I originally started with 6 3/8 " holes and cut out spark arrestor. After adding the <> G snorkle and trying every possible combination of jets and needle position I finally settled on 145/148 with one shim under needle. I was very pleased with this combination as I could actually beat out my friend on his P700 with module.

I have read about people putting larger and even more holes through their baffles for an even greater power increase. Not being one to ever stop tinkering I cut the end off again and added 4 more 3/8"holes, three were between the original 6 and the fourth right down the centre.

Now I was expecting either a little more power or no noticable change at all. What I got was a loss in low and mid range pull, what gives!!!!!

 

during the early days there were guys splitting the muffler and working on it, we never heard the results and then came the mod we call nyrocs. i thought everything that could be done to the mod had been done, and i believe most had good results or maybe didn't notice the difference,so no bad report. i would weld the extra holes up and see if it is back where you need it. not all results are successful, maybe it is a elevation thing. you are at sea level and most of us are a lot higher. good luck, pretty impressive results you had there

 

Your motor requires a small amount of back presure to get the most out of the bottom end. That is why there are different sized pipes for headers depending on use. The big open pipes build maximum top end but cost some on the bottom. Headers for tow vehicles or off roaders have smaller tubes or restrictor cones in the tubes to build better bottom end and midrange. It is a matter of balance just like setting up cams, too much lift or over lap and you lose bottom end. close up some of the holes and you will get back what you had.

 

Yep, what they said. It will loose velocity, until your engine gets in the higher rpms, and starts moving more air. A smaller aftermarket pipe will have greater low end air flow than a slightly larger pipe. Then when at higher rpms, the bigger pipe rules.

 

Ok looks like I went too far..... so I guess it may be time for an after market exhaust.

I am curious, however, if I may have the same problem with an after market due to the fact that any of them should flow better (less back pressure) than the modified stock even with the # of holes I have. I have compared the opening in the end of the modified stock exhaust, since I cut out the spark arrestor, to a big gun and the opening on the big gun was still larger.

Would this be the case???

 

Im pretty sure the aftermarket exhaust will be alot better than your modified stock exhaust. Your modified exhaust has more air tubulance, with exhaust going in different directions. An aftermarked pipe would flow smoother, and out ONE exit.

 

PLUS, aftermarket exhaust is more 'tuned'. It has a better air flow design than your home modified exhaust.

 

So would the after market ones still cause a low end loss of power or, because they are tuned, would this not apply.

What is the quietest after market and which are tunable with the supertrapp type disks.

 

prairie dust try going with bigger mains again i started with 165 160 mains when i first did hmf air box lid mod and it felt flat so i put 185 180 mains in it and WOW big differance it explodes out of the hole now no module ether

 

I was at 148/150 but plug chops indicated a rich condition so I went back to the best combo I had at 145/148. Even when I had the 148/150 combo with the additional holes in the muffler I was reading rich.
Could the problem be still not enough air even with the <>g.

I was looking at the 02 airbox and there is a spot in it that looks like a storage compartment. At about mid way into the airbox I could drill holes in the little wall inside this compartment. This would let air in almost directly above the stacks. I am thinking this may help minimize the turbulence effect some have complained about. Others have also mentioned that hot air could decrease performance, but it is still more air even if it is less dense than that coming from the snorkle....

Any thoughts .......