Thunderheader baffle mod
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Road Master
Joined: Dec 2012
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From: CO
Thunderheader baffle mod
The pic below shows the mod....you bend the tabs out to "add backpressure and therefore torque" I've read all over the internet about it. However, anyone who actually understands exhaust knows that adding backpressure never increases torque. You get more torque by increasing exhaust gas velocity, which in turn increases scavenging, which is where the torque increase comes from. Any added backpressure means the engine has to work harder to expel the exhaust gasses.
So i'm trying to wrap my head around how bending the tabs on the TH baffles, which would indeed increase backpressure, would increase torque. I know people swear by it and supposedly there are dyno sheets to prove it, but I just don't believe it. And I just don't want to start ****ing with bending the baffle just to experiment. Anybody have actual numbers to show?
So i'm trying to wrap my head around how bending the tabs on the TH baffles, which would indeed increase backpressure, would increase torque. I know people swear by it and supposedly there are dyno sheets to prove it, but I just don't believe it. And I just don't want to start ****ing with bending the baffle just to experiment. Anybody have actual numbers to show?
Last edited by Red Dragons; Jul 23, 2015 at 04:27 PM.
Road Master
Joined: Aug 2012
Posts: 854
Likes: 20
From: CT
Cam only 96" bending 3 tabs.
Mild 103" bending 2 tabs. Bottom end is from the baffle mod, top end was a timing fix. The chop is clutch slip.
Same 103 2 tabs vs 3.
I just retuned my 145hp 114" with a Thunderheader muffler on a boarzilla headpipe and picked up low end by bending 2 tabs. 3 didn't pick up anymore and lost 1 ft lb. in the middle. I don't have that dyno sheet on my phone.
Mild 103" bending 2 tabs. Bottom end is from the baffle mod, top end was a timing fix. The chop is clutch slip.
Same 103 2 tabs vs 3.
I just retuned my 145hp 114" with a Thunderheader muffler on a boarzilla headpipe and picked up low end by bending 2 tabs. 3 didn't pick up anymore and lost 1 ft lb. in the middle. I don't have that dyno sheet on my phone.
Last edited by vdop; Jul 23, 2015 at 08:27 PM.
Stellar HDF Member
Joined: Jan 2013
Posts: 2,464
Likes: 50
From: Rouses Point, N.Y.
The pic below shows the mod....you bend the tabs out to "add backpressure and therefore torque" I've read all over the internet about it. However, anyone who actually understands exhaust knows that adding backpressure never increases torque. You get more torque by increasing exhaust gas velocity, which in turn increases scavenging, which is where the torque increase comes from. Any added backpressure means the engine has to work harder to expel the exhaust gasses.
So i'm trying to wrap my head around how bending the tabs on the TH baffles, which would indeed increase backpressure, would increase torque. I know people swear by it and supposedly there are dyno sheets to prove it, but I just don't believe it. And I just don't want to start ****ing with bending the baffle just to experiment. Anybody have actual numbers to show?
So i'm trying to wrap my head around how bending the tabs on the TH baffles, which would indeed increase backpressure, would increase torque. I know people swear by it and supposedly there are dyno sheets to prove it, but I just don't believe it. And I just don't want to start ****ing with bending the baffle just to experiment. Anybody have actual numbers to show?
Stellar HDF Member
Joined: Jan 2013
Posts: 2,464
Likes: 50
From: Rouses Point, N.Y.
Cam only 96" bending 3 tabs.
Mild 103" bending 2 tabs. Bottom end is from the baffle mod, top end was a timing fix. The chop is clutch slip.
Same 103 2 tabs vs 3.
I just retuned my 145hp 114" with a Thunderheader muffler on a boarzilla headpiece and picked up low end by bending 2 tabs. 3 didn't pick up anymore and lost 1 ft lb. in the middle. I don't have that dyno sheet on my phone.
Mild 103" bending 2 tabs. Bottom end is from the baffle mod, top end was a timing fix. The chop is clutch slip.
Same 103 2 tabs vs 3.
I just retuned my 145hp 114" with a Thunderheader muffler on a boarzilla headpiece and picked up low end by bending 2 tabs. 3 didn't pick up anymore and lost 1 ft lb. in the middle. I don't have that dyno sheet on my phone.
Road Master
Joined: Aug 2012
Posts: 854
Likes: 20
From: CT
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Stellar HDF Member
Joined: Jan 2013
Posts: 2,464
Likes: 50
From: Rouses Point, N.Y.
Vdrop I like the look!!! did the guy from N.H.that you tuned his bike ever make that stepped thunder header pipe??
Last edited by target64; Jul 23, 2015 at 08:55 PM.
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Road Master
Joined: Aug 2012
Posts: 854
Likes: 20
From: CT
Also can add that my old 95" picked up 7ft lbs on the bottom from 3 tabs but I can't seem to find those sheets. I have over 300 dyno pulls on my bike, you could say I've experimented a little.
Nope, not yet. I think he's been enjoying how well it runs with a tune vs thundercrap. That bike was fun to ride. I think I'm putting an od6 and 3.37 in it this winter so hopefully he builds the pipe before then to see what it does.
Last edited by vdop; Jul 23, 2015 at 09:12 PM.
Thread Starter
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Road Master
Joined: Dec 2012
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From: CO
I get your point but results are more important than theory to me. We could talk about it all day and the dyno sheets are the same. The only bike I've ever seen no or negative results on was a sportster. Pretty much every twin cam benefits, and tuners who say otherwise don't know or are too lazy to try. If my 145hp 7000rpm screamer can benefit from this on the bottom without losing a c-hair on top I think it's the best free mod out there. It picks up at every throttle position too, not just wide open, throttle response improves.
Also can add that my old 95" picked up 7ft lbs on the bottom from 3 tabs but I can't seem to find those sheets. I have over 300 dyno pulls on my bike, you could say I've experimented a little.
Also can add that my old 95" picked up 7ft lbs on the bottom from 3 tabs but I can't seem to find those sheets. I have over 300 dyno pulls on my bike, you could say I've experimented a little.