P47 Fuel burn rate?

[HPriller]

Does the plumbing really make that much difference?

At military power according to the E6B at 52" manifold pressure the P47 is burning 550GPH in the main arena, add water and it shoots to well over 600 GPH for 60" manifold pressure.

By comparison the other R-2800 planes F6F/F4U only consume ~485GPH at 54" manifold pressure.  Punching WEP in those appears to have no effect on fuel burn rate and they are boosted up to 57.5" manifold while still maintaining 485GPH fuel burn rate.

Also interesting to note that the B26 engines average 540GPH at 52" manifold pressure military power (similar to the P47).

So anyone care to explain, does the turbo really cause that much of a drop in fuel effeciency, if so why?  Also what's the deal with the differences in WEP?

Edit:

What really adds insult to this injury is the fact that most of the time the first serious damage you take in a P47 is a main fuel leak (espescially crippling if you forget to manually manage fuel and burn the main tank before the aux tank), which seems espescially unlikely for this particular plane given all the historical anecdotes of the rear fuselage mounted Turbo charger and intercooler being so good at sucking up those pesky bullets before they could make it to the fuel tank.

[Captain Virgil Hilts]

The turbocharger increased HP. As such, it increases fuel consumption, since HP requires fuel and air. Also, the turbocharger is a restriction in the exhaust, so in some instances under some conditions, it can reduce fuel efficiency.

[Boozeman]

The turbocharger increased HP. As such, it increases fuel consumption, since HP requires fuel and air. Also, the turbocharger is a restriction in the exhaust, so in some instances under some conditions, it can reduce fuel efficiency.

Well, so does the supercharger on the other planes. In fact, turbochargers are more efficient than superchagers beacause they are driven by the enegry of the (otherwise wasted) hot exhaust gases. If anything the fuel consumption should be less at similar power levels. The restriction in the exhaust is neglectable compared to the power a supercharger draws from the engine in order to feed it.

This is really odd concerning the R2800s in the game. Thier fuel consumption charachteristics, expecially using WEP, are kind of odd. As pointed out, in some planes benefit from a lower WEP fuel consumtion, in others the consumption stays the same but power goes up, and yet again in others, it does increase.

The question is, is R2800 WEP always based on water injection? Or does it have "dry" boosting as well?

[Krusty]

Which P-47 model are you talking about?

[yankedudel]

I agree with you Booze that the turbo takes little power to turn but additionally force feeding the engine with extra air requires extra fuel to keep the mixture from leaning out.

[skribetm]

WELCOME TO THE BBS HPRILLER


(from the guy you taught how to land his 262 in MA)

[HPriller]

Which P-47 model are you talking about?

Specifically I was referring to the D models (they all have the same fuel consumption rates more or less), but since you brought it up, I tested the N and it has even more strange results.

At Military Power it burns a whopping 580 GPH, though at 54.5" of manifold pressure (scaling up from the D models this sorta makes sense).  However you punch WEP in the 'N' and you get the phenomenal effect of lowering fuel consumption to 552 GPH while simultaneously increasing manifold pressure to 72".   Also for clarification, punching WEP on a D model P-47 increases fuel consumption to 670 GPH for a manifold pressure of 60"

 Something just doesn't add up.  So far as I've read all the wartime models of the engine used Water injection for their WEP, and the differences between the various models of the engine are relatively minor, what stands out mainly about the installation in the P47 is the Turbocharger (all models were supercharged), but as has been stated this was powered by the exhaust gasses that would have otherwise been wasted, and it served mainly to provide consistent manifold pressure clear to the critical turbo altitude (~30k feet) instead of having power fall off in areas that the supercharger wasn't tuned to handle.  So far as I can tell this didn't actually increase or decrease the power output of the engine at a given manifold pressure.  I suspect the game's numbers may not be on the mark.  That said, I have no idea where you'd get accurate information regarding fuel burn rates for these engines in the first place, but it would be nice if they were a bit more consistent.

[bj229r]

I bet Widewing has this on his Blackberry

[Wingnutt]

*pulls lever on recliner*

[bozon]

Perhaps this has something to do with altitude? At low altitude you do not need the boost and the turbo wastes energy. A mechanical charger is probably more efficient in such situations. When you go higher and need much higher compression ratios, the turbo may be worth the energetic overheads. Perhaps.

[hitech]

I would have to double check, but I do not believe the P47's carried water injection. When we first did the F4U both pyro and I were suprised how fuel burn rate did not increase. After some research we found out the water cooling of the air let them run a leaner mixture, while at the same time inreased efficiency do to lower inlet tempature. Hence more HP for less fuel.

HiTech

[Rebel]

Sure did, Hitech, see below:

http://www.wwiiaircraftperformance.org/p-47/p-47.html

Also see your copy of America's Hundred Thousand- in there there's a schematic for the water injection system made factory standard from the D-11 on, I believe.

I believe it's a black and white of this diagram:

[Krusty]

The -N *does* have water injection, meaning it's displacing gas in the cylinders to cool them off (water cools it to prevent premature detonation, allowing greater compression in the cylinder, creating more power with less gas, as Hitech stated).

That's why the F4U-4 and the P-47N have less fuel consumption on WEP. I think they have the same engine, or at least different versions of the same engine.

As for the -D models, it's possible the water injection just works to a lesser extent than on the -N, maybe not so efficient. The Bf109s had WM (water-methanol mix) for the same reason, but on THEIR engines they increased fuel consumption by ungodly amounts.

Depends on the engine and the circumstances on how it works. I suppose it varries from plane to plane.

[Stoney]

Now, this chart is for the early model Jugs (B's, C's, and pre -11 D's).  I don't have one for the -59/63 engines, but I doubt there are conspicuous differences.  Multiply these values by 2 to compare them to in-game values.  Unfortunately, since the D-11 was the first to come from the factory with water injection installed, we don't have the book values for WEP fuel consumption.  I do know that the P-47N POH specifically mentions that fuel flow decreases when water is run, as the water displaces an equivalent amount of fuel from the mixture.  I've always wondered whether the D-models, and the rest of the non R-2800-C family aircraft (F6F, earlier F4U's, etc), should be getting the benefit of lower fuel consumption when in their water range, but could never find any resources to challenge it.

Personally, I couldn't get a D-11 in-game to match the minimum fuel flow numbers listed, but at the upper end of the throttle, they were pretty close.

[MjTalon]

(Image removed from quote.)

Now, this chart is for the early model Jugs (B's, C's, and pre -11 D's).  I don't have one for the -59/63 engines, but I doubt there are conspicuous differences.  Multiply these values by 2 to compare them to in-game values.  Unfortunately, since the D-11 was the first to come from the factory with water injection installed, we don't have the book values for WEP fuel consumption.  I do know that the P-47N POH specifically mentions that fuel flow decreases when water is run, as the water displaces an equivalent amount of fuel from the mixture.  I've always wondered whether the D-models, and the rest of the non R-2800-C family aircraft (F6F, earlier F4U's, etc), should be getting the benefit of lower fuel consumption when in their water range, but could never find any resources to challenge it.

Personally, I couldn't get a D-11 in-game to match the minimum fuel flow numbers listed, but at the upper end of the throttle, they were pretty close.

Going off topic a bit, But Stoney weren't you apart of the 56th FG?