Big radials fuel consumption

[bozon]

I looked at the E6B and notice that while the F4u and f6f have the exact same GPH at full throttle, the P47, while having quite a similar engine, have higher consumption (FBM set to 1, sea level):

P47D11 at 2700 rpm, 52" - 275 GPH
F4UD-1 at 2700 rpm, 54" - 242 GPH
F6F-5 at 2700 rpm, 54" - 242 GPH

They all are supposed to produce 2000 HP (at sea level?).

So engine volume is the same, and the P47 is using lower manifold preasure but still pours in 13% more fuel.

Another 2000HP engine is the typhoon's. That one extracts 2000HP from only 228 GPH, even more efficient.

When an engine is rated 2000HP at sea level, does that include losses to things like the super-charger, giving net HP on the shaft? and that is the reason that the 47's engine is less efficient?

Bozon

[Krusty]

One thing to note, the Typhooon has an inline V-12. The radials have more than 12 cylinders. Might account for the difference.

Regardless, every engine is different, even if it provides the same power. Spit1 and 109E weren't that far off for horsepower, but you can't find 2 more different engines.

My guess is that there are too many variables to say "Hey, same rpm same MAP, same HP, should be the same burn rate", just because there are hundreds of parts for each engine.

[TracerX]

I thought the P47D-11 had a larger engine than the F6F and F4u.  Wasn't it rated like 2,200 HP?  IIRC it was the latest and largest engine available from the USA, and was not available in the same numbers as the engine used in the F4u and the F6F initially.

[zorstorer]

Originally posted by Krusty
One thing to note, the Typhooon has an inline V-12. The radials have more than 12 cylinders. Might account for the difference....

Pretty sure it was a 24 cylinder H type inline

Also I am pretty sure than only the P47 had a super/turbo charger and the blue planes only used a blower.

[F4UDOA]

Bozon,

The reason is because the F4U and F6F R2800B's had carb modifications to allow them to run at auto lean when at mil power. At Combat power the use of ADI reduces fuel consumption at auto rich.

In all likelihood the P-47 had the same carb change however I do not have a new enough manual to show the change. These changes tended to lag in the documentation by a couple of years. So if the mod was in 1943 the manual would not show it until 1945. If you look at the F4U manual at Zeno's warbirds it shows the F4U with the same fuel consumption as the P-47.

Here is the F4U fuel consumption with the newer carb at auto lean.

[bozon]

thanks F4UDOA.

[Saxman]

So do FD and Widewing cruise the forums looking for ANY opportunity to dig into their chart library?

[F4UDOA]

Yess!!!:D

[joeblogs]

For some charts, and discussion, about the specific fuel consumption of the different versions of the Double Wasp, go to

http://mysite.verizon.net/vze479py/id2.html

Note that it is perfectly logical that a P47 developing more HP is going to consume more fuel, all else equal, than another plane. What should be compared is the amount of fuel consumed per horsepower generated.

Given that the -21 used a turbo supercharger it is likely the ADI system was also different. And remember, the engine charts we are comparing are from the Navy (-8 and -10) vs the airforce (-21).

Note also that at medium to high altitutdes, across almost the entire power spectrum, the turbo supercharged engine is more fuel efficient, because it is not carrying the penalty of driving a second stage supercharger. It benefits from using the nearly free energy contained in the exhaust.

-Blogs

Originally posted by F4UDOA
Bozon,

The reason is because the F4U and F6F R2800B's had carb modifications to allow them to run at auto lean when at mil power. At Combat power the use of ADI reduces fuel consumption at auto rich.

In all likelihood the P-47 had the same carb change however I do not have a new enough manual to show the change. These changes tended to lag in the documentation by a couple of years. So if the mod was in 1943 the manual would not show it until 1945. If you look at the F4U manual at Zeno's warbirds it shows the F4U with the same fuel consumption as the P-47.

Here is the F4U fuel consumption with the newer carb at auto lean.

 

[joeblogs]

It was a different model of the R2800, but not a different engine. Later versions of the P47 took advantage of the improved C block, which developed more horsepwoer than the earlier engines.

-Blocks

Originally posted by TracerX
I thought the P47D-11 had a larger engine than the F6F and F4u.  Wasn't it rated like 2,200 HP?  IIRC it was the latest and largest engine available from the USA, and was not available in the same numbers as the engine used in the F4u and the F6F initially.

[joeblogs]

[bozon]

If I read the top plot correctly, it says that at sea level (neutral blower), 2000 HP, hog's -8 is LESS efficient that the jug's -21 model. In the game it's the other way around by even a larger margin.

I assume this is takeoff power (no ram effect for the f4u).

Bozon

[joeblogs]

You refer to the top but mention the notation from the bottom chart.  

There are two charts because I am comparing two tables on the Navy engines at different points in time. There is a clear difference in the efficiency of the navy engines that come from different SEFC charts. I don't think either is using RAM.

In the first chart, the ONLY time the Navy engine is significantly more fuel efficient that the -21 Airforce engine is when it is in WEP, for exactly the reason F4udoa described. In the second, it is a bit more fuel efficient in low blower.

I am not even sure the chart I had for the P47 engine was referring to a model that had ADI. For some time ADI was not in the production P47; it was added at the front, using kits shipped to the front lines.

I imagine Aces is using data from the later charts, but I don't know that for sure.

The other thing to note is that the -21 model was a long production run with many performance improvements along the way. Unfortunately we don't know exactly which block of the -21 this chart was derived from.

-Blogs

Originally posted by bozon
If I read the top plot correctly, it says that at sea level (neutral blower), 2000 HP, hog's -8 is LESS efficient that the jug's -21 model. In the game it's the other way around by even a larger margin.

I assume this is takeoff power (no ram effect for the f4u).

Bozon

[joeblogs]

BTW I think this is the chart I used for the P47.

http://mysite.verizon.net/vze479py/id10.html

Here is a chart of fuel consumption curves for 4 American turbocharged engines:

http://mysite.verizon.net/vze479py/id3.html

Originally posted by bozon
If I read the top plot correctly, it says that at sea level (neutral blower), 2000 HP, hog's -8 is LESS efficient that the jug's -21 model. In the game it's the other way around by even a larger margin.

I assume this is takeoff power (no ram effect for the f4u).

Bozon

[bozon]

ok, that clears it. I was a bit confused of the difference between the plots.

Neat website and good info btw joeblogs.

Bozon