Tiger & Alpine Cooling Tales Are All Hot Air
(Please note:  Clicking on the images will open larger copies of the images)

By: Tiger Tom with Chuck & Andy King

There are many tales (pun intended) about Tiger and Alpine overheating scenarios and even more cures. The Tiger community is abound with antidotes that profess successful cures for overheating. Few are embraced collectively by the Tiger marque. There is an ongoing, sometimes heated (pun intended), dialogue regarding the "best" cooling system design approach. Little has been done to objectively and factually define effects of the various overheating cures and make recommendations for the marque …until now.

During the summer and fall of 2000 an engineering study under controlled and documented conditions was performed to validate, debunk and identify the most practical cures for overheating at idle and typical interstate driving conditions. No effort was expended to address cooling during application of continuous high power high speed racing conditions. However, the outcome of our study may reinforce some of these conditions.

We measured and quantified cooling effects like running the heater, opening the hood, adding LAT fender vents, blocking the space in front of the horns, high volume water pumps, water wetters, a variety of radiators, electric and engine driven fans, shroud design, smaller water pump pulleys, etc.

Before proceeding, the reader needs to know our definition of overheating. For purposes of this study, we have designated overheating as the condition where water temperature caused a carburetored car to perform erratically at idle (about 215° F) because of fuel percolation in the carburetor. While this study was primarily for Tiger overheating, some data and results apply to Alpine's as well.

MISSION

Our purpose for this study was to dispense with the myriad of Tiger community antidotes and factually determine the most effective and practical cooling system design that reduces overheating during idle and typical interstate highway driving conditions for a stock Tiger. The results will be shared with the Tiger and Alpine marque with the intent that this data will help unify the Tiger marque to a commonly accepted approach towards cooling system design.

PROGRAMME OVERVIEW

Our initial attempt was to produce a cooling system design that would have the capacity to maintain engine temperature of 180° F at 85° F plus ambient temperatures during idle and interstate speeds. We changed our idle expectations to approximately 200° F during the testing process. We focused on three areas of the cooling system.

  1. Air flow management

  2. Radiator design

  3. Water distribution (circulation), i.e. from engine to and from radiator.


We tested the following popular cooling system variables using temperature, humidity and air velocity measurement equipment with calibration traceable to National Institute of Science and Technology (NIST).

SUMMARY OF RESULTS

There was no one "magic bullet" that cured overheating. But, we have identified a variety of specific changes that when combined as part of the cooling system will reduce or even eliminate your overheating problem. We produced the most cooling gains through improved airflow management. Radiator design, while important, produced only moderate improvements among a variety of designs. To the dismay of many readers, aluminum radiators were not king of the lair from a cooling prospective. Without airflow improvements, our least measurable gain was via the water circulation system, i.e. radiator single/triple pass, high Volume pump, redistribution of water flow in the engine or to radiator. However, our observations suggest higher volume water pumps may have a positive effect.

Results of this cooling study represent only some of the cooling improvements possible. This test is incomplete.  Hot weather required to perform tests came to an end during the cooler fall months. We were unable to evaluate all the variables we planned to test. Results of this cooling study represent only some of the cooling improvements possible. This test is incomplete.  Hot weather required to perform tests came to an end during the cooler fall months. We were unable to evaluate all the variables we planned to test.

The following cooling system variables when used in unison produced the most significant cooling improvements on our test Tiger. See Figure 1 for idle and Figure 2 for interstate stock and improved test results.

The following produced insignificant or immeasurable cooling improvement compared to stock cooling system.

  • Engine driven fans: Flex-a-lite #414 or #1314 , 14" or smaller diameter.

  • Electric fans: Typically, fans with more than 7 blades of the same diameter were significantly less efficient at cooling and airflow. Some were also much louder and the high pitched noise was irritating.

  • Water Pumps: Stock, High Vol Milodon, Stewart. We did not measure a significant cooling difference with any of the three pumps tested. However, we believe there may be an advantage at idle with the use of a high volume pump when combined with interactions of other cooling system enhancements.

  • Radiators: Our results indicate the popular Griffin and Fluidyne radiators did not perform as well as the stock, FX and CX cores we tested. The Griffin did not perform as well as a stock radiator after some cooling system improvements were made. However, it was one of the best performers on the interstate. The Fluidyne was similar to stock at idle and a moderate performer on the Interstate. Based on observations and test measurements, it is our opinion that thick cores, 2" or greater, aluminum or brass, radiators impede the airflow required for efficient heat transfer at idle and road speed compared to thinner designs. The thick core radiators will likely work well under high power applications at high speeds where air pressure is available to force air through the radiator.

  • Engine compartment venting: Idle or Interstate temp did not change with LAT type fender well ports open or closed in a stock cooling system configuration. Cooling effects of open or closed ports have not been determined since increased airflow enhancements have been made. Contrary to popular perceptions, our data indicates the Tiger's tight engine compartment is not a major restriction to airflow through the radiator at idle or interstate speeds.

  • Miscellaneous: Turning the heater blower on high at Idle reduced Idle temp only 1° F. Test was not performed at interstate speeds.

The addition of Red Line Water Wetter did not produce measurable temperature changes at Idle or on the Interstate.

Making a variety of engine/radiator/expansion tank/water pump water distribution changes did not improve cooling. In fact, some changes caused the idle temperature to increase.

Look at the ADDENDUM TO THIS ARTICLE: to see additional data, performance plots of various configurations and additional explanations of the variables tested.

FAN AIR FLOW (Alpine & Tiger Fans)

Increasing airflow through the radiator is a product of optimum design of the fan, placement in the shroud (1/3 to 1/2 fan blade in shroud) and distance from radiator (1"+)and of course, the shroud. See the FAN AIRFLOW TABLE for airflow rates of some of the fans and shrouds tested.

FAN AIR FLOW

Test # FAN BLADE, ENGINE DRIVEN FANS CFM RADIATOR SHROUD
68 Alpine, 6 blade Series I-II 183 65 Alpine None
72            "                    increased pitch 477 " "
73            "                    " 623 " Tiger, stock
69 Alpine, 4 blade, Series III-up 238 " None
70            "                    increased pitch
Not recommended, blade stress cracks 		320 " None
82 Tiger Stock 623 FX core Tiger, Stock
83 Ford C9DZ-8600, cut down to 14" diameter 697 " "
89             " 953 " Custom
78             "                  15 inch diameter 751 " Tiger, stock
80             "                  15 inch w/increased pitch 843 " "
79 Flex-a-lite #414       (plastic) 14" 550 " "
62                #1314     (SS flex) 14" 623 " "
81 Imperial    #221615 (SS flex) 15" 751 " "
86 Derale      #17015   (SS flex) 15" 926 " "
   
 

JUNK YARD ELECTRIC FANS

      
77 Colt electric, 10"  puller used as a pusher (early Colt) 660 " "
76 Toyota Tercel, 10" pusher ('86) 586 " "
75 Mazda 626, 11" pusher ('89) 696 " "
74 Geo Prism, 11 1/2" pusher ('93) 843 "

"

AIR FLOW OBSERVATION NOTES:

Using fans with the most pitch and the use of a fan shroud produced the most significant gains in airflow. In addition, a design emphasizing completely enclosed shroud also increased airflow.

  1. Test #72 shows the best airflow for Alpine and Test #89 shows the best for Tiger.

  2. Test # 86 is the best airflow  for a Tiger with a stock fan shroud.

  3. Airflow with the Alpine fan, Test #72 was increased with the simple addition of a Tiger shroud Test #73.

  4. Airflow with a stock Tiger fan shroud, Test #83 was increased when using a custom designed enclosed shroud, Test #89.


TEST PROCESS
 Temperature measurements, Idle and Interstate

A stock Tiger with a 260CI engine was used for this test. A thermostat was installed and welded open at its normal 180° F position. A thermocouple in conjunction with a calibrated digital thermometer was installed in a stock hollowed out temperature sender unit that was installed in its stock location. In all testing, temperature measurements were made every two minutes using a calibrated digital timer. The results are presented in Temperature VS Time plots.

Tests were typically performed with ambient temperature range of 85° F to 90° F. Relative Humidity was typically 50% to 60%.

Idle tests were with the car stationary and engine RPM at 850 RPM +50, -0. Interstate test included a controlled thirty eight minute and 63 MPH drive on the interstate circuit.

 

AIR FLOW

A special "air flow buck" was made using the front end of an Alpine to quantify air flow rates of various fan/shroud/radiator combinations. Measurements were made with a calibrated air velocity meter. Test fans were affixed to a motor that ran at 900RPM for all idle testing.


TSI Air Velocity Meter and RPM indicator

 

 

Typical airflow test. Note the block of wood under pulley to replicate the air restriction of the harmonic balancer. Not visible in this test is the use of a Rack & Pinion. This test is evaluating a Flex-a-lite #414 and effects of shroud design changes.

Airflow buck front view

Airflow buck rear view. A two foot length section of the exhaust port is removed to show the velocity probe.

TEST MEASUREMENT

All test measurements evaluated one variable change at a time in order to eliminate interactions of multiple variables (changes)

ADDENDUM TO THIS ARTICLE for more information on test process

EPILOGUE

This test effort has made significant strides in identifying and quantifying optimum cooling system design variables for a Tiger. It is not all-inclusive. Additional work needs to be completed to validate some of our conclusions since we ran out of hot summer weather and options to test. We plan to do additional testing in the Summer of 2001. There just may be a better combination than what we have tested.

We welcome the opportunity to test and validate your cooling system solution including testing your radiator, fan for comparison. Your comments are welcome.

ACKNOWLEDGEMENTS

No effort of this magnitude is done without support of others. Special thanks to the following for allowing us to use their fans, radiators and water wetter for testing.

Dale Akuszewski (Dales Restorations), Tom Ballou, John Engle, Ed Esslinger (SOS meister Kool CAT Eddie), Doug Jennings, (Tiger Auto), Rick McCurdy, Doug Stockman and of course, Andy and Chuck King for sacrificing their Tiger and time to undertake this four month study. Several tanks of gas were used just to check the idle temperatures and hundreds of man-hours were expended among our team of three.

 

Andy King, Tiger owner (left) and Andy's dad Chuck King (right) working on one of the dozens of pump/fan/shroud/radiator changes. 

Figure 1



Figure 2