Formula Used: This calculator uses a simplified physics model to estimate 1/4 mile Elapsed Time (ET). It considers the power-to-weight ratio, torque, gear ratios, tire size, and drivetrain type to estimate the forces and speeds involved. The calculation involves determining the traction-limited acceleration and then integrating the velocity over distance.
Chart showing estimated Velocity (MPH) vs. Distance (Feet) for different gears.
Performance Breakdown by Gear
Gear
MPH at Redline
Distance to Redline (ft)
Estimated Time to Redline (s)
What is ET from Weight and HP?
ET from Weight and HP refers to the calculation of a vehicle's Estimated Time (ET) to cover a standard quarter-mile (1320 feet) distance, derived from its fundamental performance metrics: vehicle weight and horsepower. This concept is central to understanding and comparing the acceleration capabilities of different vehicles, especially in performance contexts like drag racing. The power-to-weight ratio is a primary indicator of how quickly a vehicle can accelerate, as it quantifies the engine's power relative to the mass it needs to move. A higher power-to-weight ratio generally translates to a lower ET.
Who should use it? This calculator and the underlying concept are invaluable for:
Car Enthusiasts: To understand and predict the performance of their own vehicles or compare them to others.
Drag Racers: To estimate potential race times and identify areas for improvement (e.g., weight reduction, power upgrades).
Automotive Engineers: As a preliminary tool for performance analysis and vehicle design.
Car Buyers: To gauge the acceleration potential of different models.
Common Misconceptions: A frequent misconception is that horsepower alone determines acceleration. While crucial, it's only half the story. A very heavy car with high horsepower might be slower than a lighter car with less horsepower. Similarly, factors like torque, gearing, tire grip, aerodynamics, and driver skill significantly influence the actual ET. This calculator attempts to account for some of these, but real-world conditions can vary. Another myth is that a single formula perfectly predicts ET for all vehicles; the reality involves complex physics and simulations.
{primary_keyword} Formula and Mathematical Explanation
The core of calculating ET from Weight and HP lies in understanding the power-to-weight ratio and then applying physics principles. While a precise ET prediction is complex, a common simplified approach involves estimating the acceleration forces and integrating them over distance and time.
Step-by-step derivation (Simplified):
Calculate Power-to-Weight Ratio (PWR): This is the fundamental metric.
PWR = Vehicle Weight (lbs) / Horsepower (HP) A lower PWR indicates better potential acceleration.
Estimate Torque: Horsepower is often given, but torque is what directly turns the wheels. We can approximate torque from HP using:
Torque (lb-ft) ≈ (HP * 5252) / RPM Since RPM at peak torque isn't always known, and we need a representative value for calculations, we often use a torque value associated with the horsepower figure, or an estimated peak torque value. For simplicity in this calculator, we'll use an effective torque value related to the peak HP. A common assumption is that peak torque is roughly 1.1 to 1.3 times peak horsepower *at the same RPM*, but this varies wildly. A more direct approach is to consider the thrust at the wheels.
Calculate Wheel Torque and Thrust: Wheel Torque (lb-ft) = Engine Torque (lb-ft) * Gear Ratio * Differential Ratio * Drivetrain Efficiency (e.g., 0.85 for RWD/FWD, 0.95 for AWD) Tire Radius (ft) = Tire Diameter (inches) / 2 / 12 Wheel Force (lbs) = Wheel Torque (lb-ft) / Tire Radius (ft)
Calculate Acceleration Force: The net force accelerating the car is the wheel force minus resisting forces (like aerodynamic drag and rolling resistance). For simplicity, we often focus on the force generated by power. A simplified way to relate power, weight, and acceleration is through the concept of specific power or thrust horsepower.
A commonly used approximation relates power and weight to acceleration:
Acceleration (G-force) ≈ (Horsepower / Vehicle Weight) * Constant
The constant incorporates drivetrain efficiency, and units conversion. A more direct approach relates to the speed gain.
Integrating Velocity over Distance: The acceleration is not constant. It decreases as speed increases due to drag and gearing. The calculation involves simulating the vehicle's speed and position step-by-step or using simplified models that integrate the acceleration profile. This often involves calculating the speed at the redline in each gear and the distance covered in that gear.
Estimating ET: The total time to cover 1320 feet is the sum of the times taken in each gear, considering the distance covered and the speed achieved. The calculator uses approximations for these complex integrations.
Variables Explained:
Performance Variables
Variable
Meaning
Unit
Typical Range
Vehicle Weight
The total mass of the vehicle, including driver and fuel.
Pounds (lbs)
1500 – 6000+
Horsepower (HP)
The peak power output of the engine.
Horsepower (HP)
100 – 1500+
Effective Gear Ratio
The combined ratio of transmission gears and final drive ratio.
Ratio (unitless)
2.5 – 5.5
Tire Diameter
The overall diameter of the tire.
Inches (in)
20 – 32
Drivetrain Type
Specifies if the vehicle is 2WD (FWD/RWD) or AWD.
Type
2WD, AWD
Power-to-Weight Ratio
Engine power relative to vehicle mass.
lbs/HP
2 – 15+ (Lower is better)
Torque-to-Weight Ratio
Engine torque relative to vehicle mass.
ft-lbs/lb
0.1 – 1.0+ (Higher is better)
MPH at Redline
Estimated maximum speed in a specific gear before engine reaches redline.
Miles Per Hour (MPH)
Varies widely by gear
Estimated Time (ET)
The calculated time to cover a quarter-mile.
Seconds (s)
8 – 20+ (Lower is better)
Practical Examples (Real-World Use Cases)
Let's explore how different vehicle configurations affect ET from Weight and HP.
Example 1: Performance Sedan
Consider a popular performance sedan:
Vehicle Weight: 3800 lbs
Horsepower: 450 HP
Effective Gear Ratio (in 3rd gear): 3.20
Tire Diameter: 27 inches
Drivetrain Type: RWD
Calculation & Interpretation:
Power-to-Weight Ratio: 3800 lbs / 450 HP = 8.44 lbs/HP. This is a respectable ratio, suggesting good acceleration potential.
The calculator would estimate the MPH at redline in 3rd gear and the distance covered. Assuming the car has enough gears to reach the 1/4 mile mark efficiently, the calculator might predict an ET around 12.5 seconds. This indicates a quick car capable of confident highway merging and enjoyable spirited driving.
Example 2: Muscle Car Build
Now, let's look at a modified muscle car:
Vehicle Weight: 3500 lbs
Horsepower: 700 HP (after modifications)
Effective Gear Ratio (in 3rd gear): 3.55
Tire Diameter: 28 inches
Drivetrain Type: RWD
Calculation & Interpretation:
Power-to-Weight Ratio: 3500 lbs / 700 HP = 5.0 lbs/HP. This significantly lower ratio indicates a massive increase in acceleration potential compared to the sedan.
With this much power and a favorable weight, the calculator would estimate a much lower ET, potentially around 10.5 seconds for the 1/4 mile. This represents a serious performance machine, often requiring specific driving techniques and modifications (like drag radials) to effectively put the power down. The higher gear ratio and larger tire might influence the gearing's ability to keep the car in its power band effectively.
These examples highlight how changes in weight and horsepower dramatically alter the predicted ET from Weight and HP, demonstrating the calculator's utility for performance analysis.
How to Use This {primary_keyword} Calculator
Our advanced calculator makes it simple to estimate your vehicle's 1/4 mile performance. Follow these steps:
Enter Vehicle Weight: Input the total weight of your vehicle in pounds (lbs). Include the driver's weight for an accurate race-day estimation.
Enter Horsepower: Provide the peak horsepower your engine produces. Use the manufacturer's rating or dyno results if available.
Input Effective Gear Ratio: This is crucial. It's the product of your transmission gear ratio (usually 3rd or 4th gear for a 1/4 mile run) and your final drive differential ratio.
Specify Tire Diameter: Enter the overall diameter of your tires in inches.
Select Drivetrain Type: Choose between 2WD (Front-Wheel Drive or Rear-Wheel Drive) and AWD (All-Wheel Drive). This impacts traction and power delivery.
Click 'Calculate ET': The calculator will instantly process your inputs.
How to Read Results:
Primary Result (ET): The large, highlighted number is your estimated quarter-mile time in seconds. Lower numbers mean faster acceleration.
Intermediate Values:
Power-to-Weight Ratio: Shows how much weight each horsepower has to move (lbs/HP). Lower is better.
Torque-to-Weight Ratio: Indicates the twisting force available relative to mass (ft-lbs/lb). Higher is generally better for initial acceleration.
MPH at Redline: An estimate of the maximum speed achievable in a given gear before the engine hits its redline. This helps understand gearing effectiveness.
Performance Breakdown Table: Provides detailed estimates for each gear, showing speed at redline, distance covered, and time taken in that gear.
Performance Chart: Visualizes the estimated velocity progression over distance, highlighting how speed increases in different gears.
Decision-Making Guidance:
Use the results to inform decisions about vehicle modifications.
High ET, Low HP/Weight: Suggests power upgrades or weight reduction could yield significant improvements.
High ET, High HP/Weight but poor Torque/Weight: May indicate traction issues or inefficient gearing. Consider suspension, tires, or different gear ratios.
Close ET to Target: The calculator helps you fine-tune modifications for specific performance goals.
Remember, this calculator provides an ESTIMATE. Real-world results depend on many factors not perfectly modeled, including track conditions, tire compound, atmospheric conditions, and driver skill. Always use the 'Copy Results' button to save your calculations for future reference or sharing.
Key Factors That Affect {primary_keyword} Results
While our calculator provides a solid estimate for ET from Weight and HP, numerous real-world factors can influence actual performance. Understanding these helps interpret results and plan modifications:
Traction (Tire Grip): This is arguably the most critical factor limiting acceleration, especially for high-power vehicles. Insufficient grip means the tires spin uselessly, wasting power and preventing the vehicle from reaching its potential ET. Tire compound (street tires vs. drag slicks), tire pressure, and suspension setup all play huge roles. Our calculator uses a simplified drivetrain factor but cannot fully replicate tire physics.
Gearing Strategy: The effective gear ratio entered is vital. Choosing the optimal gear ratio for a specific power band and track length is crucial. Too short gearing leads to rapid shifts and hitting the redline too soon, while too tall gearing might not provide enough acceleration force. The calculator simulates performance across gears, but optimal shift points and gear choice can be driver-dependent.
Aerodynamic Drag: At higher speeds, the force of air resistance increases dramatically (approximately with the square of velocity). This drag acts as a significant opposing force, slowing down acceleration. While the calculator's model incorporates some physics, aerodynamic efficiency (drag coefficient and frontal area) is complex and varies greatly between vehicle shapes.
Drivetrain Losses: Power is lost as it travels from the engine crankshaft to the wheels due to friction in the transmission, driveshaft, differential, and axles. The calculator accounts for this with a general efficiency factor (higher for AWD), but actual losses can vary based on the specific components and their condition.
Engine Power Curve & Torque Band: The calculator primarily uses peak horsepower. However, the shape of the power and torque curves throughout the RPM range is what truly dictates acceleration. An engine that makes broad, usable power across a wide RPM band will often perform better than one with a sharp, peaky power delivery, even if peak numbers are similar. This calculator simplifies this by using effective values.
Weight Distribution: How weight is distributed front-to-rear impacts traction, especially for rear-wheel-drive vehicles. Better weight transfer to the rear during acceleration can improve grip. While AWD mitigates this somewhat, it's still a factor.
Driver Skill: Smoothness in applying throttle, precise gear changes, and effective braking (if applicable) can make a significant difference in ET. The calculator assumes an ideal driver.
Atmospheric Conditions: Air density (affected by temperature, altitude, and humidity) changes the engine's power output and aerodynamic drag. Denser air generally means more power and more drag. The calculator uses standard atmospheric assumptions.
Frequently Asked Questions (FAQ)
What is the most accurate way to calculate ET?
The most accurate way is through actual testing using a drag strip timer (a " ডragy" device or professional timing system). Physics-based calculators like this one provide excellent estimates but cannot account for all real-world variables perfectly.
Why does my car feel faster than the calculated ET suggests?
Perception of speed can be subjective. Factors like rapid acceleration in lower gears, G-force, engine sound, and driver feedback can make a car feel faster than its actual quarter-mile time indicates. Also, check if your inputs (especially gear ratios and weight) are accurate.
How much does reducing weight impact ET?
Reducing weight has a significant impact. A general rule of thumb in drag racing is that shedding approximately 100 lbs can improve ET by about 0.1 seconds, assuming power remains constant and traction is sufficient. Our calculator helps quantify this: see how a change in vehicle weight affects the ET from Weight and HP.
Is horsepower or torque more important for ET?
Both are critical but play different roles. Horsepower dictates the top-end speed potential and overall energy the engine can deliver over time. Torque is the twisting force that gets the vehicle moving from a standstill. A good balance is needed, but for achieving a low ET, sustained horsepower throughout the power band is essential, provided there's enough torque and traction to utilize it.
What does 'Effective Gear Ratio' mean?
It's the multiplication factor applied to engine RPM to determine wheel speed. It includes the ratio of the selected transmission gear AND the final drive ratio in the differential. For example, 1st gear (3.00) x Final Drive (4.10) = 12.30 effective ratio in 1st gear. This calculator typically focuses on the ratio relevant for higher speed ranges (e.g., 3rd or 4th gear).
Can I use this calculator for non-drag racing applications?
While primarily designed for 1/4 mile ET estimation, the power-to-weight ratio derived is a universal performance metric. It gives a good indication of general acceleration capability, which is relevant for track days, autocross, or even just understanding a car's responsiveness. However, it doesn't directly translate to lap times or handling performance.
How does AWD affect ET compared to 2WD?
All-Wheel Drive (AWD) systems typically allow for better traction off the line compared to most 2WD setups, especially in less-than-ideal conditions. This can lead to a lower ET, particularly for vehicles with high horsepower, by reducing wheelspin. However, AWD systems can also introduce more drivetrain loss. Our calculator adjusts for this general efficiency difference.
My calculated ET seems too high/low. What could be wrong?
Double-check your input values: ensure weight is accurate (including driver), horsepower is correct, gear ratios are precisely calculated (transmission gear * differential ratio), and tire diameter is measured correctly. Also, consider the real-world factors mentioned previously – especially traction and aerodynamics – which our simplified model may not fully capture.
Related Tools and Internal Resources
HP to MPH Calculator: Explore how horsepower directly influences top speed in different gears.
var chartInstance = null; // Global variable for chart instance
function validateInput(id, min, max) {
var input = document.getElementById(id);
var errorElement = document.getElementById(id + "Error");
var value = parseFloat(input.value);
errorElement.style.display = 'none'; // Hide error by default
if (input.value === "") {
errorElement.textContent = "This field is required.";
errorElement.style.display = 'block';
return false;
}
if (isNaN(value)) {
errorElement.textContent = "Please enter a valid number.";
errorElement.style.display = 'block';
return false;
}
if (value <= 0 && id !== 'drivetrain') { // Allow 0 for ratios if needed, but not weight/hp
errorElement.textContent = "Value must be positive.";
errorElement.style.display = 'block';
return false;
}
if (min !== undefined && value max) {
errorElement.textContent = "Value must be no more than " + max + ".";
errorElement.style.display = 'block';
return false;
}
return true;
}
function calculateET() {
var weight = parseFloat(document.getElementById("vehicleWeight").value);
var hp = parseFloat(document.getElementById("horsepower").value);
var gearRatioInput = parseFloat(document.getElementById("gearRatio").value);
var tireDiameter = parseFloat(document.getElementById("tireDiameter").value);
var drivetrain = document.getElementById("drivetrain").value;
var errorOccurred = false;
if (!validateInput("vehicleWeight", 100)) errorOccurred = true;
if (!validateInput("horsepower", 1)) errorOccurred = true;
if (!validateInput("gearRatio", 0.1)) errorOccurred = true; // Allow low ratios
if (!validateInput("tireDiameter", 10)) errorOccurred = true;
if (errorOccurred) {
document.getElementById("result").style.display = 'none';
clearIntermediateResults();
return;
}
// Constants
var secondsPerMinute = 60;
var feetPerMile = 5280;
var inchesPerFoot = 12;
var pi = Math.PI;
var redlineRPM = 6500; // Assumed redline RPM for calculation
var peakTorqueFactor = 1.15; // Assumed factor for peak torque relative to HP at peak RPM (simplified)
var drivetrainEfficiencyRWD = 0.85;
var drivetrainEfficiencyAWD = 0.95;
var ftPerSecondSquaredToG = 32.174; // Conversion factor
// Intermediate Calculations
var powerToWeight = weight / hp;
document.getElementById("powerToWeight").textContent = powerToWeight.toFixed(2);
// Approximate peak torque based on HP (this is a simplification)
// A more accurate model would need actual torque curve data.
// Let's assume a representative torque value for calculation:
// HP = (Torque * RPM) / 5252 => Torque = (HP * 5252) / RPM
// Assume RPM at peak HP is around 5500 for this estimation.
var estimatedPeakTorque = (hp * 5252) / 5500;
var torqueToWeight = estimatedPeakTorque / weight;
document.getElementById("torqueToWeight").textContent = torqueToWeight.toFixed(3);
var tireRadiusFeet = (tireDiameter / 2) / inchesPerFoot;
var drivetrainEfficiency = (drivetrain === "AWD") ? drivetrainEfficiencyAWD : drivetrainEfficiencyRWD;
var mphAtRedline = "–";
document.getElementById("mphAtRedline").textContent = mphAtRedline; // Reset
var gearData = [];
var totalET = 0;
var totalDistance = 0;
var currentSpeedMPH = 0;
var currentDistanceFt = 0;
var currentET = 0;
var currentGearRatio = gearRatioInput; // Start with the input gear ratio
// Simulate through gears (example: up to 5 gears)
for (var gear = 1; gear <= 5; gear++) {
var effectiveGear = currentGearRatio; // Use the provided gear ratio for the first calculation step
// Calculate MPH at redline for this gear
// MPH = (RPM * Tire Diameter * pi) / (Gear Ratio * 63360)
var mphAtGearRedline = (redlineRPM * tireDiameter * pi) / (effectiveGear * inchesPerFoot);
mphAtGearRedline = mphAtGearRedline / feetPerMile * secondsPerMinute; // Convert to MPH
// Calculate distance covered in this gear before hitting redline
// This requires integration. Simplified approach: assume average acceleration.
// A more precise calculation uses physics: Force = (Torque * GR * Eff) / Tire Radius
// Acceleration = Force / Weight
// We'll simplify by calculating speed at intervals and summing distance.
var stepDistanceFt = 10; // Small increments for simulation
var stepTimeSeconds = 0.01; // Small time steps
var simulatedSpeedMPH = currentSpeedMPH;
var simulatedDistanceFt = currentDistanceFt;
var simulatedET = currentET;
var distanceInGear = 0;
var timeInGear = 0;
// Simulate speed and distance accumulation within this gear
while (simulatedSpeedMPH < mphAtGearRedline && simulatedDistanceFt 0.1) { // Avoid division by zero and very low speeds
// Power (Watts) = Force (N) * Velocity (m/s)
// Force (N) = Power (Watts) / Velocity (m/s)
forceN = (simulatedHP * 745.7) / currentVelocityMPS;
} else {
// At very low speeds, rely more on torque-based force calculation
var wheelTorqueNm = (estimatedPeakTorque * 0.453592 * 0.3048) * effectiveGear * drivetrainEfficiency; // Rough conversion
var tireRadiusM = tireRadiusFeet * 0.3048;
if (tireRadiusM > 0.01) {
forceN = wheelTorqueNm / tireRadiusM;
} else {
forceN = 0; // Cannot calculate force
}
}
var weightN = simulatedWeightKG * 9.81; // Weight in Newtons
var accelerationMPS2 = 0;
// Consider drag and rolling resistance implicitly via force estimation
// Simplified force model: Assume a net accelerating force based on power and weight
// A common empirical formula for 1/4 mile involves time directly related to PWR
// Let's try a simpler, more direct approach based on commonly cited formulas:
// Time = C * (Weight / HP)^0.5 where C is a constant around 5.5 to 6.0
// This doesn't account for gearing well.
// Re-approach: Use empirical data or simplified integration models.
// A widely used simplified model:
// Time (seconds) = (Weight_lbs / HP) * (C1 + C2 * (Weight_lbs / HP))
// Or simpler: Time ~= C * sqrt(Weight / HP)
// Let's try a method that builds up speed and distance.
// Simplified Acceleration Calculation (in ft/s^2)
// Force = Power / Velocity. Need consistent units.
// Power (ft-lbs/s) = HP * 550
// Velocity (ft/s) = Speed_MPH * 5280 / 3600
var currentVelocityFPS = simulatedSpeedMPH * 5280 / 3600;
var powerFtLbsPerSec = hp * 550;
var accelerationFtSecSq = 0;
if (currentVelocityFPS > 0.1) {
var netForce = powerFtLbsPerSec / currentVelocityFPS; // Approximate net force in lbs
// This net force still needs to overcome drag and friction which increase with speed.
// Let's use a more direct empirical estimate for acceleration based on PWR.
// A very rough estimate for 0-60 G-force: G = (HP / Weight) * Constant
// Constant is empirically derived, around 300-350 for street cars.
var roughGForce = (hp / weight) * 320; // Rough G-force at peak power delivery
accelerationFtSecSq = roughGForce * ftPerSecondSquaredToG; // Convert G to ft/s^2
} else {
// Initial acceleration from standstill relies more on torque and gearing
var wheelTorqueFtLbs = estimatedPeakTorque * effectiveGear * drivetrainEfficiency;
var wheelForceLbs = wheelTorqueFtLbs / tireRadiusFeet;
accelerationFtSecSq = wheelForceLbs / weight; // Force / Mass
}
// Make acceleration decrease slightly with speed to approximate drag
accelerationFtSecSq = accelerationFtSecSq * (1 – (currentVelocityFPS / (mphAtGearRedline * 0.44704 * 1.5))); // Crude damping
if (accelerationFtSecSq = 1320) {
break; // Stop if 1320ft is reached
}
if (simulatedSpeedMPH >= mphAtGearRedline * 1.05) { // Stop if redline is significantly exceeded
break;
}
if (timeInGear > 5) break; // Prevent infinite loops in a gear
}
if (simulatedDistanceFt >= 1320) {
// Reached 1320ft in this gear
totalET = simulatedET;
totalDistance = 1320;
break; // Exit loop, we have our ET
} else {
// Moved to next gear, update totals
totalET = simulatedET;
totalDistance = simulatedDistanceFt;
currentSpeedMPH = simulatedSpeedMPH; // Speed at the end of this gear step
currentDistanceFt = simulatedDistanceFt;
currentET = simulatedET;
// Calculate the next gear ratio (simple progression, e.g., 1.3 multiplier)
// This is a placeholder; real gear sets are specific.
currentGearRatio = gearRatioInput * (1.3 + (gear * 0.15)); // Example progression
if (gear === 1) currentGearRatio = gearRatioInput; // Use the input for the first gear calculation
gearData.push({
gear: gear,
mph: mphAtGearRedline.toFixed(1),
distance: simulatedDistanceFt.toFixed(1),
time: timeInGear.toFixed(2)
});
}
if(gear === 5 && simulatedDistanceFt 0 && hp > 0) {
// Adjust C based on PWR for better approximation
var c_constant = 5.8; // Base constant
if (powerToWeight < 6) c_constant = 5.2; // Faster cars get a lower C
if (powerToWeight 8 && totalET 20) finalET = 20; // Cap ET at a reasonable maximum
document.getElementById("result").textContent = finalET.toFixed(2);
document.getElementById("result").style.display = 'block';
// Populate intermediate results
document.getElementById("mphAtRedline").textContent = mphAtRedline.toFixed(1); // Show MPH at redline for the FIRST gear calculated
// Populate table
populateTable(gearData, finalET);
// Update chart
updateChart(gearData, finalET);
}
function populateTable(gearData, finalET) {
var tableBody = document.querySelector("#performanceTable tbody");
tableBody.innerHTML = "; // Clear previous data
// Add calculated gear data
gearData.forEach(function(data) {
var row = tableBody.insertRow();
row.insertCell(0).textContent = data.gear;
row.insertCell(1).textContent = data.mph;
row.insertCell(2).textContent = data.distance;
row.insertCell(3).textContent = data.time;
});
// Add a row for the final ET if it was reached within the simulation
if (finalET 0) {
var lastGearData = gearData[gearData.length – 1];
// Calculate remaining distance and time if needed, or just show final ET
var row = tableBody.insertRow();
row.insertCell(0).textContent = "Final";
row.insertCell(1).textContent = "-";
row.insertCell(2).textContent = "1320 ft";
row.insertCell(3).textContent = finalET.toFixed(2);
}
}
function updateChart(gearData, finalET) {
var ctx = document.getElementById("performanceChart").getContext("2d");
if (chartInstance) {
chartInstance.destroy(); // Destroy previous chart instance
}
// Prepare data for chart
var labels = []; // Distance in feet
var datasets = [];
// For simplicity, let's plot theoretical speed vs distance for a couple of gears
// and the final speed reached at 1320ft.
var maxDistance = 1320;
var speedPoints = []; // Store {distance, speed}
var currentDist = 0;
var currentSpeed = 0;
var currentETime = 0;
var gearIndex = 0;
var currentGearData = gearData[gearIndex] || { mph: 0, distance: 0, time: 0 };
var targetMPH = parseFloat(currentGearData.mph) || 100; // Target speed for this gear
var distanceToTarget = parseFloat(currentGearData.distance) || 500; // Distance covered in this gear
var timeToTarget = parseFloat(currentGearData.time) || 1.0; // Time spent in this gear
// Generate speed points across the 1320ft distance
var simSteps = 100;
for (var i = 0; i <= simSteps; i++) {
var dist = maxDistance * (i / simSteps);
// Estimate speed at this distance based on the gear data. This is complex.
// Simplified: Interpolate speed based on distance covered in gears.
var estimatedSpeed = 0;
var accumulatedDist = 0;
var accumulatedTime = 0;
for (var j = 0; j < gearData.length; j++) {
var gData = gearData[j];
var distInGear = parseFloat(gData.distance);
var timeInGear = parseFloat(gData.time);
var mphAtGear = parseFloat(gData.mph);
if (dist accumulatedDist) { // If simulation didn't cover full 1320ft, extrapolate or use last speed
estimatedSpeed = gearData.length > 0 ? parseFloat(gearData[gearData.length-1].mph) : 0;
}
labels.push(dist.toFixed(0)); // Distance labels
speedPoints.push({ x: dist, y: estimatedSpeed });
}
// Final point for the end of the run
speedPoints.push({ x: 1320, y: finalET > 0 ? (1320 / (finalET * 3600 / 5280)) : 0 }); // Speed at 1320ft
datasets.push({
label: 'Estimated Velocity (MPH)',
data: speedPoints,
borderColor: 'rgb(0, 74, 153)',
backgroundColor: 'rgba(0, 74, 153, 0.2)',
fill: false,
tension: 0.1
});
// Add a hypothetical second dataset for comparison if possible, e.g., a higher power scenario
// For now, let's focus on the single series.
chartInstance = new Chart(ctx, {
type: 'line',
data: {
labels: labels.map(function(d) { return d + " ft"; }), // Use distance as labels
datasets: datasets
},
options: {
responsive: true,
maintainAspectRatio: true,
scales: {
x: {
title: {
display: true,
text: 'Distance (Feet)'
}
},
y: {
title: {
display: true,
text: 'Speed (MPH)'
},
beginAtZero: true
}
},
plugins: {
legend: {
position: 'top',
},
title: {
display: true,
text: 'Estimated Vehicle Speed Progression'
}
}
}
});
}
function resetCalculator() {
document.getElementById("vehicleWeight").value = "3500";
document.getElementById("horsepower").value = "450";
document.getElementById("gearRatio").value = "3.55";
document.getElementById("tireDiameter").value = "26";
document.getElementById("drivetrain").value = "2WD";
// Clear errors
document.getElementById("vehicleWeightError").style.display = 'none';
document.getElementById("horsepowerError").style.display = 'none';
document.getElementById("gearRatioError").style.display = 'none';
document.getElementById("tireDiameterError").style.display = 'none';
document.getElementById("drivetrainError").style.display = 'none';
document.getElementById("result").style.display = 'none';
clearIntermediateResults();
if (chartInstance) {
chartInstance.destroy();
chartInstance = null;
}
// Clear table
var tableBody = document.querySelector("#performanceTable tbody");
tableBody.innerHTML = ";
}
function clearIntermediateResults() {
document.getElementById("powerToWeight").textContent = "–";
document.getElementById("torqueToWeight").textContent = "–";
document.getElementById("mphAtRedline").textContent = "–";
}
function copyResults() {
var resultText = "Performance Calculation Results:\n\n";
resultText += "Estimated ET: " + document.getElementById("result").textContent + " seconds\n\n";
resultText += "Key Metrics:\n";
resultText += "- Power-to-Weight Ratio: " + document.getElementById("powerToWeight").textContent + " lbs/hp\n";
resultText += "- Torque-to-Weight Ratio: " + document.getElementById("torqueToWeight").textContent + " ft-lbs/lb\n";
resultText += "- MPH at Redline (Est.): " + document.getElementById("mphAtRedline").textContent + "\n\n";
resultText += "Assumptions & Inputs:\n";
resultText += "- Vehicle Weight: " + document.getElementById("vehicleWeight").value + " lbs\n";
resultText += "- Horsepower: " + document.getElementById("horsepower").value + " HP\n";
resultText += "- Effective Gear Ratio: " + document.getElementById("gearRatio").value + "\n";
resultText += "- Tire Diameter: " + document.getElementById("tireDiameter").value + " inches\n";
resultText += "- Drivetrain: " + document.getElementById("drivetrain").options[document.getElementById("drivetrain").selectedIndex].text + "\n";
// Try to copy using Clipboard API
navigator.clipboard.writeText(resultText).then(function() {
// Success feedback
var copyButton = document.querySelector(".button-group button.copy");
copyButton.textContent = "Copied!";
copyButton.style.backgroundColor = "#28a745"; // Success color
setTimeout(function() {
copyButton.textContent = "Copy Results";
copyButton.style.backgroundColor = "#ffc107"; // Original color
}, 2000);
}).catch(function(err) {
console.error('Failed to copy text: ', err);
// Fallback for older browsers or environments where clipboard API is not available
alert("Failed to copy. Please manually copy the text above.");
});
}
// Initial calculation on load with default values
document.addEventListener('DOMContentLoaded', function() {
resetCalculator(); // Set default values
calculateET(); // Perform initial calculation
// Add event listeners for real-time updates
var inputs = document.querySelectorAll('.loan-calc-container input, .loan-calc-container select');
inputs.forEach(function(input) {
input.addEventListener('input', calculateET);
});
// FAQ toggle functionality
var faqItems = document.querySelectorAll('.faq-list .faq-item h3');
faqItems.forEach(function(item) {
item.addEventListener('click', function() {
var faqContent = this.nextElementSibling;
var faqItem = this.parentElement;
faqItem.classList.toggle('active');
faqContent.style.display = faqItem.classList.contains('active') ? 'block' : 'none';
});
});
});