SuperTrapp w/ Super E not so super

[GenShovel]

I'll make this short and to the point. 02 FLHT, Installed SuperTrapp with 20 disks and tuned CV carb and bike ran good. One the top end the bike was choking out like it was running out of fuel around 90 mph. I knew I was getting a super e in 2 weeks so I didn't tune any further. Installed the e, did some initial tuning and it runs great on the low to early top end but the bike seems to top out at 110 mph at 4500 rpms. No more power left. I have a hard time believing I am using everything the bike has.
Anyone with this setup? Trying to shorten my tuning time between jets and disks
Specs:
88 TC
Supertrapp w/ 20 disks
Super E w/ 29.5 and 70 jets
Kuriakyn Hyper Charger
everything else stock

[Heretic]

the supertrap is really not the best pipe for that bike, if you are wanting to peg the needle. You will need the cap with the hole in the end to maintain exhaust velocity....

[GenShovel]

Thanks Heretic.
I have seen a lot of posts all over talking about how to tune with an open end cap but I haven't really seen any posts about the performance increase from it. However, for the price of the open end cap it is certainly worth a shot. I will let you know how it goes

[Heretic]

Supertrap design is flawed from the very beginning. It is tuning the exhaust from the wrong end, and the effectiveness is limited

let's break this down to physics, and put it in laymens terms. The idea that the exhaust valve comes open and the piston pushes exhaust out is not really the way it happens...
There is so much residual pressure and heat in the cylinder, from combustion, that when the exhaust valve opens, gasses escape, before the piston starts upward movement. These gasses make the primary exhaust pulse..Now there are a lot of factors involved in the velocity of this . rather than get into all the variables here, let's just say this pulse exits at about 1,300 feet per second. This is within the range, and is just a number I am using for the simplicity of an explanation. Then the piston moves upwards, and pushes the secondary pulse of gasses out at about 600 feet per second.....Now idealy, you want to keep the velocity of the primary pulse high enough that it leaves a low pressure area behind it. This helps draw the secondary pulse out, with less back pressure against the piston. This is called the scavenging effect
if your exhaust scavenges correctly, the muffler does NOTHING but change the noise. tuning there is about as effective as wiping your nose before sneezing

[GenShovel]

Makes sense. I ordered the open end cap this morning. Should have it by Thursday so I should know something by Thursday night or Friday. I'm gonna start with taking out 8 disks and add the open end cap and progress from there. Thanks again! I will keep you posted.

[Heretic]

one more thing to take note of...combustion in the cylinder is insulated...the noise you hear as exhaust has more to do with exhaust velocity than the combustion process. The primary exhaust pulses are traveling faster than the speed of sound. ...Much of your exhaust noise could best be described as mini sonic booms.
The quieter you get, the less velocity, and the less effective the scavenging effect there is........This is the reason for longer pipes, and the expansion in diameter. Expansion allows the velocity to decrease. This pipe expansion must be far enough away from the head that the secondary pulses has exited before the primary pulse loses velocity

[GenShovel]

So I went to an open end cap and took out 11 disks and still no change. Gonna keep tuning and will let you know

[GenShovel]

So here is the latest; after talking to a couple of buddies they both said it sounds like I was running out of air. As a test I removed the Hypercharger cover plate to give the carb and intake all the air it could handle and there was no change. The only other thing I could think of was an ignition issue so I replaced the plug wire and plugs. Still no change but the idle did smooth out a bit so it definately need them. Now I am really stuck. Let me know what you geniuses think.