Harley Davidsons are the most customized bike in America. The most popular aftermarket upgrade? Exhausts. Your Harley’s exhaust system plays a key role in performance. So even though the new exhaust makes your bike look and sound sweet, that upgrade could come at a big cost. How do you know if your new exhaust is causing problems?
Troubleshooting Performance Issues with Aftermarket Exhausts
We’ll go ahead and assume you’ve used a quality aftermarket exhaust designed specifically for your Harley Davidson model. But even the best quality aftermarket parts can cause issues because your bike was engineered for the EOM part. All exhaust upgrades impact your exhaust flow. This includes 2-1, 2 – 2, shorties, performance mufflers, custom jobs and full system – and even slip-ons or messing with EOM baffles.
You cannot alter your exhaust without, at a minimum, visiting your dyno tuner. Quality aftermarket exhausts like Bassani, Rinehart, Rumble, and Vance & Hines must be fitted professionally and then tuned to your ride.
Woolich is Designed Specifically for Racetrack Performance
Woolich Racing is the top choice for professional motorcycle racers. Our ECU flashing allows you to tune with more precision across more engine systems. Woolich Racing’s precision tuning, especially tuning that removes limiters and adjusts air-fuel ratios, is designed for track use only. We recommend you seek advice about emissions and other applicable local laws before removing the speed limiter and adjusting your air-fuel ratio if you intend to ride on the street.
America Doesn’t Love OEM Harley Davidson Exhausts
All aftermarket part upgrades impact the performance of a bike. So what’s the big issue with aftermarket exhausts for Harley-Davidson in particular?
- Harleys have specific backpressure requirements. Aftermarket exhausts don’t always meet them.
- Aftermarket exhausts can cause your Harley Davidson to run lean (more air in the air-to-fuel ratio) which can reduce performance and cause overheating issues.
- They can cause engine inefficiency which leads to poor fuel efficiency.
- Harley Davidson OEM exhausts comply with regulations around emissions and noise. The company is legally obliged to create their exhausts to meet these standards. Your aftermarket exhaust upgrade may not comply with local laws. It can also impact your insurance coverage.
- To keep the bike running efficiently, you may need to invest further in a fuel management or air intake system.
- The biggest concern is that your aftermarket exhaust, poorly chosen or fitted, can cause excessive heat build-up in the combustion chamber. A poor-quality part or incorrect fitting can cause exhaust leaks and damage to engine components. This can trash your valves and pistons and create expensive problems in the bike.
Harley Davidson Aftermarket Part Performance Issues
After installation, you’ve noticed:
- Slower acceleration
- Clunkier gear shifting
- Your bike feels like it’s “missing”
- Decreased power and torque
- Poor handling
- Rattling or unexpected noises
- Running hot
- Slow to cool when parked
- Poor fuel efficiency
- Unexpected change in exhaust volume or tone
Should I Remove the Exhaust?
No. Assuming it’s a quality part and correctly fitted, the aftermarket exhaust is not the problem. The issue is how its design alters key elements of engine performance. You have the best Harley Davidson aftermarket exhaust for your ride – you just have to tune your engine to make it perform.
What Causes Performance Problems?
Okay, buckle in. This is going to be a wild ride! The Cliff’s Notes are:
- Air-Fuel Ratio Problems – Too much air and not enough fuel makes your bike run “lean” which can lead to a whole host of issues. Learn more about air-fuel ratio in bike performance.
- Scavenging, Reversion and Backpressure Problems – Exhaust gasses going where they shouldn’t go will impact performance, efficiency, and exhaust tone and volume.
- The Type of Harley Davidson Aftermarket Exhaust – each type of exhaust is designed for a different result – even a performance part can trash your bike’s performance without the right tune.
- ECU Flashing vs Dyno Tuning – Dyno Tuning helps tweak your bike to accommodate the new part. ECU Flashing rewrites your Harley Davidson’s “brain” to make the part perform… on steroids. Woolich ECU Flashing tunes your bike to the limit of its potential performance.
Air-Fuel Ratio Issues with Aftermarket Exhausts
Air-Fuel Ratio is the single most important factor in motorcycle engine performance. The balance of air and fuel determines how efficiently (or inefficiently, if you’re after a powerful ride) your engine runs. Every aftermarket part you install can impact your air-fuel ratio and create a chain reaction of performance problems. Learn More.
Where you ride, how you ride and what you ride all impact your AFR needs. The wrong AFR can lead to engine issues, poor fuel economy, poor torque and performance and poor throttle response. It impacts every part of your ride.
What does an AFR problem look like on a Dyno Map?
What can an ECU Flash do to improve it?
Woolich ECU Flashing tunes your bike to the limit, allowing it to perform to your specific needs. The standard ratio isn’t for everyone. An ECU Flash with Autotune lets you set your own individual parameters and have your bike adjust in real-time.
Scavenging
Scavenging is how your bike removes exhaust gasses from its engine’s combustion chamber. The key to scavenging performance is creating a vacuum – to efficiently suck out waste gas and suck in fresh air and fuel. Done right, this creates improved power, throttle response, and a nice deep exhaust note. Exhausts like Vance & Hines Power Duals and Bassani Road Rage have carefully designed longer primary tubes and collector sections for enhanced scavenging.
What does a scavenging problem look like on a Dyno Map?
What can an ECU Flash do to improve it?
A Woolich custom ECU Flashing for your Harley Davidson model rewrites the timing during the exhaust stroke of the engine, ensuring the optimal valve opening times for your specific, on-the-road performance needs. Expect improved power, better throttle response, and a satisfyingly deep Harley Davidson rumble.
Reversion
Reversion is where exhaust gasses flow back into the combustion chamber instead of evacuating through your new exhaust. This is because your exhaust system is creating pressure waves, forcing gasses back into the chamber. The result is a ride that feels “sluggish”, reduced throttle response, and it may sound, well… “farty.” It’s usually the result of a problem with the length or diameter of your new aftermarket exhaust and is especially a problem if you’ve opted for a significantly larger or smaller pipe.
What does a reversion problem look like on a Dyno Map?
What can an ECU Flash do to improve it?
A Woolich ECU Flash rewrites your bike’s brain to understand the potential and limitations of a new part and fine-tunes the engine to minimise the impact of an oversized or lean exhaust system.
Backpressure
Backpressure is the necessary resistance to the flow of exhaust system gasses. The correct level of backpressure improves low-end torque in your engine. By contrast, too little or too much backpressure reduces your engine’s performance. Backpressure imbalance can feel like loss of torque, intermittent performance problems, and a loud, unpleasant exhaust note.
What does a backpressure problem look like on a Dyno Map?
What can an ECU Flash do to improve it?
Backpressure is one of the most misunderstood elements of motorcycle engine efficiency. It’s also one of the most difficult for ‘send in flash’ products and piggyback systems to manage efficiently. Woolich ECU Flashing is the option used by performance riders because we can deliver precision (and in real-time with Woolich Autotune) to ensure backpressure levels aren’t just what the part’s manufacturer recommends but the optimal efficiency for your specific Harley Davidson – not just the model, but your specific ride with your specific aftermarket exhaust.
Types of Harley Davidson Aftermarket Exhausts that Trash Performance
The type of exhaust upgrade you choose can cause higher “risk factors” for performance problems. Your dyno tuner may be able to diagnose these, or maybe not. The best way to get the maximum performance from your new exhaust is to do a full ECU Flash.
- Full System Exhausts. Changing up your header pipes and muffler should deliver major power increases, better performance across a broader power band and improvements to throttle response. Anything short of that needs your attention.
- 2 into 1 Exhausts. Combining the two exhausts into one should drastically improve performance, improve torque and throttle response (especially at lower RPMs), and give the bike guts. Improper fitting, or the wrong aftermarket 2 into 1 part can create issues with reversion and throw out the backpressure balance.
- 2 into 2 Exhausts. While not as dramatic as 2 into 1 exhausts, you should notice improved power and torque and that signature Harley Davidson sound. If installing an aftermarket 2 into 2 exhaust has reduced your bike’s performance in any way, you should speak to your Dyno Tuner or find a Woolich Approved Dyno Tuner to do an ECU Flash.
- Shorty Exhausts. Yeah, that sound. You should notice minor performance improvements, but we know it’s all about that sound. Changing the length of your exhaust can create problems with reversion and backpressure. Any reduction in performance is a red flag.
- Performance Mufflers. Designed specifically to enhance scavenging, prevent reversion, and balance backpressure, you should notice performance gains and improved sound. These bad boys are designed specifically to improve exhaust gas efficiency. If your bike isn’t geared to that, you won’t feel the full kick. Talk to your dynotuner.
Find a Woolich Approved Harley Davidson Dyno Tuner Near Me
Baffles and Engine Performance
Removing or replacing baffles can have a major impact on your bike’s performance. Harley Davidson OEM baffles keep backpressure in balance. Removing them or replacing them can very quickly throw out your engine’s exhaust efficiency.
Harley Davidson ECU Flashing
ECU Flashing is about tuning your Harley Davidson to its limit – and getting the most from your upgrades. Woolich Racing ECU Flashing for Harley Davidsons allows you or your dyno tuner to rewrite the way your Harley engine works.
Learn more about our free ECU Flashing Course for Individuals and our Advanced Dyno Tuner ECU Flashing Course.
Harley Davidson Specific Challenges for ECU Performance Flashing
Harley Davidson ECUs are technically a little different to those from other manufacturers, so there are some key points to be aware of in order to avoid potential problems. Most models of ECU from other manufacturers can be written to using a stock bin file with the same part number as the ECU, and the bike will run fine. Harley Davidson ECUs require that the bin file first be read from the ECU using the Woolich Racing Tuned (WRT) software. This file is subsequently used as the starting point for any modification and is then written back to the ECU.
Important Note: Writing a stock bin file to a Harley Davidson directly from the Woolich Racing Tuned (WRT) software without first reading your own ECU can cause permanent damage! You can only write to a Harley Davidson ECU with a Bin File that has been read out from the same bike. Please use a copy of the backup file as your starting Bin File, as described below.
Harley Davidson uses the same electronics platform and ECU across many models. Woolich Racing categorizes the Harley Davidson models into groups (e.g. Softail, Sportster, etc.) as often the differences between individual models within a group are cosmetic or frame-related. The ECU part numbers for Harley Davidson are then shared across several models, so are not always unique like they are for other manufacturers.
How To Flash Your Harley Davidson ECU
In order to write to your Harley Davidson ECU, please follow these steps:
- Before writing to the ECU, read out the bin file from your ECU and save the file to a known location on your computer.
Do not modify this file!
Once the bin file has been read, click ‘File’ > ‘Save’, and save the file as your MASTER BACKUP file.
Use this file as a starting point that you can always revert to should you want to return your ECU to stock.
It is a good idea to use the Motorcycle VIN as the filename to easily identify it in the future. - Create a backup copy of the bin file that you read out in Step 1 above.
Save this file as your TUNING file.
Use this bin file for all changes made during tuning.
You must only use this saved TUNING file for tuning/setting changes and writing back to the ECU.
If you make significant changes, it’s a good idea to save versions of the bin file at stages that you can easily revert to if you have problems later. - When you have finished making changes to the tuning and would like to write them to the ECU, be sure to load the tuned bin file created in Step 2 above.
- Write to the ECU normally.
Correcting Harley Davidson Aftermarket Exhaust Issues
Talk to your dyno tuner about tuning your bike for the new part. If the issue can’t be resolved on the dyno, talk to Woolich Racing about how to tune your Harley Davidson to the limit. After all, if you liked limits, you wouldn’t ride a Harley.