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I have been told that both pipes need to be the same lenght for the engine to run smooth. I dont know much about exhaust besides putting one on :angel:. I was looking at some custom exhaust, and it looked to me like both pipes werent the same lenght. Is this smthg i shud really be worried about?

http://arcfabrication.com/images/DSC000075.JPG
 

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It is ideal, but the longer the pipes the less important it gets for them to be equal. Also, depending on the length you're considering, a cross over can help...
 

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In an ideal world, the exhausts are technically the same length. That is making the assumption that both exit the same and have no bends or routing constraints. Unfortunately that isn't the case. I use old calculations from Colin Chapman of Lotus fame for doing my exhaust systems. Given the diameter and the radius of the bend, one can determine the amount of restriction created -vs- a straight flow. Trick is to get even exhaust flow (CFM) from both exhaust systems.

Crossovers are great -- provided the exhaust flow (CFM) going into the crossover itself is about the same and out of phase. Problem one runs into is that with differing flow rates and the cylinders being out of phase, you can get some really strange things to happen ala one cylinder scavenging incredibly well and the other really poorly in a poorly designed system. Thus a crossover itself isn't always to ones advantage.

Search the threads -- there are numerous solutions tried by many people to build a better or unique exhaust system.
 

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doug, the guy at arc who made the system you posted a pic of is a friend and i can tell you he knows more about exhausts then anyone. his are dyno tuned/tested and make more hp then any, and i mean any off the shelf after market system. not to mention he is an artist, as you can see in the pics on his site. but, don't listen to me, email him or call him. hes one hell of a kool guy too.

pete
 

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+1 I'd defintely trust the guys over at arc, only hear good things. Why don't you pick up a Ti frame while you're at it?

;D
 

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Crossovers are great -- provided the exhaust flow (CFM) going into the crossover itself is about the same and out of phase. Problem one runs into is that with differing flow rates and the cylinders being out of phase, you can get some really strange things to happen ala one cylinder scavenging incredibly well and the other really poorly in a poorly designed system. Thus a crossover itself isn't always to ones advantage.
This is interesting info Mark. I've been kicking around the idea of a one low exit, one undertail exit set-up for my M800. I thought I brought this up somewhere else on this board, but I'll be danged if I can find it now...

Seems like one could get very near to equal length headers that way, but my concern was whether or not a crossover would be necessary. I've seen crossovers on inline twins with identical dual exhausts so I presume there is more to it than just "equalizing" disparate header lengths. Are there any good theoretical sources out there you'd recommend reading?
 

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That exhaust in the link is Stupid COOL ! [thumbsup] [thumbsup].. is there other pics of the dual exhaust for dual swingarm? thanks, Harry
 

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Desmo Elmer said:
Seems like one could get very near to equal length headers that way, but my concern was whether or not a crossover would be necessary. I've seen crossovers on inline twins with identical dual exhausts so I presume there is more to it than just "equalizing" disparate header lengths. Are there any good theoretical sources out there you'd recommend reading?
Per crossovers? I don't use them at all on my DesmoDevil BoomTube exhaust systems. There is nothing to gain with a crossover just inches from the outlets themselves -- although people always ask why I don't do one as if there was something wrong with them otherwise.

The resources I use are from Jo Marquart from my old IMSA GTP racing days. He was a designer/fabricator within Lotus racecars during their F1 / Indycar heydays years -- and later when he did his ARGO racecars for IMSA and other classes. His cars out of the gate typically won their first race and were competitive immediately.

I've talked with enough engine builders that I have a good understanding myself of what needs to be done. I'm sure the information is out there somewhere via the Internet also or via books -- I just haven't looked. If I need help, I usually pickup the phone and call people within the racecar industry that I have known for decades.

One thing I recommend is some type of baffle or restrictor ring within the exhaust itself if you go short -- ie: anything under 26" overall length. The Ducati v-twin likes a small amount of back pressure to run properly.
 

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Thanks Mark,

Per crossovers?
No, I meant front header/can exiting low near the front of the rear wheel and the rear header/can going right out the back under tail. Two discrete header /can set-ups. I couldn't imagine how one would stick a crossover in a system like that. JUst wondering if a crossover was necessary...

I don't use them at all on my DesmoDevil BoomTube exhaust systems.
That's the answer I was looking for. I don't like loud, so back pressure will be par for the course in whatever I dream up.
 

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crankmonster said:




The only problem is this guy isn't making pipes for ducati.
Zomg! Those are like the prettiest pipes I've ever seen.
 

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are those tig-craft exhaust? i have a friend w/ a mille who could not stop talking about them. i think they make other parts, also.

crankmonster said:




The only problem is this guy isn't making pipes for ducati.
 

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Yes they are tig's. A friend i ride with had the full exhaust on his Tuono Racing that he sold.

Zomg! Those are like the prettiest pipes I've ever seen.
They are even better to look at in person, realy. [thumbsup]
 

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i'm not a fan of all the unfinished welds. in my past experiences when we made custom exhausts, the part that made them so perfect was finishing them and making them look seamless
just my opinion though
 
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