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Discussion Starter · #1 ·
I'm in the process of getting a new exhaust for my bike, I already have a few cosmetic upgrades to the rear of the bike and would like to keep the factory set up so I'm kinda limited to the choices. I'm leaning towards teh Akra or Scorpion. I hear the akra has a flat spot at around 8000rpm. Anyone have any advice on which sounds/performs better? I only want opinions from ppl that heard the exhausts or have one themselves. Thanks
 

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Discussion Starter · #3 ·
everyone keeps saying that the exhaust dies out at 8k. Almost like it hit the revlimiter and picks back up.
 

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Who is "everyone?"

A flat spot in the powerband is defined as an area where the hp or torque stops increasing. Basically the curve flattens out briefly. It doesn't feel like you hit the rev limiter - as that kills ignition and makes the bike surge it just....

feels weak through that range.

Some aftermarket exhausts are prone to this problem because their back pressure characteristics do not mesh well with the engine itself (which relys upon some back pressure to help scavenge the cylinders).

Now here's the interesting thing, Akra is considered to be one of the better exhaust manufacturers, and I wouldn't have a problem putting their product on my bike should the funds fall into my hands. But I don't doubt for a second that it would have a flat spot if you didn't correctly remap the fuel system. Because there is going to be at least one spot in the throttle range where you're going to be running lean as hell, and that's going to affect performance.

A bike that is properly tuned should not be exhibiting these symptoms. So if you're going to be fitting an aftermarket pipe, do yourself a favor. Get an aftermarket intake as well, buy a power commander - then take your bike to a shop with a dyno and an exhaust/gas analyzer. If they're any good they'll build you a custom fuel map for your bike that will give a perfect ratio 13:1 or 14:1 depending on the bike through the entire throttle range.

This means you likely won't end up with that "flat spot" some people talk about.
 

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Good description Sev :mfclap

People underestimate how much time and money the manufacturers put into developing the exhaust system for each model. Yes an aftermarket system can be even better but it has to be developed at a compromise between getting that extra performance and working with the standard engine / mapping. To achieve the gains the third party manufacturer has to also take the hits somewhere in the curve which can often mean a flatspot or two.

Now consider that when you've added a system and maybe got a flatspot the engine is not running optimally when it's in that rev range - probably running lean. This in turn is adding extra wear and tear to the engine (if only a small amount) and you've also got the annoyance factor when you're riding the bike.

If you're going to spend the money on an aftermarket exhaust you really should go the whole hog and get a Power Commander and a custom map produced for it (every bike / exhaust combo will have a slight variance). If you change the air filter to a different type at a later date you should get the mapping redone again as well.
 

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yeah if u spend the money for a exhaust u won't to get a pc and get it maped for the exhaust u are runnin, and if u decide to get a aftermarket filter then wait and get everything tuned at 1 time, that way u don't have to go back and adjust anything
 

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yeah if u spend the money for a exhaust u won't to get a pc and get it maped for the exhaust u are runnin, and if u decide to get a aftermarket filter then wait and get everything tuned at 1 time, that way u don't have to go back and adjust anything
I was going to say that. Go whole hog all at once, don't just do one thing at a time.
 

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I was going to say that. Go whole hog all at once, don't just do one thing at a time.
Agreed!

I just wanted to emphasise the point that if you were to change anything later (maybe just going to a different air filter type) you should get the map redone.
 
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