Why "true duals"
Road Captain
Joined: Jan 2013
Posts: 576
Likes: 20
From: Eau Claire, WI
Dude I could roll on after I got rid of the true duals. I stand by my position as does the poster above me. And let me tell with the 103, 255 cams, and some head work I now roll on at 60MPH with no problem. You can run it through your head any way you want but you can't show me a dyno sheet and you can't show me anyone that on the road has tested them beck to back and says yup the true duals perform better. They don't. They cost you torque. And like I said I don't want to get into it but in addition to the shops telling me they were the problem I did a lot of research that proves it. I suggest you do the same.
Outstanding HDF Member
Joined: Jan 2007
Posts: 2,598
Likes: 19
From: Naples FL / Pine TWP PA
I disagree. It was definitely noticeable on my bike and I had two shops tell me so. I really hated admitting I wasted 900.00 on true duals or whatever it was and set out to research the topic. Anybody with really advanced knowledge on the topic came back with pretty much the same response, you are ruining the scavenging in the engine and don't fall for marketing hype. I put the factory head pipe back on, took it to dealer and had them install a proper map. It was the end of my roll on problems.
Last edited by FX4; Jun 3, 2013 at 07:50 AM.
Road Captain
Joined: Apr 2010
Posts: 671
Likes: 159
I disagree. It was definitely noticeable on my bike and I had two shops tell me so. I really hated admitting I wasted 900.00 on true duals or whatever it was and set out to research the topic. Anybody with really advanced knowledge on the topic came beck with pretty much the same response, you are ruining the scavenging in the engine and don't fall for marketing hype. I put the factory head pipe back on, took it to dealer and had them install a proper map. It was the end of my roll on problems.
It seems like a lot of 'tuners' these days go off of pre-made maps from existing tunes. It's a cheap alternative but a good dyno tune will get the bike running perfectly (with good gas mileage) at cruise and also get the most power at WOT.
Banned
Joined: Sep 2005
Posts: 4,341
Likes: 0
From: Dover, Oh
A loss of power is one thing but sputtering shouldn't happen just from exhaust. They probably had a bad map on in the first place. I know a dyno tune is expensive but I guarantee if they did one it wouldn't of had that issue. A loss of low end would of existed but nothing like that.
It seems like a lot of 'tuners' these days go off of pre-made maps from existing tunes. It's a cheap alternative but a good dyno tune will get the bike running perfectly (with good gas mileage) at cruise and also get the most power at WOT.
It seems like a lot of 'tuners' these days go off of pre-made maps from existing tunes. It's a cheap alternative but a good dyno tune will get the bike running perfectly (with good gas mileage) at cruise and also get the most power at WOT.
Outstanding HDF Member
Joined: Jan 2007
Posts: 2,598
Likes: 19
From: Naples FL / Pine TWP PA
Who said sputtering? I sure didn't. I said it bogged down and started pinging. I didn't say a thing about sputtering. You are putting words in my mouth. The factory 07s barely had enough torque to pull 6th gear at 70MPH and they already ran very hot. Change something that decreases torque and sixth gear became unusable. I did have the bike on the dyno with the true duals and a tune but I have never had the bike on a dyno with the factory head pipes. The numbers were pretty dismal with the true duals on the bike. And that was with both a stage one map in the factory ECM and a tuned Thunder Max (Thunder Max was supposed to take care of the tune and get my torque back, it didn't). And, like I said it is a long complicated story that I don't want to get into in this thread.
Road Captain
Joined: Apr 2010
Posts: 671
Likes: 159
Who said sputtering? I sure didn't. I said it bogged down and started pinging. I didn't say a thing about sputtering. You are putting words in my mouth. The factory 07s barely had enough torque to pull 6th gear at 70MPH and they already ran very hot. Change something that decreases torque and sixth gear became unusable. I did have the bike on the dyno with the true duals and a tune but I have never had the bike on a dyno with the factory head pipes. The numbers were pretty dismal with the true duals on the bike. And that was with both a stage one map in the factory ECM and a tuned Thunder Max (Thunder Max was supposed to take care of the tune and get my torque back, it didn't). And, like I said it is a long complicated story that I don't want to get into in this thread.
You said you had the bike on the dyno with the true duals and a tune meaning they threw a basic tune on the bike and you saw what numbers you where running correct? Not a full dyno tune which would of shown the low end loss and probably bad tune and corrected it as they tuned it further.
My 96 with drag pipes and intake would pull in 6th at 55mph on up. It certainly wasn't fast but it wasn't bogging down either. Putting a canned tune on a bike and letting the tuner figure it out sometimes works but it has to be pretty close from the start. I still 100% disagree it was the exhaust that caused you all your trouble when there are so many others who ran the same setup (myself included) and had no issues.
I don't mean to poke and prod you about it but the thread is about true duals and why people use them. I'm sure there's enough general knowledge out there and actual tuners who read this who could provide their input based on your experience and full story.
Road Captain
Joined: Sep 2010
Posts: 535
Likes: 0
From: Huntington Beach
I think that for the most part, a 2-1, equal length tube exhaust is going to give the best performance. Second to that would be a crossover 2-1-2. But 2-1 and crossovers are not solely responsible for scavenging exhaust gasses. That’s not to say they won’t improve flow velocity, just isn’t the primary element that makes up a good exhaust system with good velocity. That’s why not all true duals are created equal.
I can certainly understand if the bike is geared tall to begin with and you add an exhaust system that has less velocity at low revs than what you replaced it with, then you are possibly going to see a difference in low end grunt. Especially if you are one that is sensitive to the performance level of your bike. Some people get on and just ride and are not all that “in tune” with the way the bike is performing…. While others are paying attention to every single rev.
I have a 2012 103. I am running V&H true duals and their twin slash rounds. I have a S/E heavy breather and a PV tuner. I love the looks and the sound of the true duals and wanted to make them work. I went with the Big City Thunder head pipe monster baffles that help increase the flow velocity and increase low to mid range torque. I was skeptical when I purchased them but the results were outstanding. The volumetric efficiency is far better with this setup over stock. The low to mid range pull is way more than it ever was with the stock exhaust. Could it be better with a 2-1 or a 2-1-2 ? Possibly but I’m not sure I would notice the difference all that much in the seat.
The BCT head pipe baffles also made it sound way better. It took some of the raspy obnoxious sound out and made it a much deeper frequency. I am very pleased with this setup. I can be doing 60 in 6th gear riding 2 up and roll on the throttle a little and feel it pull strong without lugging.
BCT has a very good article on understanding exhaust dynamics, check it out.
http://www.bigcitythunder.com/images...ng_exhaust.pdf
Also check out the other tech articles on the their website, they also give dyno results.
I can certainly understand if the bike is geared tall to begin with and you add an exhaust system that has less velocity at low revs than what you replaced it with, then you are possibly going to see a difference in low end grunt. Especially if you are one that is sensitive to the performance level of your bike. Some people get on and just ride and are not all that “in tune” with the way the bike is performing…. While others are paying attention to every single rev.
I have a 2012 103. I am running V&H true duals and their twin slash rounds. I have a S/E heavy breather and a PV tuner. I love the looks and the sound of the true duals and wanted to make them work. I went with the Big City Thunder head pipe monster baffles that help increase the flow velocity and increase low to mid range torque. I was skeptical when I purchased them but the results were outstanding. The volumetric efficiency is far better with this setup over stock. The low to mid range pull is way more than it ever was with the stock exhaust. Could it be better with a 2-1 or a 2-1-2 ? Possibly but I’m not sure I would notice the difference all that much in the seat.
The BCT head pipe baffles also made it sound way better. It took some of the raspy obnoxious sound out and made it a much deeper frequency. I am very pleased with this setup. I can be doing 60 in 6th gear riding 2 up and roll on the throttle a little and feel it pull strong without lugging.
BCT has a very good article on understanding exhaust dynamics, check it out.
http://www.bigcitythunder.com/images...ng_exhaust.pdf
Also check out the other tech articles on the their website, they also give dyno results.
Last edited by 1hellbent; Jun 3, 2013 at 10:25 AM.
Thread Starter
|
Elite HDF Member
Joined: Jun 2006
Posts: 3,572
Likes: 5
From: Templeton California
OK so what I've learned here is basically what I already knew coming from the Dyna forum. If you want to make more power get a 2 into 1 if you want the look of dual exhaust without loosing power you need a cross over.The guy that did the Dyno on my Bob was a fan of true duals he claimed he could get better power out of them because it made it easier to tune each individual cylinder. He could put his exhaust Gas Analyzer in each pipe but...he was blown away by how much power my otherwise stock TC88 was making with just the Thunderheader SERT,and a SE air cleaner.I'm sure True Duals can be tuned to make good power there's just no advantage other than sound or looks.I'm going with a de-catted stock header at this point.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Outstanding HDF Member
Joined: Jan 2007
Posts: 2,598
Likes: 19
From: Naples FL / Pine TWP PA
OK so what I've learned here is basically what I already knew coming from the Dyna forum. If you want to make more power get a 2 into 1 if you want the look of dual exhaust without loosing power you need a cross over.The guy that did the Dyno on my Bob was a fan of true duals he claimed he could get better power out of them because it made it easier to tune each individual cylinder. He could put his exhaust Gas Analyzer in each pipe but...he was blown away by how much power my otherwise stock TC88 was making with just the Thunderheader SERT,and a SE air cleaner.I'm sure True Duals can be tuned to make good power there's just no advantage other than sound or looks.I'm going with a de-catted stock header at this point.
Outstanding HDF Member
Joined: Jan 2008
Posts: 3,328
Likes: 15
From: Pacific Northwest
Who said sputtering? I sure didn't. I said it bogged down and started pinging. I didn't say a thing about sputtering. You are putting words in my mouth. The factory 07s barely had enough torque to pull 6th gear at 70MPH and they already ran very hot. Change something that decreases torque and sixth gear became unusable. I did have the bike on the dyno with the true duals and a tune but I have never had the bike on a dyno with the factory head pipes. The numbers were pretty dismal with the true duals on the bike. And that was with both a stage one map in the factory ECM and a tuned Thunder Max (Thunder Max was supposed to take care of the tune and get my torque back, it didn't). And, like I said it is a long complicated story that I don't want to get into in this thread.
IF you had found a knowledgeable tune tech he could have adjusted your tune to make the most of your system no matter what it was. An incompetent tech's most often used answer is "those TD's are ruining your power".
Reading between the lines tells me that's likely what happened in your case too.
What a shame, 'cause you now have a pretty low regard for what is really a good exhaust system, particularly the stepped header versions.
Glad you like what you have now.