"P-47s don't really have exhaust stains..."

[BiggTim]

That black streak coming aft from the oil cooler shutter really looks like an oil stain to me.

 

Where is the main exhaust exit on a P-47? Isn't it at the bottom rear of the fuselage, coming off the supercharger?

 

Your guess is probably better than mine; the only reason I thought the front outlet might be at least partly exhaust is the fact that the gear bay doors are stained black while the wing stripe isn't, so they are obviously getting dirty while in the open position. That looks like exhaust to me, but I'm certainly no expert. I would think some oil leakage is probably just as likely in that location.

 

Next time I'm at FHC in Everett, I'll pay special attention to their flying P-47 and take some pics up close.

 

Tim

[Bryan]

Honestly, the "no exhaust stains" claim is sort of silly.  The plane runs on an internal combustion engine.  Now some engines stain more than others (I cannot believe the extreme exhaust staining on Skyraiders, for example), but there is bound to be some degree of soot/discoloration on the aircraft where the exhaust exits....unless it is cleaned off after every flight...which on a combat aircraft is a silly notion.

 

The only realistic question is "how much?" staining. 

[D Bellis]

Umm...seems those are oil stains, not exhaust stains.

 

 

So, do P-47s really not have exhaust stains?

In case it is not clear what you're looking at there:

 

As stated by the others, the P-47's primary exhaust outlet is under the aft fuselage. Any 'excess' exhaust gasses are vented through the Waste Gates as shown above.

 

Any oil staining from the cooler vents would be minor as shown above, and burned off aft of the Exhaust Waste Gates.

 

HTH,

D

[Juggernut]

This is a relatively easy thing.  As was said many times in previous posts, there are exhaust stains on the fuselage of ANY P-47 emanating from the wastegates on either side just behind the oil cooler exhausts.  There will also be exhaust stains/streaks around the tail wheel area where the turbocharger exhausts.  Photographic evidence suggests that the exhaust stains from the turbocharger weren't very pronounced.  When the wastegates are open, exhaust gasses are routed overboard on either side of the fuselage just behind the oil cooler exhaust.  When the wastegates are closed (turbocharger operating), the exhaust gasses are routed overboard just forward of the tailwheel well.  When the landing gear is down, you can plainly see evidence of exhaust staining on the inner gear door leading edge.  It's almost always soot black with missing paint on the door.

 

There will be oil streaks from the engine emanating from many areas around the cowl but mostly on the lower sides as gravity works.  If a radial engine isn't leaking oil, it's out of oil...it's just that simple.  The R-2800 in general requires a lot of oil but does not store it internally (wet sump engine).  Rather it has an oil tank external to the engine (dry sump engine) and relies on scavenge pumps to pump the oil from the engine.  After it leaves the engine, it's cooled (via the two ram air oil coolers) and sent back to the tank where it's picked up by the pressure pump, and routed back to the engine....rinse and repeat. 

[Bryan]

Another thing to think about...

 

I'm sure P-47 experts will correct me if I am wrong, but don't virtually all of the restored P-47s flying today have the turbocharger setup removed/disconnected and rely solely on a normally aspirated R-2800 for power?

 

If so, if one wants to model a restored bird, I'm assuming all the exhaust staining would be behind the oil cooler outlets with none on the lower rear fuselage?

[D.B. Andrus]

Hmmm..no exhaust stains. I beg to differ:

 

 

Cheers,

 

D.B.

[Rick K]

Look at any war WWII P47 and you'll see exhaust stains.  Unless its the commanders mount these birds were ridden hard and put away wet.  The cycle of war did not allow spit & polish.

 

They had exhaust stains from the waste gates to turbo charger.  Even the inboard landing gear door were not spared from exhaust stains.  Do some research and you will see. 

 

My P47D "Slick Chick", it's Hasegawa's very nice P47 Bubbletop.   Enjoy and good luck with your Jug!

Edited July 28, 2016 by Rick K

[LSP_Ron]

This is the P-47 layout, the exhaust gas valve is really called the waste gate. Most (perhaps all) restored and flying P-47's have the supercharger removed to simplify maintenance since the added power isn't needed.  They have the exhaust coming out of the waste gate exit.

[Guest Clunkmeister]

This is the P-47 layout, the exhaust gas valve is really called the waste gate. Most (perhaps all) restored and flying P-47's have the supercharger removed to simplify maintenance since the added power isn't needed.  They have the exhaust coming out of the waste gate exit.

They have he turbo removed to reduce maintenance, yes, but one of the biggest reasons is because any type of fire in the ducting (usually from a rich burn or backfire) will 100% of the time result in loss of the aircraft.

 

P-47 pilots get a worried look in their eyes when you talk about exhaust fires. With the stock ducting, it's very real concern, and one that has resulted in the loss of quite a few 'bolts over the years.

Eliminating the ducting and turbo doesn't really hurt performance for civilian needs.

Edited July 28, 2016 by Clunkmeister

[AdamR]

Bigger waste gate stain on this one -- and not such leaky rocker covers on the engine?

[LSP_Ron]

That's a resto bird, no wastegate there.  That's the exhaust.

 

A wastegate is a vent that normally is closed and opens to control the supercharger speed and vary the boost to the engine.  In that last pic you can see an exhaust pipe sticking out rather than a butter fly valve.

[AdamR]

restored and flying P-47's have the supercharger removed to simplify maintenance since the added power isn't needed.  They have the exhaust coming out of the waste gate exit.

Right. But an active duty P-47 in WWII would be running the turbo a great deal of the time at more than minimal amount of boost -- even in cruise flight, Seems like extensive exhaust staining would happen more at the turbo exhaust than at the waste gate. I still believe most of the black stains we see coming from the waste gate area are oil from the oil cooler shutters.

[BiggTim]

My P47D "Slick Chick", it's Hasegawa's very nice P47 Bubbletop. Enjoy and good luck with your Jug!

And a nicer build of it I have never seen!

[LSP_Ron]

Right. But an active duty P-47 in WWII would be running the turbo a great deal of the time at more than minimal amount of boost -- even in cruise flight, Seems like extensive exhaust staining would happen more at the turbo exhaust than at the waste gate. I still believe most of the black stains we see coming from the waste gate area are oil from the oil cooler shutters.

Yup. Agreed

[Shawn M]

this may help help with some of the how does it work questions