SuzukiSavage.com - Stepping the header pipe?

philthymike

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Stepping the header pipe?
07/17/19 at 20:39:26

It's late and I'm bored so I read this article here.
http://www.performanceindian.com/Pipes.html

Then I got here and scratched my head:

Another new trend for performance pipes is to step them. "Stepping", means to use a smaller pipe from the exhaust port for about 8"-10", and then step up the pipe size to the next size by slipping the bigger pipe over the smaller pipe, and welding it. This helps to turn the wave reflex pulses back around without entering the combustion chamber.

I thought you needed the waves to reach the combustion chamber for better scavenging. Undecided

I find this contrary to other stuff I've tried to grok about exhaust science.

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Armen Serious Thumper Offline Half-Witted Wrench-Jockey from Jersey Posts: 1431	Re: Stepping the header pipe? Reply #1 - 07/18/19 at 06:01:19 BUB exhausts did this in the 70's/80's on some of theirs. I remember talking to Dennis Maning, the owner/engineer of the company.
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Fast 650

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Re: Stepping the header pipe?
Reply #2 - 07/18/19 at 09:15:37

philthymike wrote on 07/17/19 at 20:39:26:

I find this contrary to other stuff I've tried to grok about exhaust science.

Exhaust dynamics are really strange sometimes. Like his story about the Harley KR racers. Those bikes ran faster with the slash cut exhausts vs straight cut pipes. But when they changed to the XR OHV engine, they ran better with a megaphone exhaust then.

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philthymike Serious Thumper Offline Wallowing in my own crapulence Posts: 1413 Philadelphia Area Gender:	Re: Stepping the header pipe? Reply #3 - 07/18/19 at 11:16:57 True that. Sometimes strange is normal. I think the internet promotes a new category of strange too with its plethora of contradictions and opposing viewpoints. My own understanding (or not) aside, would our thumper engines benefit from this stepping technique?
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philthymike Serious Thumper Offline Wallowing in my own crapulence Posts: 1413 Philadelphia Area Gender:	Re: Stepping the header pipe? Reply #4 - 07/18/19 at 11:22:44 Armen wrote on 07/18/19 at 06:01:19: BUB exhausts did this in the 70's/80's on some of theirs. I remember talking to Dennis Maning, the owner/engineer of the company. Do you recall any specifics from that talk regarding the stepped design?
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batman Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 3806 osceola new york Gender:	Re: Stepping the header pipe? Reply #5 - 07/19/19 at 07:10:26 All of the cams that can be used in the bike at this time provide negative, or little (dr cam- 6 degrees )overlap , so provide little or no chance of scavenging, stepping the exhaust header would do nothing , and may even harm performance at certain rpms.
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Re: Stepping the header pipe?
Reply #6 - 07/19/19 at 13:49:33

I tend to believe that building a single and tuning a single isn't as easy as one might think. Everything is critical , money spent in vein if your not up for the tuning end of it. Let's throw money at it to make go , doesn't always work out. Always better to build it for a purpose/rpm range it will be run at most of the time , especially a single. Design your engine for its intended purpose/rpm range. Find a cam that best supports that rpm range to acheive a powerband in the desired sweet spot. It's all about making your engine breath freely and then dialing in the powerband to a usable rpm range. More Math ! Stepping the exhaust , where , how much , why ? You gain in one area will be followed a loss in another area , that's what happens with intake & exhaust tuning , you must find the happy medium in your desired rpm range. Good math will expose weaknesses , but even after all the math is done you still have to test n tune. Building engines is easy , building a fast single takes math , mechanical skills and patience to test n tune.

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LANCER Serious Thumper Alliance Member Offline Savage Beast Performance Parts Posts: 10585 Oklahoma Gender:	Re: Stepping the header pipe? Reply #7 - 07/19/19 at 16:49:11 I have used a 1.75” OD/1.65” ID header for 12-13 years and I like the results. They have been homemade, one was from sections of pipe (not a stepped pipe)and the other one solid piece. Both work equally well. I have not used a stepped pipe before so cannot say about that.
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thumperclone Serious Thumper Alliance Member Offline PGR rider riding with respect Posts: 5809 Grand Junction Colorado Gender:	Re: Stepping the header pipe? Reply #8 - 07/19/19 at 16:54:16 me thinks D porting is the way
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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Stepping the header pipe? Reply #9 - 07/19/19 at 20:23:51 thumperclone wrote on 07/19/19 at 16:54:16: me thinks D porting is the way I know I'd sure like to see a Whole Buncha that D porting stuff going on..
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Dave YaBB Moderator ModSquad Offline SuzukiSavage.com Rocks! Posts: 17783 Camp Springs, Kentucky Gender:	Re: Stepping the header pipe? Reply #10 - 07/20/19 at 03:55:47 justin_o_guy2 wrote on 07/19/19 at 20:23:51: I know I'd sure like to see a Whole Buncha that D porting stuff going on.. I see what you did there. This is not the Tall Table.....JOG.
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philthymike

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Re: Stepping the header pipe?
Reply #11 - 07/20/19 at 07:23:28

Good point regarding porting. Without it any sort of custom header could be a big waste of time I suppose.
But if you do the porting isn't the stock header going to make that a waste of time too.
I read something DBMike posted about this where porting and header size had affected each other in various ways.

I read all this talk about pressure waves, backpressure, stepped pipes, powerbombs etc. But then I look at racing engines in things like dragsters with just a short stubby header pipe for each cylinder and wonder what do they know that everyone else doesn't? That can't take that much math.

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LANCER Serious Thumper Alliance Member Offline Savage Beast Performance Parts Posts: 10585 Oklahoma Gender:	Re: Stepping the header pipe? Reply #12 - 07/20/19 at 08:21:22 A racing drag bike runs basically at one speed, wide open when racing.
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Fast 650

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Re: Stepping the header pipe?
Reply #13 - 07/20/19 at 08:56:59

LANCER wrote on 07/20/19 at 08:21:22:

A racing drag bike runs basically at one speed, wide open when racing.

And the dragsters like he described are not running on gasoline either. A heavy mix of nitromethane forced into the cylinders under high boost pressure doesn't care about exhaust tuning anymore. The only real purpose of those stubby pipes is to direct the exhaust away from the driver.

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LANCER Serious Thumper Alliance Member Offline Savage Beast Performance Parts Posts: 10585 Oklahoma Gender:	Re: Stepping the header pipe? Reply #14 - 07/20/19 at 11:54:59 If I was driving I would appreciate having that exhaust directed away from me too.
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