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The variation in the decoupling effect of exhaust flexible couplings under a vertical preload caused by changes in the direction of the exhaust pipe routing was investigated. Both self-supporting and underbody flexible couplings were tested. The results indicate that, in general, a preload decreases the decoupling efficiency of both types of flexible couplings. In addition, the results indicate that the efficiency of the flexible coupling is effected by the following three conditions: the direction of preload with respect to gravity, the location of the preload relative to the coupling, and the stiffness of the various components of the flexible coupling.

The pneumatic air brake system for heavy commercial trucks is composed by a large number of components, aiming its proper work and compliance with rigorous criteria of vehicular safety. One of those components, present along the whole vehicle, is the air brake tube, ducts which feed valves and reservoirs with compressed air, carrying signals for acting or releasing the brake system. In 2011, due to a lack of butadiene in a global scale, the manufacturing of these tubes was compromised; as this is an important raw material present on the polymer used so far, PA12. This article introduces the methodology of selecting, developing and validating in vehicle an alternative polymer for this application. For this purpose, acceptance criteria have been established through global material specifications, as well as bench tests and vehicular validation requirements.

During the development of a new friction material, besides the interface between lining/drum is also fundamental take in account all aspects involving the attachment of the linings on the brake shoes. This paper presents an optimization approach to the development and manufacturing parameters of brake linings, applied on medium and heavy duty commercial vehicles, aiming to assure the correct specification of the riveted joint clamp forces. These evaluations were conducted based on the quality tools documents and the theoretical aspects of the product usage as well as the modeling of key elements of the referred mechanism throughout various known applications. A calculation methodology was developed based on brake geometry, its generated forces and braking reactions required for each vehicle family.

Two-stroke cycle direct injection engines can achieve adequate stability at idle with stratified combustion at very lean overall air-fuel ratio, but exhaust temperature is very low. A rotary valve system was designed to spill charge from the cylinder into the intake tract during the compression stroke, in order to allow stable operation at lower engine delivery ratio and thereby increase exhaust temperature. Reduction of the engine delivery ratio was not achieved due to the poor scavenging characteristics of the swirl liners used, which resulted in high content of exhaust residual gas in the spill recirculation flow. Although the concept objective of higher exhaust temperature was not realized, the results indicate that the concept may be feasible if high purity of the spill recirculation flow can be achieved in conjunction with high trapping efficiency.

The automotive industry has been increasingly researching and working on improving vehicle and passenger safety over the years. Following countries such as the United States and European Union, the Brazilian government has been publishing many resolutions with the objective of improving the safety of their fleet. With the publication of resolution 312 from CONTRAN (National Traffic Counsel), on April 3rd, 2009, the installation of ABS (Anti-lock Brake System) feature has become mandatory for all car and truck models to be sold in Brazil, following a staggered implementation starting on January 1st, 2010. The ABS system adds to the vehicle's current brake system, not allowing the wheels to lock during braking, which helps preserve the vehicle's stability and improve its safety, thus avoiding accidents. The technology, which is already available in a few car models, is not yet developed for the heavy trucks applications in this market.

A number of service fatigue history summarization statistics are examined for their suitability in regenerating the history in the laboratory. Evaluation criteria applied include: fatigue damage-per-level equivalence, implementation simplicity, waveform similarity, and fatigue life equivalence. The results suggest that a three-dimensional “From-To” matrix that includes sequence information about the original variable amplitude histories, is optimal for service history reconstruction.

A straight cut tailpipe tip was empirically evaluated for the effect that the tip's orientation to a cross-wind had on the ability to reduce exhaust system backpressures associated with the purging of the combustion products. The straight across tip was attached to a vehicle at various angles of inclination to their axes while exhaust back pressure and performance readings were recorded. Testing indicated that there is a preferred orientation to reduce backpressure. Attempts to match on-vehicle data with wind tunnel data were met with partial success.

One of the difficulties in predicting the structural behavior of vehicles such as the full size pickup trucks is the non-linearities involved during the course of the durability events. The current practice in durability and fatigue life prediction of vehicles is to conduct fatigue analysis on the structure using the measured road loads and estimate the fatigue incurred using the in-house and commercially available programs. In this paper the authors attempt to seek a different solution to the durability problem by conducting an upfront non-linear analysis. The results are then compared with the prediction by the fatigue life program in addition to the durability test results obtained on the early prototypes. To conduct the non-linear analysis ABAQUS FEA program is chosen for this investigation and for the linear analysis MSC/NASTRAN is utilized. Subsequently in-house fatigue program is used to predict the fatigue incurred.

This paper presents the experience of Ford Motor Company and Hitachi Metals Ltd., in the development and design of the exhaust manifolds for the new 1997 Ford 6.8L, Vl0 gasoline truck engine. Due to the high-exhaust temperature 1000 °C (1832 °F), heat-resisting nodular graphite irons, such as high-silicon molybdenum iron and austenitic iron with nickel cannot meet the durability requirements, mainly thermal fatigue evaluation. The joint effort by both companies include initial manifold design, prototype development, engine simulation bench testing, failure analysis, material selections (ferritic or austenitic cast steel), production processes (casting, machining) and final inspection. This experience can well be applied to the design and development of new cast stainless-steel exhaust manifolds in the future. This is valid due to the fact that US EPA is requiring all car manufacturers to meet the new Bag 6-Emission Standards which will result in increased exhaust gas temperature.

A tunable stamped collector was developed to improve vehicle performance, drive-by noise and subjective noise quality, and reduced thermal stress concentrations. The stamped collector is located at the junction of the legs of the down pipe/catalytic converter assembly for a transverse mounted V-6 engine and acts to equalize the leg length of the down pipe, as well as provide acoustic tuning volume. This collector differs from most other methods to equalize leg lengths on transverse mounted engines in that it has a tuning chamber incorporated into the design itself, which allows for specific noise frequencies to be reduced. Performance characteristics were measured for a conventional down-pipe and the stamped collector using the following analysis techniques: Frequency analysis of tailpipe noise emissions. Drive-by noise emissions. Horsepower measurements using an engine dynamometer.

Downhill tests are widely used as a method of evaluation, development and validation of braking efficiency, friction pair durability, braking balance, as well as fade characteristics and recovery of friction material properties. This test procedure is used for both: passenger vehicles and light & heavy commercial vehicles. The energy levels in the brake system are higher on commercial vehicles and the thermal characteristics much more critical. Added to the fact that such tests are conducted on public highways, it has an intrinsic security risk for both the vehicle tested and all others around. Until a few years ago, it was still feasible to conduct tests downhill on different routes keeping a high security level. Given an increasing traffic on highways, where the test is currently carried out, a need to create a similar downhill procedure (called Guaporé Mountain Test) within a Proving Ground under controlled conditions has been noticed.

A new method to predict brake squeal occurrence was developed by MSC under contract to Ford Motor Company. The results indicate that the stability characteristics of this disc brake assembly are governed mainly by the frictional properties between the pads and rotor. The stability is achieved when the friction coefficient of the pads is decreasing as the contact force increases. Based on the results, a stable brake system can be obtained without changing the brake structure by incorporating the appropriate frictional coefficient in the brake system. The method developed here can be also used as a tool to test the quality of any brake design in the early design stage.