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Old 02-29-2008, 10:26 AM   #1 (permalink)
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supertrapp disc question

I've been changing discs on my supertrapp...it was tuned with 20 disc and closed end cap, then I drilled 20 holes in the endcap with a 3/8 drill bit...reduced discs to 16...put it back on dyno...at wot, afr was 12.8 and power falls off too quick...so now I changed back to 20 disc and the "swiss cheese" endcap...how much did that lean it out at wot?
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Old 02-29-2008, 11:27 AM   #2 (permalink)
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Can't say specificly but I'm sure you leaned out some since the pipe will be flowing more from the added disk.

Can you put it back on the dyno?
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Old 02-29-2008, 11:56 AM   #3 (permalink)
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would have to drop it off, pay $75...hoping someone has observed the difference 4 discs makes
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Old 02-29-2008, 08:28 PM   #4 (permalink)
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You might ask on their forum. They are very helpful.
http://forums.supertrapp.com/

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Old 02-29-2008, 09:09 PM   #5 (permalink)
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Quote:
Originally Posted by skyhook View Post
would have to drop it off, pay $75...hoping someone has observed the difference 4 discs makes
unfortunatly all bikes react a little different. 4 discs should not make a tremendous difference in afr tho.
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Old 02-29-2008, 11:36 PM   #6 (permalink)
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when you take the end cap off it is equal to adding 10 disc, So if you are running 8 discs no cap = 18 discs,So by making swiss cheese out of the end cap you added disks in that sense, How many dont know you will need to figure that one out. my opinon would be to run at least 12 but no more then 18........with a good tuner and free flow ac. if Stock run 8 -10 discs.
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Old 03-01-2008, 05:45 AM   #7 (permalink)
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this is on a 08 screamin' eagle dyna "slightly modified"
110 cubic inches
r&r stage 4 cnc ported 96" heads
10.8 compression
se257 cams

could this motor need more than 20 discs closed?

thanks for the help!
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Old 03-01-2008, 07:47 AM   #8 (permalink)
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It could. Go to the supertrapp forum, they're extremely helpful.
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Old 03-01-2008, 09:08 AM   #9 (permalink)
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I think the the problem with the swiss cheese end cap is that the closed end cap and the factory open end cap are designed so they add a certain amount of reversion to the exhaust. It is hard to say what effect the swiss cheese end cap has on this reversion which changes the dynamics of the exhaust. It may have no effect but who knows. I bet if you ping ohiomotoxer he will have some good advice as he has been extremely helpful and knowledgable when it comes to his exhaust.
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Old 03-03-2008, 07:42 AM   #10 (permalink)
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We have never tested end caps with holes in them, the big question is how does it run? How are the plugs?
You should probably get a new end cap and loose the cheese version.

You could try running a few more discs, but when you get up to the 24 range you are starting to outflow the core.
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Old 03-04-2008, 02:01 PM   #11 (permalink)
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Unfortunately, going only by a sniffer or wide band O2 is not going to give you the best answer compared to using a 4~5 gas.

Flow changes by adding/subtracting discs. AFR will not change (it will only if you are looking at O2) Ambient conditions change AFR nothing else.

This is why using 4~5 gas is superior to only tuning to O2, if you are tuning using O2 it's a crap shoot.





Quote:
Originally Posted by skyhook View Post
I've been changing discs on my supertrapp...it was tuned with 20 disc and closed end cap, then I drilled 20 holes in the endcap with a 3/8 drill bit...reduced discs to 16...put it back on dyno...at wot, afr was 12.8 and power falls off too quick...so now I changed back to 20 disc and the "swiss cheese" endcap...how much did that lean it out at wot?
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Old 03-04-2008, 02:24 PM   #12 (permalink)
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Quote:
Originally Posted by ohiomotoxer View Post
Unfortunately, going only by a sniffer or wide band O2 is not going to give you the best answer compared to using a 4~5 gas.

Flow changes by adding/subtracting discs. AFR will not change (it will only if you are looking at O2) Ambient conditions change AFR nothing else.

This is why using 4~5 gas is superior to only tuning to O2, if you are tuning using O2 it's a crap shoot.
its been awhile since i saw the instructions for supertrapp, but doesnt it state to add more discs to lean, less to richen?
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Old 03-04-2008, 02:46 PM   #13 (permalink)
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BITD maybe......but as more and more testing equpt gets put into the mix that is not the case.

OK yes, going from 4 discs to 20 may change the engines ability to flow thus backing up the process but the change of a few should not make a difference, especially reading O2.

Last edited by ohiomotoxer; 03-04-2008 at 02:49 PM.
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Old 03-04-2008, 02:52 PM   #14 (permalink)
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claydbal is reading this now saying WTF is this?
ohio--wasn arguing with you, just pointing that out because lots of folk read it and think they can adjust a wide range by changing discs.

we all know you da man!!
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Old 03-04-2008, 03:54 PM   #15 (permalink)
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ohio or anyone,
how many discs does the motor need to make max hp?

110"
r&r stage 4 heads, 1.94 intake valve, 1.63 exhaust valve
se257 cams
10.7 compression
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