How good is the LA-7's Engine?

[F4UDOA]

aircav,

Sorry, not really argueing with you.

Your point is correct about some A/C. But I assure you that the P&W R-2800 had variable supercharger controls which could be usd to the pilots advantage as far as overboosting for periods of time while watching the tempeture control. This was recorded numerous times during the war with P-47, F6f and F4U pilots overboosting there engines during emergency's. In fact these engines were proven to be durable if not reliable under stresses well beyond factory reccomendations or limits.

FYI, MAP (boost) and RPM are not tied together. They are however in AH. I know for a fact you could hold MAP and reduce RPM on the R2800. In AH it is one control for everything from fuel mixture cylinder head temp.

This is really a whole different subject.

[Pongo]

This is a great thread.

F4 you have to own up that crow has shown you the error in your assumptions. The tests where done with 365 litres not 460 Litres.


When I grow up I want to be able to have a reasonable debate like you two can.

[aircav]

Originally posted by F4UDOA

FYI, MAP (boost) and RPM are not tied together. They are however in AH. I know for a fact you could hold MAP and reduce RPM on the R2800. In AH it is one control for everything from fuel mixture cylinder head temp.

Ok. I'm almost certain it's me that's being dense, so excuse me if that's so. But I was SURE than I can reduce revs in AH while keeping the boost needle at max. Although it does sometimes seem to be airspeed dependent. Not at home right now so can't test. Probably talking out my arse; watch this space...

[ed] The same was true of the Merlin. The most fuel efficient cruise setting was low revs, high(ish) boost, rather than vice versa; although both may have given you an identical power.

"Don't fly at night either fast or slow
With your revs too high, or your boost too low
Or you'll run out of fuel with a long way to go
And you won't get home in the morning"

- Bomber Command

[crowbaby]

Actual engine management includes such things as cowl flaps, intercooler, fuel mixture and RPM controls.

--------------------------------------------------

What two engine controls?

Do you have a seperate RPM and throttle control? Are you including the engine on/off switch?

Frankly I don't know what your talking about half the time.
-F4UDOA

I really felt for you when you said this, cos we've all been stupidly, blatantly wrong at some stage in our lives. I resisted the temptation to call you "Clueless" as you did to me.

However, I just can't read your recovery with a straight face.

[F4UDOA]

Congradulations,

You win the prize. We can manage RPM as well. I have been here since early beta and never used it. I think that actually proves my point about lack of engine control and management.

Back to the main point.

In any case I will use the reduced fuel number to calculate SFC.

Ready?

Max. H=1000m(1st sup.sp.),n=2400, Ps=1020mm Me.pl. 355 0-35

365litres=96.4 gallons burned in 35minutes or 136.5GPH for 60minutes

136.5gallons=819LBS/1650HP

SFC= .496

In other words the La-7 (ASH-82FN ) is as efficent at full military power than the R-2800 is at cruise even with 93octane fuel. In fact it is almost twice as efficient.

Does this sound right to you?

Do you realize the ASH-82FN is essentially the same engine as was in the FM-2? The FM-2 produced 1350HP with 100octane at 2700RPM.

I had no idea the Soviets were so advanced in 1943.

[F4UDOA]

Here is another way to look at it.

HP/lbs of fuel burned in one hour.

ASH-82FN

1650HP / 819LBS per hour

= 2.01HP per 1LBS of fuel burned in a hour.

P&W R2800

2000HP / 1740LBS per hour

= 1.15HP per 1LBS of fuel burned per hour

Wow those Russians were years ahead of us. How did we ever catch up?

[jconradh]

Hmmm, LA7 data might not be right?

Can anyone say, Stalin?

He never sent any engineers to the Gulag, did he?

Or worse, shot?



Jeff

[Puke]

Speak for yourself mate. My usual cruise home is done at 50-75% throttle and minimum revs. Lets me take less fuel and bug out later than I would otherwise have to.   -aircav

Why does this keep coming up in this thread?  I must be missing something.  I'm sure both aircraft's engines can run for a while with precise engine management, but I thought this comparison was ONLY about time of flight between an LA7 and F6F running 100% full throttle/RPM.  BOTH are being inefficient and are the results in Aces High close to being correct.  Not sure why this other stuff keeps coming up.  

The same was true of the Merlin. The most fuel efficient cruise setting was low revs, high(ish) boost, rather than vice versa; although both may have given you an identical power.   -aircav

That's not what this thread is about.  We aren't looking how to squeeze the most out of our engines.  Just comparing 100% throttle between small fueld aircraft and the large gas tank aircraft.

[salem]

I was responding to a blanket statement that engine management does not exist in AH. It does, for those people that choose to use it. If you do not, and run out of fuel.....

-aircav

I agree however, that it is straying off the original topic. See the 'Engine RPM / MAP' thread for more.

[joeblogs]

Actually no - we are pretty sure The LA-7 is modeled so that at military power it burns fuel as if the engine is on auto-lean.  The resulting discrepancy in endurance is on the order of 100 percent, when compared to a comparable American engine.

The discepancy is not quite so large when it is measured against the flight test data we have for the La-7.  But even that data seems too optimistic to be correct.  I have been trying to work out some way to resolve the conflicting numbers but I can't.  

We've also discovered a smaller discrepancy between actual data and AH when running the r2800 at military power (crowbaby's tests).  But the error here is only on the order of 15 percent.

-Blogs

Originally posted by Puke
Why does this keep coming up in this thread?  I must be missing something.  I'm sure both aircraft's engines can run for a while with precise engine management, but I thought this comparison was ONLY about time of flight between an LA7 and F6F running 100% full throttle/RPM.  BOTH are being inefficient and are the results in Aces High close to being correct.  Not sure why this other stuff keeps coming up.  

 

That's not what this thread is about.  We aren't looking how to squeeze the most out of our engines.  Just comparing 100% throttle between small fueld aircraft and the large gas tank aircraft.