Strange Observation about True Duals
#11
02-03-2019 | 07:58 AM
Tourer
Joined: May 2017
Posts: 418
Likes: 50
From: Xenia OH
#12
02-03-2019 | 05:02 PM
Advanced
Joined: Jan 2019
Posts: 89
Likes: 58
From: Southeast North Carolina
It more than likely has more to do with the fact that Harley V-Twins have a single crank pin, and you have two totally separate exhaust systems per cylinder with a true dual exhaust. The pipes are bent differently, they are different total lengths most of the time, there will be slight variations in sound and exhaust pressure. Another way to think about it is that an internal combustion engine is a controlled explosion. Although the engine runs well, it is impossible to say that the cylinder events are exactly the same every single time the engine fires. This video has more revving than idle clips, but listen to just how different the idle characteristics sound between a true dual exhaust and a 2-1 exhaust. When I had the Vance & Hines Big Shot True Dual exhaust system on my bike, exhaust pressure was noticeably higher on one side.
"A Harley engine has two pistons. The difference in the Harley engine is that the crankshaft has only one pin, and both pistons connect to it. This design, combined with the V arrangement of the cylinders, means that the pistons cannot fire at even intervals. Instead of one piston firing every 360 degrees, a Harley engine goes like this:
https://auto.howstuffworks.com/question325.htm
Also you ever notice how with true dual exhausts, going down the road at steady part throttle you can hear uneven exhaust pulses in each ear?
"A Harley engine has two pistons. The difference in the Harley engine is that the crankshaft has only one pin, and both pistons connect to it. This design, combined with the V arrangement of the cylinders, means that the pistons cannot fire at even intervals. Instead of one piston firing every 360 degrees, a Harley engine goes like this:
- A piston fires.
- The next piston fires at 315 degrees.
- There is a 405-degree gap.
- A piston fires.
- The next piston fires at 315 degrees.
- There is a 405-degree gap."
https://auto.howstuffworks.com/question325.htm
Also you ever notice how with true dual exhausts, going down the road at steady part throttle you can hear uneven exhaust pulses in each ear?
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Big Dave (02-05-2019)
#13
02-03-2019 | 06:46 PM
Not a Moderator!
Joined: Feb 2013
Posts: 9,220
Likes: 7,319
From: Edmonton, Alberta
My Road King has a power commander v with autotuner, 510 cams and a few other little goodies. The bike makes far more power than it has ever had and I got the look and sound I want and that's all that counts. As far as spending money to reduce power, that is subjective and besides, this is a Road King, not a sport bike. As far as a crossover, I don't like the look of those big X pipes not to mention the heat on the right side. To each his own but my little 88 will more keep up with the big boys rather nicely. 
randy
randy
#14
02-05-2019 | 11:33 AM
Road Warrior
Joined: Mar 2009
Posts: 1,485
Likes: 231
From: Ohio
Better true dual pipes will have approximately the same length pipes. I think this would be a tuned dual exhaust. My cheapies from Fulsac are not equal length. I also recall some talk about the left muffler being built with a little more back pressure than the right one because with the stock pipes, the flow is not equal. More flow out the right side.
#15
02-05-2019 | 11:41 AM
Club Member
Joined: Jun 2007
Posts: 45,429
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From: Bedford UK
Better true dual pipes will have approximately the same length pipes. I think this would be a tuned dual exhaust. My cheapies from Fulsac are not equal length. I also recall some talk about the left muffler being built with a little more back pressure than the right one because with the stock pipes, the flow is not equal. More flow out the right side.
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Big Dave (02-05-2019)
#16
02-05-2019 | 02:36 PM
Road Warrior
Joined: Apr 2016
Posts: 1,399
Likes: 305
From: Salem IN
I had V&H true duals on my 02 RK. I was reading about lollipops. So I ordered a set form DK. Removed the baffles and installed the torque lollipops. Holy ****!
I ran it without any baffles just to see. Awful ran like crap.
Installed the lollipops I was amazed!
Now I have the S&S header ...I like it.
2 into 1 is on my list.
I ran it without any baffles just to see. Awful ran like crap.
Installed the lollipops I was amazed!
Now I have the S&S header ...I like it.
2 into 1 is on my list.
#17
09-09-2019 | 09:00 PM
Stage III
Joined: Aug 2019
Posts: 3
Likes: 0
From: Canada
Full sac TD’s
So I was going to buy a set of full sac true duals for my 06 classic, I have 4” Rinehart racer slip on’s and K&N high flow intake, after the true duals I was going to take to dealership for Harley tuner and dyno, just wondering would I have to put something on left side for restriction or would I be good with what I have planned ?
#18
09-09-2019 | 10:16 PM
Road Master
Joined: Jan 2019
Posts: 1,041
Likes: 499
From: Texas
#19
09-09-2019 | 10:52 PM
Cruiser
Joined: Jun 2019
Posts: 100
Likes: 57
From: BC
I have bassani DNT's with bassani true dual on my 19 rks. I noticed the exhaust seemed to turn the exhaust tip black a lot sooner than the right. Which is strange since the left has so many more bends.
I actually had the DNT's with the stock headers as well and it was the rights that turned black first for the first few weeks. I only had this setup since the dealer screwed up and didn't know that you need to pre 2016 DNT slip ons if you use their TD header. They let me use the slip ons before changing them out along with the headers for the other ones that fit their TD's.
I thought it was an interesting observation.
Im pretty sure I noticed a small low end torque loss but I just run the bike in a higher rpm to make up for it. Its pretty fast up there, but I will probably do the torque cams next year to make up for it in the lows.
I actually had the DNT's with the stock headers as well and it was the rights that turned black first for the first few weeks. I only had this setup since the dealer screwed up and didn't know that you need to pre 2016 DNT slip ons if you use their TD header. They let me use the slip ons before changing them out along with the headers for the other ones that fit their TD's.
I thought it was an interesting observation.
Im pretty sure I noticed a small low end torque loss but I just run the bike in a higher rpm to make up for it. Its pretty fast up there, but I will probably do the torque cams next year to make up for it in the lows.
#20
09-10-2019 | 07:53 AM
Stellar HDF Member
Joined: Mar 2017
Posts: 3,169
Likes: 1,455
From: Charleston, SC
Im running V&H true duals on my 2003 Road King Classic with 4 inch S E street cannons w/ fishtails. The bike runs great however when one puts their hand behind each muffler there is a noticeable sound and pulse difference. For instance when idling, the right muffler has a rhythmic pulse to it . POP POP POP etc., however the left muffler when your hand is at the same distance from the fishtail has an almost erratic pulse. POP, P-POP, P-POP, POP as if it is missing and it isn't quite as loud. The right header comes off the from cylinder and down and straight back where as the rear cylinder has several bends in it before it joins to the muffler. I have even gone so far as to check the compression in both lungs, whish are equal and have undone each spark plug wire and started the bike so it runs on only one cylinder at idle and they both are the same. Mileage is great 44-54 depending on how I ride and does NOT burn any oil. Is my assumption on the pipes bends vrs straight correct? No codes, but really an odd observation. Has anyone every observed this?
randy
https://vimeo.com/315016372
randy
https://vimeo.com/315016372
THEY ALL DO THAT!
