WRECKSHOP
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posted February 20, 2009 11:32 AM
Smaller High Velocity Ports ???
I need the engine and cylinder head GURU'S to chime in on this one. This is a greatly debated and discussed topic on the ZX-10R.NET forum under Garth's motor thread. How are they better than a traditionally regular ported, polished and flowed cylinder head ??
  
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KZScott
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posted February 20, 2009 12:24 PM
my limited understanding is its better for low end and midrange. more responsive on the street
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01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
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2000redrocket
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posted February 20, 2009 12:56 PM
the more air you can get out of a smaller port the better but i am sure there is a limit to what a given size runner can flow. make the ports too big you will need more displacement to make up the velocity of the bigger port. then the velocity will get higher again. this is what i know. also too big of a cam with out enough cranking compression will make a peeky engine with less low end torque. longer intake runners will help things out on topend and midrange but on out zx12 and 14s we are stuck with the length somewhat.this is how i understand it . Y2k???
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tcchin
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posted February 20, 2009 03:19 PM
High port velocity is a relative term. This term is quantified by the Mach number. Exceeding recommended Mach numbers will choke flow rates through the port. A properly-designed port will address port cross-sectional area, minimum bend radius, floor height, length, taper, etc.
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KZScott
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posted February 20, 2009 03:43 PM
you lost me when you started talking about gillette razors Tim lol jk
care to elabourate on the max mach number??
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01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
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Y2KZX12R
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posted February 20, 2009 05:18 PM
I dont know where to begin.
Yea, what tim said. 
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tcchin
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posted February 20, 2009 06:35 PM
You can wiki Mach number for a cursory explanation of what it is. Basically, it's a fluid dynamics term that compares the velocity of an object in a medium to the speed of sound in the same medium (density, temp dependent). In order to achieve maximum port efficiency, the maximum Mach number achieved in the port must stay below a certain threshold (e.g., .60), at the risk of the flow contracting and straightening too much to maintain mass flux rates. The Law of the Wall says that flow velocity at the wall of the port is zero, so the velocity gradient across the flow field gets pretty steep as the Mach number increases and the flow will try to separate from the wall of the port.
In the end, port velocity has to be a compromise between providing sufficient energy to hold mixture and spin up the combustion chamber on the intake side/scavenging on the exhaust side and choking off the flow. That's why porting has to be done precisely to match an individual motor's components (cams, valves, displacement, etc.) and operating environment (drag racing, road racing, street, etc.).
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2000redrocket
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posted February 20, 2009 09:04 PM
wow
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Y2KZX12R
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posted February 21, 2009 05:57 AM
So, if the port goes into "sonic choke" it limits any further flow.
It can limit the max HP potential of the engine if the sonic choke happens too early before the engine is at its peak HP rpm.
The object, with an engine that needs a wide powerband is to get as close as possable without going over. If you have a good straight port (zx12r) or well designed dog leg one with enough radius to support those air speeds (SB2.2) then you can tune the port to take advantage of the energy in the flow.
We use Dynomation and EAP to run simulations and aquire wave data, like pressure, timing, amplitude, velocity, CFM demand, trapped volume mass, etc. as well as the static flow bench. Each tool gives you different info. They support eachother.
The flow bench gives you actual flow resistance measurements that you can use as a gauge to calculate the ports efficiency. It also allows you to measure the radial bias of the flow at any given valve lift or depth of the port.
Typically its widely thought that if the port air velocity is more than 330 FPS at 28" of water on a flow bench then the port will go into sonic choke on the running engine. But we find now that this isnt totally accurate and finite. We know now that a high radial bias in the port is a big factor. Like in an SB2.2 port with a fairly high radial biasa compared to a Busa or ZX12 intake port. The zx14 head has an extremely low radial bias due to its short turn shape from the factory.
Its commonly accepted by most that an average of .55% of the speed of sound in a port is optimal. However we (competition cnc) dont work with averages beacuse we dont have to. We have an exact digital model of the port and we know the exact flow rate and radial bias as well as the radial average for any given slice in the entire intake tract from belmouth to valve seat. This also gives us the ports total taper and volume.
As far as whats best for a given engine? Well its all about what you want to torque curve to look like. In other words, where you want the power band to be strongest.
Thats somthing that has to be decided by what you are trying to do with the engine, like road racing, oval racing, drag racing, land speed racing, marine use, etc.
If we want to make a VERY general statement then smaller ports with higher air speeds produce peak torque at a lower rpm than a larger port with slower air speeds.
But that statement is so generic its like saying an engine with more displacement produces more HP than a smaller engine. Not always true.
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entropy
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posted February 21, 2009 07:18 AM
wow-WOW
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Y2KZX12R
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posted February 21, 2009 09:22 AM
 Edited By: Y2KZX12R on 21 Feb 2009 17:53
You guys might find this interesting....
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KZScott
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posted February 21, 2009 06:21 PM
when i grow up i want to be Tim or Jim
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
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WRECKSHOP
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posted February 21, 2009 06:46 PM
Are the smaller ported cylinder heads better than the tradionally ported/polished and flowed cylinder heads ? For dragracing that is !!!
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tcchin
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posted February 21, 2009 07:13 PM
Knowing just about nothing about your application, I'll go out on a limb and say that the stock ports are probably a compromise between performance, emissions and drivability. Smaller than stock could increase the Mach number in the ports, reducing flow at high rpm. Traditional porting will typically involve enlarging the port volume, reducing the Mach number and increasing flow at high rpm. Drag racing is about getting a good launch, and then matching your torque curve to your shift points, usually near redline. Does this sound like a good match for smaller ports?
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Y2KZX12R
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posted February 21, 2009 08:10 PM
Edited By: Y2KZX12R on 22 Feb 2009 04:27
oops, heres the other pic that wont show up now in the post above....
I really wish I could edit my posts.
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Y2KZX12R
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posted February 21, 2009 08:25 PM
quote:
when i grow up i want to be Tim or Jim
Scott, I love this stuff.
Wreck, like Tim said, dragracing you want to make big peak power. But you dont want to fall completely off the torque curve at the shift recovery rpm either.
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whitehendrix
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posted February 22, 2009 06:25 PM
you guys are ridiculous.
sonic choke.. thats a new one for me.
think i'm about ready to sonic give up on learning all this shit..
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WRECKSHOP
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posted February 23, 2009 10:27 AM
Right, this stuff keeps getting better and better !!! Ok, cool so biggg peak horsepower is what a person needs and wants when dragracing.....So, the smaller high velocity ported cylinder head will not give you a big peak horsepower number as will a tradionally ported cylinder head !!!
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Y2KZX12R
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posted February 23, 2009 04:17 PM
Yea, generally speaking. But it really depends on what size the port is to start with.
A stock zx12r engine with stock cams has a peak port velocity of MACH .5
The graph above is a zx12 1427cc engine with 1mm O/S valves "bigger" cams and our stage 2 CNC port in it.
As you can see the velocity is much higher than stock. So the engine thinks the ports are smaller than a stock head even thou they are much bigger.
A stock head on a 1427 or even a 1375 zx12r is like having a restrictor plate under the throttle bodies. Engines with too high of a velocity in the ports like a lot of duration on the cams bacause they need the extra time to move the required volume of air. Reversion normally accociated with long durtation cams isnt as big of a problem because of the inertia of the column of air. Big lift cams on an unported head dont work well because the valve window area isnt the restriction, the choke in the port is.
Now a stock litre bike is another story. Sometimes those ports are too slow for strong midrange power.
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2000redrocket
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posted February 23, 2009 06:38 PM
y2k i am glad you have a zx12 bike and spend this time on knowing how to get from the whole engine what you can. all too often this happens for the susike people and us kawasai owners do not get the shops that care to do the best they can. for me it will be you or sal to port my ningas head. it would be intresting for you to look at my iron indy big block heads to see if they are all out or can be better. i guess i just deside what they are going on.( drag or pulling truck at 500cid) i want a truck i think again.
thanks for all the work and midnight oil you had to burn
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Y2KZX12R
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posted February 23, 2009 07:52 PM
We just dynoed a BB mopar with Indy heads on it last week. Made good power.
We took off the aluminum Mopar racing heads and put the indy heads on it. Picked up about 80 hp.
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WRECKSHOP
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posted February 27, 2009 01:56 PM
Whats the strongest ZX-12 motor you have seen !!! Dyno number's, timeslips etc....
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2000redrocket
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posted February 27, 2009 03:07 PM
i have aluminum older heads on my 440. the iron heads i am sitting on. how much hp do you gain picking up 40 cfms? is something you can look at a chatr for and compair or are there too many variables. the aluminum heads are around 335cfm @28 with 270cc runners and the iron heads have a guess is 330cc runners and flow about 380 to 385 cfms.
i am not wanting to put them on my 440 cause i am afraid that with the huge ports and valves it will not make good power being a 440. i am thinking they will suit a 500cid better.
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Y2KZX12R
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posted February 27, 2009 04:26 PM
quote:
Whats the strongest ZX-12 motor you have seen !!! Dyno number's, timeslips etc....
Are you asking me? 230's N/A
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Y2KZX12R
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posted February 27, 2009 04:55 PM
quote:
i have aluminum older heads on my 440. the iron heads i am sitting on. how much hp do you gain picking up 40 cfms? is something you can look at a chatr for and compair or are there too many variables. the aluminum heads are around 335cfm @28 with 270cc runners and the iron heads have a guess is 330cc runners and flow about 380 to 385 cfms.
i am not wanting to put them on my 440 cause i am afraid that with the huge ports and valves it will not make good power being a 440. i am thinking they will suit a 500cid better.
Well super flow has some formulas for flow vs. HP. I never use them because its seldom accurate. But they say an optimal tiuned engine can make .257 hp per cfm.
so.... 40 cfm x .257 x 8 = 82.24
But thats assuming the entire engine combo is optimized before and after the cfm increase.
The important thing is the ports flow coefficient. A big port will usually flow a lot of air but it may have a poor flow coefficient. which will make the engine weak on torque below peak torque.
A good flowing port may not necessairily make good power, but a poor flowing port will most certainally not make good power.
For instance, Boss 302 engines were turds. The heads flowed a ton of air but the velocity was very slow.
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