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[ERLEDIGT] Änderungen am 3.4L V6 (LA1) ab 2003
#1
Hallo Kollegen,
ich bin da gerade drüber gestolpert weil ich die Durchmesser meiner Kipphebel-Befestigungsgewinde gesucht habe. Vielleicht ist diese Info für euch auch nützlich. Leider wurde für die Export-Modelle die leidige AIR beibehalten.

2003 Model Year Summary
• Revised Crankshaft Bearing and Timing Ring
• Revised Cylinder Heads
• Revised Pushrods
• Revised Camshaft Journal
• Water Pump
• Air Injection Reaction (AIR) Eliminated
• Iridium Spark Plugs
• Maximum Oil Change Interval Extended
• Improved Starter Solenoid

FULL DESCRIPTIONS OF NEW OR CHANGED FEATURES

REVISED CRANKSHAFT BEARING AND TIMING RING
The thrust bearing on the 3.4L V6 (LA1) has been modified to optimize piston and bore oiling. The thrust bearing is fitted to the 3400's third main bearing cap to control the fore-aft movement of the crankshaft. The lower half of the bearing now has slots machined in a starburst pattern on its flange. Oil at the bearing cap is squeezed through the slots and forced in a fan pattern under the pistons and into the cylinder bore, providing another oil distribution path. This simple modification pays big dividends in improved internal lubrication and even longer engine life.
3400s built for Chevy Venture, Pontiac Montana and Oldsmobile Silhouette also have a new crankshaft reluctor or timing ring. In other 3400s the timing ring is machined into the middle of the crankshaft. Those built at Ramos, Arizpe, Mexico plant have a new assembled ring. This two-piece, fine-blank ring is heat-shrunk on the crankshaft and encoded with a 24X tooth pattern. This timing ring provides the basis for future 3400 developments.

REVISED CYLINDER HEADS
The 3.4L cylinder head castings are tapped with 8-millimeter holes for the rocker arm bolts, reducing the tap size from 10 millimeter, and the rocker arms are secured with 8-millimeter bolts. This change commonizes machining and increases assembly efficiency.

REVISED PUSHRODS
Pushrods in the 3.4L are no longer heat-treated. The pushrod guides are now made of low friction nylon, rather than steel, and no longer need heat-treating to limit wear.

REVISED CAMSHAFT JOURNAL
The 3.4L front camshaft journal has been revised with a new timing pattern. This journal is now machined with a 50/50 pattern of raised and lowered semi circles, rather than a single boss or lug. The operating principal for ignition and fuel injection timing has not changed, but the new timing pattern requires a slightly smaller cam sensor and modifications to the fuel injection wiring harness. The new timing pattern was introduced in anticipation of future LA1 development.

WATER PUMP
The 3.4L water pump has a more efficient impellor design and the latest sealing technology, featuring a drip collector under the shaft. Most water pump seals are designed to release a few drops of coolant at a constant rate. With the drip collector, the drops are contained and evaporate. The drips are less likely to be mistaken for a leak.

AIR INJECTION REACTION (AIR) ELIMINATED
The AIR system has been removed for most applications. AIR was used to lower exhaust emissions by injecting warm, fresh air into the combustion process to create an exothermic reaction. The reaction warmed the catalytic converter more quickly, speeding catalyst light-off and reducing emissions during cold starts--a critical phase in certification tests. AIR has become redundant because of efficiency improvements in catalytic converters, spark plugs, oxygen sensors and engine management calibration. The 3400 meets all 2003 federal and California emission standards without AIR.
For 2003, AIR is removed from 3400s for Chevrolet Venture, Pontiac Montana and Aztek, Oldmobile Silhouette and Buick Rendezvous (the system had been removed from passenger car applications prior to 2003). AIR continues on engines exported to Europe, where regulation requires lower oxides of nitrogen (NoX) emissions. These engines are equipped with a new air pump.

IRIDIUM SPARK PLUGS
The 3.4L benefits from the latest spark plug technology. The new plug has an iridium core in the conductor and the same internal resistance. Iridium helps maintain spark density over the life of the plug. The tip is still coated with platinum, and the spark plug maintains a recommended life of 100,000 miles, yet the electrode design improves combustion efficiency for maximum fuel economy and minimum emissions.

MAXIMUM OIL CHANGE INTERVAL EXTENDED
New calibrations in the Powertrain Control Module (PCM) extend the oil-change interval in all vehicles equipped with the 3.4L. Engineers have adjusted the Oil Life System to account for widespread use of the new GF-3 motor oil. GF-3 (for “Gasoline Fueled, Standard 3’’) contains a friction modifier, or an additive that makes the oil molecules more slippery. A new refining process leaves molecules in the base oil more stable. The oil degrades less with heat and retains proper lubricating properties longer.
Most oil change indicators work according to a predetermined mileage interval, which in turn is based on the oil’s anticipated life under some generalized operating cycle. In the 3.4L, the PCM records a number of variables, including engine speed, temperature, load or rpm variance, and period of operation at any given load and temperature. With this information, the Oil Life System calculates oil degradation and recommends an oil change when the oil is near the end of its useful life, when an oil change is actually needed. With the 2003 revisions, maximum oil change intervals have been increased approximately 20 percent. There is no upward limit on the interval. The owner’s manual in cars and trucks equipped with the 3400 will continue to recommend an oil change at least once a year.
The benefits of the unlimited mileage interval, measured by customer convenience, maintenance cost or environmental impact, are obvious. The customer should never pay for an unnecessary oil change again. Using oil for its true useful life results in less petroleum consumed and less used motor oil to be recycled or disposed of.

IMPROVED STARTER SOLENOID
The starter solenoid on all 3.4-liter engines has been improved to virtually eliminate the possibility of icing during cold-weather operation. Because of its typical location in most vehicles, the starter and its control solenoid can be exposed to moisture and ice during the winter. The solenoid's internal spool is now made of a material called liquid crystal polymer (LCP), which does not absorb moisture. Further, the solenoid wire terminals have been redesigned in a tapered, round shape rather than a flat shape to reduce the possibility that moisture and ice can collect on them.

viele Grüße,
Helmut
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#2
Vielen Dank für die Info!
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