THE HONGKONG TELEGRAPH, MOTORING SUPPLEMENT.
PONTIAC ASSUMES OAKLAND FEATURES.
The new Pontiac, two-door, sedan which is shown, here, has taken on many of the refinements found on its big brother, the Oakland. For instance, the rear transmía-
alon and axle is practically
all Onkland, while the crank.
shaft, shown in lower view, has adopted Vaxiana principies. The counterweights decrease bearing londs and prevent shaft deflection while the new harmonic balancer is placed at the
end, whown at right, to counteract twisting or vibration.
LUBRICATING MOTOR ENGINES.
(PART FOUR)
is no-pre-ignition, and may not oc- cur if the charge is fired by over- heated carbon deposits.
Thanks to prolonged acorch, we now kanw that this knock or "ping" is duo entirely to a change, in the way the fuel burns, when sub- jected to certain conditions, and is caused by an abnormal pressure condition in the cylinder due to this peculiar burning.
The tendency of various fuels to knock varies widely, depending up on the chemical structure, some, like alcohol and benzol, being free from this tendency, whereas heavy, non-volatile, kerosines, and the easily vapourized liquid, ether, de tonate with extreme violence, the latter particularly so.
There are two factors, acling elther alone or together, which will promote knocking, or detonation of the fuel "pinging."
High compression, and abnormal heating.
High compression is due to car- bon deposit reducing the clearance "apace.
Carbon, being a poor conductor prevents the free flow of heat from the charge to the metal surfaces. General overheating, due to lack of water, or other cause (scale) net in the same way. Any part of the combustion chamber not properly cooled has a smiliar effect.
When an engine is operating pro- therefore, a lighter, clean burning perly, the pressure, which is devo- oil is preferable, unless the oil con-loped as the fuel burns, increases trol. is very effective. Some en-smoothly and at a moderate rate gines are equipped with dovices of speed until all the charge is which regulate the oil supply ac- burnt. (Approximately 50' per sec.) cording to the lond, in order to pre- Carbon
Formation--All fucks ends to pump the oil into the com- vent this over oiling at light loads, and lubricating oils contain carbon,uation chamber.
Deport behind the rings will ns they are formed by the chemi-
When an engine is running ut or make them stick in the grooves, cal combination of carbon and awar its full load, the oil passing preventing then from functioning hydrogen in various proportionsnt the combustion chamber is properly, resulting in "blow-by" There is no such thing as a "ngburn along with the fuel-com, Carbonized oil Inside the hollow, carbon" sil, and the heavier the bustion is nearly complete, so that under side of the piston, bakes into oil, the more carbon.
no smpke is visible from the ex- a crust, which in time cracks and if oll did not pass the piston in- haust. to the combustion space, only the When running light the lime falls into the crunk chamber con-
taining the oil. carbon from the fuel would be de-emperature owing to the dilution Road dust is drawn into the It only requires a slight deposit posited there as "soot," So, as we with exhaust gases is insufficient cylinder with the intake air, and of carbon in a high compression en- know that oil does pass the pistons, to burn the oil with the result that forms a base to which any excess gine to do this, and it is quite when we talk about carbon, wo mean the carbon for which we blame the lubricating oil.
The amount of carbon depends generally on two things one; the amount of oil passing the pistons, and the other, the conditions of combustion.
The amount of power, and de- gree of fuel economy which can be obtained from an engine depend on the compression pressure. The higher we can make this, the more efficient is our engine, but under normal conditions with pre- sent day fuels, we cannot go much over 80 lbs. pres- sure without the engine being sen- sitive to "knocking.”.
It accumulates in the combustion oil will adhere. Soot from Imperfeasible that such an engine may chamber until the throttle is open feet combustion will also form a be very economical in oil con- ed: the quantity is then so large base.
sumption compared with an engine of low compression.
hat there is not suffleiently oxygen However, if we could keep ex- trailable for its complete com- cess oil out of the cylinder, there So we have to cònsider "knock- bustion at first, with the result that is not much chance of carbon de- ing" from a lubrication standpoint 4 is only partially burnt and issues ¡posit--the oll is at the root of it. If the engine is one which la sen- From the exhaust as blue smoke When there is an accumulation allive to carbon deposits, we must Pusage of oil past the piston hat is as partially vaporized but of carbon, the engine generally use a clean burning oil, on the other rings into the combustion chamber unburnt, oil.
tells us by knocking in a peculiar hand, if the engine is not sensitive is due to the fact that the olf is
(Whereas a black exhaust in manner, and this knock is called, and the working conditions severe, forced up against the rings on the dicates incomplete combustion, earbon knock, gas, knock, spark a heavy oil may be used without downward stroke of the piston bedue exhaust indicates burning of knock, "pluking" and "pinging," any detrimental effecta, cause the 'motion of lie pistons,xcess oil)
land it has been commonly balieved combined with its thrust against When un engine is operating un- to be due to pre-ignition of the fuel the cylinder walls, sets up con der heavy load; there is ample charge, te, actual firing before the siderable hydraulic pressure and to constime heavy lubricating oil, sparku cccurred. Such, however, is the oil is, so to speak, rolled up which, in a lightly loaded unit, not the case, fór although the against the rings; and the motion, vul distil down to a gummy knock may accompany pre-ignition, of the piston rings in their grooves parbon. With a lightly loaded unit, Et is commonly present, when there
i All these enter into the selection
of the proper oll for any motor car, engine, and it is only by carefully analysing them in the light of en- gineering practice that the selec tion of the proper oil can be made.} (To Be Continued.)
SATURDAY, MARCH 2, 1929.
The Choice
of the-
G. W. R. L. N. E. R.
and
SOUTHERN RAILWAY
for their new
RAIL-ROAD SERVICES
THORNYCROFT
SIX-CYLINDERED
COACHES & OMNIBUSES
Preferred by experienced
users!
Further particulars of our Lorries, Vans, etc., for
1 to 7 tons, and Coaches or Omnibuses for 20
to 45 passengers forwarded on request to:-
JOHN I. THORNYCROFT & CO., LIMITED.
UNION BUILDING.....
FIFTH --- ------- FLOOR.
HONGKONG
Write us and our representative will call.
Telephone Central 4831.
DEAL DIRECT.
New Chrysler "75" Town Saloon
Wire wheels extra
CHRYSLER
New Grace, New Style, New Beauty
Greater Value
Chrysler's new style is so original that imitation even in the least detail must plainly indicate the source of inspiration. Its pleas ing grace more than ever obso letes the bulky and cumbersome.
The new Chryslers differ from all other motorcarsintheirutterly new treatment of slender-pro- file radiator, air-wing mud- guards, arched windows-
to mention only a few of
SOLE AGENTS--
a host of style features--added to a performance which out-Chryslers even Chrysler. 4 The simple fact that thousands of people now re- alise that not even much more money will buy style, perform- ance, comfort, safety, depend- ability and long life equal to the new Chrysler, is arousing a demand that Chrysler's larg cat production is taxed to the limit to satisfy.
The Republic Motor Co. of China.
(Successes A. LUNG & Co. Auto Department.)
30, 32 Des Vœux Road.
You'll see it Soon
The
Outstanding Truck of Chevrolet History
CHEVROLET
The truck that has reaffirmed Chevrolet's proud claim to economical transportation In every country of the world-a Six in "the price range of the Four-a truck that offers truck users in every line of business scores of vital advantages that have never before been avaliable in any haulage unit priced so amazingly low.
The 1929 Chevrolet 6-cylinder utility truck and the 1929 6 cylinder commercial will be on display on the 6th March, at our Show Rooms.
HONGKONG HOTEL GARAGE.
25, QUEEN'S ROAD CENTRAL,
TEL, CENTRAL 4759, -