Supercharger Intake Locations

wuzak · Dec 3, 2019

sotaro said:
On a separate question, since you seem to have a lot of knowledge of the Allison engine, was the Allison every used in WWII combat without a supercharger in an airplane? I am having a debate on Quora who alleges the Mustang I used by the British did not have a supercharger. He writes that supercharged Allison engines were not allowed to be exported from the U.S.. This I assume to be a misreading of his literature. thank you.

As far as I am aware all V-1710s used in combat aircraft had a supercharger, which was attached to the rear of the crankcase.

P-38s used a turbocharged system, where the turbo fed air to the carburettor at around standard sea level pressure, which then fed the engine supercharger, which compressed the air and supplied it to the engine.

The first P-38s delivered to the RAF (the Lightning I) were not fitted with the turbocharger (or turbosupercharger as it was often known back then), which many people then describe as unsupercharged.

All Mustang Is, IAs, and IIs had a single stage single speed supercharger at the back of the engine.

sotaro · Dec 3, 2019

wuzak said:
As far as I am aware all V-1710s used in combat aircraft had a supercharger, which was attached to the rear of the crankcase.

P-38s used a turbocharged system, where the turbo fed air to the carburettor at around standard sea level pressure, which then fed the engine supercharger, which compressed the air and supplied it to the engine.

The first P-38s delivered to the RAF (the Lightning I) were not fitted with the turbocharger (or turbosupercharger as it was often known back then), which many people then describe as unsupercharged.

All Mustang Is, IAs, and IIs had a single stage single speed supercharger at the back of the engine.

tomo pauk said:
Two things (at least) can point out that V-1710 on the Mustang I have had a supercharger. For example, a quick look at here shows this line:
"3. Climb data, propeller set for 3000 R.P.M. for first five mins. with throttle open to 44" Hg. manifold pressure or wide open when below."
(my emphasis)
Manifold pressure above 29.92in Hg is generated either by a supercharger, or by pixie dust. Now, since nobody actually used pixie dust to increase the manifold pressure, it got to be a supercharger.
Second quick proof can be seen by looking at test reports for aircraft that used non-turbo V-1710s, like P-40 or P-39 - here. Always supercharged.
A look at manual for the Mustang I also disproves the notion that it was without supercharger - here. On pg. 30 the boost is again mentioned - no superchager, there will be no boost. Or at pg. 44, boost up to 44.5in Hg is stated. Altitude power chart at pg. 56 is also of interest. reding the manuals for P-40s or P-39s reveals the same thing.
People today ofted don't know that other types of supercharging are/were used, apart from use of turbochargers. And USA was exporting turbocharged engines (installed on aircraft) to the UK already in 1941, while contracts were been made in 1940. Unfortunately, most of the people that will state that V-1710 was non-supercharged came from Europe.

After all of this, there is a question of logic: why would anyone sane design a non-supercharged engine for military aircraft in 1930s?
BTW - since when quora became a fountain of knowledge?

Thank you all for your replies. I appreciate the depth of knowledge contained in this community and your willingness to share with those less learned. The links to definitive information is especially convincing.

I agree Tomo that no one would be designing a high powered aircraft engine without a supercharger in the 30's, but opinions are so common and how to persuade without being rude?
In defense of Quora, there are some really smart and hard working people on Quora. They are significantly outnumbered, in no small part because of Quora's policy of boosting the numbers of questions good, bad or indifferent.

Not to denigrate your reply Tomo, but pixie dust is one of my favorite elements...

tomo pauk · Dec 4, 2019

sotaro said:
...
I agree Tomo that no one would be designing a high powered aircraft engine without a supercharger in the 30's, but opinions are so common and how to persuade without being rude?

There is a lot of primary sources available on the 'net that can prove that V-1710 installed in aircraft was always outfitted with engine-driven supercharger. On the other hand, I haven't see any primary source that proves the V-1710 as installed in aircraft was without a supercharger.
Opinions can be challenged (and it is an unwritten rule to do it) - a failure to answer challenge with good data usualy lowers people reputation quickly.

In defense of Quora, there are some really smart and hard working people on Quora. They are significantly outnumbered, in no small part because of Quora's policy of boosting the numbers of questions good, bad or indifferent.

Roger that.
My take is that it is better to ask questions on specialized forums, this one included. Beyond it, f I want to ask questions and read good stuff on military hardware etc, there is the tanknet, or Tony Williams' forum, ot TOCH, or IL-2 forum etc.

Not to denigrate your reply Tomo, but pixie dust is one of my favorite elements...

Shortround6 · Dec 4, 2019

I would note that was very rare for any engine used in the late 30s or WW II that was over 400-500hp not to have a supercharger. This includes trainer engines.

in the late 20s and early 30s there were some unsupercharged engines of around 600hp but they faded from production as a supercharged engine of the same power could be smaller and lighter.

tomo pauk · Dec 4, 2019

Shortround6 said:
in the late 20s and early 30s there were some supercharged engines of around 600hp but they faded from production as a supercharged engine of the same power could be smaller and lighter.

Typo in mid-sentence?

Shortround6 · Dec 4, 2019

yes thanks. fixed.

sotaro · Dec 5, 2019

tomo pauk said:
There is a lot of primary sources available on the 'net that can prove that V-1710 installed in aircraft was always outfitted with engine-driven supercharger. On the other hand, I haven't see any primary source that proves the V-1710 as installed in aircraft was without a supercharger.
Opinions can be challenged (and it is an unwritten rule to do it) - a failure to answer challenge with good data usualy lowers people reputation quickly.

Roger that.
My take is that it is better to ask questions on specialized forums, this one included. Beyond it, f I want to ask questions and read good stuff on military hardware etc, there is the tanknet, or Tony Williams' forum, ot TOCH, or IL-2 forum etc.

Tomo, I just took a look at the Pilots notes. Great info. Thank you for the length and detail in your reply. There are so many assumptions and then so many oddities of history, that when someone seems knowledgeable I tend to assume that their assertions of oddities are correct. Thank you again.

tomo pauk · Dec 5, 2019

Cheers. Stick around, many times people with actual knowledge do chime in.

MIflyer · Dec 5, 2019

I recall reading (I think in Air Enthusiast) that the IL-2 was fitted with the much same engine as the Mig-3 but "without a supercharger" but I don't really believe that since it was written in much the same era as the articles that said the Allison Mustang was "without a supercharger," and because a supercharger is useful down low as well. But I suppose it is possible that it is true in the case of the IL-2.

And in many older (and usually British) articles they refer to a two speed supercharger as a "two stage supercharger."

tomo pauk · Dec 5, 2019

MIflyer said:
I recall reading (I think in Air Enthusiast) that the IL-2 was fitted with the much same engine as the Mig-3 but "without a supercharger" but I don't really believe that since it was written in much the same era as the articles that said the Allison Mustang was "without a supercharger," and because a supercharger is useful down low as well. But I suppose it is possible that it is true in the case of the IL-2.

Perhaps you might find this interesting: link

And in many older (and usually British) articles they refer to a two speed supercharger as a "two stage supercharger."

Gruenhagen, American author in his seminal book about P-51 refers to German engines aboard Fw 190 and Bf 109 as being outfitted with 2-stage engines; French were saying that crucial Soviet mod when going from HS 12Y to the M-105 was installation of a 2-stage S/C. People were likely to make that mistake, irrespective of the country.
Usually, if the author is from country A, he is well informed about the hardware of the country A, but it's work should be cross-checked when he writes about stuff from country B.

nuuumannn · Dec 5, 2019

the Allison every used in WWII combat without a supercharger

Gawd is this still going on? Soon we'll have Davebender popping up and telling us Britain had a shortage of aluminium and had to make the Hurricane and Mosquito out of wood as a result...

Shortround6 · Dec 5, 2019

Nope.

They changed the gear ratio driving the supercharger. Perhaps a few other things bu tit was pretty much like a Merlin 30 compared to a Merlin 45.
The AM-35 supercharger was geared to give high altitude performance while the AN-38 was geared to give low altitude performance.

Picture of AM-38 showing the supercharger.

MiTasol · Dec 6, 2019

silence said:
I think my confusion may be resulting from ignorance on just how the supercharger and carburetor interact with the engine.

Therefore the supercharger (my fingers seem to HATE to type that!) feeds INTO the carburetor to keep its air supply at the levels it needs.

No. Except on some Allison engines with the Auxiliary Stage Blower (ASB) the supercharger is always after the carburetor. A turbosupercharger, if fitted, is fitted before the carburetor.

For a better description see this Engine design as related to airplane power : with particular reference to performance at varying alt

From memory it does not include the ASB but that was a shaft driven external supercharger which acted in many ways like a turbosupercharger. There were several variants with the carb in different locations.

MiTasol · Dec 6, 2019

Shortround6 said:
I would note that was very rare for any engine used in the late 30s or WW II that was over 400-500hp not to have a supercharger. This includes trainer engines. .

Absolutely.

As far as the Allison went the the V-1710-1 had a take off manifold pressure of 43.5" so I would have expected that all had an internal supercharger. That said my reference (Vees for Victory) says n/a against the -2, -6, -9YV and a few others. I expect that n/a in this case means NOT AVAILABLE because the TO HP is similar to the other models - eg the -25 is 1150hp like the rest of the -21 through -31 engines.

However the -4 only develops 690hp and runs at -2.24 lbs for take off which suggests that it had no internal supercharger. Building a special rear case for one model does not make sense but the -4 was a Navy engine and my memory (not always a reliable source) says that was for airship use. It may however have been one of the boat engines GregP referred to abov though he does list separate marine engines.

Milosh · Dec 7, 2019

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Supercharger Intake Locations

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