Engine tuning

For other uses, see Tuning (disambiguation).
Vintage engine testing equipment that can test ignition timing, ignition dwell, manifold vacuum and exhaust emissions

Engine tuning is an adjustment, modification of the internal combustion engine, or modification to its control unit, otherwise known as its ECU (Engine Control Unit). It is adjusted to yield optimal performance, to increase an engine's power output, economy, or durability. These goals may be mutually exclusive, and an engine may be detuned with respect to output (work) in exchange for better economy or longer engine life due to lessened stress on engine components.

It has a long history, almost as long as the development of the automobile in general, originating with the development of early racing cars, 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 overhauls. 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.

Setting the idle speed, fuel/air mixture, carburetor balance, spark plug and distributor point gaps, and ignition timing were regular maintenance items for all older engines and the final but essential steps in setting up a racing engine. On modern engines, equipped with electronic ignition and fuel injection, some or all of these tasks are automated, although they still require periodic calibration.

Engine tune-up

Main article: Tune-up

A tune-up usually refers to the routine servicing of the engine to meet the manufacturer's specifications. Tune-ups are needed periodically as according to the manufacturer's recommendations to ensure an automobile runs as expected. Modern automobiles now typically require only a small number of tune-ups over the course of an approximate 250,000-kilometre (160,000 mi) or a 10-year lifespan.

Tune-ups may include the following:

In early days, mechanics finishing the tune-up of a performance car such as a Ferrari would take it around a track several times to burn out any built-up carbon; this is known as an Italian tuneup.

Chip tuning

Main article: Chip tuning

Modern engines are equipped with an engine management system (EMS)/Engine Control Unit (ECU) which can be modified to different settings, producing different performance levels. Manufacturers often produce a few engines which are used in a wider range of models and platforms, and this allows the manufacturers to sell automobiles in various markets with different regulations without having to spend money developing and designing different engines to fit these regulations. This also allows for a single engine to be used by several different brands, tuned to suit their particular buyer's market.

Performance tuning

Performance tuning focuses on tuning an engine for motorsport, although many such automobiles never compete but rather are built for show or leisure driving. In this context, the power output, torque, and responsiveness of the engine are of premium importance, but reliability and fuel efficiency are also relevant. In races, the engine must be strong enough to withstand the additional stress placed upon it, and so is often far stronger than any mass-produced design on which it may be based, and also that the automobile must carry sufficient fuel. In particular, the transmission, driveshaft and any other load-transmitting powertrain components may need to be modified in order to withstand the load from the increased power.

In almost all 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 air/fuel mixture into the engine, increasing compression ratio (requires higher octane gas) 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 air/fuel mixture, air fuel ratio meters are often used. The weight of this fuel will affect the overall performance of the automobile, 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 automobile.

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 smoothness at low engine speeds for improvements at high engine speeds.

Furthermore, tuners may also use analytical tools to help evaluate and predict the effect of modifications on the performance of the vehicle.

Definitions

Overhaul

An overhauled engine is an engine which has been removed, disassembled (torn down), cleaned, inspected, repaired as necessary and tested using factory service manual approved procedures. The procedure generally involves honing, new piston rings, bearings, gaskets, oil seals. When done by a competent engine builder the engine will perform as new. The engine may be overhauled to 'new limits' or 'service limits', or a combination of the two using used parts, new original equipment manufacturer (OEM) parts, or new aftermarket parts. The engine's previous operating history is maintained and it is returned with zero hours since major overhaul.

Many times aftermarket part manufacturers are the OEM part suppliers to major engine manufacturers (e.g. Ishino manufactures both the OEM and the aftermarket cylinder head and valve cover gaskets for the Nissan VG30E. Often the Nissan logo is imprinted on the OEM part while the OEM suppliers brand will be imprinted on the same exact part when offered aftermarket.)[1]

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. It may or may not include a valve job. A major overhaul however covers the whole engine assembly, which requires the engine to be removed from the vehicle and transferred to an engine stand. An overhauled engine refers to a major overhaul. By comparison, a major overhaul costs more than a top overhaul.

'New limits' are the factory service manual's approved fits and tolerances that a new engine is manufactured to. This may be accomplished by using standard or approved undersized and oversized tolerances. 'Service limits' are the factory service manual's allowable wear fits and tolerances that a new limit part may deteriorate to and still be a usable component. This may also be accomplished using standard and approved undersized and oversized tolerances.[1]

Rebuild

A 'rebuilt engine' is an engine that has been overhauled using new and used parts to new limits by the manufacturer or an entity approved by the manufacturer. The engine's previous operating history is eradicated and it comes with zero hours total time in service, even though the engine may have had used components installed that have many hours of previous operating history. Production rebuilders or marketing material sometimes use the word 'remanufactured' to describe these engines.[1]

Remanufactured

Remanufacturing is a 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 not always 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

To blueprint an engine means to build it to exact design specs, limits and tolerances created by its oem engineers or other users, such as high performance racing or heavy duty industrial equipment. It is similar to how many other kinds of mechanical machinery are researched, designed and built, such as a submarine or a hydraulic press.

Because few have the capability to actually blueprint, and because of the monetary incentive of claiming one has performed the work, many people have come to believe blueprinting only means that all the specifications are double-checked. Serious efforts at blueprinting result in better-than-factory tolerances, possibly with custom specifications appropriate for the application. Common goals include engine re-manufacturing to achieve the rated power for its manufacturer's design (because not all mass-production engines put out the rated power), and to rebuild the engine to make more power from a given design than otherwise intended (because custom engines can often be redesigned to different specifications). Blueprinted components allow for a more exact balancing of reciprocating parts and rotating assemblies so that less power is lost through excessive engine vibrations and other mechanical inefficiencies.

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. While it has nothing to do with blueprinting per se, lightening components is generally an advantage 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 0.006 inches for general use in a consumer automobile application. For an endurance racing engine which runs at consistently high temperatures, a "blueprinted" specification of 0.0045" to 0.0050" may be desired. For a drag-racing engine which runs only in short bursts, a tighter tolerance of 0.0035 to 0.0040 inch is optimal. Thus "blueprint" can mean tighter or looser clearances, depending on the goal.

History

'Igniscope' ignition tester, with display tube and outer case missing.

The 'Igniscope' electronic ignition tester was produced by English Electric during the 1940s, originally as 'type UED' for military use during World War II.[2] The post-war version, 'type ZWA' electronic ignition tester, was advertised as "the first of its kind, employing an entirely new technique".[3]

The Igniscope used a cathode ray tube, giving an entirely visual method of diagnosis. It was invented by D. Napier & Son, a subsidiary of English Electric, and British Patents 495478, 495547 and 563502 applied.[4] The Igniscope was capable of diagnosing latent and actual faults in both coil and magneto ignition systems, including poor battery supply bonding, points and condenser problems, distributor failure and spark plug gap.[5] One feature was a "loading" control which made latent faults more visible.

The UED manual includes the spark plug firing order of the tanks and cars used by the British armed forces[6]

References

  1. 1 2 3 MR, MR. "Engine Overhaul Terminology and Standards". Mattituck Services, Inc. Retrieved 20 August 2011.
  2. ↑ Instruction manuals published by The English Electric Company Ltd., Industrial Electronics Department, Stafford.
  3. ↑ Advertising brochure, page 2
  4. ↑ Edit by Mr. J. B. Roberts, May 1948, to note on page 7 of the brochure for the Model ZWA
  5. ↑ Early military and later commercial instruction manuals
  6. ↑ Manual for the "Igniscope" UED tester, Appendix 1

See also

Wikibooks has a book on the topic of: Automobile Repair/Spark plugs
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