SuzukiSavage.com - Cavi's Mikuni TM40 and Lancer's header thread

Gyrobob

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Re: Cavi's Mikuni TM40 and Lancer's header thread
Reply #30 - 12/30/12 at 16:06:25

Cavi Mike wrote on 12/30/12 at 14:57:47:

Your pictures didn't show up before but this is what I'm talking about:

http://cavimike.com/bend.jpg

I like that bend. It tucks the front of the muffler in close to the bike. The part that matters visually, though, is the side view.

I fiddled with it a long time so from the side it looks like there are only two bends: one in front of the cylinder and one in front of the muffler. Aesthetically, from the side there are only two bends with no strange ups or downs. Having the last part of the exhaust parallel to the ground is too harleyish for me. I prefer the last length of the exhaust system to be canted up some.

Some guys do mount the RYCA muffler set up so that the pipe bends up in front of the muffler, then back down for the muffler. That looks less than smooth to me.

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« Last Edit: 12/30/12 at 17:28:35 by Gyrobob »

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Super Thumper Senior Member Offline 2001 LS650 With 97mm Big Bore Kit, Stage III Cam. Posts: 469 Windsor, Vermont Gender:	Re: Cavi's Mikuni TM40 and Lancer's header thread Reply #31 - 12/30/12 at 20:28:05 Isn't the I.D. of the OEM header pipe 1.5"?
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verslagen1 YaBB Moderator ModSquad Online Where there's a will, I want to be in it. Posts: 28886 L.A. California Gender:	Re: Cavi's Mikuni TM40 and Lancer's header thread Reply #32 - 12/30/12 at 22:42:01 Super Thumper wrote on 12/30/12 at 20:28:05: Isn't the I.D. of the OEM header pipe 1.5"? no, smaller
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LANCER

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Re: Cavi's Mikuni TM40 and Lancer's header thread
Reply #33 - 12/31/12 at 03:39:41

The area of a circle is pi x r x r
stock header (1.3" ID): 3.14 x .65 x .65 = 1.33 s.i.
new header (1.5"): 3.14 x .75 x .75 = 1.77 s, i.
other example (1.65" ID): 3.14 x .825 x .825 = 2.14 s.i.

1.3" ID vs 1.5" ID is a 13% diameter increase
1.33 s.i. vs 1.77 s.i. is a 25% area increase

1.3" ID vs 1.65" ID is a 21% diameter increase
1.33 s.i. vs 2.14 s.i. is a 38% area increase

So a small increase in diameter yields a larger increase in surface area and tube volume, and that extra volume allows much more air to move through the tube.

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Cavi Mike Serious Thumper Offline Thumper n00b Posts: 1005 Rochester, NY Gender:	Re: Cavi's Mikuni TM40 and Lancer's header thread Reply #34 - 12/31/12 at 04:09:03 Yeah, it's a 2:1 ratio. Doubling the diameter of an exhaust quadruples its area. A 4" exhaust doesn't flow twice as much as a 2" exhaust, it flows 4x as much.
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Super Thumper Senior Member Offline 2001 LS650 With 97mm Big Bore Kit, Stage III Cam. Posts: 469 Windsor, Vermont Gender:	Re: Cavi's Mikuni TM40 and Lancer's header thread Reply #35 - 12/31/12 at 07:12:41 I nominate Lancer as professor of the month
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teabowl13 Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 535	Re: Cavi's Mikuni TM40 and Lancer's header thread Reply #36 - 12/31/12 at 07:16:16 HEY PROFESSOR! What kind of metal are you having your header fabricated from? Is it going to be steel? Or Stainless? When you get them ready for production, are you planning to offer different options? Obviously for different prices; stainless would be more expensive...
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ralfyguy Serious Thumper Offline Posts: 932	Re: Cavi's Mikuni TM40 and Lancer's header thread Reply #37 - 12/31/12 at 08:15:27 Stainless is cool, but will discolor quickly, especially in the header area.
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LANCER

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Re: Cavi's Mikuni TM40 and Lancer's header thread
Reply #38 - 12/31/12 at 09:47:19

This prototype is mild steel tube but stainless could be an option. I would have to verify that though, I've not talked with him about that yet.
Would it be cost effective ? Don't know. The cost of this prototype is not nailed down yet either. I know the cost of the tube & cost per bend but not the machine cost for the steel flange at the top yet. Christmas has slowed everything down of course so we wait.

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Gyrobob

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Re: Cavi's Mikuni TM40 and Lancer's header thread
Reply #39 - 12/31/12 at 10:31:49

ralfyguy wrote on 12/31/12 at 08:15:27:

Stainless is cool, but will discolor quickly, especially in the header area.

Some folks like the specific way stainless colors/discolors because it advertises to everyone it is stainless. With unground but tidy welds, and the many varied shades around the welds, plus the hues from the exhaust heat later, such tubes look like performance machinery, rather than chopper glitz.

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Charon

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Re: Cavi's Mikuni TM40 and Lancer's header thread
Reply #40 - 12/31/12 at 12:57:39

Lancer is correct - a larger diameter tube will allow a higher flow for the same pressure drop. But there is a side effect (there always is). The larger tube will also allow pressure pulses to reflect back and forth more easily, and those pressure pulses are what makes a straight pipe difficult to tune. There seems to be a perpetual state of confusion between pressure pulsations and back pressure. Remember, there is nothing steady-state about the flows, either in the intake or the exhaust.

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Cavi Mike Serious Thumper Offline Thumper n00b Posts: 1005 Rochester, NY Gender:	Re: Cavi's Mikuni TM40 and Lancer's header thread Reply #41 - 12/31/12 at 13:31:51 "Tuning" exhausts on a 4-stroke is a myth. There is only one good exhaust for a 4-stroke and that's a non-existent one.
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Charon Serious Thumper Offline Posts: 1811 Harvard, NE Gender:	Re: Cavi's Mikuni TM40 and Lancer's header thread Reply #42 - 12/31/12 at 18:18:06 Perhaps you will find this link - http://www.epi-eng.com/piston_engine_technology/exhaust_system_technology.htm - to be interesting.
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Gyrobob

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Re: Cavi's Mikuni TM40 and Lancer's header thread
Reply #43 - 12/31/12 at 20:13:47

Charon wrote on 12/31/12 at 18:18:06:

Perhaps you will find this link - http://www.epi-eng.com/piston_engine_technology/exhaust_system_technology.htm - to be interesting.

An interesting article. It does show that exhaust systems can have a beneficial effect over venting a short pipe to the atmosphere.

I'd like to see an article showing how different lengths and diameters on single cylinder motors (or at least individual cylinders on multi-cylinder machines) can be worked for various states of tune for the motor. I'm sure the ideal exhaust pipe length and diameter for a 35 hp 5,000 rpm motor like ours would be very different for a similar motor with a cam, and carb set up for 50 or 60 hp at 7,500 rpm.

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LANCER

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Re: Cavi's Mikuni TM40 and Lancer's header thread
Reply #44 - 01/01/13 at 06:07:03

Charon wrote on 12/31/12 at 18:18:06:

Perhaps you will find this link - http://www.epi-eng.com/piston_engine_technology/exhaust_system_technology.htm - to be interesting.

Very interesting indeed.
Besides the lengthy info about exhaust systems & functions, I also read the writeup on the failure of a secondary drive system in a helicopter, since I spent a lot of time in those wacky machines.
All good stuff.

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