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Engine tuning or '''engine building''' is the adjustment, modification or design of Internal Combustion Engine s to yield optimal performance, either in terms of power output or economy. It is a popular pastime with amateur mechanics or "gearheads" and " Petrolhead s". It has a long history, almost as long as the development of the Car in general, originating with the development of early Racing Car s, and later, with the post-war Hot-rod movement. ''Tuning'' can describe a wide variety of adjustments and modifications, from the routine adjustment of the Carburetor and Ignition System to significant engine modifications. On older engines, setting the idling speed, mixture, carburetor balance, spark plug and distributor point gaps and ignition timing were both regular tasks on all engines and the final but essential steps in setting up a racing engine. On modern engines some or all of these tasks are automated. At the other end of the scale, performance tuning of an engine can involve revisiting some of the design decisions taken at quite an early stage in the development of the engine. ENGINE TUNE-UP ''Tune-up'' describes the normal, routine adjustments -- without modifications -- of the engine to meet the manufacturer's specifications. Tune-ups are periodically needed, for example every 12 months or 19,000 Km to ensure an automobile runs as expected. Modern vehicles now often run over 160,000 Km (or 10 years) without requiring a tune-up. Tune-ups may include the following:
The engine manufacturer specifies the schedule and method of engine-tuneup. However, the engine tuning that this article focuses on goes far beyond the manufacturer's suggestions. PERFORMANCE TUNING Performance tuning focuses on tuning an engine for Motor Sport , although many cars built by hobbyists never compete but rather are built for display at motor shows or the simple pleasure of owning and driving such a car. In this context (and depending on the particular event), the power output, torque, and responsiveness of the engine are of premium importance, but reliability and economy are also relevant. To win, a car must complete the event. This means the engine must be strong enough to do so, often far stronger than the ''production'' design on which it is based, and also that the vehicle must carry sufficient fuel. The weight of this fuel will affect the overall performance of the car, so fuel economy is a competitive advantage. This also means that the performance tuning of an engine should take place in the context of the development of the overall vehicle. In particular, Transmission , Suspension and Brakes must match the performance of the engine, otherwise the car will be unreliable, uncompetitive, and perhaps extremely dangerous. In most cases, people are interested in increasing the power output of an engine. Many well tried and tested techniques have been devised to achieve this, but all essentially operate to increase the rate (and to a lesser extent efficiency) of combustion in a given engine. This is achieved by putting more fuel/air mixture into the engine, using a fuel with higher energy content, burning it more rapidly, and getting rid of the waste products more rapidly - this increases Volumetric Efficiency . In order to check the amount of the fuel/air mixture, Air Fuel Ratio Meters are often used. The specific ways to increase power include:
The choice of modification depends greatly on the degree of performance enhancement desired, budget, and the characteristics of the engine to be modified. Intake, exhaust, and chip upgrades are usually amongst the first modifications made as they are the cheapest, make reasonably general improvements (whereas a different camshaft, for instance, requires trading off performance at low engine speeds for improvements at high engine speeds), can often improve fuel economy, generally don't affect engine reliability much (because no moving parts are modified), and are in any case essential to take full advantage of any further upgrades.
Examples of models using one engine with different ECU software providing varying specifications: The Volvo V70 D5 Euro IV is available as 126 bhp, 163 bhp, and 185 bhp, all sharing the same 2.4 turbo diesel engine. The Mini One and Mini Cooper are available as 90 bhp and 127 bhp respectively, both sharing the same 1.6 normally aspirated engine. The Ford Focus ST225 and Volvo S40 T5 both share the Volvo 2.5 turbo petrol engines, with different power outputs controlled by the engine management system. There are currently a variety of analytical tools to help tuners evaluate and predict the effect of modifications. Predictive models include RaceSim , RaceDataPower , and data system products from AIM, MoteC, Pi, Stack and others. DEFINITIONS NOTE: None of these terms necessarily mean new pistons, block line-boring, balancing, etc. The proof is in the fine print. Ask your engine builder for details in writing before committing to purchase engine work. Overhaul An engine Overhaul means putting the engine back to factory specifications. This generally involves new Piston Rings , Bearings and gaskets. When done by a competent engine builder, you can be confident the engine will perform as new. A top overhaul only covers the replacement of components inside the Cylinder Head without removing the engine from the vehicle, such as valve and rocker arm replacement. A '''full overhaul''' however covers the whole engine component replacement which requires the engine to be removed from the vehicle, such as replacing the connecting rods and crankshaft bearings. By comparison, a full overhaul service costs more than a top overhaul service. Rebuild Rebuild is a marketing term with no fixed definition. It is often taken to mean a professional overhaul with certain parts replaced with new units whether needed or not. For example some rebuilders will always replace the pistons (which not usually replaced during an overhaul unless damaged). Re-manufacture Re-manufactured is a marketing term to mean an engine put together to match factory specifications e.g. "as new". Although often a buyer may take this to mean all-new parts are used, this is never the case. At the very least, the Cylinder Block will be used, as may most other parts. High-quality rebuilds will often include new pistons and line-boring of the crankshaft and camshaft bores. Blueprinting In engine blueprinting, all the specifications are double-checked. Usually this indicates closer-than-factory tolerances, with custom specifications appropriate for a street car or a race car. The goals usually are to:
or
Ideally, blueprinting is performed on components removed from the production line before normal balancing and finishing. If finished components are blueprinted, there is the risk that the further removal of material will weaken the component. However, lightening components is generally an advantage in itself provided balance and adequate strength are both maintained, and more precise machining will in general strengthen a part by removing stress points, so in many cases performance tuners are able to work with finished components. For example, an engine manufacturer may list a piston ring end-gap specification of 0.003 to 0.005 inches for general use in a consumer automobile application. For an endurance racing engine which runs hot, a "blueprinted" specification of 0.00045 to 0.00050 may be desired. For a drag-racing engine which runs only in short bursts, a tighter 0.00035 to .00040 inch tolerance may be used instead. Thus "Blueprint" can mean tighter or looser clearances, depending on the goal. SEE ALSO |
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