Supertrapps and the discs

[vannlater]

Hi.
I have supertrapps with 4 discs in each and open end cap.
What happends if I add 4 more discs in each supertrapp ?
Do the sound change, performance etc ?

 

[SvenDGAF]

Hi.
I have supertrapps with 4 discs in each and open end cap.
What happends if I add 4 more discs in each supertrapp ?
Do the sound change, performance etc ?

More discs means more sound, but less back pressure. I think this will change the power curve, giving you more top-end performance. But not a lot.

Less discs, quieter, but more back pressure.

 

[vmax2extreme]

More discs means more sound, but less back pressure. I think this will change the power curve, giving you more top-end performance. But not a lot.

Less discs, quieter, but more back pressure.

Your thinking is opposite, the more discs the better. I run 8 discs with the comp open endcapps. The less discs, the less back pressure! If you dont believe me, call Kerker and ask. I did! My carbs are all stock, added a K&N filter and all is well. I get about 42mpg and the bike runs/sounds awesome.

BTW, Kerker recommends to run about 8 discs per side with the open or closed caps on a stock vmax.

 

[85vmax]

Your thinking is opposite, the more discs the better. I run 8 discs with the comp open endcapps. The less discs, the less back pressure! If you dont believe me, call Kerker and ask. I did! My carbs are all stock, added a K&N filter and all is well. I get about 42mpg and the bike runs/sounds awesome.

BTW, Kerker recommends to run about 8 discs per side with the open or closed caps on a stock vmax.

Not to be an *ss, but you got it wrong.....and probably misunderstood the kerker tech, or he didn't know what he said.
-More is not better, unless you follow the Harley tradition....(more noise is better.):rofl_200:
-less disc you have on with closed endcaps means more back pressure.
-more disc on with closed end caps....less back pressure.
- why would the amount of disc make a difference with open endcaps...probably just the sound....elongating the exhaust tunnel....should not make a difference in performance with open endcaps...they are baffles that are not working.:confused2:
-remember the disc are used to according to kerker scavenge the exhaust from the pipes with closed caps...what are they scavenging with open caps....your running straight through exhaust.unk:

I've runn 4, 6, 8, and 10 on a stock max....1/8 mile and seat of pants.
6...best performance wise for the street.....10 best for sound wise and top end......8 best of both worlds....on a stock bike.

And I won't call kerker if thats the answer he gave you..........
my 15 cents.

 

[vmax2extreme]

Your not an *ss, just clarifying, but I wonder why they told me the opposite since I bought the setup strait from them with open endcaps. They stated to run the 8 discs. I see your point with the closed endcaps with less space, more pressure.

So the real question is does it even matter the amount of discs one runs on an open end system?

 

[85vmax]

BTW....I do stand corrected.........as you said with your open end caps... with 8 disc, there is more backpressure than with 4....because the lentghening of the system ....but with open exhaust...marginal if any increase in hp.

15 cents more

 

[85vmax]

Your not an *ss, just clarifying, but I wonder why they told me the opposite since I bought the setup strait from them with open endcaps. They stated to run the 8 discs. I see your point with the closed endcaps with less space, more pressure.

So the real question is does it even matter the amount of discs one runs on an open end system?

I have no idea....I also ran 8 disc with open caps...and couldn't figure out why I should keep the disc on....took em off only difference was the slight change of exhaust tone .......I think a 2 - 4 disc set-up would be more appealing asthetically to keep the endcap just off the muffler end.

 

[vmax2extreme]

I have no idea....I also ran 8 disc with open caps...and couldn't figure out why I should keep the disc on....took em off only difference was the slight change of exhaust tone .......I think a 2 - 4 disc set-up would be more appealing asthetically to keep the endcap just off the muffler end.

I just spoke with Bruce @ Kerker. We all understand the closed endcap with less is more backpressure and more is less.....

As to our open end caps, they stated that just the open endcap alone is equivalent to a closed at 10- 12 discs. So we are running 8 discs with open end cap so thats actually 18 to 10 discs. Bruce told me I should be running very lean ---->>> more disc --->>> more flow --->>>more lean and opposite for less discs etc.... I know I run rich with my setup and I will double check this tonight. Bruce was very curious since he said my plugs should be light ash color from a lean condition.....I will chime back in later this afternoon once I check since I just rode her yesterday.

 

[SpecOps13]

The more open the exhaust the richer it will run....
Easier flow letting exhaust gasses out.
More vacuum to pull gas through the carbs.

 

[vmax2extreme]

The more open the exhaust the richer it will run....
Easier flow letting exhaust gasses out.
More vacuum to pull gas through the carbs.

That is correct!

 

[vannlater]

Okidoki, thanks a lot for clearing it up

 

[acammer]

+1 for Spec-ops - you'll go rich as you open up breathing after the motor (new exhaust, open pipes, etc.), leaner as you open it up before (ie. removing the airbox Y, filter pods, etc.) The more discs you add, the richer it should run. I don't really know how much I buy super-trapps line that they are getting any significant scavenging from the disc shape as they claim, but you should be able to change the a/f mixture some by make changes there, I would imagine you hit diminishing returns after you get to 8-10+ discs.

I am running Supertrapps with open end caps, and 2 discs. From what research I have done, the open end cap has the approximate same breathing result as 6-8 discs. I ran the bike first when I got the pipes with 10 discs per side, and then switched to 2 discs per side plus the open caps. I did not appreciate any change to the performance of the bike between these two setups. I did appreciate a louder and slightly sharper exhaust note and deeper idle, although it was already quite loud with 10 discs per side.

I'm due for a carb sync, and once that is squared away in the next week or so I am going to grab some new plugs and grab a WOT chop to get an idea where the mains are at. If it's real rich, (I am expecting it to be to some extent) I'm going to try pulling the stock airbox Y out and see if that gets me closer to where I want to be - although I fear it'll probably be too lean on the pilots then. Easy enough to play with at any rate, maybe I can find a sweet spot with it shimmed.

 

[sidwin]

my bike runs super rich. I get maybe 33 mpg. it used to go 90 miles before fuel light comes on then i did the fan temp change and that gets her to about 80 miles. i talked to sean about putting on the supertraps to lean her back out but he's thinking rejetting the stock bike. i rather not have to rejet the bike to be honest. he said i would run even richer with the super traps. will they get me back to 40mpg if i have the right amount of disc?

thanks,
sid

 

[vmax2extreme]

my bike runs super rich. I get maybe 33 mpg. it used to go 90 miles before fuel light comes on then i did the fan temp change and that gets her to about 80 miles. i talked to sean about putting on the supertraps to lean her back out but he's thinking rejetting the stock bike. i rather not have to rejet the bike to be honest. he said i would run even richer with the super traps. will they get me back to 40mpg if i have the right amount of disc?

thanks,
sid

Are you running completely stock? Getting 33mpg doesnt sound right. My bike with trapps get 40mpg + if I'm not getting on it. I average around 40mpg with my trapps. If your getting less all stock, I'd suggest getting atleast K&N air filter to help it breath better, but perhaps your carbs arent tuned correctly. You shouldnt have to rejet a stock vmax in my opinion so something doesnt sound right with your stock setup! Make sure your carb circuits are all clean and clear of debri, get them sync'd, check air/fuel screws (if drilled).

Just my 2 cents.....

 

[acammer]

Agreed, I get 40 mpg or better with my open capped trapps, stone stock intake track. Something sounds weird with that. I can get under 40, if I hammer it the entire time, to the point were my shoulders are sore from hanging on. But barring that type of riding, something is definitely off.

 

[sidwin]

i only have 6k on the bike and she's had crappy fuel economy since i bought her at 3k. i already have kn air filter on the bike. I don't ride my bike that hard at all to be honest.

40mpg would be a dream. how loud are the supertraps say at 80mph? I had vance and hines pipes on another bike and it was miserable at 80mph. after riding 90 min, i couldn't hear squat.

 

[acammer]

i only have 6k on the bike and she's had crappy fuel economy since i bought her at 3k. i already have kn air filter on the bike. I don't ride my bike that hard at all to be honest.

40mpg would be a dream. how loud are the supertraps say at 80mph? I had vance and hines pipes on another bike and it was miserable at 80mph. after riding 90 min, i couldn't hear squat.

The supertrapps are pretty loud, I have them about as loud as they are going to get with 5 discs and open caps, at 80mph for an extended time they will wear on you. They are not unreasonable at lower revs/light throttle, but just cruising anywhere north of 3000rpm is pretty loud... keeps the cars aware that I am around, which was the point for me in the first place. And it sounds great when you pull it through a few gears at full song.

6k on the bike and the mileage sucks, that is very strange. Something is definitely amiss, stockers should do 40+mpg when ridden conservatively.

 

[vmax2extreme]

The supertrapps are pretty loud, I have them about as loud as they are going to get with 5 discs and open caps, at 80mph for an extended time they will wear on you. They are not unreasonable at lower revs/light throttle, but just cruising anywhere north of 3000rpm is pretty loud... keeps the cars aware that I am around, which was the point for me in the first place. And it sounds great when you pull it through a few gears at full song.

6k on the bike and the mileage sucks, that is very strange. Something is definitely amiss, stockers should do 40+mpg when ridden conservatively.

I was running 8 discs open endcaps...a screamer, but now just 2 discs and alls good. I love the sound and I wear earbuds with my ipod and radar detector setup for long trips.

As to the bad mileage. I would check your plugs to see if your lean or too rich. Make sure your carbs are in sync, clean all the carb circuits with the shotgun and if air/fuel screws are drilled/exposed, check those adjustments.

 

[sidwin]

when i bought the bike with 3k on it, i put new plugs, coolant, kn air filter, brake fluid, drive shaft oil, tires, pretty much every maintenance thing a person can think of besides syncing carbs and jetting the bike. i'm a fuel injected guy and honestly dread jetting. that's why i don't own an aftermarket exhaust yet I was riding my fz1 today and forgot how awesome it is to be able to go 130 miles before putting 3.5 gallons in. i'm probably closer to 34 mpg if that....

 

[acammer]

I can make 130 miles on 3.5 gallons, its not the exhaust, something is up.