AUTOMOTIVE ENGINE HEATERS*

INTRODUCTION

Virtually all automobiles in the prairieregion of Western Canada are equippedwith automotive engine heaters. Engineheaters are essentia] for trouble-free start

ing in the severe winter temperatures.Outdoor temperatures well below 0°F(-18°C) are not uncommon during themonths of January and February. Datacollected at the Saskatoon Weather

Station (1) over a period of 38 yearsshows the maximum average temperaturefor the month of January was 9°F(-13°C) and the average daily minimumtemperature was -18°F (-28°C). Theminimum extreme temperature recordedduring this 38 year period was -55 F(-48°C).

The most common type of automotiveengine heater in use is the block-typeheater which is installed in the frost plugof the engine block and heats the coolantcontained in the engine block. Most sixcylinder engines are equipped with onlyone such heater, while V-8 engines oftenhave a block-type heater on each side ofthe engine block.

Other coolant heaters commerciallyavailable are: 1. Headbolt-type engineheaters, where the heater is installed inplace of one of the headbolts, 2. Acirculating-type engine heater, installedin-line with the heater hose, whichcirculates the coolant through a thermostatically controlled heating chamber bymeans of a small circulating pump, 3. Ahose heater installed in-line with thebottom radiator hose. As coolant is

heated, it rises and circulates throughoutthe engine block via the water pumpby-pass, 4. A dipstick-type heater thatheats the crankcase oil in which it is

immersed, and 5. An exterior heater,

* Paper presented at the American Society ofAgricultural Engineers Pacific NorthwestRegional Meeting, 1970. ASAE relinquishedright to first publication at author's request.

E.H.Wiens

Member CSAE

Department of Agricultural Engineering

University of Saskatchewan

Saskatoon, Saskatchewan

installed on the bottom of some air-

cooled engine crankcases, that heats theoil.

The above types of automotive engineheaters vary in output from 100 watts forsome exterior crankcase oil heaters to

1500 watts for certain circulating-typeengine coolant heaters.

OBJECTIVE

This study was conducted using theblock-type coolant heater which is installed in the frost plug of the engineblock. The study included tests with 400,600, 750 and 1000 watt heater elementsinstalled in a six and an eight cylinderengine.

The objective of the tests was to determine the rate of rise of coolant temperature as well as the extent of the temperature rise for the various block heater

elements. In addition, crankcase oiltemperatures and combustion chamberair temperatures were obtained.

EQUIPMENT

Six Cylinder Engine

The six cylinder engine used for thetests was a 1939. G.M. 48 engine, modelno. 3836327. Although this was an oldengine, the basic G.M. block design hadchanged very little and was also typical ofother six cylinder engines.

The engine was instrumented withiron-constantan thermocouples at variousstrategic locations throughout the blockcoolant passages to obtain coolanttemperature variations within the block(Figure 1) The thermocouples wereinstalled by drilling small holes in eitherthe frost plugs or pipe plugs and insertedso that they were immersed in thecoolant. The holes were then sealed with

"epoxy resin" cement. A thermocouplewas also immersed in the crankcase oil,

the dipstick opening. The roomRECEIVED FOR PUBLICATION NOV. 29, 1972

temperature was measured by a thermocouple placed adjacent to the engine.

Figure 1. Location of thermocouples and blockheater — six cylinder engine.

The heater, (Figure l), located in theleft front frost plug was installed with theheater element pointed up into the block.Tests were performed with 400, 600, 750and 1000 watt block heater elements.

Eight Cylinder Engine

The eight cylinder engine used for thetests was a 1956, 272 cubic inch, V-8Ford engine. This engine was instrumented in a similar manner to the six

cylinder engine with thermocoupleslocated on either side of the engine blockto measure coolant temperatures. Inaddition, a thermocouple was located inone combustion chamber on either side

of the engine block to determine airtemperature in the combustion chambersdue to heater operation. A thermocouplewas also immersed in the crankcase oil to

measure oil temperature. Room

15 CANADIAN AGRICULTURAL ENGINEERING, VOL. 14, NO. 1, JUNE, 1972

temperature was obtained by a thermocouple located adjacent to the engine.The thermocouple locations werenumbered from 1 to 12 (Figure 2).

12-—>

r~—:

RIGHT SIDE OF ENGINE

Instrumentation

The thermocouple temperature readings were indicated by a 12 point indicating potentiometer (A, Figure 3). A chart

REAR VIEW OF ENGINE

LEFT SIDE OF ENGINE

Figure 2. Location of thermocouples and block heaters —eight cylinder engine.

Block heaters were located on either

side of the engine block in the front frostplugs with the heater element pointeddown into the coolant passages of theblock (Figure 2). Tests were performedwith 400, 600, 750, and 1000 watt heaterelements.

Cold Room

It was usually possible to maintain thecold room temperature to within ±2°F(1.1°C) of the desired temperature.Slightly higher variations were experienced at the lower cold room temperatures, especially when using two blockheaters in the eight cylinder engine.

Two fans were in continuousoperation within the cold room resultingin an average air velocity around theengine of 2-1/2 mph (4.0 km/hr.). Thiswas considered to adequately simulatethe conditions encountered by a carparked outdoors. Average wind velocitymeasured under the hood of a car stand

ing outside in a 12-1/2 mph (20.1 km/hr)wind was 1-1/2 mph (2.4 km/hr.) (2)

recorder (B) was used to constantlymonitor the cold room temperature.

Figure 3. Cold room and instrumentation.

Coolant

The coolant used was a half and half

mixture of permanent type ethylene-glycol base anti-freeze and water. Thismixture was adequate to prevent freezingof the coolant at all cold room temperatures encountered.

EXPERIMENTAL PROCEDURE

Tests were conducted at several cold

room temperatures, ranging from +10°F

CANADIAN AGRICULTURAL ENGINEERING, VOL. 14, NO. 1.JUNE, 1972

(-12°C) to -40°F (-40°C), for each size ofheater. The engine under test was placedin the cold room with the thermocoupleleads led through the cold room outletand connected to the 12 point indicatingpotentiometer. The cold room, enginecoolant and crankcase oil were allowed to

stabilize at the desired room temperaturebefore commencing a test. Initial readingswere taken before "plugging-in" theheater and readings were taken every halfhour for a total of seven hours. The room

temperature was then changed and subsequent tests were conducted in a similarmanner.

In the case of the block heaters in the

eight cylinder engine, additional testswere performed at two cold roomtemperatures for each size of heater tocompare the performance when using ablock heater on one side of the engineblock as opposed to a heater on bothsides of the engine block.

DISCUSSION OF RESULTS

The temperatures obtained at thevarious thermocouple locations throughout the engine block indicated that thecoolant reached its highest temperature atthe top of the engine block, with decreasing temperatures at the locations lowerdown on the block. Subsequent discussion of the results will pertain to averagetemperatures of the coolant in the block,which were obtained by averaging thecoolant temperatures at the various locations throughout the engine block.

Six Cylinder EngineRepresentative plots of average

coolant temperatures versus time, obtained at various cold room temperaturesfor the 600 and 1000 watt heater ele

ments, are shown in Figures 4 and 5.Similar data were also obtained for the

400 and 750 watt elements. The block

heater was operated for a period of sevenhours to reach the equilibrium temperature of the coolant. In most cases verylittle temperature increase was experienced after five hours of heater operation. The total temperature increase for agiven size of heater was approximatelythe same regardless of initial cold roomtemperature. At a cold room temperatureof 0°F (-18°C) the coolant temperatureincreased from 0°F (-18°C) to 72°F(22°C) in 5 hours. A total increase of72°F (40°C) was also experienced after5hours at a cold room temperature of-25°F (-32°C) when the coolant temperature increased from -23°F (-31°C) to49°F (+9°C) (Figure 4).

16

Small increases in crankcase oil tem

perature, due to block heater operation,were experienced (Table II). Total rise incrankcase oil temperature was similar atthe various cold room temperatures for agiven size of heater.

for 5 hours at a cold room temperature of-15°F (-26°C), the coolant temperatureincreased from -16°F (-27°C) to 77°F(25°C), a total increase of 93°F (52°C).At a cold room temperature of -40°F(-40°C) the coolant temperature increas-

TABLE II CRANKCASE OIL TEMPERATURES USING VARIOUS BLOCKHEATERS IN A SIX CYLINDER G.M. ENGINE

3 4 5 6 7

TIME - HOURS

Figure 4. Coolant temperature vs time for a600 watt block heater in a six

cylinder G.M. engine at various coldroom temperatures.

I20r

Size of heater element

(watts)

400

600

750

1000

Figure 5. Coolant temperature vs time for a1000 watt block heater in a six

cylinder G.M. engine at various coldroom temperatures.

The rate of warmup of the coolant wasfairly constant, regardless of initialtemperatures, for a given size of blockheater. The temperature increase and percent of total increase in each hour for fivehours for each of the four sizes of blockheater, are shown in Table I.

Eight Cylinder Engine

Plots of average coolant temperaturesversus time at various cold room temperatures for the 600 and 1000 watt block

heaters in the eight cylinder engine areshown in Figures 6 and 7. Similar datawere also obtained for the 400 and 750

watt block heaters. Although the blockheaters were operated for seven hours,very little increase was experienced in thecoolant temperature after five hours. Aswith the six cylinder engine, the totaltemperature increase at the various coldroom temperatures was approximatelythe same regardless of the initial coldroom temperature for a given size ofblock heater. For example, when usingonly one 600 watt block heater (Figure6) for 5 hours at a cold room temperatureof -15°F (-26°C) the coolant temperatureincreased from -17°F (-27°C) to 32°F(0°C), atotal increase of 49°F (27°C). Ata cold room temperature of -40°F(-40°C) the coolant temperature increased from -38°F (-39°C) to 11°F(-12°C), also a 49°F (27°C) rise in temperature. When using 2-600 watt heaters

TABLE I RATE OF ENGINE COOLANT WARMUP USING VARIOUS BLOCKHEATERS IN A SIX CYLINDER G.M. ENGINE

Size of heater

element (watts)

400

600

750

1000

Temperature rise per hour (°F) & % of total temperature rise1 hour 2 hours 3 hours 4 hours 5 hours Total °F/KWH

25 11 5 3 1

56% 24% 11% 7% 2%

37 18 9 5 3

51% 25% 13% 7% 4%

47 23 12 7 4

51% 25% 13% 7% 4%

61 27 13 7 4

54% 24% 12% 6% 4%

45

72

93

112

563

600

620

560

Total temperature rise in

5 hours (°F)

11

ed from -37°F (-38°C) to 58°F (14°C),also a total increase of 93°F (52°C).

COLD ROOM NOOFNO. TEMR'F HEATERS

-5 2-15 2-25 2-40 2-15 I-40 . I

2 3 4TIME - HOURS

Figure 6. Coolant temperature vs time for the600 watt block heaters in a Fordeight cylinder engine at various coldroom temperatures.

4 5

HOURS

Figure 7. Coolant temperature vs time for the1000 watt block heaters in a Ford

eight cylinder engine at various coldroom temperatures.

17 CANADIAN AGRICULTURAL ENGINEERING, VOL. 14. NO. 1. JUNE, 1972

During the first two hours of blockheater operation, 67 to 77 percent of thetotal coolant temperature increase wasexperienced (Table III). In the fifth houronly 4 to 8 percent of the total temperature increase was experienced. The totalcoolant temperature increase was greateras the size of heater was increased and

also the coolant temperature obtainedwhen using only one block heater wasapproximately 1/2 that experienced withtwo block heaters.

The total average increase in crankcaseoil temperature after five hours of heateroperation for the various sizes of blockheater in the eight cylinder engine isShown in Table IV. The total increase in

oil temperature varied from 10°F(-12°C)when using 2-400 watt block heaters to

25°F (-4°C) when using 2-1000 wattheaters. The increase in oil temperaturewhen using only one block heater variedfrom 6°F (-15°C) for 1-400 watt heaterto 9°F (-13°C) for 1-1000 watt heater.

Combustion chamber air temperatureswere obtained for two of the combustion

chambers on the eight cylinder engine.Air temperatures within the combustionchambers were found to be identical to

the coolant temperatures surrounding thecombustion chambers.

Comparison of Heater Effectiveness inthe Six and Eight Cylinder Engines

The total coolant temperature increasein the six cylinder engine after 5 hourswas greater for each size of heater thanthe increase in coolant temperature using

TABLE HI RATE OF ENGINE COOLANT WARMUP USING VARIOUS BLOCKHEATERS IN AN EIGHT CYLINDER FORD ENGINE

Tempierature rise per hour (:nF) & °/'oSize of heater No. of heat

ers used

<Df total temperal:ure rise

element (watts) 1 hr. 2 hr. 3 hr. 4 hr. 5 hr. Total "F/KWH

400 2 26 21 11 6 •3 67 418

39% 31% 17% 9% 4%

400 1 14 10 5 4 3 36 450

39% 28% 14% 11% 8%

600 2 40 28 15 8 5 96 400

42% 29% 16% 8% •5%

600 1 21 13 7 5 3 49 408

43% 27% 14% 10% 6%

750 2 54 30 15 9 5 113 377

48% 27% 13% 8% 4%

750 1 28 14 9 5 3 59 393

48% 24% 15% 8% 5%

1000 2 74 39 17 IP 6 146 365

50% 27% 12% ' 7% . 4%

1000 1 34 19 11 7 4 75 374

46% 25% 15% 9% 5%

TABLE IV CRANKCASE OIL TEMPERATURES USING VARIOUS BLOCKHEATERS IN AN EIGHT CYLINDER FORD ENGINE

Size of heater No. of heaters Tota1 temperatureelement (watts) used rise in 5 hours ( °F)

400 2 10

600 2 12

750 2 191000 2 25

400 1 6600 1 7

750 1 91000 1 9

CANADIAN AGRICULTURAL ENGINEERING, VOL. 14, NO. 1, JUNE, 1972

only one heater in the eight cylinderengine. Possible causes for this differencecould be the greater amount of coolantwhich the one block heater must heat and

also due to the greater heat loss from alarger surface area exposed in the case ofthe eight cylinder engine. Although usingtwo block heaters in the eight cylinderengine resulted in higher total temperature increases of the coolant, the amountof temperature rise per kilowatt-hour wasless for the eight cylinder engine than forthe six cylinder engine. A comparison ofthe amount of temperature rise perkilowatt-hour input, based on the totaltemperature rise in 5 hours, for thevarious sizes of heaters in both the six

and eight cylinder engines is shown inTables I and III.

The difference in crankcase oil tem

perature when using only one heater inboth the six and eight cylinder engineswas negligible. Crankcase oil temperatureswhen using two heaters in the eightcylinder engine were approximatelydoubled.

CONCLUSIONS

The rate of increase in coolant temperatures, based on a percentage of thetotal increase, was slightly higher for theblock heaters in the six cylinder enginethan for the heaters in the eight cylinderengine. For the six cylinder engine, 76 to80 percent of the total temperatureincrease was experienced in the first twohours of operation while an increase of67 to 77 percent was experienced in theeight cylinder engine.

Equilibrium temperatures of thecoolant were reached after five hours of

block heater operation. The total rise incoolant temperature, for a given size ofheater, was the same regardless of initialcold room temperatures. The total temperature increase of the coolant in the sixcylinder engine varied from 45°F (25°C)when using a 400 watt heater to 112°F(62°C) when using a 1000 watt heater.Total temperature rise in the eightcylinder engine varied from 36°F (20°C)when using 1-400 watt heater to 146°F(81°C) when using 2-1000 watt heaters.

The total rise in crankcase oil temperature in the six cylinder engine rangedfrom 3°F (-16°C) to 11°F (-12°C)depending on the size of block heater. Inthe eight cylinder engine, the total rise incrankcase oil temperature varied from6°F (3°C) when using 1-400 wattheater

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to 25°F (14°C) when using 2-1000 wattheaters.

The temperature of the air inside theengine combustion chambers was foundto be identical to the coolant temperaturesurrounding the combustion chambers.

SUMMARY

Cold weather conditions during thewinter months in Western Canada dictatethat automobiles be equipped with anengine heater to enhance ease of starting.The rate of coolant temperature rise as

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well as the total temperature rise, whenusing 400, 600, 750 and 1000 watt blockheater elements in both a six and eightcylinder engine, were investigated atvarious simulated weather conditions in a

cold room.

The rate of coolant temperatureincrease was most rapid during the firsttwo hours of block heater operation withequilibrium temperature being reachedafter five hours. The total rise in coolanttemperature was dependent upon the sizeof heater used, but was the same for one

size of heater regardless of initial coldroom temperature.

REFERENCES

1. Environmental Data Service. 1969.Climates of the world. U.S.Department of Commerce Environmental Science Service Administra

tion. January.

2. Zoerb, G.C., 1967. University testsengine block heaters. Design Engineering 13 (11): 61.

CANADIAN AGRICULTURAL ENGINEERING, VOL. 14, NO. 1, JUNE, 1972