Stihl MS 391 Performance Parts Upgrade (3 Pro Tips)

It’s a solid saw right out of the box, but like any machine, it can be optimized for even better performance. Upgrading parts can give you more power, better handling, and overall improved efficiency. Over the years, I’ve tinkered with countless chainsaws, including the MS 391, and I’ve learned a thing or two about which upgrades really make a difference. Today, I’m going to share my top three pro tips for upgrading your Stihl MS 391, along with a detailed look at the costs involved, potential performance gains, and everything else you need to consider.

Expert Picks and Why They Matter

Before diving into the specifics, let’s talk about expert picks. It’s easy to get lost in a sea of aftermarket parts, all promising incredible gains. My expert picks are based on real-world experience, performance data, and a healthy dose of understanding what the MS 391 engine can realistically handle. I’m not just throwing out names of expensive parts; I’m focusing on upgrades that offer the best bang for your buck and truly enhance the saw’s capabilities.

My Top 3 Pro Tips for Stihl MS 391 Performance Upgrades:

1. High-Performance Air Filter: This is often the first and easiest upgrade. A better air filter allows the engine to breathe more freely, resulting in increased power and throttle response.

2. Modified Muffler or Muffler Mod: Opening up the exhaust flow can significantly improve power, especially at higher RPMs. This upgrade requires some careful consideration to avoid damaging the engine.

3. Upgraded Chain: While technically not a “part” of the saw itself, the chain is the business end. A higher-quality, sharper chain can dramatically improve cutting speed and efficiency.

The Nitty-Gritty: Diving into Cost and Performance

Let’s get down to the brass tacks. Upgrading your MS 391 isn’t free, and you need to understand the costs involved before you start wrenching. I’ll break down each upgrade, discuss its potential performance benefits, and provide a detailed look at the associated expenses.

1. High-Performance Air Filter

Performance Benefits:

• Increased Airflow: Allows the engine to breathe more efficiently, resulting in improved throttle response and power.
• Better Filtration: Many high-performance filters offer superior filtration compared to the stock filter, protecting the engine from harmful debris.
• Improved Engine Longevity: By keeping the engine cleaner, a good air filter can extend its lifespan.

Cost Breakdown:

• Aftermarket Air Filters: These typically range from $20 to $50, depending on the brand and material. Some popular options include K&N, UNI Filter, and aftermarket filters designed specifically for Stihl chainsaws.
• Cleaning Kits: If you choose a reusable filter (like K&N), you’ll need a cleaning kit, which usually costs around $15 to $25.
• Installation: Installation is straightforward and usually involves removing the old filter and replacing it with the new one. No special tools are typically required.

Personal Story: I remember working on a large firewood project a few years back, cutting primarily seasoned oak. The stock air filter on my MS 391 was constantly getting clogged with sawdust, causing the saw to bog down. After switching to a UNI Filter, the difference was night and day. The saw ran smoother, had better throttle response, and I didn’t have to clean the filter nearly as often.

Data Point: According to a study by the Society of Automotive Engineers (SAE), improved air filtration can increase engine horsepower by 2-5% in small engines. While this might seem small, it can make a noticeable difference in cutting performance.

Practical Example: Let’s say you’re cutting firewood and your MS 391 takes 10 seconds to cut through a 12-inch log with the stock filter. With a high-performance filter, you might be able to reduce that time to 9.5 seconds. Over the course of a day, those small time savings can add up significantly.

2. Modified Muffler or Muffler Mod

Performance Benefits:

• Increased Exhaust Flow: Allows the engine to expel exhaust gases more efficiently, resulting in a significant power increase, especially at higher RPMs.
• Improved Throttle Response: The engine can rev up more quickly, making it more responsive to changes in throttle input.
• Potentially Cooler Engine Temperatures: Better exhaust flow can help reduce engine temperatures, which can improve engine longevity.

Cost Breakdown:

• Aftermarket Mufflers: These can range from $50 to $150, depending on the brand and design. Some popular options include those from aftermarket chainsaw parts suppliers.
• Muffler Mod: This involves modifying the existing muffler by drilling additional holes or removing internal baffles. This can be done yourself with basic tools, but it requires careful planning and execution. The cost of materials (drill bits, welding supplies if necessary) is typically around $10 to $30.
• Professional Modification: If you’re not comfortable modifying the muffler yourself, you can hire a professional to do it. Labor costs typically range from $50 to $100.

Important Considerations:

• Engine Tuning: Modifying the muffler can change the engine’s air-fuel ratio, which may require adjusting the carburetor. This can be done yourself with some basic knowledge of carburetor tuning, or you can take the saw to a professional.
• Noise Levels: Modifying the muffler will likely increase the saw’s noise level. Be sure to wear appropriate hearing protection.
• Warranty: Modifying the muffler may void the saw’s warranty.

Personal Story: I once worked with a logger who had heavily modified his MS 391’s muffler. The saw was incredibly powerful, but it was also incredibly loud. He didn’t adjust the carburetor properly, and the engine ended up running too lean, which eventually caused it to overheat and seize. This is a cautionary tale about the importance of doing your research and taking the necessary precautions when modifying your chainsaw.

Data Point: According to tests conducted by various chainsaw enthusiasts and mechanics, a well-executed muffler mod can increase chainsaw horsepower by 10-15%. This is a significant increase that can make a noticeable difference in cutting performance.

Practical Example: Imagine you’re felling a large tree with your MS 391. With the stock muffler, it might take you 5 minutes to cut through the trunk. With a modified muffler, you might be able to reduce that time to 4 minutes and 15 seconds. Again, these small time savings can add up significantly over the course of a day.

Cost Optimization Tip: If you’re on a tight budget, consider doing the muffler mod yourself. There are plenty of online resources and tutorials that can guide you through the process. Just be sure to do your research and take the necessary precautions.

3. Upgraded Chain

Performance Benefits:

• Faster Cutting Speed: A sharper, more aggressive chain can cut through wood much faster than a dull or low-quality chain.
• Reduced Vibration: A well-maintained chain can reduce vibration, making the saw more comfortable to use.
• Improved Fuel Efficiency: A sharper chain requires less effort to cut through wood, which can improve fuel efficiency.

Cost Breakdown:

• Standard Chains: These typically cost around $20 to $30.
• High-Performance Chains: These can range from $30 to $60, depending on the brand and type. Some popular options include Oregon and Stihl chains designed for specific cutting applications.
• Chain Sharpening Tools: You’ll need a file and guide to sharpen your chain. These typically cost around $15 to $30.
• Chain Grinder: For more precise sharpening, you can invest in a chain grinder, which can cost anywhere from $50 to $200.

Personal Story: I used to be content with using whatever chain came standard with my chainsaw. However, after trying a high-performance Oregon chain, I was amazed at the difference. The saw cut through wood like butter, and I was able to get through my firewood project much faster.

Data Point: According to Oregon, their high-performance chains can cut up to 20% faster than standard chains. This can translate to significant time savings, especially on large projects.

Practical Example: If you’re cutting a cord of firewood, an upgraded chain could potentially save you an hour or more of cutting time.

Cost Optimization Tip: Invest in a good chain sharpening tool and learn how to sharpen your chain properly. A sharp chain is essential for efficient and safe cutting.

The Big Picture: Budgeting for Upgrades

Now that we’ve broken down the costs of each upgrade, let’s talk about budgeting. It’s important to consider your budget and prioritize the upgrades that will provide the most benefit for your specific needs.

Factors Affecting Project Costs:

• Wood Type: Hardwoods like oak and maple are more difficult to cut than softwoods like pine and fir. This can affect the amount of time and effort required to complete a project.
• Location Accessibility: If you’re working in a remote location, it may be more difficult and expensive to transport tools and materials.
• Seasonality: The price of firewood can fluctuate depending on the season. Demand is typically higher in the winter, which can drive up prices.

Cost Components:

• Timber Purchase or Harvesting Costs: If you’re harvesting your own timber, you’ll need to factor in the cost of permits, equipment rental, and labor.
• Tool Maintenance: Chainsaws require regular maintenance, including sharpening, cleaning, and lubrication.
• Labor Wages: If you’re hiring someone to help you with your project, you’ll need to factor in their wages.
• Permits: Depending on your location, you may need permits to harvest timber or sell firewood.

Industry Benchmarks and Statistical Data:

• Average Price per Cord of Firewood: The average price per cord of firewood varies depending on location and wood type, but it typically ranges from $200 to $400.
• Timber Prices: Timber prices fluctuate depending on market conditions. You can find current timber prices from various sources, such as the U.S. Forest Service and state forestry agencies.
• Equipment Rental Fees: Chainsaw rental fees typically range from $30 to $50 per day.

Cost Optimization and Budget Management Tips:

• Prioritize Upgrades: Focus on the upgrades that will provide the most benefit for your specific needs.
• Shop Around: Compare prices from different retailers before making a purchase.
• Do It Yourself: If you’re comfortable with basic mechanical work, consider doing some of the upgrades yourself.
• Maintain Your Equipment: Regular maintenance can extend the lifespan of your equipment and prevent costly repairs.
• Buy in Bulk: If you’re buying firewood or timber, consider buying in bulk to save money.

Relevant Calculations and Formulas:

• Calculating Volume of Logs in Board Feet: Board feet = (Length in feet x Width in inches x Thickness in inches) / 12
• Calculating Volume of Logs in Cords: A cord is a stack of wood that measures 4 feet high, 4 feet wide, and 8 feet long, or 128 cubic feet.
• Estimating Drying Time Based on Moisture Content: Drying time depends on various factors, including wood type, climate, and stacking method. As a general rule, firewood should be dried for at least 6 months to reduce its moisture content to below 20%.

Challenges Faced by Small-Scale Loggers and Firewood Suppliers

Small-scale loggers and firewood suppliers face numerous challenges, including fluctuating timber prices, high equipment costs, and increasing competition. They often operate on tight margins and need to be efficient in order to survive. Upgrading their equipment can help them improve their productivity and profitability.

Common Challenges:

• Fluctuating Timber Prices: Timber prices can fluctuate depending on market conditions, making it difficult for loggers to predict their income.
• High Equipment Costs: Chainsaws, skidders, and other logging equipment can be expensive to purchase and maintain.
• Increasing Competition: The logging industry is becoming increasingly competitive, making it difficult for small-scale loggers to compete with larger companies.
• Environmental Regulations: Loggers must comply with various environmental regulations, which can add to their costs.

How Upgrades Can Help:

• Improved Productivity: Upgrading their equipment can help loggers improve their productivity, allowing them to harvest more timber in less time.
• Reduced Downtime: Reliable equipment can reduce downtime, allowing loggers to work more consistently.
• Increased Profitability: By improving their productivity and reducing downtime, loggers can increase their profitability.

Case Studies: Real-World Examples of Upgrade Benefits

Let’s look at a couple of real-world examples of how upgrades can benefit wood processors and firewood suppliers.

Case Study 1: Small-Scale Logger

A small-scale logger in Oregon was struggling to compete with larger companies. He decided to upgrade his MS 391 with a high-performance air filter and a modified muffler. As a result, he was able to increase his daily timber harvest by 15%, which significantly improved his profitability.

Case Study 2: Firewood Supplier

A firewood supplier in Maine was having trouble keeping up with demand during the winter months. He invested in an upgraded chain for his MS 391 and was able to cut firewood much faster. This allowed him to meet the increased demand and increase his sales.

Actionable Takeaways and Next Steps

So, you’re ready to upgrade your Stihl MS 391? Here are some actionable takeaways and next steps:

1. Assess Your Needs: Determine which upgrades will provide the most benefit for your specific needs.
2. Set a Budget: Determine how much you’re willing to spend on upgrades.
3. Do Your Research: Research different brands and models of aftermarket parts.
4. Shop Around: Compare prices from different retailers.
5. Install the Upgrades: Install the upgrades yourself or hire a professional.
6. Tune Your Engine: Adjust the carburetor if necessary.
7. Test Your Saw: Test your saw to make sure the upgrades are working properly.
8. Maintain Your Equipment: Regularly maintain your equipment to ensure optimal performance.

Final Thoughts: The Value of a Well-Tuned Machine

Upgrading your Stihl MS 391 can be a worthwhile investment, but it’s important to do your research and plan carefully. By understanding the costs and benefits of each upgrade, you can make informed decisions and optimize your saw for maximum performance. Remember, a well-tuned machine is not only more efficient but also safer and more enjoyable to use. So, get out there, get wrenching, and get cutting!

Learn more