Improving Acceleration and Top Speed
Every performance car enthusiast dreams of having a vehicle with lightning fast acceleration and a crazy high top speed. While engine mods like turbochargers and superchargers can definitely help, the drivetrain also plays a crucial role in getting more power to the wheels. Upgrading components like the clutch, flywheel, and axles can make a big difference in acceleration and max speed.
Performance Clutches
A performance clutch is one of the best upgrades for improving acceleration. The factory clutch is designed for smooth starts and gradual acceleration. Performance clutches have higher clamping force to handle increased torque loads without slipping.
- Made with performance friction materials that grip better
- Designed for quick, hard engagment
- Hold much more torque to transfer power faster
Lightweight Flywheels
The clutch disk connects to the engine through the flywheel. Lightweight flywheels reduce rotational inertia allowing the engine RPMs to jump up faster. This decreases throttle response time for quicker acceleration.
Upgraded Axles
The axles send power from the transmission to the wheels. Upgrading to chromoly or forged axle shafts increases strength for handling more torque without twisting or breaking.
| Axle Type | Benefits |
|---|---|
| Chromoly | Stronger than OEM |
| Custom Forged | Optimized strength for racing |
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Conclusion
The fastest way to improve acceleration and top speed is upgrading the drivetrain to handle the extra power. A performance clutch, lightweight flywheel, and strong axles will transfer more torque to maximize your car's potential.
Performance Clutches
The clutch is one of the most important components connecting the engine to the transmission. Upgrading to a performance clutch allows you to hold and transfer more torque for improved acceleration.
How Clutches Work
The clutch sits between the engine and transmission. It has a clutch disc spline that slides into the flywheel on the engine crankshaft. When you press the clutch pedal, the disc disengages from the flywheel allowing you to shift gears.
Advantages of Performance Clutches
Here are some of the main benefits of upgrading your stock clutch:
- Higher clamping force to hold more torque
- Better grip from performance friction material
- Faster response and harder engagement
- Built to withstand repeated quick launches
Types of Performance Clutches
| Type | Description |
|---|---|
| Street/Strip | Good balance for street and track use |
| Single Disc | One disc for minimal slippage |
| Triple Disc | Multiple discs for ultimate grip |
Conclusion
Upgrading your clutch is one of the best ways to improve acceleration. Performance clutches can hold more torque and transfer power to the wheels far more effectively.
Lightweight Flywheels
The flywheel is connected to the end of the engine crankshaft and provides inertia to keep the engine spinning between power strokes. Switching to a lightweight flywheel can improve throttle response and acceleration.
How Flywheels Affect Performance
A heavier flywheel has more rotational inertia which keeps the engine RPMs from dropping too quickly. However, this also resists acceleration. A lightweight flywheel reduces that inertia so RPMs can jump up faster when you step on the gas pedal.
Benefits of Lightweight Flywheels
- Faster throttle response
- Improved acceleration
- Higher max RPM capability
- More power to the wheels
As an example, shaving off 5 lbs of weight from the factory flywheel of a 350Z can reduce 0-60 mph times by .2 seconds. That's a significant improvement from just a single bolt-on part.
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Materials Used
Lightweight flywheels are typically made from chromoly steel or aluminum. Chromoly steel is stronger than mild steel so it can be made thinner while still handling high RPMs. Billet aluminum is also popular for its lightness while still maintaining structural rigidity.
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Potential Drawbacks
The downsides of switching to a lightweight flywheel include:
- Increased noise and vibration
- Stalling issues at low RPMs
- More frequent clutch replacement
These issues can be mitigated by choosing a flywheel with a damper, or upgraded motor mounts. Overall, lightweight flywheels provide one of the most cost-effective ways to improve acceleration.
Conclusion
Reducing the weight of your flywheel allows the engine to gain RPMs faster for better throttle response. This simple upgrade can shave tenths of seconds off your acceleration times.
Smoothing Out Shifting
Getting smooth, fast shifts can greatly improve the driving experience and performance of your manual transmission car. Upgrading certain components can help smooth out the shifting process.
Problems with Rough Shifting
Some common issues that can cause rough shifting include:
- Worn shifter bushings
- Loose shifter assembly
- Low quality shifter cables
- Transmission or engine mounts worn out
These problems allow too much "slop" or play in the shifting mechanisms leading to vague feel and difficulty getting into gear smoothly.
Upgrades for Smoother Shifting
Short Throw Shifters
Short throw shifters reduce the distance the shifter travels between gears. This allows for quicker, more precise shifting actions.
Shifter Bushings
Upgraded polyurethane or brass bushings for the shifter replace sloppy factory rubber bushings for tighter feel and response.
Shifter Cables
High quality stainless steel shifter cables won't stretch or bind like cheaper cables, also ensuring smoothgear changes.
Benefits of Smooth Shifting
- Faster shift times
- Less missed shifts
- Lower wear on synchronizers
- More enjoyable driving experience
As an example, upgrading to a short shift kit on an Acura RSX typically improves shift throws by 30%, allowing the driver to change gears more quickly and precisely.
Conclusion
Smoothing out the shifting on your manual transmission is one of the most rewarding upgrades. Investing in a quality short shifter, bushings, and cables results in faster, more precise shifts and a better overall driving experience.
Short Throw Shifters
Short throw shifters are one of the most popular upgrades for manual transmission vehicles. Reducing the shift throw distance allows for faster, more precise gear changes.
How Short Throw Shifters Work
Short throw shifters mechanically modify the lever ratios to reduce the distance the shifter moves between each gear. This is usually done by replacing shift lever pivot points to optimize the linkage geometry.
Benefits of Short Throw Shifters
- Quicker shifting times - Reduce throw distance by 30% or more
- Eliminates sloppy feel from worn shifter components
- Allows faster acceleration with less time between gears
- More precise shifting improves drivability
Types of Short Throw Shifters
| Type | Description |
|---|---|
| Pivot ball | Replaces OEM rubber grommet with bearing |
| Remote cable | Relocates shifter mechanism closer to transmission |
| Linkage kits | Modify length of shift rods and levers |
Drawbacks of Short Throw Shifters
Potential downsides include:
- Increased noise and vibration
- Harsher mechanical feeling
- Won't fix worn transmission components
These can be mitigated by combining the shifter with upgraded bushings, mounts, and cables.
Conclusion
Installing a short throw shifter provides one of the biggest improvements to manual transmission performance and driving experience. The shorter, more precise shifts allow faster acceleration and more enjoyable driving.
Shift Bushings and Brackets
The shifter mechanism in manual transmission vehicles uses rubber bushings and brackets to pivot and locate the shift lever. Upgrading these components can greatly improve shifting feel and precision.
Problems with Factory Bushings
The OEM rubber bushings are designed to dampen vibration and noise. However, with age they break down and become soft, resulting in:
- Excessive side-to-side play
- Sloppy/vague shifting feel
- Increased effort to shift gears
This lack of precision makes it difficult to shift smoothly and quickly.
Polyurethane and Brass Bushings
Performance bushings are available in stiffer materials like polyurethane or brass. Benefits include:
- Tighter tolerances reduce slop
- Improved precision and response
- Long lasting durability under performance use
For example, replacing the factory shifter bushings in an S2000 with fresh polyurethane ones typically tightens up the side-to-side play by 50% or more.
Upgraded Shifter Brackets
Reinforced brackets and mounts help keep the entire shifter assembly firmly located in the chassis. This prevents distortion that can make smooth shifting difficult.
Conclusion
Fresh high performance bushings and mounts are a quick, low cost way to improve the feel and response of your manual transmission. Reducing slop in the shifter mechanism allows you to shift faster and smoother.
How To Calculate Drivetrain Loss?
Drivetrain loss is the power lost between the engine and the wheels due to friction and other factors. Here are the steps to calculate drivetrain loss:
- Find the engine horsepower (HP) and wheel horsepower (WHP) of the vehicle.
- Subtract the WHP from the HP to get the horsepower loss (HP loss).
- Divide the HP loss by the HP.
- Multiply the result by 100 to get the drivetrain loss percentage.
It's important to note that drivetrain loss varies depending on the vehicle and its components, so there is no universal rule or percentage. Some factors that affect drivetrain loss include the type of transmission, driveline components, and drivetrain layout. There are also online calculators and efficiency formulas available to help calculate drivetrain loss.
Drivetrain Loss Percentage
Drivetrain loss percentage is the amount of power lost between the engine and the wheels due to friction and other factors. Here are some ways to calculate drivetrain loss percentage:
- Subtract the wheel horsepower from the engine horsepower, divide by the engine horsepower, then multiply by 100 to get the drivetrain loss percentage.
- Drivetrain loss varies depending on the vehicle and its components, so there is no universal rule or percentage. However, some sources suggest that front-wheel-drive cars generally lose 15%, rear-wheel-drive cars lose 30-33%, and four-wheel-drive cars lose 27-30% .
- Another way to calculate drivetrain loss is to use the formula: EDHP - CDHP = drivetrain loss (DL), then (DL/EDHP)x100 = % drivetrain loss.
- Some sources caution against using a fixed drivetrain loss figure, as every vehicle experiences different levels of drivetrain loss determined by the design of its transmission and driveline components.
It's important to note that drivetrain loss is affected by many factors, and the percentage loss will vary depending on the vehicle and its components.
