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| THE READ FOR SPEED by Ned Erkman |
| CHAPTER 2 |
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Engine Power
The high performance engines that produce power for sports cars and racecars are known as internal combustion engines. As the name implies, an internal combustion engine produces power by combusting fuel and air inside cylinder walls that are designed to contain combustion. Although the production of power is primarily considered dependent on the amount of fuel and air that is consumed, there is much more to total power output that requires further review.
The total power produced by an internal combustion engine is determined by the following dynamic events that occur in the engine:
- Volume of air and fuel consumed
- Air and fuel mixture quality
- Air fuel ratio
- Efficiency of combustion process
- Ignition intensity and spark timing sequences
- Flame propagation and burn rate
- Type and quality of fuel consumed
- Mechanical and frictional losses
In order to produce more power, the following events should occur:
- Increase consumption of air and fuel
- Improve air fuel mixture quality
- Increase combustion burn rate
- Improve combustion efficiency
- Improve mechanical efficiency
- Reduce friction
The power production of an internal combustion engine is primarily determined by the size and operating range of the engine, the quality of the cylinder head, the flow capability of the intake manifold and the valve timing events and valve lift produced by the camshaft.
Increasing engine displacement can help to generate more power by being able to consume more air and fuel. Increasing the crankshaft stroke can help to develop more power, but the acceleration rate may be reduced as the longer stroke requires more time to complete a full crankshaft rotation. The associated frictional and mechanical losses of the rotating assembly, for an engine with a bigger stroke crankshaft, can also contribute to reducing engine efficiency.
Horsepower Per Cubic Inch of Displacement Formulas
The measure of a good high performance engine can be calculated by a horsepower to cubic inch formula.
A good high performance engine should be capable of producing one horsepower per cubic inch. Examples of this are the Corvette LS1 engine that is rated at 350 hp with a 346 cid engine or a 505 cid Viper engine that is rated at 500 hp.
Properly modified high performance street engines should be able to produce 1.3 horsepower per cubic inch.
Technologically advanced street engines can produce over 1.5 horsepower per cubic inch, naturally aspirated.
Maximum effort street engines that run on pump gasoline can produce over 1.6 horsepower per cubic inch of displacement
High technology Pro Stock race engines can produce over 2.9 horsepower per cubic inch, where a 500 cid engine generates 1450 horsepower, naturally aspirated.
Nitrous oxide injected V8 race engine can produce 3.5 horsepower per cubic inch of displacement.
Centrifugal Supercharged V8 Race Engines can produce 4.5 horsepower per cubic inch.
Turbo Charged V8 Race Engines with a single turbocharger can produce 6 horsepower per cid.
Turbo Charged V8 Race Engines with twin turbochargers can produce 7 horsepower per cid.
Evaluating engine power output, by using a horsepower per cubic inch formula, provides a quantifiable measure to determine reasonable horsepower objectives based on engine size.
Ned Erkman
Author of The Read for Speed
Copyright © 2005 The Read For Speed. All Rights Reserved.
Reproduction in whole or in part without expressed written permission from the author
is strictly prohibited.
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