Exhaust Headers - MVAgusta.net
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post #1 of 21 (permalink) Old 12-23-2007, 09:08 AM Thread Starter
lee
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Exhaust Headers

I pulled the headers to have them done in Jet Hot Sterling. Looking into the pipe I didn't like what I saw. The bore of the flange that the gasket bears on is smaller than the ID of the gasket leaving a .025" sharp edge sticking out in the flow. Not good. The joint between the flange and the pipe had alot of weld bead also sticking out. These headers are already handicapped due to the tight radius bend right after the port and they certainly don't need any restrictions/sharp edges/protrusions to either restrict, or worse, create turbulent flow. Especially right out of the port. So I massaged them to make the path as smooth as possible.

The other thing I found is at the end of the header there is a sleeve welded inside the pipe which slides into the mid pipe. I don't know the purpose unless it's to better seal the joint. But I do know that the front edge of that sleeve is going to really disrupt the flow and generate turbulence which is not good as it slows down the gases as they go through the pipe. Don't know what I'm going to do with it yet. Maybe just remove it.

Before/after pics of the flange end of the pipe and one of that sleeve attached.

Does anyone really care about these little posts of mine? I assume they're of interest but if they aren't I'm not going to take the time.
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post #2 of 21 (permalink) Old 12-23-2007, 09:45 AM
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Lee,
Not a bad idea to improve the header flow. But, you must be very careful on how much material you remove, especially the welds. It does not take very much to weaken them. If they are good quality full penetration welds it still matters on how much you remove. They could easily see enough vibration and stress to crack the weakened welds. So be careful. With your improved flow. I would guess it will only be a fractional horsepower gain. I would assume it is more emotional than effective.
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post #3 of 21 (permalink) Old 12-23-2007, 02:37 PM Thread Starter
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Schlep,

Yes I know about the weld fragility and am going to Tig them where the welds are to reinforce the areas where I've been working. It's not a power gain I'm after but rather just smoothing and blending areas which I consider to adversely affect the flow. I doubt I'll see any gain to speak of. But it'll be right.

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post #4 of 21 (permalink) Old 12-23-2007, 03:09 PM
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I think smooth flow of gases is more important on intake than on exhaust side.

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post #5 of 21 (permalink) Old 12-23-2007, 03:14 PM
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This sort of thing is of interest to me so I would say, yes, keep posting it if you don't mind.

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post #6 of 21 (permalink) Old 12-23-2007, 07:37 PM
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Lee, please don't stop posting. I enjoy your posts, as I'm sure many others do. I may not act on your ideas and improvements myself, but I do learn a lot from your point of view.
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post #7 of 21 (permalink) Old 12-23-2007, 07:44 PM
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Hey Lee, interesting find there. These are the stock headers, eh?


Anyway, keep the posts coming.... definitely interesting reads.... Plus, it's cool to see some guy from the 'burgh posting up.... I spent some time there, kinda liked the town....


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post #8 of 21 (permalink) Old 12-23-2007, 07:50 PM Thread Starter
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Quote:
Originally Posted by norpet
I think smooth flow of gases is more important on intake than on exhaust side.
Oh quite the contrary. Ideally there should be "laminar" flow from the port to the end of the pipe with no turbulence or disruption of the flow. The much bandied about figure for exhaust gas velocity is 280-300 fps. The instant you put something in the way of the gases it disrupts the flow and creates turbulence which in turn slows the gases which reduces scavenging and raises pressure at the point of turbulence. If you run a raw steel pipe you can literally see these points in the pipe as they will turn a darker shade of blue/purple. Doesn't even have to be an edge to cause it. A tight radius bend in the pipe will cause the flow to "break away" from the surface of the short side radius creating eddys (turbulence) and slow the flow. I for one believe the exhaust design is much more critical and has a much larger effect on performance than the intake tract, and I would do everything I could, however minor, to assist the gasses in getting out of there as smoothly and efficiently as possible.

Re the comments. Yes they're the stockers. Thank yunz (Burgh talk) all for the ++ feedback. A favor. If you disagree don't hesitate to say so and kindly be blunt and frank.

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Last edited by lee; 12-23-2007 at 07:55 PM.
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post #9 of 21 (permalink) Old 12-23-2007, 07:56 PM
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lee, if you dont cc, port and flow bench the heads while your at it, I will be disappointed.

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post #10 of 21 (permalink) Old 12-23-2007, 08:09 PM Thread Starter
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Lewdoggie,

I don't have a flowbench and my jackhammer is broken so I can't do my usual porting job. But I did pull the top end to decarbon the chambers (wasn't much actually) and CC'd the chambers while I was at it. They were within 15 cc's +or- of each other and that's well within my limits. A leftover from my HD days I fear.

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