Author Topic: Spit Mk1A climbrate (Read 3484 times)

Wotan · « **Reply #60 on:** August 07, 2005, 09:57:09 AM »

I saw that but it mentions modifications the boost control cut-off...

It states that above 10k Ft boost will drop to normal (below 12lbs).

http://www.spitfireperformance.com/spit1-12lbs.jpg

This shows that you gain 28/34 mph only below 10k...

Angus · « **Reply #61 on:** August 07, 2005, 10:00:02 AM »

You talking speed or climb.
AFAIK the increased boost in early Spits didn't increase top speed a lot, - but clearly affected ROC.
Engine torque you see.......

Angus · « **Reply #62 on:** August 07, 2005, 10:01:50 AM »

Oh, - and the docs:

Wotan · « **Reply #63 on:** August 07, 2005, 10:04:06 AM »

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Originally posted by Angus
Now, Wotan, you're just getting silly.
Firstly, see the above document from Justin.
Secondly this:
"That is MW's site and it does not prove what you claim it does"

You should be perfectly aware that MW's site usually offers a link to the scans of the original documents.
You can of course sit put and say nonono untill someone posts the scans directly, - then what are you going to say?

Of course there were some modifications being done to get the most out of the 100 oct fuel, as your car will also need to be set for 95 or 98 (although I've ran some on aviation fuel without probs, hehe) and as you can see from my data from MW's data with my calculations BTW, the usage of another merlin with 100 oct instead of 87 increased the climb rate by a handsome margin.
The CS to a 2-blade did more though.
And again, running on very strong juices was no novelty to RR.

What Justin posted has nothing to do with your reply...

You said:

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So, why bother pouring stronger fuel into a tank?

It has nothing to do with the what I suggested:

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Things like compression, adjustment in timing etc. are necessary to take advantage of the higher octane fuel.

Even the link Justin provided deals with the boost control cut-off not and does not answer my question.

Angus · « **Reply #64 on:** August 07, 2005, 10:18:06 AM »

What is your question then?
I mean, I gave a strong responce since you chose to doubt the benefit of using stronger octane fuel, as well as discarding evidence indicating othewise.
From what I can see, engine needed to modded only slightly to benefit from the 100 octs, - or did you ever change plugs?

Kurfürst · « **Reply #65 on:** August 07, 2005, 11:56:28 AM »

The question that was raised Angus, is that to operate on higher (+12 lbs) boost, at least 100 octane fuel was required. Evidence would be needed to see how much 100 octane fuel was used compared 87 octane fuel (which would mean +6.25 boost), so we can decide if +12 was typical boost rate during the battle or not...

The easiest way to see this is to look up the the consumption rate of 87 and 100 octane fuel by FC during the Battle.

Angus · « **Reply #66 on:** August 07, 2005, 11:57:50 AM »

I recall it from the boards, but where the heck was it again...

Nashwan · « **Reply #67 on:** August 08, 2005, 10:46:37 AM »

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I don't care what boost the Spit Ia used as standard in BoB but I will point out that just pouring high octane fuel into a tank doesn't necessarily mean you will see any significant performance gains. Things like compression, adjustment in timing etc. are necessary to take advantage of the higher octane fuel.

Yes, the whole purpose of 100 octane for Fighter Command was to allow increased boost, up from 6.25 lbs on 87 octane to 12 lbs with 100 octane.

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Outside the claims of 'stockpiles of 100 octane fuel' does any one have anything more substantial to show that 100 octane was used by:

quote:18 Spitfire squadrons during the BoB.

Rather then 'MW said so'...

Try this page on MW's site:

http://www.spitfireperformance.com/spit1vrs109e.html

About a third of the way down are extracts from combat reports by various pilots, showing the use of 12 lbs boost. Most of them have a scan of the actual document provided.

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I saw that but it mentions modifications the boost control cut-off...

It states that above 10k Ft boost will drop to normal (below 12lbs).

http://www.spitfireperformance.com/spit1-12lbs.jpg

This shows that you gain 28/34 mph only below 10k...

Looking at the performance charts, 12 lbs boost gives around 30 mph increase over 6.25 lbs up to about 11,000ft, the speed then drops back until at about 19,000 ft there is no difference. So 12 lbs actually gives a performance advantage up to about 19,000ft, although the advantage is decreasing from 11,000ft up.

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Even the link Justin provided deals with the boost control cut-off not and does not answer my question.

I don't understand, what questions do you have that this doesn't answer? Increasing boost at the same rpm will lead to a power increase.

Nashwan · « **Reply #68 on:** August 08, 2005, 11:06:17 AM »

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You are telling us a FC Spitfire carries 4 times as much fuel as a FC Spitfire ?

Huh?

I said 8th AF fighters (Mustang, Thunderbolt, Lightning) would carry many times as much fuel as a 1940 Spitfire.

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That`s silly. A Spit would carry 85 gallons, in 1940 or 1944.

Um, no. In 1940 all the Spitfires in service carried about 85 gallons.

In 1944 Spitfire XIVs carried more fuel, most Spitfires were using drop tanks, a IX with a 90 gallon tank carried 175 gallons, even one with a 30 gallon tank carried 35% more fuel than the 1940 Spitfire.

Plus in 1944 Fighter Command had quite a few Mosquitos, and they'd carry a lot more.

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According to whom... you?

No, according to mathematics.

We've had this sort of debate before over the Spitfire cooling, where you seem unable to understand basic maths.

The Spitfire carried 85 gallons. 1 gallon weighed 7.2 lbs. There are 2240 lbs in a ton. 22,000 tons = 49,280,000 lbs = 684,44 gallons = 80,522 85 gallon tank fulls. 80,522 full tanks over 13 weeks = 6,194 full tanks used per week.

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An Australian report that is a copy of a British report.

Says Pips. Have you actually seen this report? No, neither have I.

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Show me these 'British reports'

Both from Neil Sterling:

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The, the November report says only Fighter Command, and now you are making up things.

No it doesn't. In fact, it talks about overall stocks, and consumption.

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None of them used 100 octane fuel, of course.

Source? Bomber Command at least certainly switched to 100 octane.

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He of course, showed anecdotes about the use of 100 octane fuel in 18 Squadrons - out over 50 Sqns that saw action during BoB..

No Isegrim, he's shown use of 100 octane fuel in 18 Spitfire[/i] squadrons, out of 19 Spitfire squadrons in the BoB (19 iirc). Remember, Mike's is a Spitfire site, not a Hurricane one.

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OTOH you have reposted a precis from an Brit, that hasn't been backed up by any original documents.

See above. I thought you'd already seen these, though.

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Strangely, when I ask Neil Stirling about the use of 100 octane fuel in Bob, he suddenly disappears... what does that tell you.

He's got better things to do than listen to your barrage of insults?

Kev367th · « **Reply #69 on:** August 08, 2005, 01:46:14 PM »

Nice guys, well that should effectively kill all Kurfys objections off.
Meanwhile he is still to post ANYTHING that shows C3/1.98ata use by a single K-4, in another thread.
Lots of we can assume, presume etc, I asked for cold hard evidence...still waiting.

Guppy35 · « **Reply #70 on:** August 08, 2005, 01:54:54 PM »

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Originally posted by Kev367th
Nice guys, well that should effectively kill all Kurfys objections off.
Meanwhile he is still to post ANYTHING that shows C3/1.98ata use by a single K-4, in another thread.
Lots of we can assume, presume etc, I asked for cold hard evidence...still waiting.

What it comes down to is "I want you to trust me cause I'm not biased and what I say is truth, while I don't trust you and everything you say is biased so it's a lie."

Those arguments never end

Dan/CorkyJr

Wotan · « **Reply #71 on:** August 08, 2005, 08:57:06 PM »

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Yes, the whole purpose of 100 octane for Fighter Command was to allow increased boost, up from 6.25 lbs on 87 octane to 12 lbs with 100 octane

Ya think..?

Higher octane fuel detonates at a higher temp / pressure. However, high octane fuel run in an engine with a low compression ratio would not burn as clean and you would end up with a dirty intake and not much of a performance boost. You may run into problems with spark plugs fouling, excessive heat etc...

Basically you won't get any real benefit from running higher octane gas then the engine is rated (set up) to use...

A Spit running 87 one day and pouring in 100 the next doesn't sound plausible. The question is there any evidence that shows that those spits / hurris running 100 octane under went any sort of maintenance other then what justin posted about the boost control cut-off modifications?

Just as you couldn't just dump C3 in the tank of G-10 or K-4 with out some modifications I doubt you do the same with the Spit and Hurri.

As I said before give the Spit Ia in AH 12lbs boost I don't care...

I would assume that making the engine adjustments to take advantage of 100 octane fuel would take some period of time.

Kev367th · « **Reply #72 on:** August 08, 2005, 11:05:23 PM »

Well it took 1 day to convert a whole squadron from 100 to 150, and 1 day of flight tests, similar time for 87 to 100 maybe?

The first bulk shipment of 100-octane fuel had arrived in Britain in June 1939 from the Esso refinery in Aruba. This and subsequent tanker shipments from Aruba, Curacao and the USA were stockpiled while the RAF continued to operate on 87 octane petrol. Having secured sufficient quantities of 100 octane, Fighter Command began converting its engines to this standard in March 1940, allowing boost (manifold) pressures to be raised without the risk of detonation in the cylinders.

Starting to wonder just HOW many times we have to go over this AGAIN AND AGAIN AND AGIAN.

Guppy35 · « **Reply #73 on:** August 08, 2005, 11:08:59 PM »

Quote

Originally posted by Wotan
Ya think..?

Higher octane fuel detonates at a higher temp / pressure. However, high octane fuel run in an engine with a low compression ratio would not burn as clean and you would end up with a dirty intake and not much of a performance boost. You may run into problems with spark plugs fouling, excessive heat etc...

Basically you won't get any real benefit from running higher octane gas then the engine is rated (set up) to use...

A Spit running 87 one day and pouring in 100 the next doesn't sound plausible. The question is there any evidence that shows that those spits / hurris running 100 octane under went any sort of maintenance other then what justin posted about the boost control cut-off modifications?

Just as you couldn't just dump C3 in the tank of G-10 or K-4 with out some modifications I doubt you do the same with the Spit and Hurri.

As I said before give the Spit Ia in AH 12lbs boost I don't care...

I would assume that making the engine adjustments to take advantage of 100 octane fuel would take some period of time.

Not sure about 87 to 100, but when the 100 to 150 octane switch was going on, the pilots notes, and limits were set if the Spit driver landed at a field without 150 octane. The amount of boost usable was then only +18. So they were planning for the potential of one type or the other being used in the same bird. They changed the color of the 150 octane fuel too so that there was less chance of a mistake.

Dan/CorkyJr

Wotan · « **Reply #74 on:** August 08, 2005, 11:30:25 PM »

Well the lower octane fuel would detonate so its understandable that boost would be limited if lower octane fuel was used.

You can go down, you can't go up...

You can run lower octane as long as you don't over boost...

However, to get the most out of the engine the engine is set up to run with 150 grade.

Kev it didn't take 1 day, it took 2. The second day for testing...