Huricane Mk I 100 Octane perormance tests 1.07.18301
 

Here are my results taken from my Flight Data script and converted to Excel/OO charts.

I have done the basic Level Speed and Climb tests and extracted some other info.

Level Speed: Anywhere from 80%-90% below historical data.
Climb: 130% to 180% slower to height than Historical data.


Other:
R.O.C.: Falls away form near-historical above 5000 ft. Bad at 15000 ft (about 35% of historical). Excuse my up and down ROC but its clearly wrong.

"Boost": Does not respond to Boost Cutout Override. Two data sets emerge. One is the gauge reading (Manifold Pressure) which never gets above 6.2lbs and another which does not appear in the cockpit is the Boost C# parameter for Boost rather than Manifold Pressure and ranges from 8.8 through 11.1 and back to 8.1. Not clear which is driving performance (if either)

Max Speed at SL achieved at 2650-2670 RPM

Thumbnails attached.
Mission zip file Performance.zip attached for anyone wanting to do some tests themselves. I can explain the chart building of you need.

When was that admitted that the Merlin delivered 12lb boost in 1940 ?

lol

Ok let me try your scientific sense of history....

I dated Jenny Lopez... I dated Jenny Lopez... I dated Jenny Lopez... I dated Jenny Lopez... I dated Jenny Lopez...

When was it approved for sustained climbs?????

Please explain the chart building and how to do this. I would not mind doing this for the 109, cheers.

In 1940 you joker :grin:

Great test klem, thanks for the effort.

you might reset your clock then.

... and check your language :evil:

Thx Klem briliant test!

I dont know how to program so i do that manualy, anyway, nice work!

Im glad to see you guys are testing too! ;)

Great test Klem Thanks for the effort.

It was approved for 5mins at 12lb boost/3000rpm in 1940, and it was up to the pilots on how and when to use the power; including sustained climbs:

http://www.wwiiaircraftperformance.org/ap1590b.jpg

and:

http://www.wwiiaircraftperformance.o...-l1717-cal.jpg

But Seadog, Crumpp says the Pilot's handbook says nothing about 12lb boost. :eek: ;);)

Don't start trolling that old argument in this thread too. You know it has been done to death elswhere.

I did not use Boost Cutout Override in my tests, it does not work, see attached.

Farber, there is an explanation in the .doc file in the zip file in my OP. Its basically chart building from the output data using Excel or OpenOffice. Let me know if there's anything that isn't clear or needs expanding.

EDIT: I just updated my OP as I saw I had not attached the zip file and then I replaced it with a few corrections to the instructions.

I would also like to see ME-109 climb and performance tests. I bet it's borked too

Thanks for posting Klem

Hurricane MkI 87 octane vs 100 octane
 

Just did a quick comparison of Hurricane Mk I 87 Octane vs 100 octane at 1000, 5000 and 10000 feet.

Seems the old 87 octane is faster than the 100 octane :(

Would appreciate it if anyone else would like to check that.

[/QUOTE]Merlin II and III got 12lb boost in WEP settings with 100oct fuel...

Spitfire IIa ALL them got 100oct engines (Merlin III or Merlin XII), so... hurricanes too

We will test all them again =) its no problem ok?

cya

Your figures are without boost. The difference was AIUI (which may or may not be correct :confused:) that 100 octane allowed more boost at low level. So figures without boost shouldn't show a difference, and with boost only up to FTH.

I think that's precisely the point (or problem) that there shouldn't be a difference ingame between the 87 and 100 octane without boost but there is. All I hope is that the devs had said that the FM were still WOP and so data like this is good as it can highlight problems with the current ingame FMs.

There will be variations between runs at exactly the same settings (unless they are flown by utterly flawless autopilots). If the variation between runs with different settings is in about the same range as the difference between runs with the same settings, then that's the best that can be expected, and that graph looks as if it might be the case. If more tests show similar variations between runs at the same settings, it's probably alright, if with the same settings you come up with identical numbers time after time, and there is a significant (in the technical statistical sense) difference between settings, then there might be a cause for concern.

I shan't bother to do any testing myself.

Oh absolutely and the difference in the graph between 87 and 100 tested in game appears small - repeat tests may well show the difference is due to random variation between tests rather than a real difference between the models in game. Perhaps I misread your post, I was merely pointing out that there should not be a real difference between 87 and 100 octane without boost.

Something that does seem off in the Spit 1a 100Oct vs 87Oct is engine overheat, particularly in the climb and at altitude (not using boost) where the Spit 1a 100Oct is far more sensitive to overheating and so I find I have to use lower power settings in the 100Oct version currently than in the 87Oct version. I haven't done much testing in the Hurricane versions but it wouldn't surprise me if it was a problem here also. It's important to have people testing the new FM as they are WIP and so they can be modeled properly and it's great that people are doing so.

The big cause for concern at the mo is the difference between the modeled ac and rl performance which is off in both the Spit 1a and Hurricane, I haven't seen much data for the 109 but would love to as it's important that all aircraft in game are modeled as accurately as possible and it may well turn out that the 109 is also suffering under-performance.

No Milo,

I said the Notes on a Merlin Engine does not list 100 Octane as the specified fuel. That points to the extent of use and service.

By January 1942, 100 Octane was common enough for the Notes on a Merlin Engine to distinguish 100 Octane as the fuel for operations and 87 Octane for training.

I can see why you would be confused.

The extent of use and service is pointed to by the expenditure of thousands of tons of 100 octane fuel, numerous RAF documents stating its use during the BofB, numerous combat reports, and pilot accounts of 12lb boost and a complete lack of evidence of the same for 87 octane...but this is an argument long past now.

This issue now is that 87 and 100 octane performance in CLoD is completely FUBARed.

Tht's only your interpretation. It wld be more honest to point it in the right manner.

As for an example and as already said, an article of "Flight" reviewing just after the war's end and written at the occasion of the Merlin anniversary list all Merlin version with the type of fuel used. It does not state any Fighter powered with Merlin using 100oct before 41/42.

More can be said of course. But if all this has been alrdy written it does not mean that it could be swapped out like you did summing it up.

And frankly thinking seriously about it I wonder how you can imagine that a fighter aircraft designed to be operated above the cold seas of the Channel and the North sea would have seen is fuel swapped with as much technical care as a Ford Hotrod boosted for the quarter mile.

The arguement about 100 octane fuel use is over. However, the fact is that the Merlin II/III was engineered for 100 octane use right from the start, so that when 100 octane was approved for RAF FC, it was a simple matter to convert the engines over to 100 octane. The documentation on how this was done, on a per aircraft basis, has been presented here numerous times, but here it is again:
http://www.wwiiaircraftperformance.org/ap1590b.jpg

and no, it is not just my interpretation regarding universal 100 octane fuel use by RAF FC; the available evidence, from numerous sources, points to universal 100 octane use by RAF FC during the battle.

I have repeatedly challenged the 100 octane fuel deniers to produce evidence for even a single RAF FC Hurricane or Spitfire 87 octane sortie during the BofB, and so far there's no takers.

It is like this Eugene: no 100 octane fuel, no 12lb boost.

So that must be why those in denial of 100 octane fuel use during the BoB can't name the 16 squadrons that they claim were the only squadrons to use 100 octane during the BoB.

However did the Bf110s and the few Bf109s use C3 fuel then?

S!

Well, Bf110C with DB601N engines/C3 and Bf109E-4/N using C3 are not modelled in game at the moment but no-one is complaining ;) Bf110C with 100oct would be easily faster than Hurricane and faster than Spit at some altitudes, but still no-one is whining for them, even they existed ;) Will be added if devs deem it OK based on data supplied to them. No need to make a drama out of it at all.

I flew red on ATAG and damn that Spitfire Mk.Ia 100oct and Spitfire Mk.II are easy to fly, even with slightest grasp of retaining E with proper maneuvers the Spits eat Bf109's for breakfast. The view out is best bar none and handling so forgiving, saw a lot of Bf109's spin out of the sky. Sure CEM caused a bit of problems for me but initial impression of Spitfire was pleasing. Sure maybe not up to speeds and all that but it can hold it's own easily with a competent pilot :)

Of course, they're German planes.

I did date Jenny Lopez... I did date Jenny Lopez... I did date Jenny Lopez... I did date Jenny Lopez...

You haven't seen Kurfurst's sig have you?

Bring them on as long as it isn't a sky full them and no other 110s and/or 109s.

wow, what a riposte.

you have totally changed my mind with that stunning evidence.

carry on in your dream world.

I'm sure that you believe that.

Just as you do.

What he is saying it is no different than you taking evidence and reading only what you want to see.

The BoB was a transition period and the extent of use depends on the date you pick for the battle to end.

I don't understand the obsession anyway. It was summertime during the battle and the envelope for high manifold pressure/high rpm is greatly reduced. In fact, it will result in poorer performance than a lower manifold pressure/rpm under such conditions.

I believe the evidence was presented that 100 Octane made less of a difference in the battle than CSP's.

Look at the paper performance on a standard day, it is quite an improvement. Why do you think that was not so stunning an improvement in the air?

High density altitude conditions of summer is why!!

So are you now trying to blame the performance increase on the English weather?

Which is what Crumpp does all the time.

Yep, the B of B was a transition from all frontline fighter units of FC using 100 Octane fuel to all Commands using 100 octane, and when the Battle ended, 31 October or May 1941, is immaterial.

You claim to be a pilot but do not understand the differences in summer and winter performance?

Density altitude effects?

http://www.google.com/url?sa=t&rct=j...rCDcByVdDIdgPg

If you had experienced an english summer you would know what I am talking about.

They are variable, you need to experience five or six to begin to get a feeling. This one is wet so far, but there are some months yet to go. I think it was 1978 that was hot and dry. They are all different.

Yeah, summer in England is typically a "standard day"...:)

These are the mean highs and lows for July - Oct 1940 for Lowestoft:

yyyy mm tmax tmin af rain sun

1940 7 20.2 11.0 0 157.6 211.3
1940 8 20.5 10.8 0 19.1 ---
1940 9 18.2 9.0 0 27.7 170.1
1940 10 13.9 7.6 0 37.8 ---

As you can see the mean temp for July-Aug is about 15.5c, Sept about 13.6c and 10.75c for Oct.
Southhampton:
1940 7 20.2 11.7 0 98.3 208.0 (mean = 15.9)
1940 8 22.1 12.1 0 0.0 238.1 ( Mean = 17.1)
1940 9 19.4 9.3 0 41.4 193.1 (Mean = 13.35)
1940 10 14.1 7.6 0 115.8 112.9 (Mean = 10.9)


And for Oxford:
1940 7 20.5 11.1 0 61.0 165.1
1940 8 22.1 11.1 0 1.8 199.5
1940 9 19.2 8.6 0 24.1 179.5
1940 10 13.9 6.0 1 67.1 95.5

Ross on Wye:
1940 7 19.7 10.5 0 72.8 166.8
1940 8 21.1 10.3 0 6.6 207.1
1940 9 18.6 7.3 0 18.0 183.6
1940 10 13.2 5.8 2 107.0 65.4

data from:
http://www.metoffice.gov.uk/climate/uk/stationdata/

But only a limited number of stations have data for 1940.

I certainly do believe that you believe that.

Pray tell us; where does the 100 octane deniers club meet?

Oh well I am just illustrating your auto convincing scenario. Just changed the desired subject to something more able to "boost" anyone.

And again, by the way, "denying" something that has not happened (or not in the sense you project it) is an utter non-sense grammatically.

Non believer I think is more correct.

more mean high and low temps for summer 1940
 

These are the mean highs and lows for July - Oct 1940 for Lowestoft:

yyyy mm tmax tmin af rain sun

1940 7 20.2 11.0 0 157.6 211.3
1940 8 20.5 10.8 0 19.1 ---
1940 9 18.2 9.0 0 27.7 170.1
1940 10 13.9 7.6 0 37.8 ---

As you can see the mean temp for July-Aug is about 15.5c, Sept about 13.6c and 10.75c for Oct.
Southhampton:
1940 7 20.2 11.7 0 98.3 208.0 (mean = 15.9)
1940 8 22.1 12.1 0 0.0 238.1 ( Mean = 17.1)
1940 9 19.4 9.3 0 41.4 193.1 (Mean = 13.35)
1940 10 14.1 7.6 0 115.8 112.9 (Mean = 10.9)


And for Oxford:
1940 7 20.5 11.1 0 61.0 165.1
1940 8 22.1 11.1 0 1.8 199.5
1940 9 19.2 8.6 0 24.1 179.5
1940 10 13.9 6.0 1 67.1 95.5

Ross on Wye:
1940 7 19.7 10.5 0 72.8 166.8
1940 8 21.1 10.3 0 6.6 207.1
1940 9 18.6 7.3 0 18.0 183.6
1940 10 13.2 5.8 2 107.0 65.4

Nairn (Scotland):
1940 7 16.0 10.4 0 215.2 99.0
1940 8 17.6 10.4 0 38.1 132.7
1940 9 14.5 7.9 0 42.2 104.7
1940 10 12.1 6.4 1 82.1 88.3


data from:
http://www.metoffice.gov.uk/climate/uk/stationdata/

But only a limited number of stations have data for 1940.

Nice site that.

Manston is a name we all know.
Temperatures are the mean daily max/min temps and the total rainfall for the month

In June 1940 the max temp was 20.4 c and the min temp was 11.7 with 3.8 mm of rain
In June 1941 the max temp was 17.2 c and the min temp was 10.9 with 15.2 mm of rain

and while we are on a roll
In June 2011 the max temp was 19.5 c and the min temp was 10.9 with 62.5 mm of rain

As far as the weather in the UK goes, you pays your money and takes your chance

That's for sure.

However, the main point to this, is that from about 1PM or earlier in the day, is likely have SL temps of ~15c or less. Mean Temps of 19C or higher would be rare and typically restricted to late afternoon. The idea being pushed by the 100 Octane Deniers that English Summer Weather automatically means 19c or higher is nonsense.

Have a look at this site for WX refs.

http://forum.netweather.tv/topic/631...weather-diary/

And have a look at this Report on London Weather 1940:
July: Cool, with above average rainfall and sunshine.
August:Very dry with above average sunshine and slightly below normal temperatures.
September:Rather cool, dry and sunny.
October:Rather cold with above average rainfall and slightly below normal sunshine.

Cool, slightly below normal temperatures, etc - and London, as a large, urban environment can be approx 2° C warmer than rural areas.

Mind you, that's only talking about temperatures at ground level - the temperatures and pressures can fluctuate at altitude depending on all sorts of conditions - to make a flat statement that performance is conditional on "High density altitude conditions of summer" is a gross over simplification of what can happen in reality.

Britain is an Island, not a large continent like America and its weather patterns are conditioned by the oceanic (Atlantic) climate. So flight conditions over S-E Eng are very different to those over continental America. As an example the 8th AF USAAF found flight conditions in Britain to be very different to those most of its trainee pilots and aircrew had encountered at their American based flight training schools, even during the summers.

Another site on Britain's weather patterns http://www.metlink.org/weather-clima...imate.html#2.1

Wow.........

:rolleyes:

You guys really believe England meets standard atmospheric conditions for most of the day in August 1940??? Even with the temperature of 15C and 1013Mb?

You think England in August has RH = 0???

Come on all you pilots!!!

:rolleyes:

Manston:
1940 7 19.9 11.8 --- 56.9 (mean daily temp = 15.9C)

What ground temperature would a Luftwaffe raid, arriving over Manston at 8am in mid July 1940, be likely to find?


What ground temperature would they likely encounter over the English Channel?

I have provided the mean high and lows for various locations, and it is pretty obvious that 15C or lower ground temp is a distinct possibility for any likely location, especially before noon, and in the Late (daylight) afternoon (say after 7pm).

Goodie Goodie More abbreviations in an attempt to bamboozle the masses.
RH for what its worth is relative Humidity.

As it is I am pretty sure the CLOD atmospheric model doesn't even model "Humidity" per see.

Well, argument on summertime conditions is pretty much pointless.

The FTH depends on pressure altitude so at summertime conditions the FTH for given manifold pressure actually increases in the density altitude scale. In other words, the full 12lbs boost in summertime conditions is available at higher density altitude than at standard conditions.

Physical explanation is fairly simple: The supercharger increases the density in manifolds by keeping the pressure constant up to the FTH. In summertime the warmer air is less dense than in standard conditions so given manifold pressure gives less power than at standard conditions. However, the ability of the supercharger to keep the pressure depends on pressure difference between manifolds and outside atmoshere (plus dynamic pressure) and in summertime the pressure at given density altitude is higher than in standard conditions, hence the FTH increases in the density altitude scale while staying constant at the pressure altitude scale.

All this can be found from the USAF Flight Test Engineering Handbook, available from Scribd:

http://www.scribd.com/doc/19204672/U...ering-Handbook

The problem here is that some members have stated something else and they can't never admit that they were wrong...

The usual story, Crumpp thinks he's an expert on British weather conditions during the Battle of Britain, when it has been very carefully explained to him that conditions can be so variable. Flying in Britain - or NZ for that matter - is very different from flying in mid-West America, for very good reasons.

Has Crumpp got any detailed figures for Britain's atmospheric temperatures and pressures at different altitudes during Summer 1940?

In August??

:rolleyes:

Probably not and completely irrelevant to the conditions of the Battle of Britain.

Look guy,

The charts are in pressure altitude because the aircraft data is in pressure altitude.

The temperature correction is the density correction.

An engine sees density altitude and your FTH will reflect.

That is not being a "know it all". It is just how it works.

Why Crumpp has decided to pick on August alone is anyone's guess, but its typical of an attempt to pretend that he knows British weather patterns in 1940 better than anyone else.:rolleyes:

As are most of Crumpp's speculative arguments...

If you chaps want a really good laugh for a change, just take a look at the current 'British Summertime Weather Patterns'.

Makes me want to emigrate somewhere nice and dry, such as Burma, or the Amazon basin. :(

Sorry for OT.

Yes, 'tis Bit of a worry for the Olympics. All the best for London, hope the weather behaves! :cool:

Do you mean the basin of an ... ? :rolleyes:

There is no speculation. It is facts. It is not my fault folks do not understand the relationship of humidity to density but only focus on a simplistic picture based on what they have learned on a gaming forum.

Why don't you give some facts instead of emotional appeals. Try reason for a change!!

Ohh yeah, because you can't discredit the information with facts and reason. You have no other recourse than emotional appeals.

The supercharger sees only the pressure and it's ability to compress air depends on pressure difference between atmosphere and manifolds, hence the FTH depends on pressure altitude (plus dynamic pressure). The density inside the manifolds depends on pressure and temperature and that is why power should be corrected with temperature.

Temperature correction does not change the FTH in the pressure altitude scale, only the power at the given pressure altitude. See the example calculations and the graphs and perhaps one day you will understand...

... and then you will state that you have said so right from the beginning :)

Ok you are flying at the fth at a given pressure and temp, engine runing at a give rpm.

What would you think if I start to spray (cold) water in the supercharger inlet ?

The relation of perfect gazes work only with gazes in perfetc conditions ;)

Most of the time the variation will be minimal, just like in British summertime for a British engineered plane.

What is utmost funny is that the same guys tell us that changing the type of fuel have no effect at all and the eng will run fine despite the much higher thermal energy that this imply.

:confused:

I am getting confused but I know since long that is what they want. Hence their frenetic charges against who ever get a technical view inappropriate with their.

I repeat, has Crumpp got any detailed information figures for Britain's atmospheric temperatures and pressures at different altitudes during Summer 1940?

Has Crumpp got detailed readings of the relative humidity for each day of summer 1940?

Nor has Crumpp twigged to the fact that Britain has an Oceanic climate, dominated by the Atlantic ocean, which means that atmospheric air temperatures, humidity and pressure are variable and can change quickly, even at the height of summer:

One reason why the USAAF's pilots and aircrews had so much trouble adapting to Britain's weather conditions was because they had trained in the relatively settled climactic conditions experienced on the continental USA, with mostly clear skies, higher average temperatures and lower humidity than anything experienced in Britain.

Making a blanket statement:

Shows a profound ignorance of how the weather conditions in Britain can change rapidly in the space of a few hours, as others, who actually live there and know this, have been trying to tell Crumpp.

No, the engine see density not pressure.

1. Whenever you include temperature, you are really talking about density.


IF the engine is equipped with a density controller. If it has a pressure relief valve, then it is dependent upon density altitude.

If it has an absolute pressure valve or a variable pressure controller then it is subject to density altitude effects.

Well, you are just avoiding the facts here:

1. The engine we are talking here, Merlin (and the US radials in the USAF handbook), keeps constant manifold pressure up to the critical altitude. There are other manifold pressure/density regulating systems but that's another story.

2. The temperature correction does not change the FTH at the pressure altitude scale in these engines. This means that in the density altitude scale the FTH varies according to temperature difference from the standard conditions while the FTH stays constant at the pressure altitude scale.

3. Read the USAF handbook instead waste our time, it's all there. RTFM :)

If you're talking about switching from 87 up to 100 octane, you need to go look at what the definition of an Octane number is. Octane number does not mean the fuel has more energy in it.

Well you are right but you are playing with the words Doggles.

No I'm not playing with the words.

No, You need to read the handbook.

In fact, give Lycoming customer service a call. They will be glad to help you out.

1-570-323-6181

P=nRT/V from perfect gazes theo.

The pressure output from the comp of a gaz depend of the volume V and the Temp T achieved before detonation*

The less volume at the end, the more P.

The temp T at which the gas will detonate under pressure is the leading factor here.

The derivative energy (work) that someone can output of a compression work (isentropic**): dW=-dP/dV wich as you see is a function of the octane number for a specified eng design

AS the Tot energy of a gas equate the sum of it's internal molecular energy that is in the theo of perfect gazes is the sum of the work done on that gas and the total output heat achievable (see the first law of thermodynamics (here : http://en.wikipedia.org/wiki/First_l...thermodynamics)

Then I think I am right ;) - sry for the boring refreshing cursus - didn't do that pretentiously.

You can read more here :http://en.wikipedia.org/wiki/Octane_rating

Well now we are good to open another new thread

*n is a ref numbers in moles (or molecules per volume at a specified state) and R is a cte defining the ratio btw the products

**means here without any modification of the gazes's product state (which is never fully achievable in virtue of the second principle of thermodynamics)

Well, you just avoid admiting that you are wrong.

The end of argument.

He does this all the time, nothing to worry about. ;)

Hey! This is internet, the land of the free, anyone can be an expert here :cool:

and we have one resident expert of experts of everything....

(in his own mind anyway)

For once Tomcat is talking sense here!
I'm not a pilot (but I am a practicing physicist) perhaps others can confirm or refute the following suggestion: I strongly suspect that the RAF/Farnborough & Boscome Down used an Atmosphere that was representative of British conditions (particularly latitude), also probably spring/summer/autumn temperatures because aircraft would do most of their flying time at these times. I also suspect that the International Standard Atmosphere was not available until post-war.
However I do not know whether the testing authorities normalised their measurements to some British standard atmosphere.

SO - as long as the CloD atmosphere is reasonably representative of British conditions the speed or climb variations due to minor (day-to-day, or during the day) can be easily corrected by correcting for the density for a particular atmosphere in CloD without having to do anything more sophisticated.

(As an aside - temperature DOES affect the compressibility in the supercharger, as well as input density, but it'll be fairly second-order because the two are coupled in a gravitationally stratified atmosphere)

This is what I believe Klem has done (at least in some of his other posted data, I haven't checked this post).

The differences between CloD data measured by Klem and measured performance (albeit slightly affected by local conditions on the day) are now so large (and even worse - inconsistent between 'plane variants - and even more worse, between red and blue) that issues of British atmospheric variations pale into insignificance.

56RAF_phoenix

Quite insulting... again:evil:

But I am with you on that except for the suspected source of historic perfs (let me guess it's a website with the words "Spit" and "Performances" :rolleyes: )

+1 so

The first versions of a standardised atmosphere model between nations was in the 1920's as far as I know, almost certainly those nations would have included the bulk of Europe.

Here check this NASA article....

http://ntrs.nasa.gov/archive/nasa/ca...2002153481.pdf

I wasn't trying to insult, but I do try and distinguish between those who have their preferred 'planes, argue for their merits, but are prepared to accept genuine evidence and reasoned argument (e.g. me & Klem on the red side; and I would say Kwaitek on the blue interested side); and some of those others who never seem to accept reasonably authenticated evidence.

Now I haven't checked, but I have no reason to believe Spitfire Performance would post altered or faked data. However I would fully understand if the "blue side" wished to question the context of the data, or unpublished associated data that would be relevant to what was published. But that needs to be done in a reasoned way where the participants are prepared to accept they might be wrong when presented with evidence.

It's called the scientific method.

It is to your credit that your posts here at least seem to be trying to understand the physics.

[ BTW: the conditions for detonation of the fuel-air mixture are not really to do with a particular temperature. Detonation happens because the sound-speed is higher on the high-pressure portion of a pressure pulse, so the pulse gradually sharpens-up until it becomes discontinuous - a detonation. So I'm afraid the run-length of the pressure pulse (i.e. the geometry of the cylinder) is a big factor. ]

56RAF_phoenix

Thanks bongo, Always happy to be corrected by some evidence!

56RAF_phoenix

[EDIT] P.S. As is often the case with the English Internet, it's rather US centric. Have you got anything on British equivalents?

Why am I going to pursue a pointless argument. The engine sees density, that is a basic fact.

You are going to claim you are correct despite the fact every other word in your argument is "temperature". Really?? :confused:

It is retarded.

Again, call Lycoming.....

Their customer service will answer your questions and you can argue with them and the FAA.

I don't, I face much the same trouble, but if you are a Physicist then perhaps you have better access to stuff from the scientific community, I dare say the British equvalents are available...just not so much on t'interweb.

Great point. But in the case of changing the fuel of an engine without modifying the design, the geo of the cylinder is fixed. Tht's why I am talking about T=f(octane grade) that is becoming the prime factor for the E you can output from the fuel (I might have the formula somewhere... In Canada, damn !).

My answer was to this :

If you change the fuel, the minimum you wld need is to modify the compression volume and material of the pistons/cylinders that you have an equivalent heat flux. Today, tuner can play with the injection para to artificially reset the volume or modify the air compression ratio playing with the boost ratio (carburated and injected) .

But this imply modifying extensively the engine. Especially if your daily hobby is a long and lonely flight in a single engine plane above the sea!

You need to understand the difference between detonation and deflagration.

http://en.wikipedia.org/wiki/Detonation

http://en.wikipedia.org/wiki/Deflagration

Lower octane fuel detonates.

No one denies that engine power depends on density on the manifolds, however, the argument was if the FTH depends on the density altitude or the pressure altitude in the case of the Merlin. As pointed out earlier, the supercharger of the Merlin keeps constant pressure up to the FTH regardless the density of the air (indicated by temperature), so it's clear that the FTH depends on pressure altitude, just like in the case of the radial engines with similar superchargers in the USAF handbook.

I end this discussion here, you just keep flossing a dead horse...

http://www.youtube.com/watch?v=Lb_IbFBdKw0

I don't see where I said the contrary but thx for the refresh. Pls explains what you mean instead of this mystic answer. I am not here to show off any knowledge but because I like others to understand better what this sim is emulating.

Again my reply was about the assumption form D. that octane grade had no link with the E that you can output. Damn do we really read each others ? Or is nailing and plinking becoming a sport here ? Because if you still don't know we have the ATAG server to that ;)

No. You are wrong.

If your engine was designed to run on a particular octane, at a particular compression ratio, and you put fuel in that has a HIGHER octane than before, the minimum that you need to do is nothing. The octane number is just a measurement of it's anti-knock performance. Octane number does not mean the fuel burns hotter, or has more energy in it, or has a "greater heat flux". You don't need to modify the engine if you want to put higher octane fuel in it.

On the other hand, if you want to run at a higher compression ratio, then you are required to increase the octane rating of your fuel.

CoD Hurricane Mk1 87 versus 100 octane
 

Results of my comparision demonstrate a marginal increase in performance of the 100 octane over the 87 octane Mk 1 Hurricane when using the boost cut out. There does not appear to be any increase of performance other than slight improved acceleration for the 87 octane when the boost cut out is pulled. What is demonstrated is that the 100 octane Mk1 is very prone to failure soon after employing the boost cutout. Works best at low altitude, but you have only 1 minute to engine destruction. At 20,000, the 100 octane will hold a steady at 210 mph +2.5 beyond 6 minutes whereas the 87 octane at +3 210 mph blows up after two minutes. Otherwise, you can run the 87 octane at +5.5 lbs all day at 240 mph. So my assessment is that the 87 octane is a better option for combat operations (e.g. very slight trade off in performance, versus substantial improvement in reliability)

Mk1 Hurricane Comparison between 87 and 100 Octane Rotol

100 Octane
87 Octane
Wind: 0 mph/0 % deflection
Boost Start 0 psi
Weight 3177 lbs
Fuel 100%
Start Speed 180 mph
Rad 100% Open
X engine failure

2,700 RPM SPEED & ACCELERATION
Altitude 1 min 2 min 3 min 4 min 5 min 6 min (BOOST)
5000 ft 240 mph 260 mph 260 mph X Goveror failure X +8
5000 ft 210 mph 230 mph 230 mph 240 mph 240 mph 240 mph +6.2

10000 ft 240 mph X Gasket failure X X X +8
10000 ft 220 mph 240 mph 240 mph 240 mph 240 mph 240 mph +6.1

15000 ft 220 mph 240 mph 240 mph 240 mph 240 mph 240 mph +7.2
15000 ft 230 mph 230 mph 240 mph 240 mph 240 mph 240 mph +6.1

20000 ft 190 mph 200 mph 210 mph 210 mph 210 mph 210 mph +1.5
20000 ft 200 mph 210 mph 210 mph 210 mph 210 mph 210 mph +3

3,000 RPM SPEED & ACCELERATION
Altitude 1 min 2 min 3 min 4 min 5 min 6 min (BOOST)
5000 ft 260 mph X Gasket failure X X X +8
5000 ft 220 mph 240 mph 240 mph 240 mph 240 mph 240 mph +5.5

10000 ft 240 mph X Gasket failure X X X +8
10000 ft 220 mph 240 mph 240 mph 240 mph 240 mph 240 mph +5.5

15000 ft 220 mph 240 mph 240 mph 240 mph 240 mph 240 mph +8
15000 ft 230 mph 240 mph 240 mph 240 mph 240 mph 240 mph +5.5
no BCO 220 mph 230 mph 240 mph 240 mph 240 mph 240 mph +5.5

20000 ft 190 mph 200 mph 210 mph 210 mph 210 mph 210 mph +2.5
20000 ft 200 mph 210 mph X Burnt intake X X +3

All engine failures were confirmed with a second test
All tests conducted with Boost Cut Out pulled

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Ok next time you take a Diesel, I suggest yu might try to put some 95 or 98 gasoline while I'll try myself to put diesel in a gasoline car. We will see who has the biggest bill.

First of all there was no argument. You are the sole voice of discontent. The engine sees density.

FTH depends on density altitude. Only in an engine equipped with a density controller will it reflect just pressure altitude. AFAIK, they did not have them in WWII.

http://quizlet.com/2496371/print/

What the hell does diesel have to with this?

Thanks for confirming you have no idea what you're talking about. Diesels use compression ignition. Gasoline engines have a spark plug.

I'm done talking to you now, have a nice day!

Damn the Diesel have a low eq octane number. This is an example. An illustration. Ok got it now?

I will remind you that you slipped the purpose of our conversation from : "the octane does not rate what E you can output in a compression work" to "detonation and deflag."

But as always simplistic argument and quick assumption on individual are the way to go with the 100octaner. One more in a long series.

Do you really think that I don't know the diff btw Diesel and gasoline? If such salute and have a good day back to your black and white world.*

What i was showing you is that with higher grade you hve higher energy in the same volume of the cylinder hence more heat hence (what I was expecting you'd understand by yourself) more wear since the eng is not designed for that amount.

We are not talking about a 2L 90Hp car but 1000HP with primitive engine technology with low compression ratio (a lot more fuel flow).

Thx for loosing my time too.

*I hve to admit that writing this my blood was boiling up to its flash point. Sry for being rude

Back on topic....

"British Performance Reduction Methods for Modern Aircraft", D Cameron - A. & AEE Report No. Res/170, 1942.

Is cited by papers on googlescholar. Spitfireperformance.com has many references to test data from later Spitfire marks being normalised using this method to some standard atmosphere.

I've looked on "Web of Knowledge" and some other places but have not been able to get a copy.

I suspect that, since Cameron felt it necessary to write a paper in 1942 to standardise the methods, other variants were probably used before. I'll continue trying to find it.

56RAF_phoenix

take care that perf predictions were not accurate during the war as they didn't hve the knowledge that became available after the war*. I think there is something with the Glauert correcting factor that you might be interested to investigate.

*does not apply in calibrated range (rare)

Search the PROCAT for:

DSIR 23/12282

ha ha yeah. diesel is a lot different than 100LL

humm Gympy put that hand ON the table

?? I dunno just from a fuel aspect.

my .02 is that we just give ALL the planes the best Octane available have 100 Octane Me-109's, Spits etc. etc.

then nobody can complain

even on the CoD forum ? :rolleyes: