SuzukiSavage.com - Drag pipes, drag pipe sag and pipe length tuning

RocketScienceSmurf

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Drag pipes, drag pipe sag and pipe length tuning
04/03/20 at 05:31:09

Having searched the internet and this forum for information I understand that the basic recommendation for using straight pipes as exhaust is: DON'T!

You're in for a world of trouble and no matter how good you do it, you WILL loose performance compared to a good muffler with baffles.

But what if you REALLY want to run straight drag pipes? I believe that the length of the pipe and the desired RPM range plays a significant roll.

I found this great video that explains the problem and also tries to provide partial solutions. https://www.youtube.com/watch?v=KjKUKhHQLHg

What I miss is an equally good video/explanation of what happens when you lengthen or shorten the pipe significantly.

I also found a nice tool to simulate/calculate the resonance frequency of a pipe at different temperatures. http://hyperphysics.phy-astr.gsu.edu/hbase/Waves/opecol.html#c1 It can show the huge difference in speed of sound at "room temperature" vs "exhaust temperatures" but I am not sure how to apply it the my application.

The main reason I want to give drag pipe a chance is the sound. I would like to get a really fat, low, thumping sound and I expect a longer pipe will give me that since the resonance frequency goes down as the length goes up. I know that its crap performance wise but i like the looks and think I want the sound.

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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Drag pipes, drag pipe sag and pipe length tuni Reply #1 - 04/03/20 at 05:50:51 While you're hunting that sound don't drop the idle.
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RocketScienceSmurf Senior Member Offline SuzukiSavage.com Rocks! Posts: 268 Sweden Gender:	Re: Drag pipes, drag pipe sag and pipe length tuni Reply #2 - 04/03/20 at 06:11:18 Excellent advice! I think I read somewhere that ~1100 RPM is a good rule to not go below
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Armen Serious Thumper Offline Half-Witted Wrench-Jockey from Jersey Posts: 1452	Re: Drag pipes, drag pipe sag and pipe length tuni Reply #3 - 04/03/20 at 07:20:09 Two things about really loud noise for long periods of time: Tinnitis Hearing aids They ain't fun. Guess how I know?
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Matchless G11 Senior Member Offline SuzukiSavage.com Rocks! Posts: 451 Newfoundland NJ	Re: Drag pipes, drag pipe sag and pipe length tuni Reply #4 - 04/03/20 at 07:40:16 Armen wrote on 04/03/20 at 07:20:09: Two things about really loud noise for long periods of time: Tinnitis Hearing aids They ain't fun. Guess how I know? Yea, Loud pipes save lives? No loud pipes annoy wives. (of legislators that pass laws against motorcycles)
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verslagen1

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Re: Drag pipes, drag pipe sag and pipe length tuni
Reply #5 - 04/03/20 at 09:01:45

Matchless G11 wrote on 04/03/20 at 07:40:16:

Armen wrote on 04/03/20 at 07:20:09:

Two things about really loud noise for long periods of time:
Tinnitis
Hearing aids
They ain't fun.
Guess how I know?

Yea, Loud pipes save lives?

No loud pipes annoy wives.
(of legislators that pass laws against motorcycles) Embarrassed

Well if that's what it takes to get them off their phones.

I just hope tesla autopilot can avoid m/c's better than a soccer mom.

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Fast 650

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Re: Drag pipes, drag pipe sag and pipe length tuni
Reply #6 - 04/03/20 at 09:39:07

RocketScienceSmurf wrote on 04/03/20 at 05:31:09:

But what if you REALLY want to run straight drag pipes? I believe that the length of the pipe and the desired RPM range plays a significant roll.

The main reason I want to give drag pipe a chance is the sound. I would like to get a really fat, low, thumping sound and I expect a longer pipe will give me that since the resonance frequency goes down as the length goes up. I know that its crap performance wise but i like the looks and think I want the sound.

Slowing down the exhaust velocity will deepen the exhaust. Bigger diameter and more length is what you want for a deeper tone. Longer duration cams and bigger ports help with that too.

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LANCER Serious Thumper Alliance Member Offline Savage Beast Performance Parts Posts: 10668 Oklahoma Gender:	Re: Drag pipes, drag pipe sag and pipe length tuni Reply #7 - 04/03/20 at 11:20:34 The length of the stock header is good. That low sounding thump is what I like too, as well as the deep sounding O-W-H-H-H-H on a high speed & rpm deceleration. For me, that is achieved with a good reverse cone with proper baffling around a central straight through core. 18-20” long That’s just me.
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RocketScienceSmurf

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Re: Drag pipes, drag pipe sag and pipe length tuni
Reply #8 - 04/09/20 at 01:37:57

[quote author=11362423616267570 link=1585917069/0#6 date=1585931947]RocketScienceSmurf wrote on 04/03/20 at 05:31:09:

Slowing down the exhaust velocity will deepen the exhaust. Bigger diameter and more length is what you want for a deeper tone. Longer duration cams and bigger ports help with that too.

From what I understand increasing the pipe diameter may effect torque in a negative way. When searching for explanations on how to calculate and tune exhaust system for four stroke engines I found this page: https://www.musclecardiy.com/performance/exhaust-system-performance-math/</a>

I tried to make a spread sheet to help me with adapting the formulas tp the Savage engine and this is what I came up with:
https://docs.google.com/spreadsheets/d/e/2PACX-1vQ8ZDdoBIssUDQologQ5XHm7DPvs9...

Is the exhaust valve opening value for the Savage available anywhere? If anyone is interested you can PM me for a link so you can edit the numbers yourself and see how it changes the other numbers.

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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4406 Honolulu	Re: Drag pipes, drag pipe sag and pipe length tuni Reply #9 - 04/09/20 at 02:50:24 Cam timing data and curves are in this old post. http://suzukisavage.com/cgi-bin/YaBB.pl?num=1543987585 Good luck.
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RocketScienceSmurf

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Re: Drag pipes, drag pipe sag and pipe length tuni
Reply #10 - 04/09/20 at 04:38:56

Thanks Mike. I couldn't figure out the exact timing for when the exhaust valve opened but I figured it was somewhere around 70-65 degrees

http://suzukisavage.com/yabb2.2/Attachments/Stock_vs_466_Exhaust_Plot.jpg

However it seem to have a very low impact on the pipe length compared to rpm so if I decide to make straight exhaust for my bike I will probably start out at around 2.5 meters and cut small sections away until I like the sound and character of the bike

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zevenenergie

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Re: Drag pipes, drag pipe sag and pipe length tuni
Reply #11 - 04/09/20 at 04:46:26

LANCER wrote on 04/03/20 at 11:20:34:

The length of the stock header is good.
That low sounding thump is what I like too, as well as the deep sounding O-W-H-H-H-H on a high speed & rpm deceleration. For me, that is achieved with a good reverse cone with proper baffling around a central straight through core. 18-20” long
That’s just me.

I have heard that when you have a cone on the end of the pipe that works like a pipe of various lengths, is that what you mean?

Would you like to make a sketch of what you mean?

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Do what you know is right. (you can always use fear as a counselor later)

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LANCER

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Re: Drag pipes, drag pipe sag and pipe length tuni
Reply #12 - 04/09/20 at 09:13:57

UUzevenenergie wrote on 04/09/20 at 04:46:26:

LANCER wrote on 04/03/20 at 11:20:34:

The length of the stock header is good.
That low sounding thump is what I like too, as well as the deep sounding O-W-H-H-H-H on a high speed & rpm deceleration. For me, that is achieved with a good reverse cone with proper baffling around a central straight through core. 18-20” long
That’s just me.

I have heard that when you have a cone on the end of the pipe that works like a pipe of various lengths, is that what you mean?

Would you like to make a sketch of what you mean?

A sketch ?
You want me to make a sketch on an electronic device ?
It seems I did try it a few times and that was a few years ago.
So, until I can get my wife to do a little tutoring for me I will try this.
My muffler is an old R&D unit from Cone Engineering years ago, maybe 15 yrs. it is the inside functional portion of a large ballgna shaped chrome HD type. I cut of the chrome shell and that inside functional section is what I use.

I will need to go back later with photo & sketch if my wife is successful with my training.

It is all stainless, 20” L, 1.75”-3.0” OD
The first 3 inches are 1.75”OD, then 7” widening to 3”OD, and then 3”OD for another 10”.

It has a straight through core of 1.5-1.6”, and around that core is a set of spirals. When I spoke with guy I purchased it from (that had the test assignment from Cone Engineering) he said the engineers told him of the construction design. It was designed to push exhaust through the entire can are low-mid rpm and produce a very nice rumble and aid Torque. As rpm rises something about the shape inside causes the higher speed air to exit mostly through the central core, making a nice wail and my engine likes it.

It is a forgiving muffler regarding carb tuning and responds 99.9% of the time by never backfiring on me. It sounds GOOD. 😎.
On the rare occasion I’ve had a backfire it’s been due to an upstream air leak.

Was this helpful at all ?
Will work on the sketch or photos.

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SoC

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Re: Drag pipes, drag pipe sag and pipe length tuni
Reply #13 - 04/09/20 at 12:07:15

If what you are looking for is sound, I went with the VooDoo slashcut, mounted with a down turn and added an extra 4.5" baffle internally. The sound is loud but not too loud and the look is cleaner. I have not fully worked out the carb setting/jets yet. Though it runs strong, issue is backfire on hard de-excelleration.

At idle it is fairly quiet, but when you open it up it has a nice tone. I am contemplating a different baffle possibly. There is some dsicoloration on muffler I think due to heat from redirecting the exhaust flow with the second added baffle which is right in the front where it is attached to header.

The VooDoo mufflers are cheap and making the connector and mounting bracket are not particularly hard if you have any fabrication skills. I even have the blanks for the connector and the bracket. I can send a video of what it sounds like.

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zevenenergie

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Re: Drag pipes, drag pipe sag and pipe length tuni
Reply #14 - 04/09/20 at 12:13:36

Dear lancer,
I shure hope your wife is patient enough to explain how to make an electronic drawing.
Is it an idea to make a pencil sketch and scan it?

I now understand roughly what a special construction this damper has and am now curious about what it looks like exactly.
I have changed the original pipe a bit, and am looking for a good idea for the muffler.

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