THE HONGKONG TELEGRAPH. MOTORING SUPPLEMENT. SATURDAY, MARCH 2
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 transmis- sion and axle is practically
all Oakland, while the crank.
shaft, shown in lower view, has adopted Oakland principles. The counterweights decrease bearing loads and prevent shaft deflection while the new harmonic balancer is placed at the
end, shown at right, to counteract twisting or vibration.
LUBRICATING MOTOR ENGINES.
(PART FOURY--
fuels
ends to pump the off into the com- ustion chamber.
Carbon Formation.-An and lubricating oils contain carbon, as they are formed by the chemi When an engine is running at, or cal combination of carbon
and agar its full load, the oll passing hydrogen in various proportions to the combustion "clumber is There is no such thing as a "no-burnt along with the fuel-com- carbon" oil, and the heavier the bustion is nearly complete, so that oil, the more carbon.
no smoke is visible from the ex-
The amount of carbon depends generally on two things one, the amount of oil passing the platons, and the other, the conditions of combustion...
is po-pre-ignition; and rasy not oc cur if the charge is fired by over heated carbon deposita.
Thanks to prolonged search, wa now know that this knock or “ping” is duo entirely to a change in the way the fuel burns, when sub- jected to certain conditions, and la caused by an abnormal pressure condition fn the cylinder due to this pecullar burning.
די
The tendency of various fuels to knock varies widely, depending up on the chemical structure, 'qonte, like alcohol and benzol, being free from this tendency, whereas heavy, non-volatile kerosines, and the cally, vapourized liquid, ether, de tonate with extreme violence, the latter particularly 80.
There are two factors, acting. either 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 space, S
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 (scalo -) act In the same way. Any part of the combustion chamber not properly cooled han smiliar effecti
When an engine is operating pro- therefore, a lighter, clean, burning porly, the pressure, which is deve oil is preferable, unless the oil con-loped as the fuel burns, Increases trol is very effective. Some en-roothly and at a moderate rate gines are equipped with devices of speed until all the charge is which regulate the oil supply ne- burnt. (Approximately 60' per soc.) leording to the load, in order to pre- The amount of power, and de
vent this over oiling at light loads. groe of fuel economy which can be Deposit behind the rings will obtained from an engine. depend make them stick in the grooves, on the compression pressure. The preventing them from functioning higher we can make this, the more properly, resulting in "blow-by, efficient our engine, but under Carbonized oil inside the hollow, normal under side of the piston, bakes into a crust, which in time cracks and falls into the crank chamber con- taining the oil.
conditions with pre- sent day: fuels, we cannot go
much over 80 lbs. pres-: sure without the engine being sen- sitive to "knocking."
ing"
So
if
*
If oll did not pass the piston in-haust. to the combustion space, only the When running light the flame carbon from the, fuel would be de- emparature 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, o 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, we accumulates in the combustion oil will adhere. Soot from Imper-fensible that such an engine may mean the carbon for which we hamber until the throttle is open- feet combustion will also form a be very economical In oil con- blame the lubricating oil.
ed; the quantity is then so large base.
sumption compared with an engine that there is not sufficiently oxygen However, if we could keep ex- of low pression,^> wailable for its complete com ceas oil out of the cylinder, there
veto. consider "knock- bustion at first, with the result that if not much eliance of carbon de-
fubrication standpoint tla only partially burnt and issues posit--the ofl is at the root of it.
fe is one which is sen From the exhaust as blue smolic"
When there is an accumulation: sitive on deposits, we must Passage of oil past the piston hat is as partially vaporized but of carbon, the engine generally use Arilirning oil, on the other rings into the combustion chamber unburnt oil.
tells us by knocking in a peculiar hand the engine is not sensitive is due to the fact that the oil is
(Whereas a black exhaust. In- manner, and this knock is called, and working conditions savere, forced up against the rings on the dicates Incomplete combustion, a carbon knock, gas knock, spark a heat oil 1 may be used without downward stroke of the piston be-blue exhaust indicates burning of knock, "pinking" and "pinging." any de mental effects cause the motion of the pistons, excess oil.)
and it has been commonly believed
All a enter into the selection combined with its thrust against When an engine is operating un- to be due to pre-ignition of the fuel of the proper oll for any motor car the cylinder walls, sets up a con- der heavy load, there is ample charge, ie, natual firing before the engine, and it is only by carefully siderable hydraulic pressure and to consume heavy lubricating oil, sparke cecurred: Such, however, is analysing thent' in the light of en- the oll is, so to speak, rolled up which, In a lightly louded unit, not the case, for although the gineering practice that the selec against the rings; and the motion would distil down to a gummy knock may accompany pre-ignition, tion of the proper oil can be mado, of the piston rings In their grooves | arbon. With a lightly loaded unit, fit is commonly present when there (To Be Continued.)
The Choice
of the -
1939
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 14 to 7 tons, and Coaches or Omnibuses for
to 45 passengers forwarded on request to :—
JOHN I. THORNYCROFT & CO., LIMITED.
UNION BUILDING.
FIFTH
FLOOR.
Write us and our representative will call.
DEAL DIRECT.
HONGKONG
Telephone Central 4881.
کم گہیر کہیں
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(Successes A. LUNG & Co. Auto Department:)
30, 32 Des Vœux Road.
You'll see it Soon
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'': * ,
HONGKONG
26) QUEEN'S ROAD CENTRAL,
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HOTEL GARAGE.
TEL.
NTRAL 4759,
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