Backpressure - Page 2 - Harley Davidson Forums: Harley Davidson Motorcycle Forum
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post #11 of 76 (permalink) Old 11-03-2012, 10:42 AM
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Originally Posted by webco2 View Post
I want it all. I want lowend torque and topend HP. So..what do I do??? Punt???
own two bikes..........one of each
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post #12 of 76 (permalink) Old 11-03-2012, 10:49 AM
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post #13 of 76 (permalink) Old 11-03-2012, 06:19 PM
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I'd trade my exhaust for stock any day for the right back pressure the motor was made for. I'm think'n it will last longer, an't got the $$$ to do any thing about it.

knuckle buster

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post #14 of 76 (permalink) Old 11-04-2012, 06:47 AM Thread Starter
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How come horsepower actually went up when adding more restriction in my Thunderheaders?

I would have to hazard a guess that your exhaust is too open. Everything needs to be tuned to work together at the same RPM's. If say a 1.75" pipe was ideal, and a 2" was added it wouldn't work as well. If the engine was tuned to run in the 2500-4500 rpm range, and the pipes in the 3500-5500 rpm range performance will suffer. Some of the scavaging effect was lost at lower rpm's. Nothing was gained at the higher rpm's as the engine didn't breath well enough to take advantage of the bigger pipes.

Just adding one thing such as bigger carb, cam, exhaust or what ever usually doesn't help anything. It all needs to work together.
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post #15 of 76 (permalink) Old 11-04-2012, 07:17 AM
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You mean a Thunderheader doesn't have enough backpressure?

'05 Carbed Night Train
111 rwhp, 112 rwtq
Best 1/4 ET 12.557s
Best 1/4 MPH 108.59
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post #16 of 76 (permalink) Old 11-04-2012, 07:56 AM
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You mean a Thunderheader doesn't have enough backpressure?

2011 Road King Classic, Python slip-ons, Stage 1 SE a/c, Power Commander V

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post #17 of 76 (permalink) Old 11-04-2012, 08:32 AM
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With just a ev27 cam, S&S shorty/with thunderjet carb tuner ,dyna signle fire and "Python" thunder headers, it takes for ever to warm up, and you cant dog the bike at all. 3&4 gear are a pain, its where its needs the the back pressure the most, and cold start ups.
If you run it like down the strip when riding it runs great. The best way to ride it is to keep the rpm's up. Python thunder headers are tuned exhaust and a good street/drag every day use. Still wish there was $$ to put stock exhaust back on , even trade so some one else can make noise & play with horse power

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post #18 of 76 (permalink) Old 11-04-2012, 08:47 AM
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Pythons and Thunderheaders are 2 different exhausts.

'05 Carbed Night Train
111 rwhp, 112 rwtq
Best 1/4 ET 12.557s
Best 1/4 MPH 108.59
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post #19 of 76 (permalink) Old 11-04-2012, 08:50 AM
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Pythons and Thunderheaders are 2 different exhausts.
help fill me in with that, They came with the bike and its been a learning thing for me
thanks, Kainam

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post #20 of 76 (permalink) Old 11-04-2012, 08:54 AM
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You have Thunderheaders:




These are Python's 2-1




D&D FatCats, and V&H 2-1 look similar to the Python.

'05 Carbed Night Train
111 rwhp, 112 rwtq
Best 1/4 ET 12.557s
Best 1/4 MPH 108.59
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