 |
Home > Tech Stuff > Racers Math > Racers Math 2
Racers Math - 2
Racers
Math - 2:
This section of the site is for calculating aspects of your own cars
performance and is specifically for drag racing. If you have an
idea of the types of things you'd like to be able to calculate, let
us know. Please bear in mind that these calculators are approximations
only. Although the
information is based on a 5.0 liter Mustang, it is general enough to apply to
any car used for drag racing. Note, you must have a
JavaScript enabled browser and it must be turned on to use these
calculators. Test your browser by clicking
the button below. If nothing happens, you're not enabled.
For more detailed calculations, check out the engine
analyses available at the SlowGT
store.
Links to all of the calculators on all pages in the site.
|
Performance Vs Altitude Stuff |
|
|
Gear Ratio Stuff |
Engine Mechanical Stuff |
|
Horsepower, Weight and Performance Stuff |
Engine Air Flow Stuff |
Basic Horsepower Versus Altitude
This is a basic calculator that is useful for calculating the effects of elev1 (altitude) change on engine horsepower production. This calculator is specifically intended for use in calculating numbers for naturally aspirated cars. The calculator assumes equal humidity and relative barometric pressure at both altitudes. Please note that these calculations are estimates only.
-
Current Elevation From Sea-Level is the altitude at which you currently know your horsepower.
-
Current Horsepower is just what you think it is. You can use the horsepower calculator to calculate this value.
-
New Elevation From Sea-Level is the new altitude at which you want to know your horsepower based on elev1 change.
-
After you have calculated a result, if you would like to see a curve showing the effect of altitude on your horsepower, select "Plot It".
[ Top of Page ]
Maximum Piston Speed and Acceleration
The following calculator can be used to calculate the piston speed and acceleration for a given combination. Use this calculator to verify critical engine parameters for your combination. The second column of inputs is so that you can compare two combinations "side-by-side". If you enter any invalid inputs in any of the second column, no output will be calculated or plotted.
-
Stroke and Rod Length are in inches.
-
Maximum engine RPM is the maximum RPM the engine will experience.
-
Begin Plot is the crank angle at which the plotting will begin and Plot Range is the total number of crank angle degrees that will be plotted.
-
Two different plots are available, Piston Velocity and Piston Acceleration. Each one is overlaid with a plot of Piston Location as a function of crank angle.
Now for some output parameters.
-
Maximum Piston Speed is the maximum speed the piston will experience.
-
Maximum Positive Piston Acceleration is the maximum acceleration the piston experiences near top dead center. This is where the rod is being stretched as the piston is pulled down the cylinder bore away from top dead center.
-
Maximum Negative Piston Acceleration is the maximum acceleration the piston experiences near bottom dead center. This is where the rod is being compressed as the piston is pushed back up the cylinder bore from bottom dead center.
-
Crank Angle is the number of degrees after top dead center at which the maximum piston values above occur. Crank angle is measured as the number of degrees after top dead center.
-
Piston Travel is the piston travel away from top dead center at which the maximum piston values above occur. Piston location is measured as the number of inches down the cylinder bore from top dead center. Top dead center is represented as 0. Bottom dead center is represented as the full stroke number.
[ Top of Page ]
The following calculator can be used to calculate the displacement, or swept volume, of an engine.
-
Stroke and Bore should be entered in inches.
-
Number of Cylinders is just what you think it is and should be a whole number.
-
When plotted, the calculator will display how engine displacement changes with common over-bore values (0.030 inches through 0.120 inches).
[ Top of Page ]
Engine Mechanical Compression Ratio
Use this calculator to calculate the mechanical compression ratio for an engine as well as the total displacement of each engine cylinder. The input terms are below:
-
Bore, Stroke, Head Gasket Compressed Thickness and Cylinder Head Hole Diameter are given in inches.
-
Piston Deck Height is the distance between the top of the piston and the cylinder block deck at top-dead-center. Also enter this value in inches. Enter the number as negative when the piston is above the block deck at top-dead-center. Enter it as positive if the piston is below the block deck at top-dead-center.
-
Piston Dome Volume is the total volume of the piston dome and dish/valve notches. A flat top piston will have a piston volume of 0, a domed piston will have a positive value and a dished piston will have a negative value. Enter this value in cc (available from most piston manufacturers).
-
Piston Volume Above the Compression Ring is exactly what it sounds like. It is usually approximately 1.0 cc (available from many piston manufacturers). Enter this value in cc.
-
Chamber Volume is the total cylinder head chamber volume with valves in place. Enter this value in cc.
-
When plotted, the calculator will show how compression ratio will change with combustion chamber volume.
[ Top of Page ]
Minimum Intake Port Cross Sectional Area
The following calculator can be used to calculate the minimum intake port cross sectional area for a given engine.
-
Bore and Stroke are given in inches.
-
Peak power RPM is the RPM at which the engine makes peak power.
Now for the output parameter.
-
Minimum Intake Port Cross Section is just what it states. This is the smallest cross sectional area required to adequately support the air flow for the engine size and RPM for the combination.
-
When plotted, the calculator shows how minimum intake port cross sectional area will change with engine combination.
[ Top of Page ]
The following calculator can be used to calculate the header dimensions best suited to your combination. The input terms are below:
-
Bore and Stroke are given in inches.
-
Exhaust Valve Opening Point is given in degrees after top dead center (ATDC). A typical street cam will be around 100 degrees ATDC and a common race cam can be closer to 65 degrees ATDC. Entered values should be greater than 0.
-
Peak Power RPM is the RPM value at which your engine makes peak power.
-
When plotted, the calculator shows how header dimension requirements will change with engine combination.
[ Top of Page ]
The following calculator can be used to calculate the intake air flow requirement for your combination. The input terms are below:
-
Bore and Stroke are given in inches.
-
Number of Cylinders is just what you think it is and should be entered as a whole number.
-
Volumetric Efficiency of the engine at peak horsepower should be entered as a whole number. A typical street type engine will be approximately 85% volumetrically efficient at peak power and a well-tuned, free-flowing race engine can be as much as 105% efficient.
-
Peak Power RPM is the RPM value at which your engine makes peak power.
Now for the output parameter.
-
Required Intake Flow Capacity is the minimum cubic feet per minute (CFM) air flow capacity required to support the power capability of your combination. This air flow capacity is required through the entire intake assembly up to the point where the intake path splits into individual runners.
-
When plotted, the calculator shows how minimum intake air flow requirement will change with engine combination.
[ Top of Page ]
For more detailed
engine-building information, check out the analyses
and books
available at the SlowGT store.
This web site is dedicated to 5.0 Liter Mustang Drag Racing.
The technical information on this site is provided based on the owners personal experience.
No warranty is expressed or implied. Best viewed at 800x600
resolution
or larger with 4.0 browsers or higher.
All rights reserved. ASR Corporation 2000. http://www.slowgt.com
Questions and comments about this site should be directed to the SlowGT
webmaster
Last Updated: May 23, 2001
5.0 liter Mustang drag racing 5.0 liter Mustang drag racing 5.0 liter Mustang drag racing 5.0 liter Mustang drag racing