Spit Mk1 Boost?

[pupo162]

Originally Posted by TomcatViP

I think you are the one that do my dear.

If you think that the FC was modifying the Merlin's engines like a car tuner will do, tht is a real problem.

As I have alrdy said it's not my personal thinking that prevail in my word. You are wrong on the all line. If I had a personal idea on the subject I won't bother other with my own thinking.

I think you 100octer and 17lber shld read this with much attention and stop lobbying every forum that deal with the Spitfire and smokes any discussions with insult and name calling etc.. etc..;

As I alrdy said, this theory does not makes any sense either on historical or mechanical grounds.

If there was a switch for emergency boost right on summer 1940 it certainly wasn't for a 17lb boost that even in 1944 still posed some problem.

Oh yeah let me guess, if you unfold your SpitPufPuff.com doc you certainly are already with injected nitroglycerin and so on at this same date.

The fact is that guys like you are bitching so much on every forum with YOUR idea of the spit (not the real one) that no sim devs can makes a FM with serenity.

What is senseless is that if such is done, it would be a really good plane to fly and fight.

By the way stop bad mouthing on me Osprey that's getting pretty boring. You don't know me. Thx

you clearly missed the point.

the plane could go to 17+ boost, but would go BOOOM if they tried to go that way. Im sure eventually they got aroudn that problem and managed better engines who could go more than +6.5.

Even myself who thinks of a pittie as a uselless kite, can get the fair point wedge is making.

[TomcatViP]

Believe me or not but military services do test planes to remove any Go&Boom features.

If there was such a lever, it wld be instantly sealed, locked and patched with every possible red tapes

Bench test is not Flight test that is no Op Tests that are not them self Op limits. And I did it short.

[41Sqn_Banks]

Sorry Tomcat you really didn't understand the concept of a supercharged engine. Below full throttle height every supercharged engine produces more boost than it can handle. Guess where the name full throttle height comes from ... exactly it's the height where the throttle can be moved fully forward without overboosting the engine.

There is no magic device needed to get +17 boost from the engine, it's simply the supercharger that is capable of producing this pressure at sea level. Of course this is a overboost condition for the engine and will kill your engine in no time. That's the problem with supercharged engines, the pilot has to keep the boost below the limits and has to adjust the throttle with every altitude change (as boost changes with altitude).

Thats why there is the automatic boost control that limits the engine boost below full throttle heigth automatically. However there might be a failure in the automatic boost control or a emergency situation ... so there was a boost control cut-out that disabled it and allowed the pilot to control the boost himself. Then however he could seriously overboost the engine. So they modified the engine that even with disabled boost control the boost pressure couldn't be raised above +12 boost.

So the "modification" didn't allow the engine to produce higher boost, in fact it limited the boost from around +17 to +12.

PS: Please use whole words to write your sentences it's hard to make sense of these abbreviations.

[Valec]

http://www.airpages.ru/eng/uk/spitf1.shtml http://www.airpages.ru/eng/lw/bf109e1.shtml

[TomcatViP]

One Question Banks : when do you actually get max boost with a supercharged engine ?

And by the way if you were not charging us every three month on the same subject and with the same arguments I would hve been pleased to check out any abbreviations out of my phrases.

As I hve alrdy said, in the RR test manual the latter merlin is rated at 9lb of boost at 15kft not 12 or ...17

By the way I think I am qualified to deal with that subject - just went to check my diplomas just in case

[41Sqn_Banks]

Originally Posted by TomcatViP

One Question Banks : when do you actually get max boost with a supercharged engine ?

I suspect this is a hypothetical question: Highest boost possible boost is at lowest possible altitude at highest possible engine rpm with throttle valve fully open.

Highest allowed boost is available at with highest allowed engine rpm at all altitudes below full throttle height.

But really it's not about getting a high boost at low altitudes but make the engine survive the high boost. No one is telling that +17 boost didn't kill the engine.

As I hve alrdy said, in the RR test manual the latter merlin is rated at 9lb of boost at 15kft not 12 or ...17

So what is your point? There is a difference between "maximum-possible-boost-produced-by-the-supercharger-at-sea-level-that-the-engine-can't-handle-at-all" (around +17), "maximum-allowed-boost-in-case-of-emergency-for-no-longer-than-5-minutes" (+12 for 100octane fuel, +6 1/4 for 87octane fuel), "maximum-allowed-boost-for-no-longer-than-30 minutes" and "maximum-boost-for-infinite-time-...-well-not-infinite-as-your-engine-will-die-even-with-that-boost-after-200hrs-running-without-inspection"

There is no difficulty in getting a high boost at low altitudes from a supercharged engine. The difficulty are:
- Find the highest boost that does only acceptable "damage" to the engine and find ways to reduce the "damage" even further to permit (=allow) the use of higher boosts
- Find ways to maintain the high boost at high altitudes

[Osprey]

Originally Posted by TomcatViP

And by the way if you were not charging us every three month on the same subject and with the same arguments I would hve been pleased to check out any abbreviations out of my phrases.

But he's not giving you an argument. He's giving you a documented fact from Rolls Royce and the RAF. If you don't believe this to be true then I would suggest you provide the evidence, though I suspect you've been asked in the past and haven't managed to. My questioning was around understanding this evidence because I have seen this data in the past and never understood what it actually meant. I want to operate the engine properly and I am grateful to Wedge and Banks for the explanation, now I understand what the cutout actually does.

PS. A personal diploma isn't evidence btw, it just says you went to a college and passed some tests. Congratulations.

[TomcatViP]

Originally Posted by Osprey

PS. A personal diploma isn't evidence btw, it just says you went to a college and passed some tests. Congratulations.

So you throw the insults. I respond politely to calm you down and then you add another layer of xxxxxxxx ?

Where is your mum that I made an urgent request for some (boosted) slap on your pinky butt ? That also I hev done and was rather good

Just to remind you after reading BlkDg post : btw 1940 and 1944 there was Four (4) years of harsh technological development. If they had such boosted Merlin, the MkII would hve been called a MkIX etc.. etc..

WHen dealing with history You need to put things in perspective or you end with acrobatic assumptions such as where we are now.

When dealing with a fleet of airplane at war you need to understand taht factory made does not mean fleet wide or you'll end to say that the F35 is actually in full service just because a couple have just been delivered to an instructor unit (both wings are still on guys ) .

And by the way I did alrdy put RR data on the forum. It does not say 17lb at all : 9 lb max op boost at rated alt. And it was in late 1940 early 41 (cant remember).

I would come back latter for the max boost and alt question but I think I (we) hve alrdy discuss this one alrdy. Just remind that that the boost (the supercharger) was not there for max low speed but for increasing the climb rate and maximizing the overall speed at alt. As I hve alrdy said this is not a car tuning. You don't plug the biggest supercharger to get the max peak power.

~S

PS: the FM of the spit is more of a concern for me
PSS : I am (wwe are) not historian(s). Instead of recreating evidences we shld stick to what are the data in the literature. There is enough to discuss on how any data cld impact the FM. Valec as alrdy post a realy good link to source out any perfs

Originally Posted by Valec

http://www.airpages.ru/eng/uk/spitf1.shtml http://www.airpages.ru/eng/lw/bf109e1.shtml

[Robo.]

Originally Posted by TomcatViP

And by the way I did alrdy put RR data on the forum. It does not say 17lb at all : 9 lb max op boost at rated alt. And it was in late 1940 early 41 (cant remember).

TomcatViP, you seem to be wrong - Merlin III in question was rated +6.25PSI and +12PSI with BCC-O and 100 octane fuel before the BoB actually started (10.7.1940), there many are official documents and with this topic being well documented, there is not much space for arguing or guessing I am afraid.

I really recommend reading any good book about this topic, ''Merlin in prespective'' is pretty much comprehensive and sheds a lot of light on how RR approached aircraft engines in that era compared to say DB - awesome reading.

The +17PSI is not mentioned in any Spitfire book, this is simply a figure the Merlin III achieved (not safely mind you!) without limiting the boost to certain PSI considered as safe and giving the engine reasonable life. That PSI is called 'rated boost' and it was +6.25PSI for Merlin III until they rated it for +12PSI with better fuel. The +12PSI was not standard rating, but highest permissable for short periods of time. Simple as that.

If you have any information about Merlin III being rated at +9PSI max, please provide, I quite like reading about engines.

[Ze-Jamz]

Originally Posted by TomcatViP

Where is your mum that I made an urgent request for some (boosted) slap on your pinky butt ?

Brilliant..