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Development of a Low Heat-Capacity Exhaust Manifold for SULEV

Article of Honda R&D Technical Review Vol.14 No.2

Summary

A dual-wall exhaust manifold was developed that has low heat capacity in order to reduce the time taken to reach the catalyst activation temperature. An austenitic stainless steel with significantly improved high-temperature strength and oxidation resistance was developed by optimizing the composition design so that the inner tube could be made as thin as possible. The use of this material made it possible to increase the buckling strength at high temperatures and to make the inner tube wall 0.4 mm thick. In United States emission modes, a dual-wall exhaust manifold with an inner tube having a wall 0.4 mm thick is able to reach the catalyst light-off temperature 3 seconds faster than an ordinary single-wall manifold that is 2 mm thick. This achieved a reduction of approximately 22% in hydrocarbon (HC) emissions. The combined application of air-fuel ratio (A/F) control technology and catalyst technology together with the developed exhaust manifold made it possible to reduce the amount of precious metals used in an under-floor converter by approximately 20% compared to a 2001 model vehicle with SULEV specifications.

Reference

(1) Kishi, N. et al.: Development of the High Performance L-4 Engine ULEV System, SAE paper, SAE980415 (1998)
(2) Kitagawa, H. et al.: Super Ultra Low Emission System for “ACCORD SULEV”, HONDA R&D Technical Review, Vol. 12, No. 2, pp. 37-44 (2000)
(3) Kishi, N. et al.: Development of the Ultra Low Heat Capacity and Highly Insulating (ULOC) Exhaust Manifold for ULEV, SAE paper, SAE980937 (1998)
(4) Hashimoto, H. et al.: Development of a Low Heat-capacity, 4-2 Connection Exhaust Manifold for High Output Engines, HONDA R&D Technical Review, Vol. 11, No. 1, pp. 85-92 (1999)
(5) Long, C.J. et al.: The Ferrite Content of Austenitic Stainless Steel Weld Metal, The Welding Journal, Vol. 7, pp. 281-297 (1973)
(6) Ishii, K. et al.: Effect of Ti, Zr and Hf on High-Temperature Oxidation Resistance of Fe-20Cr-5Al-0.1La Alloy Foiles, Materials Transactions, JIM, Vol. 39, No. 10, pp. 1040-1045 (1998)
(7) Fukaya, M.: Material Properties of Fe-Cr-Al Alloy Foil for Metal Support, SAE paper, SAE970790 (1997)
(8) Irvine, K.J. et al.: High-strength austenitic stainless steels, Journal of the Iron and Steel Institute, vol. 199 (2), pp. 153-175 (1961)
(9) Hosoi, Y. et al.: The Effect of Nitrogen Additives on High Temperature Oxidation of Austenite Stainless Steel, The 119th Corrosion Prevention Symposium material “High Nitrogen Stainless Steel – The Current Situation and Problems”, pp. 43-49 (1998)
(10) Ishii, K. et al.: Evaluation of Thermal Fatigue Life on the Exhaust Manifold by Analyzing Restraint Ratio, Seoul 2000 FISITA World Automotive Congress, F2000G295 (2000)

Author (organization or company)

Kazuo ISHII(Tochigi R&D Center)、Takeshi MUNEMURA(Tochigi R&D Center)、Nobuyuki YOSHIDA(Tochigi R&D Center)

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