Exhaust Manifold Heat Shielding:Materials and Performance

The use of exhaust manifold heat shields in automobiles is increasing rapidly due to emission laws, autoignition temperatures of fluids and packaging constraints. The standard materials are presented and selected composite combinations offered by Midwest Acoust-A-Fiber along with those offered by competition were tested for thermal testing using SAE 135 1 setup and acoustical testing using ASTM C384.

The SAE 135 1 showed the thermal performance offered by Acoust-A-Fiber composites to be better than the competition. The best performing composites were as follows:

1. 1]
   0.006″ SS 304 / Ceramic Fiber (1/8″ thick, 12 lbs / cu.ft. density) 10.006″ SS 304
2. 2]
   0.006″ SS 304 / Ceramic Fiber (1/8″ thick, 12 Ibs / cu.ft. density)
3. 3]
   0.026″ Aluminized Steel / Ceramic Fiber (1/4″ thick, 8 Ibs / cu.ft. density)

The acoustical testing per ASTM C384 showed Acoust-A-Fiber composites having a better acoustical absorption coefficient and over a broader range of audible frequencies than those offered by competition.

More work needs to be undergone to understand the transmission coefficient of these materials.There is also a need to do extensive dyno testing and FEA modeling to develop heat shield design guidelines for automotive engineers.