Octane Rating of Canadian WWII vehicles

[Hanno Spoelstra]

Read the Imperial Oil Review, Summer 1944 for an article on "100 octane aviation gasoline - The story behind the develpment of the fuel that helped to give the United Nations air superiority over Germany"

http://wartimecanada.ca/document/wor...ew-summer-1944

[Tony Smith]

Agreed. Like Lynn, the only references I can find on this subject seem to point to only wartime US aviation fuel being a higher Octane than British production.

It seems that US motor fuel was just as low as Britain's until the Post-War years

[Dan Martel]

I originally read about this on the "Axis History Forum" under the thread "Unserviceable Lorries - Jul - Sep 44." It runs to 26 pages in total.

On post #12 it reads:

Something ELSE happened over the summer of 1944 that might have led to heating issues on particular motors...

The octane rating of Pool Petrol rose! During the war the octane rating of "Pool" went down as low as 67 octane, but in the summer of 1944 what would have been coming out of the pump at PLUTO in Normandy apparently rose to around 80 octane.

The nearest we were able to get to a breakdown of such magnitude was the engine failure of countless British Trucks following the introduction of Higher octane MT80 fuel. British Engines were not designed for operation on 80 octane petrol and as a result those of certain makes and types (we do not know which) developed severe burning of the valves. Changes were made to exhaust valves and guides for operation on leaded fuel and new engines were provided with valves made from an alloy steel containing 20 (Vs, 8) percent of chromium to lengthen engine life between overhauls.

In fact...it's entirely possible that in an engine designed for very low octane "Pool"....the range of adjustment in its magneto ignition system (it was WWII...) MAY simply not have allowed the ignition timing in the K5's new engine to actually be advanced enough to cope with what was - after all - a 20% rise in octane rating...and the heating problems that caused - within the design parameters of the original engine 8O ...

Warning, if you start reading this thread, it will suck you in to all 26 pages before you know it.

Cheers,
Dan.

[Lynn Eades]

Dan, as the octane rating goes up, the flame front travels faster and so, the ignition timing requires retarding. (not advancing)This allows the piston to reach t.d.c. before the pressure on the piston builds too much.
I'm surprised that Richard F. hasn't chimed in because I faintly recall a discussion about Bedfords and Morris's that had piston problems and I don't recall the reason.

[Keith Brooker]

Found this info from my copy of Supplies and Transport Voll 2, i can put more info from the REME Vol 2 Technical if you want more.
Keith

[Richard Farrant]

Originally Posted by Lynn Eades

I'm surprised that Richard F. hasn't chimed in because I faintly recall a discussion about Bedfords and Morris's that had piston problems and I don't recall the reason.

Hi Lynn,
This subject came up before, I think on HMVF forum, which I participated in. Also on an Axis form, I have lost the links now. The lorries of concern were a batch of Austin K5 4x4 in NW Europe campaign which were having engine problems, apparently with excess bore wear.. The discussions on Axis forum were with non-technical people as I recall (I could only read that forum), but from my research I found that there were a batch of Austin K5's which were supplied for wading, at a guess for unloading from sea transport. These had a special waterproof brake servo. What I did find out from Austin manuals was that the bores were given a greater piston clearance, my guess is that when the engine was warmed up on the landing craft, then plunged into cold water the rapid chill could seize the engine, but of course later on the extra clearance would then mean oil consumption and low compression. If REME were not aware of this they would automatically think that the engines were faulty.
To quote the K5 manual;
"piston skirt clearance has been increased from .0025"-.0028" to .004"-.0045" to make engines with new pistons immediately suitable for wading through water without fear of seizure. Pistons with the original smaller clearance can be used for engines of vehicles which it is known will not be called upon for wading".

Regarding the change to leaded petrol, it was the deposits on valve stems that caused problems and many British manuals gave information on combating the problem, with mods to valve guides, increased valve clearances and alterations to ignition timing. I have quite a bit of tech info on this but am short of time at present.

regards, Richard