zrxdean
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posted January 19, 2004 01:48 PM
Question: exhaust port
Hey porting gurus; should the exhaust port end in a sharp edge as it meets the pipe? Will smoothing this edge to a short radius help flow, or should I leave it? Thanks, Dean
  
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MadMike
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posted January 19, 2004 01:58 PM
dean, dont totally quote me here but, from what I have been told (or how I understood it) the exhaust needs to be as smooth as possible almost Mirror finish with no seams or anything disturbing air flow, so to me that would mean leave it sharp. But I am learning all of the time also. so any pro's out there care to correct me or join in?
Mad Mike
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zrxdean
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posted January 19, 2004 10:08 PM
Thanks Mike. Just seems strange to have such a sharp cutoff to the round primary.
Dean
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Y2KZX12R
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posted January 20, 2004 10:23 AM
Dean, do you mean the intake port?
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VincentHill
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posted January 20, 2004 10:55 AM
I remember the "D" Shaped exhaust holes. and you sure did not want to remove the straight part of the "D". Clean it but to not reshape it.
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zrxdean
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posted January 20, 2004 11:19 AM
I mean the exhaust port Y2K. The header primary is round, and wider than the edge of the port, so I'm wondering whether the sharp 'dropoff' affects flow.
I've seen the D-shaped exhaust ports VH, and the D-shaped exhaust spigots they mate to - that's when I started wondering if the transition from port to primary should be flush.
Dean
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Y2KZX12R
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posted January 20, 2004 11:51 AM
Ok, the picture of the intake port made me ask.
The short answer is no. Dont radius the port flange.
If you look at the inside diameter of the factory exhaust header at the port you'll see that its about the same size as the port. The factory matched it nicely. This keeps the velocity and turbulance to a minimum as it enters the pipe. As tempting as it may look, dont open the port to match the larger dia header. The exhaust port doesnt need more flow potential, it allready flows about 86% of the intake flow, and it would only reduce the port velocity.
The headers larger dia reduces the velocity as it is and also causes turbulance. Both not good for low end and midrange power.
I dont know how long you've been on this board Dean, but i posted some pictures a few years ago of some "d" shaped exhaust inserts that transitioned the port to a large round tube cross section over a 3" length.
They slip into the head pipe with a flange that matched the machined bore of the outer part of the exhaust port. They fit a yoshimura pipe but possably could fit other pipes. Or they could be made to.
I dont have any web space for pictures anymore so you'll notice all the pics i've posted over the years in the threads have disapeared.
I should still have the pics somewhere on CD if you wanted to see what they looked like as i was making them. I still have the tooling die i made to form them but i dont have any more of the thick wall 316 tube used to actually make them. They are fairly time consuming to make and each one is fit to each cylinder because of the angle of the pipes as they leave the head.
I thought about making them for other board members that have a yosh pipe but they were so time consuming to make it wouldnt be worth it.
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zrxdean
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posted January 20, 2004 12:21 PM
Thanks for the useful info Y2K, and I should've said this up front: this is a ZRX1100, not a ZX12 head. The picture above is the exhaust port. I'm using a Muzzy sidewinder pipe with large primary diameter, larger than the port, even at it's widest point. Also I'm spraying nitrous, and therefore concerned about exhaust flow. I still have need for acceptable midrange for getting off the line, but for the most part I'm looking for top end power. Does this change your opinion at all?
If you (or anyone) have those pics of your inserts, I'd like to see them, thanks. You could send them to if you can't post them.
Dean
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zrxdean
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posted January 20, 2004 12:22 PM
My addy got deleted somehow, it's: sabat - at - ufl.edu
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Y2KZX12R
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posted January 20, 2004 12:30 PM
 Edited By: Y2KZX12R on 21 Jan 2004 05:15
Yea it does change things. I've never had a ZRX head on the flow bench. So i can only speculate as to what might work. I think someone with zrx head expierience could guide you better.
But theres some general things that may help.
The exhaust port is similar to the intake port as far as velocity is concerned, with a few more things thrown in like heat and volume.
But typically you want to keep the first 3 inches or so smaller to increase the scavenging effect of the moving column of hot gas. Having s sudden increase in cross sectional area where the pipe meets the head reduces the scavenging effect, especially in the low and midranges. This is where "serpent" pipes should work well. And also could be one reason theres a sag in torque with some pipes on the zx12r at about 4500 rpm. Another thing is flow. Air has mass and it want to travel in a straight line. It will travel in a straight line unless it has to turn a corner. Even if you make it turn a corner its going to want to stay tight to the inside of the turn at the apex and then go to the outside of a turn. Just like you would take a turn racing a motorcycle.
This means that you would want to raise the roof and floor of a port. Most of the flow happens on the short turn radius of a port.
So widening the floor halfway down the port where most of the flow is increases flow.
I dont know about 4 valve heads and Nitrous. Its not somthing i've messed with. But you are pumping more btu's/volume out of the given port. So the velocity is expected to be higher. I dont know what the gas expansion factor is for a given shot of nos and gasoline. Like i said i havent done r&d on nos engines.
But ports in general are a compromise to achieve the power curve you desire.
Hopefully muzzys can help you more.
But I havent seen much proprietairy information come from them, but i can totally understand why.
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Y2KZX12R
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posted January 21, 2004 05:24 AM
I couldnt find the pictures of the spigot inserts. Maybe someone on here saved them??
I do have some pics of the mild steel prototypes used to check fitment and design. They are unuseable because they would burn away from the heat.
But they would give you an idea of what they look like.
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zrxdean
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posted January 21, 2004 08:22 AM
Thanks for taking the time to explain. I'll run it as is for now, keep collecting info and and consider whether to make changes later. Maybe I need to talk to a Pro Mod tuner. I'd appreciate seeing your prototype inserts - I'll post them on this thread.
Dean
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Marcos Peguero
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posted January 21, 2004 10:41 AM
From what I know a good idea to improve a couple of Hp in R6 is to make the exaust port smaller, by putting a "restriction" in the port,
to the gas cannot turn back. If you look to the port you see a flat face. My zx9 looked like that in the exaust port.
I know that this gives the r6 like 3-4 rwhp.
Does your inserts are like that?
How many Hp they make in the ZX12r?
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Y2KZX12R
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posted January 22, 2004 02:52 AM
Damn, i cant find the pics. I'll have to take some new ones.
Fish, theres no backup ofthe pics i had posted?
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frEEk
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posted January 22, 2004 11:02 AM
y2k, assuming the pics were hosted elsewhere (not on this server), no, we wouldnt have backups. we only backup the actual site content, which includes the link to the pic, but not the pic itself.
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zrxdean
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posted January 22, 2004 11:36 AM
I can visualize your inserts Y2K, don't worry about the pics. A 3" slope from the bottom half of the exhaust port to the header.
Thanks,
Dean
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Y2KZX12R
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posted January 22, 2004 12:22 PM
Basically they were mandrel bent stainless tube about 3" long. that slipped in the pipe. One end wad d shaped to match the port. Also a stainless flange ring that fit in the head boss and was d shaped to match.
The tube and flange are tig welded together.
Its basically a port extension.
Freek, i'm not done looking. i have a few more places to look. But if not i'll take some pics tonight of the prototypes that arnt in the bike.
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Marcos Peguero
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posted January 22, 2004 01:05 PM
That will be great to see.
What are the gains?
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Y2KZX12R
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posted January 22, 2004 02:05 PM
Edited By: Y2KZX12R on 22 Jan 2004 14:11
Dean, whats your email?
I can only say that the graph smoothed out below 5000 rpm or so. I think it stoped some reversion. The idle is smoother with them also.
Dont expect big hp gains. The fuel curve didnt need any changes.
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zrxdean
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posted January 22, 2004 02:45 PM
Edited By: zrxdean on 22 Jan 2004 14:46
That sounds good.
sabat@ufl.edu
thanks again,
Dean
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Marcos Peguero
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posted January 23, 2004 06:05 AM
Please send them to me also!
motoseteo@go.com
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zrxdean
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posted January 23, 2004 08:14 AM
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Y2KZX12R
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posted January 23, 2004 06:51 PM
Thanks for posting the pic.
Notice the increase in sideward tilt. This is why they are made for each port.
I wish i still had the pic of the nice stainless finished ones.
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hondo
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posted January 26, 2004 01:08 PM
First reply didn't make it to the thread.
I added S/S Harley-Davidson "exhaust port anti-reversion sleeves" to my 12.
They are thin wall stub pipes with a formed flat flange that perfectly fit into the cylinder head against the gasket surface. The stub pipe fits into the header pipes (Yoshimura).
One exhaust port on my 12 had significant flashing left from the machining of the gasket surface and the port outlet was smaller than the other three. I made up a template that tightly fit into the head against the gasket surface from one port (the most uniform) and traced the outline onto the three other exhaust port gasket surfaces. The bottoms of all four ports were uniform, I didn't touch them. Two ports had very minor flashing on the sides and one significant to the extent that the exit was smaller than the others by 1mm and formed a lip. The exits were not enlarged, well one was, but I was looking for uniform exits not hogging out the ports. The port exits are still smaller than the ID of the gaskets but are exactly the ID of the stubs. The stubs are round, not "D" shaped but I feel there is a better transition now from the ports to the header.
Gaskets to the head.
Stub pipe into the header pipes with a thin layer of high temperature silicne on the BACK side of the stub flange.
Header pipes into the head and torque the flanges.
Couldn't be any easier.
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