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Changing Exhaust, What is a tune?


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This is the first bike I've ever owned and I own a 97 Geo prizm for a car. I have never really had to opportunity to learn alot about vehicles and how to work/upgrade them. I have always been interested bu have never owned anything I felt like was worth the money/time/effort.
I want to change my exhaust out for something a little more rumbly and I seen and heard the Akrapovic and I like it alot. Though before I commit to buying it I really want to know what I'm in store for with installation (Could this be something I would be able to do?). After installation I have heard from some of my coworkers is that it would need a tune. I also saw online something called an EJI kit and is that the same thing as a tune or two totally different things? How does a tune work and how does and EJI work and what exactly do they do?

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  • Global Moderator

Hi and welcome. Great to see you posting and asking questions. There is a lot of info on exhausts and tunes, it is a very popular mod. A great place to start is here. They have everything you need and you can't beat the price and expertise. Do a little search here and you will find even more info.
I don't think it is a must to have a tune when you just change the exhaust but the bike will benefit form it even if the exhaust is stock. They come very lean from the factory to accommodate strict emissions. A tune will everything smooth out and taps into the full potential of the engine.
If you take it further and open up the intake, a tune will be necessary because you will lean it out even more (you basically add even more air when opening up the intake).
If it is a DIY job depends on your experience and tools. It is not difficult, basically these kits are bolt on/plug in, but you need to know what you are doing. Bolts need a specific torque so you will need a torque wrench etc.. but the forum and Dobeck can help you for sure. 
I am sure others will chip in. I have been wrenching for quite some time so I wouldn't hesitate doing it myself. 

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  • Premium Member

Some of the exhaust options are built around not having to change the air:fuel ratio. That's all a tune does is give the bike the optimal ratio.
For example the titanium akrapovik with the catalytic converter installed is designed to be plug and play. If you omit the cat, or open up the air box then the ratio is off and something like the EJK (electronic jet kit) is required to increase fuel delivery across the RPM range.
Like Guru said, US emissions controls already has the bike near its limit for running lean (more air, less fuel). Lean ratios run hotter than rich ratios would(more fuel less air) but spit out fewer emissions.
If you're not confident in your mechanics skills, there might be some members local to your area or nearby willing to help. Otherwise you can fork over .5 hr to 1 hr labor at a shop who will install it. Usually around $75/hr shop labor plus some small fees.

Everything went braap.

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