I was on the Mikuni web site and noted this:

Exhaust system:

Straight pipes:

Open straight pipes perform poorly in the 2500 to 3800 rpm range. If they are 34" or longer, they do not perform really well at any rpm.

Symptoms include missing, backfiring through the carburetor, reversion (fuel dripping out of the air cleaner) and poor acceleration.

Open mufflers:

"Gutted" mufflers with stock (or stock-like) header pipes tend to perform poorly in the same rpm range as straight pipes and exhibit similar symptoms.

Long thin mufflers:

Long, small diameter mufflers with full-length baffles often exhibit the same symptoms as straight pipes, although their over-all performance may be better.

High performance 2-into-1 systems:

These systems are often poor performers in the 2000 to 3000 rpm range. Most 2-into-1 exhaust systems deliver a significant torque dip at 2500 which is slightly less than 60 mph in top gear for most stock Harley Big Twins.

Header pipe diameter:

The great majority of Harley engines, of any displacement, do their best work with 1-3/4" diameter exhaust pipes. Larger pipes tend to suppress mid-rpm performance and, for that matter, seldom deliver the best power at high rpm either.

Header pipe length:

The stock header pipe is about 30". Multiple tests, made by several groups, confirm this length as being very nearly the best for all-round performance. Shorter (less than 27" and longer (over 32" header pipes significantly reduce peak power, throttle response and over-all performance. An exception to this "rule" are a couple of the high performance 2-into-1 systems which work very well with longer (and un-even) header pipe lengths. Stock Harley header pipes are near-perfect in diameter and length.

Muffler size:

It is not possible to make a muffler quiet, small and powerful at the same time. One can choose power and small, quiet and small but not all three. The reason stock mufflers are poor performers is because they are small and quiet.

However, small and loud is not a guarantee of performance. In general, small mufflers with large straight-through, perforated tube baffles (looks like a tube with many holes drilled in it) make the most power and the most noise. An exception to this rule (there may be more) are the popular H-D Screamin' Eagle (and Cycle Shack) small slip-on mufflers which perform very well yet are not straight-through designs. The popular louvered core baffles restrict flow at full throttle & high rpm and reduce power a bit as a result.

I'm sure it does matter to the power curve. It would be interesting to see the charts for different pipes on the same bike.

I don't think you can compare that info for our engines. Hd's have a higher rpm rev limit, so I don't think their rpm ranges would be anywhere close to ours. They mention in top gear at 60mph they are 2500rpm, we aren't near that at all, think we are closer to 1800 rpm, 700rpm difference is quite a bit. I'm still in 4th gear at 60 and still running less than 2500rpm.

Best way to tune a carb as I mentioned before is by AFR in the 3 ckts; I used the AFR chart here:
http://www.daytona-sensors.com/tech_tuning.html
I also recently found the same type charts in a couple other sites as well. So I gather there is some credence to these numbers.

As you can see, there is a spread in AFR for each ckt. Also, I think the very first one is when choke is on, but they do not say that, just makes more sense to me that it is with choke. Also, if you notice, if you look at either their economy AFR or their performance AFR #'s, from all 3 ckt's, there is only an approx a 1.2 spread thruoghout from their richest to leanest. Keep this in mind too:
maximum engine torque occurs at about 13.5 AFR. While the torque curve appears relatively flat from 12 to 14.7 AFR, the effect on cylinder head temperature is more pronounced.
So why run a AFR of 12.5 at cruise if at this point it's gonna eat a lot of gas and result in poor cruise mpg's. And when you get on it anyway, you should be going richer and get to that AFR that will give you the max TQ anyway.

I did a lot of as much as possible controlled test, cruise AFR 13 yielded 40mpg, cruise AFR 14 yielded 50mpg (cruise speed 65mph)
cruise @60mph AFR 13 4th gear punch it to 80mph was a seat of the pants diffcerence compared to a AFR 14 @60mph and a punch to 80. There was no noticable seat of the pants of a 13.5 afr @ cruise to the 14. It took a full point for me to notice a seat of the pants, at least this was my own observations. Any of my tests were done multiple times, too many to count, all done on the same road as well, so as you can see, I was quite anal about it. My cruise test was a minimum of 125 miles, 65 to 70mph, no blipping, no quick acelerating, just a good steady pace to see what mpg was attainable in the best possible conditions. And all were done during the ride season with temps over 75deg's, but would say mostly 80 to 85. I also used the same Dyna for all my runs, all runs done when engine was fully warmed by at least a hours
ride, close to same ambient temps, the humidity was probably the only thing that changed, then again, that's Fl for ya. lol

I don't know about all that science. I just put on V&H Short Shots and could not be happier. Removed the AIS and no jet changes or anything. There is no backfire, popping, just great sound and it feels like there is a bunch of new power and smoothness, but it just might be the new sound.

Lemual, I too have the V&H Short Shots...you want to feel and hear a difference in the rumble and the torque, get yourself some Big City Thunder Monster baffles for them....totally amazing, they bring out the devil in them

Jona wrote:
Lemual, I too have the V&H Short Shots...you want to feel and hear a difference in the rumble and the torque, get yourself some Big City Thunder Monster baffles for them....totally amazing, they bring out the devil in them +1 Jona, I have them in my Long Shots and they rock!

Lemual; I could not agree more. I changed from the 3' big straights from Hardkrome to the V&H short shots and simply love em. The sound is great and the engine really does seem to run very smooth with them. I could not be happier with the short shots.

Jona; what do the monster baffles do for the short shots. I am not familiar with the name and know nothing about them,

Some info. http://www.bigcitythunder.com/

2wheels, well, they lower the timbre to a "Barry White" rumble at idle, and get frenzied in a "Joe Cocker" fashion when ya give it the juju...and they add HP as the icing on the cake...you'll love them

I second that!!