expect it to, I believe HTC uses numbers equal to what I can find (which are about the same as that F4U chart except for the apparent reversal of MIL and WEP fuel usage).


LA7 fuel use at low altitude is very important with regards to AH, both because people fly around a lot at low levels in AH and because that's the only level where the engine reaches max rated power.  

I am still trying to find more info on the V-1650-7.  Remember that the Merlin in the Spitfire we have in AH should use less gas because it operated at lower power settings.  The P-51D in AH certainly runs at about 150 GPH at MIL at normal arena altitudes.  The chart posted there is a Korean War-era chart.



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"The fact of the matter is that both of these engines would be within a few percentage points of one another in efficiency which does NOT account for the difference in fuel consumption under full load. "

You seem to think the LA7's engine and F6F's engine develop equal amounts of power.  They don't.  It's not even close.  At MIL power the F6F is probably developing 500 or more extra HP than the LA7, which would account for a large drop off in efficiency.  

J_A_B

[HFMudd]

Just as kind of an aside that harks back to various strat changes...

These issues would really stand out if we loaded fuel in gallons rather than percentage as I and many others have suggested.

(In case you've missed some of the past strat bits, the idea would be to limit the amount of fuel loadable to volume rather than percentage as a strat effect.  By way of example, this is because a Yak that is limited to 25% of it's full fuel load is paying a far greater penalty than a P51 at 25%.)

[J_A_B]

"Currently the Hurricaine has longer range than the F4U, F6F, P-38 and is equal to the P-47. Funny I don't remeber the Hurri being a long range escort fighter??"

The Hurri does NOT have a longer range.  Stop flying around at full throttle all the time and maybe you'll notice that.  

At MIL power the Hurri 1 gets LESS than half the power of the F6F/F4U/P-47.  It also uses FAR less fuel because of this.   WHY, WHY does it surprise you that at MIL power the Hurri 1 stays airborne longer than the F6F?????  Do you REALLY think the F6F/P-47/F4U should use the same amount of fuel at 2000HP as the Hurri 1 does at 900 HP???

If you want range, USE CRUISE POWER instead of wasting huge amounts of fuel.  Why do you think REAL F6F/P-47/P-38/P-51 pilots flew around at 35'' or so MAP, because they liked going slow?  No, because flying at high power reduced range too much.


AH might not be perfect. It probably has some small errors.  But it isn't as badly off as you're trying to make it out to be.

J_A_B

[Spritle]

J_A_B,

500HP less is NOT half of the R-2800 HP.  The La-7 engine uses HALF the fuel at WEP compared to the R-2800.  THAT ISN'T RIGHT!  Is that so difficult to understand?  

Also remember the discussion is about fuel burn rate at full load/full engine output.  It is NOT about cruise settings.  

Assuming the La-7 engine made 1500HP and the R-2800 made 2000HP then the fuel burn rate of the La-7 should be about 75% of the R-2800 +/- a few percent under full load.  The fact of the matter is that it is HALF of the R-2800.  That means that if the R-2800 had a 25% efficiency (note: 25% is GOOD for 4 stroke gasoline engines) then the La-7 engine was 50% efficient.  Hah!  You obviously don't have a clue.  Modern gasoline engines don't even approach 50% efficiency.  And modern engines have the benefit of computer designed intake and exhaust ports, computer designed combustion chambers, exotic materials, modern quality controls, exotic lubricating oils, etc.  The list goes on.  But this majical 1940's technology La-7 engine somehow is more efficient!?  Think man, think!

Spritle

[HoHun]

Hi Jab,

>I notice that in the F4U chart you posted, it shows a number of 275-290 GPH for MIL power, but only 245 GPH for WEP.   That strikes me as being sort of odd.  

Indeed! :-)

Could it be that WEP is based on water injection? Since at military power the engine is run at a very rich mixture for cooling, I'd expect water to substitute a considerable amount of the extra fuel. Water actually cools better than fuel, so total liquid consumption might still be lower at WEP than at MIL.

Well, that's a quick guess :-)

Regards,

Henning (HoHun)

[J_A_B]

That might explain it Henning, but the chart doesn't mention anything about water injection--the engine listed should have a W in it if it used water injection (like the F6F-5's using the R-2800-10W). Still, something is up.

F4UDOA--

Are you saying you want the F6F's endurance at MIL power decreased further in AH?


Spritle--

So you think fuel consumption will be totally linear as you increase power?  Take a look at those charts up there, for example the F4U chart.  Notice how, from cruise to MIL power, the engine uses triple (or more) fuel for less than double the power?

It's not always linear, there are other factors in play.  You know that.

How can you claim that AH must be wrong when we don't even have all the facts?  Do you know what mixture the LA7 uses at its 41'' MAP power setting?  For that matter, do you know how much power the LA7 develops at 41'' (remember that 1500 HP at 41'' was my GUESS!!!)?  Do you have good HP/GPH info for the M-82FN engine?  You claim I don't know what I'm talking about, yet you're willing to condem AH when you don't even have all the facts.  I hope you never serve on a jury!

Oh, BTW, you're even wrong in your own post.  We weren't talking about WEP in the first place, the LA7 does in fact use more than half the fuel of the F6F at WEP (actually it uses better than 2/3 of the fuel).

J_A_B

[Spritle]

J_A_B,

You guessed wrong.  Here are some specs for the ASh-82FNV engine that is used in the La-7.  

Displacement 41.2 liters =  2514 cubic inches.  

Rated HP  =  1850.

Based on that the R-2800 makes .803 hp/in^3
and the ASh-82FNV only makes .735 hp/in^3

http://www.aviation.ru/La/

http://www.btinternet.com/~fulltilt/Engine.html

So now you are saying that the La-7 engine producing 1850 HP uses half the fuel of the R-2800 producing 2250?  Remember the difference in displacement is lass than 300 cubic inches.  

Did you actually look at the plot of the fuel flow rate vs. horsepower?  I made a plot of this and besides the rather odd data point of 290 gph for 2000HP it looks pretty damn linear to me.  It certainly isn't an exponential increase.  

So what say yea?

Spritle

[J_A_B]

"So now you are saying that the La-7 engine producing 1850 HP at WEP uses half the fuel of the R-2800 producing 2250?"

No I never said that, and I have no idea where you got that from.   And why do you keep talking about WEP, you're the only person in thid thread who keeps on discussing WEP.

J_A_B

[J_A_B]

Oh BTW, on the one website you posted, it lists two figures for LA7 fuel use at sea level--310 litres/hour and 274 litres/hour

At 5400 feet fuel use is listed at 355 litres/hour.

It takes 3.78 Litres to = 1 US gallon.  

274 = 72.5 GPH, 310 = 82 GPH, 355 = 94 GPH

It looks like those fuel consumption figures are for some cruise setting, NOT MIL power and certainly not for WEP.  It lists MAP as being 1200mm, but that is equal to the LA7's WEP and there is NO WAY it gets 82 GPH at WEP.  


Are you a native English speaker Spritle?  


That website gives the very useful information that this engine is umtimately derived from the Wright Cyclone.  This might be useful info.



J_A_B

[F4UDOA]

JAB,

HoHun beat me to the punch on the less fuel consumption with WEP. Indeed the engine runs a leaner mixture and stays cooler as well as saves more fuel.

As far as you satement about "Stop running around wasting fuel", that is rediculous. Your not getting the point at all.

ALL OF THE A/C ARE RUNNING AROUND WASTING FUEL!!

I'm posting accurate pages on the fuel consumption and you keep telling me that the La-7 which produces 1500HP at Mil power(That number is your guess) which is 75% of the 2000HP the R2800 puts out but only uses 50% of the fuel to do it in the same amount of time. Meaning that the ASh-82FNV is 25% more efficient. Not!!

That is the whole arguement in one sentence and the La-7 engine is NOT 25% more efficient than the R2800 causing many AH A/C to carry far more fuel than neccesary to accomplish the same mission.

BTW. Spritle seems to know what he is talking about you may want to read his post.

[J_A_B]

"That is the whole arguement in one sentence and the La-7 engine is NOT 25% more efficient than the R2800 causing many AH A/C to carry far more fuel than neccesary to accomplish the same mission. "

The only problem is we don't KNOW what the LA7 does on MIL power.  I'm not saying AH is right or wrong with regards to the LA7, I'm saying WE DON'T KNOW.  If someone would be so kind as to locate good data on the engine settings of the LA7 at MIL power (41''), then we would have something useful to look at.

For all we know MIL power in the LA7 might be the same thing as a lean-mixture high cruise setting in the F6F.   That's sure as heck what it looks like.

You are so convinced that AH must be wrong that you're ignoring the fact that much of what we're discussing is based on guesswork and assumptions.   It's good for discussion, but NOTHING in this thread *proves* anything.

*IF* the LA7 indeed produces 1500HP at MIL power (we don't know), and *IF* it's running on a rich mixture like the F6F is at MIL (we don't know), THEN I would expect it to use a similar amount of gas to develop X amount of power.  

I *suspect* that at MIL the LA7 is running on a leaner mixture than the F6F because the F6F needs additional cooling at the higher power output.  Run the F6F in a high cruise configuration at ~1500 HP at low alt like the LA7 and I bet that R-2800 would be just as efficient or dang close.   On your chart up above, at 1675 HP at low alt the F6F gets 220 GPH and it's still on auto-rich....reduce this by another 200 HP and use auto-lean and I don't think it'd be far from 140 GPH.

It's equally possible that AH might be wrong.  It's *possible*, but we haven't PROVED anything, either way.


J_A_B

[F4UDOA]

Your right JAB,

Nothing is proven becuase we don't know the numbers for Mil power consumption for the La-7. I also have serios doubts about weather a 14 cylinder engine even today could put out 1500HP in a high cruise mode. No one else could do it with anything close to the same size displacement and the Russians didn't have the quality of castings for engines that the Americans, British or Germans had at the time.

In anycase you can expand that arguement to the Spit and 109's. They all seem to out distance all of the longer ranges birds. Compare the Spit and the Mossie. Same engines, the Mossie has four times the fuel and two engines.

Why on earth does the Spit IX have the same endurance as the Mossie?? The Mossie should not have to take 500 plus gallons of fuel to fly the same distance as the Spit with 130 gallons of fuel.

Somethings rotten in Denmark!!

[214thCavalier]

Lol JAB i am happy to see i am not the only one having problems with Spritle putting words in my mouth

Btw the fuel consumption i posted earlier was as i said tested for a scenario which ran a 1.5 burn rate it was not reffering to the chart posted above i posted it only to show how much fuel consumption could be affected.

From that site Spritle linked and if they are accurate ?

As this one is limited to 10 minutes its reasonable to assume its Wep and at sea level.

Engine speed 2500 rpm
Manifold pressure 1200 mm mercury = 47 inch map.
Fuel consumption 310 l/hr
Duration 10 minutes maximum per flight

This one drops 100 rpm and 200mm mercury, so probably Mil setting and as stated at sea level.

Engine speed 2400 rpm
Manifold pressure 1000 mm mercury = 39 inch map.
Fuel consumption 274 - 310 l/hr


@ 1,650 m ( 5,400ft) (1st stage boost)
Engine speed 2400 rpm
Manifold pressure 1000 mm mercury = 39 inch map.
Fuel consumption 310 - 355 l/hr

Ok found this one as well from  http://www.ctrl-c.liu.se/misc/ram/eng_ash-82.html

Refers to engine ratings of 1460HP / 1850) HP i assume Mil and Wep settings?

Worth noting this site refers to Fuel consumption as g/hp/h now could that in fact be grams per HP per hour and not litres per hour ? ?

Now if it is Grams per HP per Hour then plucking some figures out of the air:-

For the Ground max rating (call it sea level) we have 1430 Hp quoted and a consumption of 315 to 340 now if its grams and using the max figure thats 0.340 KG fuel per HP per hour multiply by 1430 Hp and we get 486 KG of fuel per hour, multiply by 2.2 to convert to lbs and we get 1069 lbs of fuel.
Using a specific gravity for the fuel of 0.6 thats 6 lbs per US gallon we can work out that it uses 178 US gallons per hour.

(Using both figures the range works out at 165 to 178 US gallons per hour)

That is 136 to 147 Imperial gallons per hour pretty damn close to the figure JAB worked out earlier quoted here.

I have no idea how much fuel LA7's engine uses. Multiplying it out suggests that at military power the LA7 uses around 140 GPH in AH. Military power in the LA7 is I believe 41 inches MAP.

So F4UDOA and Spritel does that make it easier to swallow ?

Nearest Cyclone i found power wise is this one but no fuel consumption data as a rough comparison found yet.

SPECIFICATIONS
Model: R-2600-13 (Wright Cyclone Model C14B)
Type: Static Radial, Air Cooled, Double Row
Number of Cylinders: 14
Bore: 6.125 in.
Stroke: 6.312 in.
Piston Displacement: 2603 cu.in.
Compression Ratio: 6.90:1
Blower Gear Ratio: 7.06:1 and 10.06:1
Blower Diameter: 11.00 in.
Rated RPM of Crankshaft: 2400
Rated BHP/RPM at 6700 ft: 1500/2400
Rated BHP/RPM at 13,000 ft: 1350/2400
Take-Off BHP/RPM: 1700/2600
Rotation of Crankshaft (from anti-propeller end): Clockwise
Rotation of Propeller (from anti-propeller end): Clockwise
Propeller Reduction Gear Ration (crankshaft to propeller): 16:9
Average Weight of Engine: 1978.50 lbs.
Overall Length of Engine: 63.10 in.
Overall Diameter of Engine: 54.26 in.