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View Full Version : Endcap swap on Screamin eaglre Fatshot



roadglide man
09-29-2009, 09:45 PM
I have had tuning issues on these mufflers. Talked to my tech who also does dyno tuning and has knowledge with superttapps says it is hard to make a noticeable change to the performace of the bike when running open end caps and removing only a few dics either way. So I ordered 24 new discs 12 per side. I think I may have compressed them from over tightening. Just a precaution. And also order solid endcaps. I will start at 12 like they come from supertrapp. I noticed that you guys also recommened 10 if the motor is stock. Does that mean bone stock. No high flow air cleaner or down load. Because I have the air cleaner and stage 1 download. Should I try 12 at first or will that be to lean. I hope the capping off will cause more back pressure and give me the preformace that I am looking for. Please advise.

bschultz
09-30-2009, 09:19 AM
Yes, 8-10 discs "bone" stock. Traditionally (history) tells us most OEM exhaust are restrictive and an after market exhaust will usually allow the engine to breathe better. A higher flowing air filter, means more air flow and a "staged download" should mean more fuel, which should complement each other AND the initial logic is you will need more exhaust flow; however if the exhaust flow was initially MORE than adequate the additional flow needed may already be there.

roadglide man
09-30-2009, 11:24 PM
I was following ya and ya lost me. I am changing to a closed end cap so I can create a better back pressure. A little more silent running. I guess what I need to know from you is this going to be a better set up closed with 12 or open like they came with 10. I know that with the open end it will deliver more horsepower and closed more torque. I like bottom end power. Pull is what I like. Top end is not my thing. I own a diesel truck. I like torque. Although I am not pulling or hauling anthing on my bike I like to pull away at low speeds or up steep grades with power to spare. I dont really like to rev it very high. I dont mean to lose ya. What do ya mean by more that adequate. I am a little comfused. Thx.

bschultz
10-01-2009, 07:25 AM
The flow should be adequate with 12 discs and the "closed" end cap, if you find it flat on top start adding discs. I would even try experimenting with 10 or even 8 per muffler. Make sure you use anti-seize EACH and EVERY time you swap out discs.

roadglide man
10-01-2009, 08:43 PM
Thx. I assume you mean 12 discs per muffler. When you say flat on the top do ya mean when I take it to redline? I aasume adding disc would be like adding small amounts of horsepower. I worry about it being lean with so many discs at top end speed. Although I dont ride that way. On occasion I may roll it on hard but never through the gears. I will use anti-seize each and everytime. Also I will torque them to spec 15 to 25 inch lbs. As soon as I recieve them and the weather gets better I will begin tests. Thx for the advice.

bschultz
10-02-2009, 09:18 AM
Correct, per muffler. Flat - no longer pulling or falls off on power, can be an indication of not enough exhaust flow and can be remedied by adding discs. Keep us posted.

ccraig
10-21-2009, 12:53 PM
Hi, I'm still trying to understand the use of disc's and disc count wheh using an open ended cap.

bschultz
10-21-2009, 03:34 PM
Example; You have a bike that has one of our pipes on it (w/4" discs) and it's running great but you are looking for more sound. It's currently running 20 discs with the "closed" end-cap. Remove 10-12 discs and the closed end cap and replace them with an "open" end-cap and the flow/performance/tune will remain the same; however the results will be more sound.

ccraig
10-21-2009, 06:17 PM
Right, I understand about the sound but with the open end cap the exhaust gases are going straight out the open end cap, what makes the gases want to make a 90 degree turn and go out between the discs? When using the open end cap what need is there for the discs?
Thanks

bschultz
10-22-2009, 07:11 AM
The size of the hole in the open end cap is smaller than the disc hole and core diameter. The exhaust gases exit the open end cap at a specific flow rate with the excess gases exiting the discs.

ccraig
10-22-2009, 10:57 AM
Thanks, Craig