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2003-01-0410 Turbocharging the Chrysler 2.4L Engine

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2003-01-0410 Turbocharging the Chrysler 2.4L Engine Downloaded from SAE International by Old Dominion Univ, Wednesday, October 19, 2016 SAE TECHNICAL PAPER SERIES 2003-01-0410 Turbocharging the Chrysler 2.4L Engine Garry W. McKissick Jr. and David M. Schmidt DaimlerChrysler Corporation Reprinted From: New SI Engine and Component Design (SP-1747) 2003 SAE World Congress Detroit, Michigan March 3-6, 2003 400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 Web: www.sae.org Downloaded from SAE International by Old Dominion Univ, Wednesday, October 19, 2016 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. For permission and licensing requests contact: SAE Permissions 400 Commonwealth Drive Warrendale, PA 15096-0001-USA Email: [email protected] Fax: 724-772-4028 Tel: 724-772-4891 For multiple print copies contact: SAE Customer Service Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-1615 Email: [email protected] ISSN 0148-7191 Copyright © 2003 SAE International Positions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. A process is available by which discussions will be printed with the paper if it is published in SAE Transactions. Persons wishing to submit papers to be considered for presentation or publication by SAE should send the manuscript or a 300 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE. Printed in USA Downloaded from SAE International by Old Dominion Univ, Wednesday, October 19, 2016 2003-01-0410 Turbocharging the Chrysler 2.4L Engine Garry W. McKissick Jr. and David M. Schmidt DaimlerChrysler Corporation Copyright © 2003 SAE International ABSTRACT A turbocharged version of the 2.4L engine has Several internal modifications were required to been developed by the Chrysler Group of DaimlerChrysler satisfy durability and emissions requirements. The Corporation. This new engine is derived from the proven modifications include new valves, pistons, piston rings, 2.4L 4-cylinder, with significant changes to achieve a connecting rods, crankshaft, and bearings. durable, high performance package for the PT Cruiser vehicle. The package includes an integrated turbocharger / A unique, extremely compact exhaust manifold exhaust manifold, oil squirters for piston cooling, and and turbocharger unit was developed to work within the numerous other upgrades to satisfy the demanding minimal under-hood packaging space. The turbocharger performance, emissions, and durability requirements is integrated into the exhaust manifold as one assembly. unique to this powertrain. The purpose of this paper is to This feeds the newly designed aluminum intake manifold describe the mechanical changes to the base engine, the via an air-to-air intercooler mounted in the front fascia. unique turbocharger configuration, and the new parts necessary to accommodate the higher output. 300 300 GENERAL ENGINE DESCRIPTION 250 250 200 200 The 2.4L Turbo engine (Figure 1) shares a common 87.5 mm bore, 101 mm stroke, and 2429 cm3 150 150 BHP (HP) Torque (ft-lbs) displacement with its naturally aspirated (NA) counterpart. 100 100 The rated output, 332 N-m (245 ft-lb) @ 3600 RPM and 50 50 160 kW (215 HP) @ 5000 RPM, (Graph 1) is approximately 51 percent greater in torque and 43 percent 0 0 1500 2500 3500 4500 5500 6500 higher in power than the standard 2.4L engine. RPM Turbo HP NA HP Turbo Torque NA Torque Graph 1. 2.4L Turbo vs. NA Power & Torque Variations of the 2.4L Turbo engine are used in three different vehicles: PT Cruiser, SRT-4, and the Mexican Stratus R/T. Although all versions are derived from the same basic design, there are significant differences (especially manifolds, oil pump, and accessories) due to packaging constraints in each vehicle application. This paper specifically describes the PT Turbo engine. OBJECTIVES The principal design objectives for the engine were to: Figure 1. 2.4L Turbo Engine · Provide significantly improved output to offer increased performance in the PT Cruiser vehicle. Downloaded from SAE International by Old Dominion Univ, Wednesday, October 19, 2016 · Fit within the limited space of the engine process. It was determined early in the program that the compartment without changes to the vehicle desired strength could be obtained from a cast piston structure. without the added cost and potential noise issues of a forging. A full floating pin design was chosen due to the · Achieve maximum performance using high specific output (89.6 hp/l) and cylinder pressures. premium grade fuels and provide satisfactory The “ski-ramp” pop-up on the crown was carried over from operation with “regular” fuel. the 2.4L NA engine. On both the turbocharged and NA 2.4L engines, the ski-ramp design showed improvements · Maintain maximum commonality with the to the combustion chamber air/fuel mixture through existing 2.4L engine, both in design and computational fluid dynamics (CFD) analysis. These manufacturing. improvements were confirmed through dynamometer testing and translated into improved WOT spark and idle stability. The top land height was set at 4 mm to help NEW AND REDESIGNED ENGINE meet hydrocarbon emission requirements. Due to the small top land and the predicted temperatures and COMPONENTS pressures, hard anodizing was added to the top ring groove to prevent microwelding of the upper compression Many new base engine components were ring. necessary to accommodate turbocharging the 2.4L engine. Several of the changes have subsequently been In another effort to reduce crevice volume, the incorporated into the NA engine to further improve its piston is machined with a double-ovality profile. This durability and maintain maximum component machining allows for tighter clearances between the top commonality. land and bore in the pin axis than otherwise would have TM been possible. The skirts are coated with Mahle Grafal PISTONS – New pistons were designed to meet the to protect against scuff and improve NVH. Final piston-to- following requirements: bore clearance was selected to minimize friction during break-in and hot scuff, while still surpassing the goals for - Strength for peak cylinder pressures that are cold and hot NVH. 50% higher than in the NA engine. - Strength at higher in-cylinder temperatures, Due to the high thermal loading expected on the protecting for stoichiometric wide open piston, block-mounted oil squirters were added to help throttle (WOT) operation per US-06 federal cool the pistons. Targeting the underside of the piston test requirements. crown for the full length of its stroke, tests demonstrated - Minimized crevice volume to help meet future that the squirters reduced piston temperatures enough so emissions requirements. that higher cost piston materials were not required. - Reduced mass so that a common balance Temperatures were measured real-time using thermistors shaft assembly could be used for both the mounted at various locations on the piston. This allowed turbocharged and the NA engines. for greater accuracy than end-of-test hardness measurements and also gave information as to the effects of calibration changes on piston temperatures. Through testing, a compression ratio of 8.1:1 was chosen as optimum for such things as performance, WOT spark (knock limit), fuel economy and idle quality. In order to obtain this compression ratio with the proposed pop-up crown geometry, the compression height of the piston was set at an aggressive 28.0 mm. Although this did help in driving the mass of the piston down to 335 grams, 18 grams less than the NA piston, it left very little room in which to package the rings. PISTON RINGS – The 1.2 mm upper compression ring is a barrel shaped, steel ring with a positive twist and a plasma sprayed molybdenum face coating for added wear resistance. The lower compression ring is a 1.5 mm, Figure 2. 2.4L Turbo Piston micro-Napier design made of grey iron. With the full face contact of the micro-Napier edge, no chrome plating is The pistons (Figure 2) are made from a Mahle 124 required in order to meet wear and durability objectives. In eutectic aluminum alloy using a permanent-mold casting addition to cost and environmental benefits, the absence of chrome also yielded the advantages of a faster seat-in Downloaded from SAE International by Old Dominion Univ, Wednesday, October 19, 2016 time for the ring and not requiring outside diameter chamfers that tend to hurt oil consumption. Pressure BEARINGS – The main and connecting rod bearings used balancing of the ring pack, and thus control of the ring in the turbocharged engine are aluminum–tin alloy on motion during piston travel, was obtained through steel backing. They were derived from the bearings used judicious specification of the end gaps. The 2.5 mm oil in the NA versions of this engine, with two major ring assembly is a flexvent (ES-80) three-piece design differences. First, the new connecting rod bearings have featuring a stainless steel expander and chrome-plated holes to feed the oil squirt feature in the connecting rod. steel rails. It was designed to be lower tension and a Second, due to higher transmission thrust loads, the smaller radial thickness than the NA ring, thus upper and lower thrust bearings have contoured faces to maintaining conformability for oil control while reducing provide a higher load-carrying capacity. Standard mains friction for fuel economy. are carried over from the NA 2.4L engine. CONNECTING RODS – New connecting rods were INTAKE MANIFOLD – The unique underhood packaging of designed to meet the durability requirements of the the intercooler plumbing drove a new design for the intake engine.
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