Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Neil Stirling on February 28, 2007, 09:35:32 AM
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Mosquito http://www.wwiiaircraftperformance.org/mosquito/mosquito.html
FM-2 http://www.wwiiaircraftperformance.org/f4f/fm-2.html
Neil.
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:aok Neil, thanks.
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Thanks Neil, you gents are providing priceless data.
From the FM-2 test:
(http://www.wwiiaircraftperformance.org/f4f/fm-2-level.jpg)
This clearly shows that the current supercharger mapping for our FM-2 is incorrect.
My regards,
Widewing
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U de Man Neil, thanks.
Have already notified the mossie fraternity.
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holy moly!
Mosquito VI doing 354 mph on the deck with external DT!
(http://www.wwiiaircraftperformance.org/mosquito/hx809-level.jpg)
(http://www.wwiiaircraftperformance.org/mosquito/mosquito-level-ss.jpg)
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Our mosquito VI does only 14 lbs boost on the deck (vs. 18 and 25 in the tests) . Is that a result of the exhaust dampeners modeled or is it simply a lower boost setting?
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The dampers just add drag, they don't reduce boost. Ours just has an early boost modeled.
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Originally posted by Krusty
The dampers just add drag, they don't reduce boost. Ours just has an early boost modeled.
Umm they do hinder exhausts flow, which can hinder intake flow .
Just like any engine.
Bronk
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I don't think they'd do that to the point of reducing the boost pressure. The shrouds just covered up the exhausts, with air inlets in front and outlets behind. Not quite restrictive, just "hidden".
I think our mossie (like our spit9) just has low boost modeled, for whatever reasons HTC chose.
Edit: just my guess
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It's less the exhaust guards as the saxophone exhausts beneath them.
Saxophone exhausts had two stubs at the front of a longer vessel, thusly:
(http://www.users.bigpond.com/MSN/mhuxtable/AECZ00aa00fy.jpg)
They produced a good deal less exhaust thrust than stub ejectors, as well as (so I recall HoHun saying) producing some backpressure on the engine.
I may be taking HoHun's name in the case of the latter statement, apologies if so.
The saxophone exhausts took around 15 mph off speed, the drop tanks a further 5 mph (going from memory on the tanks).
The two key quotes from Neil's site (in terms of the Mossie) are:
"It will be seen that at constant boost the effect on true air speed of fitting the multi stub exhaust system is a gain of 15 mph in MS supercharger gear and 13 mph in FS supercharger, "
and
"Comparison of results @ +18 lb/sq.in. boost with those of Mosquito VI HJ.679, indicate that the speed of that aircraft is of the order of 10-15 mph below average, thus supporting the conclusion made in the 7th part of report No. A. & A.E.E./767,e, that HJ.679 was not fully representative of the type. "
Sadly, HJ679 is the aircraft which AH appears to model.
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Originally posted by Scherf
(http://www.users.bigpond.com/MSN/mhuxtable/AECZ00aa00fy.jpg)
Thank you for posting this.
This much more than Just a shroud with a hole at each end.
This set up is a tuners nightmare.
While the front half of the engine would get good exhaust scavenging the rear would not, due to back pressure.
At any given setting, I'd bet if one half is running at an optimal air/fuel mix.
The other half is either lean or rich.
Any information if they experienced spark plug problems on mossies fitted with this pipe?
Bronk
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I don't know about spark plug problems due to saxaphone exhausts, but those Mosquito's that did use +25lbs boost had multi ejector exhausts as the saxaphone exhausts burnt out. This document from the Austailian archive (DH data) shows the sort of performance obtained when using +25lbs boost and multi ejector exhausts. http://www.wwiiaircraftperformance.org/mosquito/mosquito-performance-aussie.pdf
Neil.
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I can understand why. As a hobby I play with older cars and mess with engine building and tuning. One of the biggest no-nos in tuning is sharp turns in an exhaust system, especially a header .
Bronk
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Originally posted by Bronk
Thank you for posting this.
This much more than Just a shroud with a hole at each end.
This set up is a tuners nightmare.
While the front half of the engine would get good exhaust scavenging the rear would not, due to back pressure.
At any given setting, I'd bet if one half is running at an optimal air/fuel mix.
The other half is either lean or rich.
Any information if they experienced spark plug problems on mossies fitted with this pipe?
Bronk
Hiya:
Sorry, I've no information about spark plug performance, other than to say that on long patrols at cruising speed, it was recommended that the engines be given a burst of power every 30 minutes or so to clear the plugs. I believe this was the case regardless of the exhaust type fitted.
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Originally posted by Scherf
Hiya:
Sorry, I've no information about spark plug performance, other than to say that on long patrols at cruising speed, it was recommended that the engines be given a burst of power every 30 minutes or so to clear the plugs. I believe this was the case regardless of the exhaust type fitted.
Interesting, were they concerned with all or just some of the plugs loading up?
Bronk
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I've only ever seen references to "the plugs" in general terms - seemed to be a risk for all cylinders at long periods of low power.
That said, I've never seen any account of the Mosquito's war through the eyes of the groundcrew - it's a big gap really.
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Krusty,
The Mossie in AH is at +18lbs boost on WEP at the critical altitudes.
No Mosquito Mk VI was limited to +14lbs boost. The Merlin 21 and 23 were limited to +12lbs boost and the Merlin 25 (like in AH) was limited to +18lbs boost and later to +25lbs boost with 150 octane.
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"Interesting, were they concerned with all or just some of the plugs loading up?"
AFAIK, the problem was not the plugs itself but the deposits forming on the plug electrodes (because of the additivs in 150 Oct) which tended to burn and form on electrodes permanently if the engine was not run up at higher boosts from time to time. The new plugs just were up to withstand the higher thermal stresses of increased boosts. The engine would run on old plugs as well but the possibility of a plug failure would be significantly increased.
-C+
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Charge I understand deposits on plugs .
What I'm looking to figure is if was just some of the plugs on a given bank.
(http://www.users.bigpond.com/MSN/mhuxtable/AECZ00aa00fy.jpg)
Looking a this picture tells me the last 3 cylinders for this bank receive less exhaust scavenging than the first 3.
Trying to jet a carb for best performance through all rpm ranges is tricky enough.
Compounding it with uneven exhaust flow, i picture tech guys pulling there hair out.
If I jet for optimal air/fuel mixture at WOT (Wide open throttle) for the back 3 cylinders I risk burning out the first 3. This would be due to a lean condition cause by better exhaust flow.
I am guessing they jetted the carb for optimal WOT on th first 3.
While this might cause a slight rich condition on the back 3 at WOT . It would run without risk of losing a cylinder.
During slow / normal cruse however I suspect you would run the risk of fouling the 3 rear plugs on each bank.
Bronk
Edit:
I'm referring only to the sax pipe. Not the damper system as a whole.
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Bronk,
There is a reason only about one third of Mosquito Mk VIs had an exhaust shroud instread of ejector stacks designed simply to boost the jet effect.
I hear the ground crews hated the flame dampers due to maintainance headaches too.
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Originally posted by Karnak
Bronk,
There is a reason only about one third of Mosquito Mk VIs had an exhaust shroud instread of ejector stacks designed simply to boost the jet effect.
I hear the ground crews hated the flame dampers due to maintainance headaches too.
Are you referring to the shroud or the sax pipe?
Bronk
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Mosquito FB VI Pilots notes. Boost limits Merlins 21,23 and 25.
http://www.wwiiaircraftperformance.org/mosquito/mosquito-vi-pilot-notes-op-data.jpg
http://hometown.aol.co.uk/JStirlingBomber/Mossi+VI+Merlin21.jpg
Neil.
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Originally posted by Bronk
Are you referring to the shroud or the sax pipe?
Bronk
The whole thing.
Look at photos of Mosquito Mk VIs and you'll see that most have exhaust stacks that look the same as the Spitfire's.
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I think the Mosquito may be next in line for an update. If you think about it there aren't many allied aircraft left to do, especially those that fit with the 8th Airforce theme and would have the range to go into Germany.
Would certainly be fun to go in doing some tree top level sorties in the Mossie. Or even high level 400+ mph stuff in the bomber mossies if they add them, or photo recon if they make a feature of it in CT.
The Mosquito has so much AH gameplay potential which is sadly missing :(
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Every word true.
Ball and Karnak :aok