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Old January 30th 04, 03:19 PM
Dave Eadsforth
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In article
thlink.net, Orval Fairbairn
writes
In article ,
Dave Eadsforth wrote:

Good day, good people,

I wondered if anyone out there (in all probability, Peter!) could help
me understand more fully the process by which the Merlin engine was
enabled to use 150 octane fuel; one feature of which was the addition of
the Xylidine anti-knock compound. (This was touched on in a thread
last year, I recall.)

I understand that 150 octane fuel became available during 1944 - I don't
know when (a date would be welcome), but it was available in time to
boost the performance of those Spitfires that were assigned to knocking
down the V1s. What I would like to find out is what might have been
done to the Merlin to allow it to run on the stuff?

Was the use of 150 octane restricted to particular marks of engine?

I read somewhere that it was supposed to provide an effective increase
in power of about 15 percent - by allowing a higher manifold pressure.
Is that figure of 15 percent correct?

Was the conversion to 150 octane done by merely adjusting the existing
arrangements for the supply of fuel, or was there a need for new fuel
supply components (carbs etc.)? And would the permitting of the
additional boost have mandated the exchange of some internal engine
parts (bearings, crankshafts, etc.)?

Would the use of 150 octane have automatically permitted a higher
ceiling for the machines that used it? Or don't things work quite that
simply! (I understand that specially prepared Spitfires had been able
to fly to at least 44,000 feet by 1943. Would I be right or wrong to
simply assume that 150 octane would have enabled them to go higher?)

Thanks in anticipation.

Cheers,

Dave


150 octane means that you can add more boost to the superchargers
without damage to engine components. There MAY ahve been materials
compatability issues with the octane boosters, however.

You can run "rubber" components (seals, hoses, etc.) on petroleum-based
fuels and have no problems; you can run the same components on
naptha-based fuels and have no problems. It is when you switch from one
to the other (either way, BTW) that hoses crack and seals leak.


Thanks for that point.

(It rings a bell - I read that when the US first entered the war,
Britain supplied the Pacific-based USAAF with some aviation fuel that
had originated from a SE Asian oilfield, and it was so differently
formulated that it actually did corrode the seals and hoses.)

Cheers,

Dave

--
Dave Eadsforth