How much extra HP and Torque?

3473 Views 8 Replies 5 Participants Last post by marvin4239, Jan 12, 2006

03fatty

Discussion Starter · Jan 11, 2006

Quick Question: I have a 2003 Fatboy, Carb, with a Stage 1, and SE II pipes ( 2 into 2). I just purchased a set of 2 into 1 Thunderheaders. What can I expect to gain (if any) in HP and Torque? Any input is appreciated. Thanks.

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nvsteve

· #2 · Jan 11, 2006

You'll get alot of opinions, so here's mine.
I don't think you'll gain alot of hp/tq with basically a stock motor.
The SE11's aren't actually that bad.
You should however be able to get better tq. earlier in the curve.
If tuned properly you should have a good "seat of the pants" feel.
It should sound better. You might have to tune the baffle a bit.

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03fatty

Discussion Starter · #3 · Jan 11, 2006

Thanks. I plan on getting it dyno tuned after I put on the Thunderheaders. A dealer by me quoted $200 for dyno tuning and $35 for rejetting (if needed), and $8 for a new jet (if needed). Does this sound decent? I believe they know what they are doing and they seem to have experienced technicians.

Another shop by me has it for $175 which would include the rejetting but I haven't been happy with their service in the past and I wouldn't expect anything different now. I think they have one certified technician.

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nvsteve

· #4 · Jan 11, 2006

03fatty said:
Thanks. I plan on getting it dyno tuned after I put on the Thunderheaders. A dealer by me quoted $200 for dyno tuning and $35 for rejetting (if needed), and $8 for a new jet (if needed). Does this sound decent? I believe they know what they are doing and they seem to have experienced technicians.

Another shop by me has it for $175 which would include the rejetting but I haven't been happy with their service in the past and I wouldn't expect anything different now. I think they have one certified technician.

Not familiar with cost of dynoing a carb bike. My fi bike costs $275 to dyno/remap with a PC111r.
You might ask them if they have experience with "tuning" the baffle while
on the dyno. Most people I know with the TH have modified it a bit.
Usually closing it up a bit, I think.

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marvin4239

· #5 · Jan 12, 2006

When I had my bike dynoed Doc made about 6 runs on the dyno just tuning the thunderheader to eliminate some of the torque dip around 2500 rpm's. He closed the baffles a little made a run and closed them a little more til he got just what he was looking for. This made a lot of difference in the sound of the pipe at cruising speed and eliminated some of the dip. Wasn't nearly as loud until you get down on it then it comes alive. I'd asked the tuner about tuning out the torque dip. If he doesn't know what your talking about I'd look elsewhere. Good Luck.

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ratt

· #6 · Jan 12, 2006

03fatty said:
Quick Question: I have a 2003 Fatboy, Carb, with a Stage 1, and SE II pipes ( 2 into 2). I just purchased a set of 2 into 1 Thunderheaders. What can I expect to gain (if any) in HP and Torque? Any input is appreciated. Thanks.

LOL.. another set of pipes hanging in your garage. Sorry couldnt help myself lol. rat

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03fatty

Discussion Starter · #7 · Jan 12, 2006

I have read about "tuning" a baffle but can't say I quite understand what is being done. Is it just a matter of bending it/drilling it to either increase or restrict the exhaust flow? How easy is it to "tune" the thunderheader baffle?

I plan on going to the 95'' stage III in a couple of years (when the bike is payed off). Would you suggest having the baffle tuned (which I think is bending it) now and then again when I go to 95''? Or, am I better off to wait?

Any more comments on the HP and Torque gain with a stock 88", carb, stage I, with thunderheaders is appreciated. I expect the dealer to change the jets with the increased air flow of the thunderheader exhaust, but I assume this will cause a pretty small HP/Torque gain... am I correct?

Thanks.

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csoday

· #8 · Jan 12, 2006

The lower end torque gain will be enough to make you smile.

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marvin4239

· #9 · Jan 12, 2006

03fatty said:
I have read about "tuning" a baffle but can't say I quite understand what is being done. Is it just a matter of bending it/drilling it to either increase or restrict the exhaust flow? How easy is it to "tune" the thunderheader baffle?

What I watched Doc do and explain went as follows. He put the bike on the dyno and did a run to get a baseline to work from. Then he inserted a long screwdriver in the pipe And slightly bent the baffle to restrict flow and thus increase back pressure. Next he did another dyno run to observe what he accomplished. He did this four different times until his numbers started to fall off then he went the other way. He did six runs just to tune the pipe and did a total of 33 runs to tune the bike. I had been running the TH and build about a month before getting Doc to tune it so I had a pretty good seat of the pants idea how the bike ran before and after. Bike ran great and pulled hard but the biggest seat of the pants difference I noticed after the tune with the pipe was at crusing speed the pipe was not nearly as loud.

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