“DOPED” FUEL.

Timaru Herald, Volume CXXV, Issue 17756, 17 September 1927, Page 11

“DOPED” FUEL.

EFFECT ON ENGINE

“Dolled - ' petrol, that is, motor spirit to which tetra ethyl lead, picric acid, i or other chemicals have been added, is used rather extensively in America, and drivers of sporting types ot cars who wish for a little more power or less “pinking” use these mixtures eons.stently. " Motor-cyclists are even more inclined to experiment with "dopes, and there has been much speculation regarding the supposed injurious c.lcct of the chemicals which are added. To obtain data on this point the Fngli.sli motoring journal, Ihe Autocai, conducted a tost over 20(10 miles with a motor-cycle. Tile, engine was powered with a single cylinder engine. 1 Before the test was commenced the ’cylinder head, valve head, the piston, on tile crown and underneath, were eonipleieiv cleansed of carbon deposit and .'iron’a polish, the valves were ground until thov seated perfectly, the oil sump was Idled with fresh ml, and. m '-be lank, fuel reputed to contain eight e.c. . of tetra ethyl lead to each gallon was used throughout the trial. r l he liioasuiod compression ratio of the engine was 4 IS to 1. The most, noticeable feature of the machine's running was its flexibility due to the fact that lor the first Sod "miles it was impossible to make it ‘•'pink ” a result entirely -due to the fuel ’From 8b() miles onward there was occasional “pinking” thought to bo due, in all probability, to flakes iiom the mica insulation oil tile plug. I When the engine was dismantled it was noticeable that the carbon deposit was verv slight, reddish in colour m places and very hard. There had been • no action between the fuel and the aluminium piston or cast iron head, neither 'was there definite evidence, so tar as . ! could he readily ascertained ot an> , | harmful effect on the walls of the O- . Minder. The head of the exhaust vahe ; Iliad a red deposit, as though it had

been running at very high temperature, 1 though, during the test, the engine had .shown no signs of abnormal heat, \ ei> little grinding was necessary, to reniorc the apparent trace of pitting, except m one portion of the face on which .small pits were more difficult to remove. . Iho i . valve was in no sense unuseable, and it seemed as though tho face was covered ( with a deposit, and holes in the deposit gave the effect of pitting under a mag- . infvmg glass, ft is not thought that - the pitting actually found on the valve _ face was definitely the result of using ■ tetrn etlivl lead fuel, but it does seem probable that, with this fuel valves will ■ pave lo be'ground to then* .seats more I |. ( w,uently it they are to remain gas- ! tight. , , i The inlet valve had a more normal de--1 posit,, ami no obvious deposit on its Bice i but owing to a badly-worn valve guide it was in poor condition. Both valves wore of three per cent, nickel steel, i At first sight the sparking plug seemed ‘unaffected, the gap between the points being wider than usual, though this, apparently, was not due to corrosion. When the plug was dismantled it was found that the mica insulation exposed to combustion was of reddish colour and had begun to flake. On the mica, also, wore traces of a metallic deposit, Tho plug fired perfectly, but seemed ns though it would not last much longer. . | I Here was no sign of corrosive effect, I either on the petrol tank.. externally, on j the nickel filler cap, or in any part of I Hie carburetter. I