Exhaust Pros and Cons

[Buckethead]

Biggest questions here are:  will 1000 header fit 800, and can you run either system without ECU?  I can't imagine that the Termi full system performs that much better than the Arrow that it requires ECU mods and the Arrow doesn't.

AFAIK, it is POSSIBLE to run any aftermarket system without changing the fueling AS LONG AS you don't change the intake.

Same amount of air in + same fueling + free-flowing exhaust = you can get away with it.

If you look at a DP accessories catalog, every exhaust system that comes with an ECU also includes a new airbox lid/filter.

More air in + same fueling + free flowing exhaust = dangerously lean mixture.

Your power gains from JUST an exhaust system will be minimal. In fact, freeing up the exhaust with the same fueling, while it does increase top-end HP slightly due to increased flow ability, has also been shown to LOWER low-midrange torque.

The Arrow and Termi full systems are comparable. Neither one flows decidedly more than the other. Where the Termi system comes out ahead is that the guys who designed your bike figured out how your bike would behave with the system installed and made a factory ECU optimized for that system.

You can get comparable, possibly even better, results from the Arrow system, but it will require an aftermarket fuel-management system (nemesis, etc) and will require tuning.

As far as the headers, I couldn't tell you. I'd say PM ducvet.

[Howie]

Slip-ons made little difference on the bikes with the narrow crossover and no cat.  Tom's bike is a much different case, big drop in back pressure and little space for expansion.

Someone I know has a 900 with a full system.  Big difference. 

[Ivan]

Not true. When I had my custom shortie exhaust on last year, I lost power becasue the baffles were too close to the heads.

That has little to do with back pressure in absolute terms, and a lot to do with the timing of the pulses that are reflected back to the exhaust port on the head.  If the pressure reflection hits the exhaust port when the valve is open and the engine is trying to push the exhaust gasses out, you end up with reversion.  I once had a Sportster with wild cams that provided a lot of overlap (intake and exhaust valves open at the same time).  With short pipes, the reversion was so bad you could actually see a fog of fuel/air being pushed back out of the carburetor.  For the most part, short pipes suck when it comes to performance.