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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Stepping the header pipe? /cgi-bin/YaBB.pl?num=1563421166 Message started by philthymike on 07/17/19 at 20:39:26 |
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Title: Stepping the header pipe? Post by philthymike on 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. :-/ I find this contrary to other stuff I've tried to grok about exhaust science. |
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Title: Re: Stepping the header pipe? Post by Armen 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. |
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Title: Re: Stepping the header pipe? Post by Fast 650 on 07/18/19 at 09:15:37 6D757471697564707476781D0 wrote:
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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Title: Re: Stepping the header pipe? Post by philthymike on 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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Title: Re: Stepping the header pipe? Post by philthymike on 07/18/19 at 11:22:44 12213E363D530 wrote:
Do you recall any specifics from that talk regarding the stepped design? |
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Title: Re: Stepping the header pipe? Post by batman on 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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Title: Re: Stepping the header pipe? Post by Ruttly on 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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Title: Re: Stepping the header pipe? Post by LANCER on 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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Title: Re: Stepping the header pipe? Post by thumperclone on 07/19/19 at 16:54:16 me thinks D porting is the way |
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Title: Re: Stepping the header pipe? Post by justin_o_guy2 on 07/19/19 at 20:23:51 534F524A574255444B484942270 wrote:
I know I'd sure like to see a Whole Buncha that D porting stuff going on.. |
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Title: Re: Stepping the header pipe? Post by Dave on 07/20/19 at 03:55:47 796660677A7D4C7C4C74666A21130 wrote:
I see what you did there. This is not the Tall Table.....JOG. |
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Title: Re: Stepping the header pipe? Post by philthymike on 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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Title: Re: Stepping the header pipe? Post by LANCER on 07/20/19 at 08:21:22 A racing drag bike runs basically at one speed, wide open when racing. |
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Title: Re: Stepping the header pipe? Post by Fast 650 on 07/20/19 at 08:56:59 48454A4741561613240 wrote:
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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Title: Re: Stepping the header pipe? Post by LANCER on 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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Title: Re: Stepping the header pipe? Post by justin_o_guy2 on 07/20/19 at 11:59:22 If I was driving it wouldn't matter much which way it was pointed,, I wouldn't be breathing anyway. Those people are Crazy! I read recently that they are turning the pipes up and back to help shove down on the car, but it's on the internet, so, it's obviously true, right? |
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