11/07/2023
Here is a bit of tech information for those who are wanting to understand a little bit more about their Harley and how they can improve (or in our worked example) hinder the performance of their bike.
Your exhaust system is responsible for removing exhaust gasses (scavenging), creating back pressure, removing heat, and muffling the sound of the engine.
But with so many designs, fitments, and manufacturers out there; how does the customer (you) know exactly which system is best for them? Do you want:
Something that performs the best (based on your modifications)?
Something that sounds the best?
Something that looks the best?
Or a combination of a few of those things?
In this write-up we will cover the performance of an exhaust system on a Harley and how it can impact or improve the overall running of the motorcycle.
As mentioned earlier the design of the exhaust system effects the running of the motorcycle. The best designed systems can create a level of back pressure (good for low down torque/response) and remove (scavenge) the exhaust gasses effectively at high RPM.
By using a combination of a stepped header pipe design, coupled with a good high flow collector and muffler - a well-designed system can do all of this and more!
If a system is too free flowing (open pipes/drag pipes) then the bike cannot build up the back pressure it needs earlier on in the rev range to give the initial torque/punch. This can result in a “flat” feeling bike or a bike that feels like it needs to be “wound right out” (high RPM) to make any power.
Alternatively, if an exhaust system is too restrictive then the exhaust gasses may not be scavenged or removed from the engine causing excess heat/pressure build-up and a loss of top end power.
So again, how do you as a customer know you are getting the right exhaust for your bike?
Talk to your local dealer! We can advise you about systems we know work well, systems we have fitted and tuned ourselves and can stand by our numbers/results.
Be warned! There are Wolves in Sheep’s clothing when it comes to exhausts. Below is a dyno graph showing the direct impact of a poorly designed exhaust which was badged as a “Vance and Hines” exhaust! A customer of ours purchased this so-called Vance and Hines system off the internet, only to find out the hard way (once fitted) that it was anything but! After re-fitting a quality pipe (and making no other mods/tuning) the bike instantly ran how it should.
Give us a call here today at Harley Davidson Feilding and we can talk to you about your exhaust and what modifications you have (or are wanting to do) so we can tailor a package that works well for your setup. We can then dyno tune your bike and have everything working as it should!
2019 Harley-Davidson dealer of the year