High Octane Petrol

[seacue]

Here in the USA, great noises were made during WW2 about "our" high octane petrol and the performance advantage therefrom.

I gather that the Axis didn't have petrol with such high octane, yet their engines / planes were at least competitive.

Anyone wish to comment?

seacue

[rotorfossil]

100/150 octane fuel allowed very high boost pressures to be used without detonation. Typically up to +25 psi for war emergency ratings, like for chasing V 1's. It was almost entirely due to this that the later Merlins with two stage two speed superchargers were producing 2000 hp by the end of the war with no increase in cubic capacity compared to the 990 ofthe early versions.
German fuel was no higher than 87 octane as far as I know, with the result that they either had to use bigger engines or resort to exotic short term boost increases using water meth or nitros oxide injection.

[CV880]

I came across this somewhere recently and I think the German fuel was even lower than 87 octane. Rotorfossil is basicaly correct although two speed supercharging was more to do with power recovery at high altitude, high speed blower only being available above a certain height.
The DB601 engine powering the Me109 for example had a similar power output to the RR Merlin but was about 6 or 7 litres bigger in capacity.

[seacue]

Thanks for the info.
seacue

[The AvgasDinosaur]

This may be of related interest.
Especially the reply from Spekesoftly.
http://www.pprune.org/forums/showthread.php?t=238563
Hope it helps
Be lucky
David

[Agaricus bisporus]

Standard piston fuel was 100/130 surely? ("Wun-Wun-Thirty")

Was there really a 150 octane too?

[GOLF_BRAVO_ZULU]

There was;

F–22 115/145 AVGAS Aviation gasoline, grade 115/145.

See page 318 of DEF STAN 01-5 Issue 15. http://www.dstan.mod.uk/data/01/005/00001500.pdf

[Mike7777777]

NF Mosquitos were reportedly flown with 150 and nitrous when chasing V1s. That must have been exciting.

[WHBM]

As I understand it the Lockheed Constellation/DC-7 in the 1950s had separate small tanks for 115/145, which was only used for high-power high-weight takeoffs, regular fuel for other times. If you weren't careful the regular could contaminate the high octane via the overflow pipes. Another task for the FE. Their Wright engines were a development of what the B-29 was fitted with.

How were things organised on these WW2 types ? Separate tanks as well, for a little burst when needed ? Didn't it burn the valves ?

[Milt]

Was/is there any advantage in the use of high octane fuel at boost pressures below your normal lower octane fuel detonation range?

And what process produced 150 octane fuel? Was it just the addition of more tetra ethyl lead to 100 octane?

[WHBM]

I've just dug out some stuff I have on the Grumman Albatross that Jimmy Buffett owns and parks at his restaurant in Orlando, Florida.

It says the Curtiss-Wright R-1820s of the Albatross produce 1425 hp on 115/145 "military fuel" and 1400 hp on 100LL.

It seems an awful lot of messing about with special fuel just for an extra 25 hp.

[henry crun]

From what I have read the Mossies only shot down the V1's, and were mostly confined to night ops.

They did not have the speed to catch them at max straight and level, so they relied on being on patrol well above the usual V1 height, then diving down to gain enough speed to get into position for a shot.

The nav would use his AI radar to tell the pilot when he was within firing range.

[GOLF_BRAVO_ZULU]

norman atkinson. The one I quoted was this Century. It is not an AP; it's a Defence Standard, as per the link. AVGAS 115/145 (Joint Service Designation F-22) is not a current spec, though, as it has ceased to have a military aplication.

[Mike7777777]

In "standard" condition, I doubt if any Allied aircraft could catch a V1 in level flight at traditional V1 height (3k?)

http://www.wwiiaircraftperformance.org/ is worth ploughing through

[R2G2]

Aviation Fuel History and Specification

Folks
This is the best source of information I've found so far. Scroll down to para 7 for aviation gasoline. I know no more than I've read in the link so I haven't the knowledge to answer any questions.
Regards
R2G2
http://www.chevron.com/products/prod...nfuel/toc.shtm

[con-pilot]

I can tell you that way back when I was flying as a co-pilot on a Howard 350 with R-2800 CB-16 engines. We had, I think, 6 different Manifold Pressure setting for take off depending on the type of fuel and whether we had water injection available for takeoff. Basically it was the following. (Sorry, it's been way too long and I cannot remember the max manifold pressure for the fuel grades.)

Highest allowed was 115/145 with ADI , next 115/145 without, 100/130 with etc. down to 80/87 without.

Even back then, the early 70s, it was very hard to find 115/145, so we seldom were able to use that fuel.

However, when we could get 115/145 and had the ADI the power on takeoff was impressive.

[411A]

As I understand it the Lockheed Constellation/DC-7 in the 1950s had separate small tanks for 115/145, which was only used for high-power high-weight takeoffs, regular fuel for other times.

Never heard of this and I have flown both the 1649 Constellation and the DC-7C.
Now, the TCDS and the relavent AFM states quite clearly that if any fuel other than 115/145 is used in these aeroplanes, the engines must be operated in low blower only and the mixtures must remain in autorich during cruise.

Now you know why hardly any of these old aeroplanes are operated anymore.

[411A]

Basically it was the following. (Sorry, it's been way too long and I cannot remember the max manifold pressure for the fuel grades.)
Highest allowed was 115/145 with ADI , next 115/145 without, 100/130 with etc. down to 80/87 without.

Close, but no cigar.

R-2800CB16/17 (and yes all CB16 engines had a CB17 rating).
Fuel required, either 100/130 or 108/135.
115/145 could however be used in lieu of 108/135.

CB16 rating, 2400 BHP wet, 2800 RPM/59.5 inches MP/243 BMEP, 100/130 fuel....or...2050 BHP Dry, 2700 RPM/53 inches MP/215 BMEP.

CB17 rating, 2500 BHP wet only, 2800 RPM/61 inches MP/255 BMEP, 108/135 or 115/145 fuel.

These engines could however be operated at the CB3 rating, low blower only, but this limited the available maximum altitudes for cruising.

80/87 fuel never allowed.

[norman atkinson]

There is a remarkably accurate account of when the Brits gave a few Hurricane 11's with XX Merlins to the Russians.
There was a problem of fuel. I asserted that Merlins ran on 100 octane.
Google the story. Google how 100 octane is blended. Google the story of SS San Demetrio- and the film.

We, at RAF Hendon in 1949 had 87 octane and 100 octane bowsers.
Great for cleaning dirty 'blues' We had operational Spitfires and three 'toys for the boys'. Now the operational Spits gave gone- and one of the toys is still there. I presume someone still plays at being 'Foreskin fusiliers'

[Milt]

Was/is 100 octane always tinted green and does it always contain lead?