Dynomation-5 Combustion Model Feature Focus

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FEATURE FOCUS: Combustion/Ignition Modeling


The new Dynomation-5 Combustion Component Category is the location of all combustion-related specifications for the engine under test, including: Fuel Type, Compression Ratio, Nitrous Augmentation, Air/Fuel Ratio, Combustion-Chamber Design, and Ignition-Timing.

Easy-to-use Combustion Camber modeling in Dynomation-5 allows you to instantly specify the combustion-chamber geometry for the test engine. Dynomation-5 provides nine combustion-chamber geometries to choose from. Within this group you will find the slowest-burn-rate, disc-shaped chamber, provided primarily for comparison purposes, to the fastest-burning pentroof designs used in many modern high-performance and racing engines. Clicking on the Chambers Quick-Access™ button offers an overview of these chamber shapes, including the basic Ignition Timing Requirement required for each design.

The combustion chamber shape dictates, to a great extent, the fuel burn rate and innate combustion efficiency. For example, a “disc-shaped” chamber with a side-mounted sparkplug generates the lowest turbulence and flame speed. The burn-rate differences between this archaic chamber shape and modern pentroof designs with squish-assisted turbulence can change ignition-timing requirements by 30-degrees or more; the compensation needed to offset the substantial variations in fuel burn-rate.

The basic Ignition Timing value for each chamber is the least timing advance required to produce optimum power with that geometry. As engine speed increases, or if non-optimum air/fuel ratios are used (plus several other factors), greater ignition lead will be required to regain optimum power. This minimum timing requirement for optimum power is often called MBT (or Minimum Timing lead for Best torque). Dynomaiton-5 will automatically estimate the best MBT ignition-timing curve throughout the rpm range by simply activating the Estimate Ignition Timing checkbox. Dynomation-5 MBT calculations take many factors into consideration, including: Compression Ratio, Bore and Stroke dimensions, Fuel Type, Air/Fuel Ratios, RPM, and more!

You also can enter your own "manual" ignition-timing specifications by simply specifying the initial "crank" timing and the advance curve rate. You can also instruct Dynomation-5 to limit timing advance when the engine reaches a specific rpm.

You will find the new Combustion Category a simple, intuitive way to test fuels, chamber shapes, ignition timing and more! Like other Component Categories in Dynomaiton-5, DirectClick™ choices let you quickly explore the effects of any combustion-related engine specification.

 

Model Most Common
Combustion Chamber Shapes
In Seconds!

Predict Ignition-Timing Requirements!


Easy-To-Use Combustion Related Direct-Click™ Selections Allow Rapid Testing Of Combustion-Chamber Shapes, Fuels, Ignition Timing, More.

The Combustion Category groups all combustion-related components and specifications. Included are Compression Ratio, Fuel Type, Air/Fuel Ratio, Combustion-Chamber geometry, and Ignition Timing. Each of these specifications directly affect how fuel is burned in the engine. This category also includes a Compression Ratio Calculator and a Chamber-Selection dialog (see below). Clicking the Estimate Ignition Timing checkbox, Dynomation-5 will determine the MBT for the engine at each rpm point!

 

Dynomation-5 provides nine combustion-chamber geometries from the slowest-burning disc shape to the fast-burn pentroof designs used in many modern high-performance and racing engines. Clicking the Chambers Quick-Access™ button in the Combustion Category provides an overview of these chambers, including the basic Chamber Timing Requirements of these designs.

Brief Combustion Theory Overview:

A mathematical analysis of the fuel-burn process in an IC engine (that can be thought of as simply a rapid pressure rise) reveals that peak power would be obtained if the fuel burned instantly at an optimum crank angle ATC. This would produce the greatest push on the piston at the point at which this pressure is most efficiently converted into the highest torque on the crankpin (approximately 20- to 30-degrees ATC in many applications). While an instant fuel burn (and pressure rise) is not possible for several reasons, including pressure-induced knocking and mechanical shock damage, in general, the faster the pressure rises in the cylinder the more power the engine will produce. As a result, modern chamber designs are optimized for high turbulence and fame speeds within the constraints of preventing pre-ignition and detonation.

 

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