Experience with Thunderheader baffle mod? Vdop?
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Road Master
Joined: Aug 2013
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From: Wyoming
Experience with Thunderheader baffle mod? Vdop?
I've read the threads re the Thunderheader baffle mod were you bend the ends of two or three baffles outward to get rid of the low end torque dip without adversely affecting horse power. Unfortunately, the YouTube video referenced in some of the threads is no longer active. Nonetheless, I understand the concept of how to bend the baffle tips.
However, what I am curious about is the process for when to bend them, and how to know how many to bend.
So... with a new build that's had its gentle break-in miles and is ready to be dyno tuned... do I have it fully tuned and then, only if there is a low end torque dip, modify the baffles? Or do I bend the baffles before beginning the tuning process?
If the answer is that I have it tuned first, then bend the baffles, do I tune it, bend a couple of baffles, retune it (or just check the output) and then bend a third baffle if there is a still a dip and assuming I haven't lost horse power?
I guess what I would appreciate is someone writing a walk-through of the process they used, and what they saw or didn't see.
Thanks.
However, what I am curious about is the process for when to bend them, and how to know how many to bend.
So... with a new build that's had its gentle break-in miles and is ready to be dyno tuned... do I have it fully tuned and then, only if there is a low end torque dip, modify the baffles? Or do I bend the baffles before beginning the tuning process?
If the answer is that I have it tuned first, then bend the baffles, do I tune it, bend a couple of baffles, retune it (or just check the output) and then bend a third baffle if there is a still a dip and assuming I haven't lost horse power?
I guess what I would appreciate is someone writing a walk-through of the process they used, and what they saw or didn't see.
Thanks.
Last edited by jmb79; Jan 22, 2015 at 11:11 PM.
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Road Master
Joined: Aug 2013
Posts: 837
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From: Wyoming
Nope, I understand how to bend the baffles, and why, etc. Actually, I'm not sure I'll even want to bother with it. The Thunderheader torque dip is more rare than you would think but if I have it, I'll want to see if I can get rid of it. It's more a matter of how much time I need to set aside to ensure the tune is good. Maybe I'll ask my question over on HTT too and then compare the responses. 
Road Master
Joined: Aug 2012
Posts: 854
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From: CT
Once I get the wot tune close enough to observe what the curve is going to look like, I'll start modifying the baffle. It doesn't affect the tune drastically, so if you're about halfway through the tune, then dial in the baffle, then finish the tune it barely takes much extra time. I usually start with 2, see how the curve responds, then try a third. For the majority of mild builds 3 seems to be the magic number. A lot of times there's big gains. I could probably dig up some sheets if you wanted.
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Road Master
Joined: Aug 2013
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From: Wyoming
vdop,
Thanks. What you wrote makes sense. If you wouldn't mind sharing some sheets of your tuning work, I'd certainly appreciate it. Feel free to send them to me via PM or post them, whatever works for you.
Also, if the curve shows that you've gone too far (lost some horse power for example), can you, and do you, pry the last bent baffle back open?
Thanks. What you wrote makes sense. If you wouldn't mind sharing some sheets of your tuning work, I'd certainly appreciate it. Feel free to send them to me via PM or post them, whatever works for you.
Also, if the curve shows that you've gone too far (lost some horse power for example), can you, and do you, pry the last bent baffle back open?
Last edited by jmb79; Jan 23, 2015 at 08:42 AM.
Ultimate HDF Member
Joined: Apr 2008
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From: Out on Deranged
I haven't done this but what I understand from target64 is that your bike should be nearly dialed in and while still on the dyno is the time to expirement. As someone else said it's hardly an exact science. So yeah! what Vdop said!!!
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Road Master
Joined: Aug 2013
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From: Wyoming
Thanks, maddghost.
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Stellar HDF Member
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From: Rouses Point, N.Y.
JMB79
dan thayer tune my bike and found the typical torque dip of the thunder header as he was tuning the engine when in the finally stage of the tune. I asked him if bending the baffle would help with the dip. he said some work and some don't , I told him to try it and see where it goes. He bend in all four tabs of the baffle till they were about 1/4 '' from the inside of the main body of the pipe and did another run and the torque raised up and he smiled and said we can get this dip out of her and kept adjusting fuel and timing and brought all the torque dip out the exhaust. and pulled it off the dyno and said take it for a ride. you could feel the difference right away out of the bottom end and when in 5th and 6th gear with a roll on the throttle was where i was really impressed of the performance.
dan thayer tune my bike and found the typical torque dip of the thunder header as he was tuning the engine when in the finally stage of the tune. I asked him if bending the baffle would help with the dip. he said some work and some don't , I told him to try it and see where it goes. He bend in all four tabs of the baffle till they were about 1/4 '' from the inside of the main body of the pipe and did another run and the torque raised up and he smiled and said we can get this dip out of her and kept adjusting fuel and timing and brought all the torque dip out the exhaust. and pulled it off the dyno and said take it for a ride. you could feel the difference right away out of the bottom end and when in 5th and 6th gear with a roll on the throttle was where i was really impressed of the performance.
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HDF Community Team
Joined: Jun 2008
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From: Out West
Target, your bike just makes some serious lickity-split, that's all there is to it!
Not that you'd want to flog it that hard but it would be interesting to see how well it could do some all-out 1/4 mile times.
That would be a hoot
Not that you'd want to flog it that hard but it would be interesting to see how well it could do some all-out 1/4 mile times.
That would be a hoot
Stellar HDF Member
Joined: Jan 2013
Posts: 2,464
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From: Rouses Point, N.Y.
the kid I sold my hillside stage II heads and 107 cylinders and pistons to, after his bike was tuned took his over to naperville quebec drag strip and ran his streetbob there and told me his best time was 11.50 in the 1/4 mile and wanted me to take mine over and let him ride it.said it would do 10 seconds all day. we have raced a few times and I leave him in third gear!