Surface Temperatures
Detailed Information and References

Underhood Surface Temperature Tests: Summary of Published Results

1999 Ford Explorer [1]
Engine idle for approximately 1 hour at 1500-1800 RPM
Measurements made with welded thermocouples

Left Exhaust Manifold Runner Cylinder 3 610oF
Left Exhaust Manifold Collector 750oF
Right Exhaust Manifold Runner Cylinder 2 540oF
Right Exhaust Manifold Collector 720oF
Left Exhaust Manifold Take-Down Pipe 610oF

1999 Honda Accord [2]
Engine idle for approximately 70 minutes at 1500-1800 RPM
Measurements made with welded thermocouples

Left Exhaust Manifold Runner Cylinder 3 610oF
Right Exhaust Manifold Runner Cylinder 4 514oF
Right Exhaust Manifold Collector 754oF
Left Exhaust Manifold Heat Shield Surface 178oF

1999 Chevrolet Camaro [3]
Engine idle for approximately 3 hours for the test vehicle, and 1 hour for the control vehicle, for 1500-1800 RPM
Measurements made with welded thermocouples

  Control Vehicle Test Vehicle
Right Exhaust Take-down pipe 750oF 720oF
Exhaust Manifold Runner Cylinder 1 790oF 680oF
Right Exhaust Manifold Collector 750oF 900oF
Exhaust Manifold Runner Cylinder 4 970oF 970oF
Exhaust Manifold Runner Cylinder 3 820oF 750oF

Two Camaros were used in full-scale burn tests. One was a control vehicle that had OEM parts; the test vehicle had an HVAC component made with flame-retardant chemicals. Both Camaros were running at high idle at the time of the crash test. The report also documented a 210 degrees F drop in the temperature of the control vehicle exhaust manifold runner for cylinder 4 within 3 minutes after the time of the crash test. It did not specify whether the engine remained running after the crash test.

1996 Dodge Caravan Sport [4]

  34 mph Idle for 11 min. (900 RPM) Idle 900 RPM 11 minutes + ~1200 RPM 20 min.
Exhaust gas (in manifold) 1134oF 802oF 1008oF
Catalytic converter surface 667oF 396oF 563oF
Front exhaust manifold surface 275oF 277oF 282oF

Instrumented tests of 4 vehicles [5]
Thermocouples attached with hose clamps

Qualification: This study was superseded by a later study by the same author [9] that showed the instrumentation used in the original study under report actual temperatures, potentially by a significant amount. There are few published studies of surface temperature, so values from the original paper [5] are used herein for reference only, and to represent the differences from one test condition to another. The absolute temperatures should not be relied upon.

Table 6: Summary of measured temperatures from the hottest vehicle components
 during the level road driving tests

Note: Cells that exceed the lowest autoignition temperature of underhood fluids are shaded

 

Table 7: Summary of measured temperatures from the hottest vehicle components
 during the uphill driving tests

Note: Cells that exceed the lowest auto ignition temperature of underhood fluids are shaded

The hill for these tests was a 7% grade.

Instrumented tests of 3 vehicles [6]
Thermocouples attached with hose clamps

Qualification: Because this study was conducted with thermocouples attached with hose clamps the absolute temperatures should not be relied upon and may underestimate the actual temperatures by a significant amount.

Tests were conducted comparing the effect on exhaust system surface temperatures for E85 (mixture of 85% ethanol and 15% gasoline) versus 100% gasoline. It was found that the surface temperature differences were minimal. Tests were performed on surface streets with speed limits from 25-70 mph and involved some variations in traffic conditions. Representative graphs (below) show the ranges of measured surface temperatures for both fuels throughout the 40 minute, 23 mile driving cycle.

 

 

References

Engine compartment surface temperatures - recent studies:

  1. Santrock, J., LeDue III, D., "Full Scale Vehicle Fire Tests of a Control Vehicle and a Test Vehicle Containing an Intumescent Paint on its Underbody," NHTSA docket number 98-3588-204, 1998.
  2. Santrock, J., Hodges, S., "Evaluation of Fire Suppression Systems in a Full Scale Vehicle Fire Test and Static Vehicle Fire Tests," NHTSA docket number 98-3588-202, 1998.
  3. Santrock, J., "Full Scale Vehicle Fire Tests of a Control Vehicle and a Test Vehicle Containing an HVAC Module Made from Polymers Containing Flame Retardant Chemicals," NHTSA docket number 98-3588-190, 1998.
  4. Jensen, J. et al., "Evaluation of Motor Vehicle Fire Initiation and Propagation; Part 2: Crash Tests on a Passenger Van," NHTSA docket number 98-3588-30, 1998.
  5. Fournier, E., "Under Hood Temperature Measurements of Four Vehicles," MVFRI, 2004.
  6. Engle, J. et al., "A Comparison of the Effect of E85 vs. Gasoline on Exhaust System Surface Temperatures," SAE 2007-01-1392, 2007.
  7. Eriksson, L., "Mean Value Models for Exhaust System Temperatures," SAE 2002-01-0374, 2004.
  8. Ranganathan, D., et al., "Exhaust Manifold Gas Temperature Predictions using System Level Data Driven Modeling," SAE 2005-01-0698, 2005.
  9. Spreen, K., et al., "Catalytic Converter Thermal Environment Measurement Under Dynamometer Simulated Roadloads," SAE 000-01-0216, 2000.
  10. Fournier, E., Bayne, T., "Under Hood Temperature Measurements," SAE 2007-01-1393, 2007.

The following studies provide measurements made with infra-red (non-contact) thermometers that were not corrected for surface conditions. Measurements appear to include a large variability and should be used with caution.

  1. Jensen, J. et al., "Evaluation of Motor Vehicle Fire Initiation and Propagation; Part 8: Crash Tests on a Sport-Utility Vehicle." NHTSA docket number 98-3588-139, 1998.
  2. Jensen, J. et al., "Evaluation of Motor Vehicle Fire Initiation and Propagation; Part 11: Crash Tests on a Front Wheel Drive Passenger Vehicle." NHTSA docket number 98-3588-179, 1998.
  3. Authors rely upon proprietary data from surface temperature tests they conducted which are not available for publication.
  4. Santrock, J. “Flammability Properties of Engine Compartment Fluids Other than Gasoline,” NHTSA 98-3588-193, 1998.
  5. Colwell, J. D., et al., “Hot Surface Ignition of Automotive and Aviation Fluids,” Fire Technology, 41, pages 105-123, 2005.

Engine compartment surface temperatures - studies of older vehicles:

  1. Gulau, J., "Temperature Environment of Engine Compartment Wiring," SAE 710093, 1971.
  2. Harrison, R., "Catalytic Converter Temperature Tests," SAE 760781, 1976.
  3. Johnson, N., Sanderson, S., "Spilled Fuel Ignition Sources and Countermeasures," DOT-HS-501 722, 1975.

Studies of ignition temperatures

  1. LaPointe, R., et al., "Hot Surface Ignition of Gasoline on Engine Materials," SAE 2006-01-1013, 2006.
  2. Davis, S., et al., "Hot Surface Ignition of Flammable and Combustible Liquids," SAE 2006-01-1014, 2006
  3. Epling, W., et al., "Evaluation of Automobile Fluid Ignition on Hot Surfaces," SAE 2007-01-1394, 2007.
  4. Somandepalli, V., et al., "Hot Surface Ignition of Ethanol-blended Fuels and Biodiesel," SAE 2008-01-0402, 2008.